A century of science in America

by Unknown

Origin of Greenstone.

Does the greenstone of the Connecticut afford evidence in favour of the Wernerian or of the Huttonian theory of its origin? Averse as I feel to taking a side in this controversy, I cannot but say, that the man who maintains, in its length and breadth, the original hypothesis of Werner in regard to the aqueous deposition of trap, will find it for his interest, if he wishes to keep clear of doubts, not to follow the example of D’Aubuisson, by going forth to examine the greenstone of this region, lest, like that geologist, he should be compelled, not only to abandon his theory, but to write a book against it. Indeed, when surveying particular portions of this rock, I have sometimes thought Bakewell did not much exaggerate when he said in regard to Werner’s hypothesis, that, ‘it is hardly possible for the human mind to invent a system more repugnant to existing facts.’

On the other hand, the Huttonian would doubtless have his heart gladdened, and his faith strengthened by a survey of the greater part of this rock. As he looked at the dikes of the old red sandstone, he would almost see the melted rock forcing its way through the fissures; and when he came to the amygdaloidal, especially to that variety which resembles lava, he might even be tempted to apply his thermometer to it, in the suspicion that it was not yet quite cool ... (p. 59).

By treating the subject in this manner I mean no disrespect to any of the distinguished men who have adopted either side of this question. To President Cooper especially, who regards the greenstone of the Connecticut as volcanic, I feel much indebted for the great mass of facts he has collected on the subject. And were I to adopt any hypothesis in regard to the origin of our greenstone, it would be one not much different from his” (p. 60).

By 1833 and more clearly in 1841 Hitchcock had come to recognize the distinction between intrusive and extrusive basaltic sheets in the Connecticut valley. Dawson also came to regard the Acadian sheets as extrusive, and Emerson in 1882 recalled again the evidence for Massachusetts (24, 195, 1882). Davis, however, went a step further and by applying distinctive criteria not only separated intrusive and extrusive sheets throughout the whole Triassic area, but by using basalt flows as stratigraphic horizons unraveled for the first time the system of faults which cut the Triassic system. His preliminary paper (24, 345, 1882) was followed by many others.

From 1880 onward begins the period of precise structural field work. The older geologists mostly conceived their work after reconnaissance methods. From 1870 to 1880 a group of younger men entered geology who paid close attention to the solid geometry and mechanics of earth structures. In their hands physical and dynamical geology began to assume the standing of a precise and quantitative science. In the field of intrusive rocks the opening classic was by Gilbert, who in his volume on the geology of the Henry Mountains, published in 1880, made laccoliths known to the world. With the beginning of this new period we may well leave the subject of intrusive rocks and turn to the progress of knowledge in regard to those deeper and vaster bodies now known as batholiths. These, since erosion does not expose their bottoms, Daly separates from intrusives and classifies as subjacent. The batholiths consist typically of granite and granodiorite, and introduce us to the problem of granite.

Views on the Structural Relations of Granite.

Conscientious field observations were sufficient to establish the true nature of the intrusive and extrusive rocks. The case was very different, however, with the nature and relations of the great bodies of granite, which may be taken in the structural sense as including all the visibly crystalline acidic and intermediate rocks, known more specifically as granite, syenite, and diorite.

The large bodies of granite, structurally classified as stocks, or batholiths, commonly show wedges, tongues, or dike networks cutting into the surrounding rocks. The relations, however, are not all so simple as this. Granites may cover vast areas, they are usually the older rocks, they are generally associated with regional metamorphism of the intruded formations, which metamorphism is now understood to be due chiefly to the heat and mineralizers given off from the granite magma, associated with mashing and shearing of the surrounding rocks. The granite was often injected in successive stages which alternated with the stages of regional mashing. A parallel or gneissic structure is thus developed which is in part due to mashing, in part to igneous injection. Where the ascent of heat into the cover is excessive, or where blocks are detached and involved in the magma, the latter may dissolve some of the older cover rocks, even where these were of sedimentary origin.

Thus between mashing, injection, and assimilation the genetic relationships of a batholith to its surroundings are in many instances obscure. Nevertheless, attention to the larger relations shows that the molten magma originated at great depths in the earth’s crust, far below the bottoms of geosynclines, and consists of primary igneous material, not of fused sediments. From those depths it has ascended by various processes into the outer crust, where it crystallized into granite masses, to be later exposed by erosion. The amount of material which can be dissolved and assimilated must be small in comparison with the whole body of the magma. The original composition of the magma was probably basic, nearer that of a basalt than that of a granite. Differentiation of the molten mass is thought to cause the upper and lower parts of the chamber to become unlike, the lighter and more acidic portion giving rise to the great bodies of granite. With the exception of certain border zones the whole, however, is regarded as igneous rock risen from the depths.

The complex border relations, but more particularly certain academic hypotheses, led to a period of misunderstanding and retrogression in regard to the nature of granites. It constitutes an interesting illustration of the possibility of a wrong theory leading interpretation astray, chiefly through the magnification of minor into major factors. This history illustrates the dangers of qualitative science as compared to quantitative, of a single hypothesis as matched against the method of multiple working hypothesis. This flux of opinion in regard to the nature of granites may be traced through the volumes of the Journal.

E. Hitchcock in 1824 (6, 12) noted that in places granite appeared bedded, but in other places existed in veins which cut obliquely across the strata. Silliman, although careful not to deny the aqueous origin of some basalts, yet held that the field evidence of New England indicates for that region the igneous or Huttonian origin of trap and granite (7, 238, 1824).

In 1832 the following article by Hitchcock appeared in the Journal (22, 1, 70):

Report on the Geology of Massachusetts; examined under the direction of the Government of that State, during the years 1830 and 1831; by Edward Hitchcock, Prof. of Chemistry and Natural History in Amherst College.

A footnote adds that this is “published in this Journal by consent of the Government of Massachusetts, and intended to appear also in a separate form, and to be distributed among the members of the Legislature of the same State, about the time of its appearance in this work. It is, we believe, the first example in this country, of the geological survey of an entire State.”

This article includes a geological map of the state and covers the subject of economic geology. The report brought forth the following remarks from a French reviewer in the Revue Encyclopédique, Aug. 1832, quoted in the Journal (23, 389, 1833):

“A single glance at this report, is sufficient to convince any one of the utility of such a work, to the state which has undertaken it; and to regret that there is so very small a part of the French territory, whose geological constitution is as well known to the public, as is now the state of Massachusetts. France has the greater cause to regret her being distanced in this race by America, from her having a corps of mining engineers, who if they had the means, would, in a very short time furnish a work of the same kind, still more complete, of each of the departments.”

The complete report published in 1833 is a work of 700 pages. Pages 465 to 517 are devoted to the subject of granite. Numerous detailed sketches are given showing contact relations. Nine pages are given to theoretical considerations and many lines of proof are given that granite is an igneous rock, molten from the internal heat of the earth, and intruded into the sedimentary strata. His statement is the clearest published in the world, so far as the writer is aware, up to that date, and marks Edward Hitchcock as one of the leading geologists of his generation in Europe as well as America. Unfortunately his views were largely lost to sight during the following generation.

In 1840 the first American edition of Mantell’s Wonders of Geology gave currency to the idea that granite is proved to be of all geological ages up to the Tertiary (39, 6, 1840). In 1843 J. D. Dana pointed out (45, 104) that schistosity was no evidence of sedimentary origin. He regarded most granites as igneous as shown by their structural relations, but considers that some may have had a sedimentary origin.

Rise and Decline of the Metamorphic Theory of Granite.

Up to 1860 granite was regarded on the basis of the facts of the field as essentially an intrusive rock, but gneiss as a metamorphic product mostly of sedimentary origin. It seemed as though sound methods of research and interpretation were securely established. Nevertheless, a new era of speculation and a modified Wernerism arose at that time with a paper by T. Sterry Hunt, marking a retrogression in the theory of granite which lasted until his death in 1892.

In November, 1859, Hunt read before the Geological Society of London a paper on “Some Points in Chemical Geology” in which he announced that igneous rocks are in all cases simply fused and displaced sediments, the fusion taking place by the rise of the earth’s internal heat into deeply buried and water-soaked masses of sediments (see 30, 133, 1860). The germ of this idea of aqueo-igneous fusion was far older, due to Babbage and John Herschel, neither of them geologists, but such sweeping extensions of it had never before been published. Hunt had the advantage of a wide acquaintanceship with geological literature and chemistry. He wrote plausibly on chemical and theoretical geology, but his views were not controlled by careful field observations. In fact he wrote confidently on regions which apparently he had never seen and where a limited amount of field work would have shown him to have been fundamentally in error. A man of egotistical temperament, he sought to establish priority for himself in many subjects and in order to cover the field made many poorly founded assertions. Building on to another Wernerian idea, he held that many metamorphic minerals had a chronologic value comparable to fossils—staurolite for example indicating a pre-Silurian age—and on this basis divided the crystalline rocks into five series. Although there is much of value buried in Hunt’s work it is difficult to disentangle it, with the result that his writings were a disservice to the science of geology. Although carrying much weight in his lifetime, they have passed with his death nearly into oblivion.

Marcou, with a limited knowledge of American geology, and but little respect for the opinions of others, had published a geologic map of the United States containing gross errors. In support of his views he read in November, 1861, a paper on the Taconic and Lower Silurian Rocks of Vermont and Canada. In the following year he was severely reviewed by “T,” who states positively in controverting Marcou (33, 282, 283, 1862) that “the granites (of the Green Mountains) are evidently strata altered in place.”

“Mr. Marcou should further be informed that the granites of the Alpine summits, instead of being, as was once supposed, eruptive rocks, are now known to be altered strata of newer Secondary and Tertiary age. A simple structure holds good in the British Islands, where as Sir Roderick Murchison has shown in his recent Geological map of Scotland, Ben Nevis and Ben Lawers are found to be composed of higher strata, lying in synclinals. This great law of mountain structure would alone lead us to suppose that the gneiss of the Green mountains, instead of being at the base, is really at the summit of the series....

We cannot here stop to discuss Mr. Marcou’s remark about ‘the unstratified and oldest crystalline rocks of the White mountains’ which he places beneath the lower Taconic series. Mr. Lesley has shown that these granites are stratified, and with Mr. Hunt, regards them as of Devonian Age. (This Journal, vol. 31, p. 403.) Mr. Marcou has come among us with notions of mountains upheaved by intrusive granites, and similar antiquated traditions, now, happily for science, well nigh forgotten.”

It is seen that Marcou, notwithstanding the general character of his work, happened to be nearer right in some matters than were his critics, and that “T” had adopted to the limit the views of Hunt.

The recovery of geology from this period of confusion was partly owing to the slow accumulation of opposed facts; especially to a recognition of the fact that the overplaced relation of the granite gneisses in western Scotland was due to great overthrusts; also to the evidence of the clearly intrusive nature of many of the Cordilleran granites. The recovery of a sounder theory was hastened, however, by the application of criticisms by J. D. Dana in the Journal. In 1866 (42, 252) Dana pointed out that sedimentary rocks in Pennsylvania, in Nova Scotia, and other regions which had been buried to a depth of at least 16,000 feet are not metamorphic. Mere depth of burial of sediments was not sufficient therefore to produce metamorphism and aqueo-igneous fusion. The baseless and speculative character of the use of minerals as an index of age and of Hunt’s interpretation of New England geology in general was shown by Dana in 1872 (3, 91). The following year Dana pointed out clearly that igneous eruptions in general have been derived from a deep-seated source and did not come from the aqueo-igneous fusion of sediments. As to gradations between true igneous rocks and fused and displaced sediments he makes the following statements (6, 114, 1873):

“Again, the plastic rock-material that may be derived from the fusion or semifusion of the supercrust, (that is, of rocks originally of sedimentary origin,) gives rise to “igneous” rocks often not distinguishable from other igneous rocks, when it is ejected through fissures far from its place of origin; while crystalline rocks are simply metamorphic if they remain in their original relations to the associated rocks, or nearly so.

Between these latter igneous rocks and the metamorphic there may be indefinite gradations, as claimed by Hunt. But if our reasonings are right, the great part of igneous rocks can be proved to have had no such supercrust origin. The argument from the presence of moisture or of hydrous minerals in such rocks in favor of their origin from the fusion of sediments has been shown to be invalid.”

The injected marginal rocks and the post-intrusive metamorphism of most of the New England granites has, however, obscured more or less their real igneous nature so that the gradation from metamorphic sediments through igneous gneisses to granites could be read in either direction. These features misled Dana who accepted the prevailing idea of the general metamorphic origin of granite. Dana makes the following statement (6, 164, 1873):

“But Hunt is right in holding that in general granite and syenite (the quartz-bearing syenite) are undoubtedly metamorphic rocks where not vein-formations, as I know from the study of many examples of them in New England; and the veins are results of infiltration through heated moisture from the rocks adjoining some part of the opened fissures they fill.”

Granite, although regarded at this time as the extreme of the metamorphic series and originating from sediments, was looked upon as typically Archean in age, though in some cases younger. Such a doctrine permitted such extreme misinterpretations as that of Clarence King and S. F. Emmons on the nature of the intrusive granite of the Little Cottonwood canyon in the Wahsatch Range. This body cuts across 30,000 feet of Paleozoic rocks and to the careful observer, as later admitted by Emmons, shows clear evidence of its transgressive nature. But at that time it was generally considered that granite mountains were capable of resisting the erosion of all geological time. Consequently it did not seem incredible to King and his associates that here a great granite range of Archean origin had stood up through Paleozoic time until gradual subsidence had permitted it to be buried beneath 30,000 feet of sediments.[^[82]]

It may seem to the present day reader that such a misinterpretation, doing violence to fundamental geologic knowledge as now recognized, was inexcusable; but in the light of the history of geology as here detailed it is seen to have been the interpretation natural to that time. It is true that a careful examination of the facts of that very field would have proved the post-Paleozoic and intrusive nature of that great granite body now known as the Little Cottonwood batholith, but Emmons has explained the rapid and partial nature of the observations which they were compelled to make in order to keep up to their schedule of progress (16, 139, 1903).

Whitney had found some years earlier that the granites of the Sierra Nevada were igneous rocks intrusive into the Triassic and Jurassic strata. The Lake Superior geologists began to show in the eighties that granite was there an intrusive igneous rock. R. D. Irving and Wadsworth noted these relations. Lawson in 1887 pointed out emphatically (33, 473) that the granites of the Rainy Lake region, although basal, were younger than the schists which lay above them. The granite gneisses he held were of clearly the same igneous origin as the granites and neither gave any field evidence of being fused and displaced sediments. From this time forward the truly igneous nature of granite became increasingly accepted until now the notion of its being made of sedimentary rocks softened and recrystallized by the rise of the isogeotherms through deep burial is as obsolete as the still older doctrine of the Neptunists that granite was laid down as a crystalline precipitate on the floor of the primitive ocean.

The recognition of the truly igneous nature of granites has been followed in the present generation by a series of studies on their structural relations and mode of genesis. A number of important initial articles on various aspects of structure and contact relations have appeared in the Journal, but this sketch of the history of the subject may well stop with the introduction to this modern period.

Orogenic Structures.

Views of Plutonists and Neptunists.

Orogenic structures are, as the name implies, those connected with the birth of mountains. Nearly synonymous terms are deformative or secondary structures. On a small scale this division embraces the phenomena exposed in the rock ledge or quarry face, or in the dips and dislocations varying from one exposure to another. These structures include faults, folds, and foliation. On a larger scale are included the relations of the different ranges of a mountain system to each other, relations to previous geologic history, relations to the earth as a whole, and to the forces which have generated the structures.

In order to see the stage of development of this subject in 1818 and its progress as reflected through the publications of a century, more particularly in the Journal, it is desirable to turn again to those two treatises emanating from Edinburgh at the beginning of the nineteenth century and representing two opposite schools of thought, the Plutonists and Neptunists.

Playfair, in 1802, devotes nineteen pages to the subject of the inflection and elevation of strata.[^[83]] He places emphasis on the characteristic parallelism of the strike of the folds throughout a region, as shown through the intersection of the folds by a horizontal plane of erosion. He contrasts this with the arches shown in a transverse section and enlarges on our ability to study the deeply buried strata through the denudation of the folded structure. He argues from these relations that the structures can not be explained by the vague appeal of the Neptunists to forces of crystallization, to slopes of original deposition, or to sinking in of the roofs of caverns. The causes he argues were heat combined with pressure. As to the directions in which the pressure acted he is not altogether clear, but apparently regards the pressure as acting in upward thrusts against the sedimentary planes, the latter yielding as warped surfaces. His method of presentation is that of inductive reasoning from facts, but he stopped short of the conception of horizontal compression through terrestrial contraction.

Jameson, professor of natural history in the same university, in 1808 contemptuously ignores the work of Hutton and Playfair in what he calls the “monstrosities known under the name of Theories of the Earth.” In a couple of pages he confuses and dismisses the whole subject of deformation. He states:[^[84]]

“It is therefore a fact, that all inclined strata, with a very few exceptions, have been formed so originally, and do not owe their inclination to a subsequent change.

When we examine the structure of a mountain, we must be careful that our observations be not too micrological, otherwise we shall undoubtedly fail in acquiring a distinct conception of it. This will appear evident when we reflect that the geognostic features of Nature are almost all on the great scale. In no case is this rule to be more strictly followed than in the examination of the stratified structure.

By not attending to this mode of examination, geognosts have fallen into numberless errors, and have frequently given to extensive tracts of country a most irregular and confused structure. Speculators building on these errors have represented the whole crust of the globe as an irregular and unseemly mass. It is indeed surprising, that men possessed of any knowledge of the beautiful harmony that prevails in the structure of organic beings could for a moment believe it possible, that the great fabric of the globe itself,—that magnificent display of Omnipotence,—should be destitute of all regularity in its structure, and be nothing more than a heap of ruins.”

This was the attitude of a leader of British opinion toward the subject of deformational geology from which the infant science had to recover before progress could be made. The early maps were essentially mineralogical and lithological. The order of superposition and the consequent sequence of age was regarded as settled by Werner in Germany and not requiring investigation in America. The early examples of structure were sections drawn with exaggerated vertical scales and those of Maclure do not show detail.

Recognition of Appalachian Structures.

Following the founding of the Journal in 1818 there is observable a growth in the quality and detail of geological mapping. Dr. Aiken, professor of natural philosophy and chemistry in Mt. St. Mary’s College, published in the Journal in 1834 (26, 219) a vertical section extending between Baltimore and Wheeling, a distance of nearly 250 miles, on a scale of about 7 miles per inch. The succession of rocks is carefully shown and the direction of dip, but no attempt is made to show the underground relations, the stratigraphic sequence, and the folded structures which are so clear in that Appalachian section. The text also shows that the author had not recognized the folded structure. Furthermore, where the folds cease at the Alleghany mountain front, the flat strata are shown as resting unconformably on the folded rocks to the east.

R. C. Taylor, geologist, civil and mining engineer, was from 1830 to 1835 the leading student of Pennsylvanian geology as shown by the publication in 1835 of four papers aggregating over 80 pages in the Transactions of the Geological Society of Pennsylvania. His work is noticeable for accuracy in detail and no doubt was influential in setting a high standard for the state geological survey which immediately followed.

H. D. and W. B. Rogers have been given credit in this country, and in Europe also, as being the leading expounders of Appalachian structure. Merrill speaks of H. D. Rogers as unquestionably the leading structural geologist of his time.[^[85]] To the writer, this attributed position appears to be due to his opportunities rather than to scientific acumen. The magnificent but readily decipherable folded structure of Pennsylvania, the relationships of coal and iron to this structure, the considerable sums of money appropriated, and the work of a corps of able assistants were factors which made it comparatively easy to reach important results. In ability to weigh facts and interpret them Edward Hitchcock showed much more insight than H. D. Rogers, while in the philosophic and comprehensive aspects of the subject J. D. Dana far outranks him.

H. D. Rogers in his first report on the geological survey of New Jersey, 1836, recognizes that the Cambro-Silurian limestones (lower Secondary limestones) were deposited as nearly horizontal beds and the ridges of pre-Cambrian gneiss (Primary) had been pushed up as anticlinal axes (p. 128). He also clearly recognized the distinction between slaty cleavage and true dip as shown in the Ordovician slates (p. 97). Between 1836 and 1840 he had learned a great deal on the nature of folds as is shown in his Pennsylvania report for 1839 and the structure sections in his New Jersey report for 1840.

R. C. Taylor, who had now become president of the board of directors of the Dauphin and Susquehanna Coal Company, published in the Journal in 1841 (41, 80) an important paper entitled “Notice of a Model of the Western portion of the Schuylkill or Southern Coal Field of Pennsylvania, in illustration of an Address to the Association of American Geologists, on the most appropriate modes for representing Geological Phenomena.” In this paper he calls attention to the value of modeling as a means of showing true relations in three dimensions. He condemns the custom prevalent among geologists of showing structure sections with an exaggerated vertical scale with its resultant topographic and structural distortions. Taylor was widely acquainted with the structure of Pennsylvania, Maryland, and Virginia.

Nature of Forces Producing Folding.

In 1825 Dr. J. H. Steele sent to Professor Silliman two detailed drawings and description of an overturned fold at Saratoga Lake, New York. As to the significance of this feature Steele makes the following statement (9, 3, 1825):

“It is impossible to examine this locality without being strongly impressed with the belief that the position which the strata here assume could not have been effected in any other way than by a power operating from beneath upwards and at the same time possessing a progressive force; something analogous to what takes place in the breaking up of the ice of large rivers. The continued swelling of the stream first overcomes the resistance of its frozen surface and having elevated it to a certain extent, it is forced into a vertical position, or thrown over upon the unbroken stratum behind, by the progressive power of the current.”

So far as the present writer is aware this is the first recognition in geological literature of the evidence of a horizontally compressive and overturning force as a cause of folding.

To E. Hitchcock belongs the credit of being the first to describe overturning and inversion of strata on a large scale, but without clearly recognizing it as such. In western Massachusetts metamorphism is extreme in the lower Paleozoic rocks in the vicinity of the overthrust mass of Archean granite-gneiss which constitutes the Hoosic range. The Paleozoic rocks of the valley to the west are overturned and appear to dip beneath the older rocks. Farther west the metamorphism fades out and the series assumes a normal position. Such an inverted relation, up to that time unknown, is described in 1833 as follows by Hitchcock in his Geology of Massachusetts (pp. 297, 298):

“But a singular anomaly in the superposition of the series of rocks above described, presents a great difficulty in this case. The strata of these rocks almost uniformly dip to the east: that is, the newer rocks seem to crop out beneath the older ones; so that the saccharine limestone, associated with gneiss in the eastern part of the range, seems to occupy the uppermost place in the series. Now as superposition is of more value in determining the relative ages of rocks than their mineral characters, must we not conclude that the rocks, as we go westerly from Hoosac mountain, do in fact belong to older groups? The petrifactions which some of them contain, and their decidedly fragmentary character, will not allow such a supposition to be indulged for a moment. It is impossible for a geologist to mistake the evidence, which he sees at almost every step, that he is passing from older to newer formations, just as soon as he begins to cross the valley of Berkshire towards the west. We are driven then to the alternative of supposing, either that there must be a deception in the apparent outcrop of the newer rocks from beneath the older, or that the whole series of strata has been actually thrown over, so as to bring the newest rocks at the bottom. The latter supposition is so improbable that I cannot at present admit it.”

Hitchcock tried to reconcile the evidence by a series of unconformities and inclined deposition, but finds the solution unsatisfactory.

In this same year, 1833, Elie de Beaumont, a distinguished French geologist, published his theory of the origin of mountains. He advanced the idea that since the globe was cooling it was condensing, and the crust, already cool, must suffer compression in adjusting itself to the shrinking molten interior. He concluded from the evidence shown in Europe that the collapse of the crust occurred violently and rapidly at widely spaced intervals of time. This hypothesis introduced the idea of mountain folding by horizontal compressive forces. The theoretical paper of de Beaumont, together with further observations by Hitchcock and others, led the latter in 1841 to a final belief in the inversion of strata on a large scale by horizontal compression. His conclusions are expressed in an important paper published in the Journal (41, 268, 1841) and given on April 8, 1841, as the First Anniversary Presidential Address before the Association of American Geologists. This comprehensive summary of American geology occupies 43 pages. Three pages are given to the inverted structure of the Appalachians from which the following paragraphs may be quoted:

“We have all read of the enormous dislocations and inversions of the strata of the Alps; and similar phenomena are said to exist in the Andes. Will it be believed, that we have an example in the United States on a still more magnificent scale than any yet described?...

Let us suppose the strata between Hudson and Connecticut rivers, while yet in the plastic state, (and the supposition may be extended to any other section across this belt of country from Canada to Alabama,) and while only slightly elevated, were acted upon by a force at the two rivers, exerted in opposite directions. If powerful enough, it might cause them to fold up into several ridges; and if more powerful along the western than the eastern side, they might fall over so as to take an inverted dip, without producing any remarkable dislocations, while subsequent denudation would give to the surface its present outline....

Fourthly, we should readily admit that such a plication and inversion of the strata might take place on a small scale. If for instance, we were to press against the extremities of a series of plastic layers two feet long, they could easily be made to assume the position into which the rocks under consideration are thrown. Why then should we not be equally ready to admit that this might as easily be done, over a breadth of fifty miles, and a length of twelve hundred, provided we can find in nature, forces sufficiently powerful? Finally, such forces do exist in nature, and have often been in operation.”

The advanced nature of these conceptions may be appreciated by contrasting them with those put forth by H. D. and W. B. Rogers on April 29, 1842, before the third annual meeting of the same body (43, 177, 1842) and repeated by them before the British Association at Manchester two months later. In their own words, the Rogers brothers from their studies on the folds shown in Pennsylvania and Virginia, conceived mountain folds in general to be produced by much elastic vapor escaping through many parallel fissures formed in succession, producing violent propulsive wave oscillations on the surface of the fluid earth beneath a thin crust. Thus actual billows are assumed to have rolled along through the crust. They did not think tangential pressure alone could produce folds. Such pressures were regarded as secondary, produced by the propagation of the waves and the only expression of tangential forces which they admitted was to fix the folds and hold them in position after the violent oscillation had subsided (44, 360, 1843). The leading British geologists De la Beche and Sedgwick criticized adversely this remarkable theory, stating that they could see no such analogy in mountain folds to violent earthquake waves and that in their opinion the slow application of tangential force was sufficient to account for the phenomena (44, 362–365, 1843).

H. D. Rogers in the prosecution of the geological survey of Pennsylvania displayed notable organizing ability and persistence in accomplishment, even to advancing personally considerable sums of money, trusting to the state legislature to later reimburse him. Finally, after many delays by the state, the publication was placed directly in his charge and he produced in 1858 a magnificent quarto work of over 1,600 pages, handsomely illustrated, and accompanied by an atlas. It is excellent from the descriptive standpoint, standing in the first class. Measured as a contribution to the theory of dynamical geology, the explanatory portions were, however, thirty years behind the times. The same hypotheses are put forth in 1858 as in 1842. There is no acceptance of the views of Lyell concerning the uniformitarian principles expounded by this British leader in 1830, or of the nature of orogenic forces as published by Elie de Beaumont in 1833. Rogers rejects the view that cleavage is due to compression and suggests “that both cleavage and foliation are due to the parallel transmission of planes or waves of heat, awakening the molecular forces, and determining their direction.”[^[86]] Thus a mere maze of words takes the place of inductive demonstrations already published.

In following the play of these opposing currents of geologic thought we reach now the point where a period of brilliant progress in the knowledge of mountains and of continental structures begins in the work of J. D. Dana. In 1842 Dana returned from the Wilkes Exploring Expedition and the following year began the publication of the series of papers which for the next half century marked him as the leader in geologic theory in America. His work is of course to be judged against the background of his times. His papers mark distinct advances in many lines and are characterized throughout by breadth of conception and especially by clear and logical thinking. His work was published very largely in the Journal, of which after a few years he became chief editor. His first contribution on the subject of mountain structures, entitled “Geological results of the earth’s contraction in consequence of cooling,” was published in 1847 (3, 176). The evidence of horizontal pressure was first perceived in France as shown by the features of the Alps. Elie de Beaumont connected it, by means of the theory of a cooling and contracting globe, with the other large fact of the increase of temperature with descent in the crust. Dana credits the Rogers brothers with first making known the folded structures of the Appalachians, but objects to their interpretation of origin. He showed by means of diagrams that the folds are to be explained by lateral pressure, the direction of overturning indicating the direction from which the driving force proceeded.

The Rogers brothers and especially James Hall, in working out the Appalachian stratigraphy, had noted that the formations, although accumulating to a maximum thickness of between 30,000 and 40,000 feet, showed evidences that the successive formations were deposited in shallow water. It suggested to them that the weight of the accumulating sediments was the cause of subsidence, each foot of sediment causing a foot of down sinking. This idea has continued to run through various text books in geology for half a century, yet Dana early saw the fallacy and in 1863 in the first edition of his Manual of Geology (p. 717) states “whether this is an actual cause or not in geological dynamics is questionable.” In 1866 in an important article on “Observations on the origins of some of the earth’s features,” Dana deals more fully and finally with this subject (42, 205, 252, 1866). He shows that such an effect of accumulating sediment postulates a delicate balance, a very thin crust and no resistance below. If such a weakness were granted it would be impossible for the earth to hold up mountains. Furthermore such subsidence was not regular during its progress and finally in the long course of geologic time gave place to a reverse movement of elevation.

Hall had pointed out the fact that the sediments were thickest on the east in the region of mountain folding and thinned out to a fraction of this thickness in the broad Mississippi basin. Hall argued that the mere subsidence of the trough would produce the observed folding and that the folding was unrelated to mountain making or crustal shortening. In supposed proof he cited the fact that the Catskills consist of unfolded rock, are higher than the folded region to the south, and nearly as high as the highest metamorphic mountains to the east.[^[87]] Hall and all his contemporaries were handicapped in their geological theories by a complete inappreciation of the importance of subaërial denudation. For subscribing to these errors of their time even the ablest men should not be held responsible. Hall was the most forcible personality in geology in his generation. His contributions to paleontology were superb. His perception of the relation existing between troughs of thick sediments and folded structures was a contribution of the first importance; yet in the structural field his argument as to the production of the Appalachian folds by mere subsidence during deposition indicates a remarkable inability to apply the logical consequences of his hypothesis to the nature of the folds as already made known by the Rogers. Dana pointed out in reply to Hall that the folding did not correspond to the requirements of Hall’s hypothesis, especially as the folding took place not during, but after the close of the vast Paleozoic deposition. Dana states in conclusion on Hall’s hypothesis (42, 209, 1866) that “It is a theory of the origin of mountains with the origin of mountains left out.”

The Theory of Geosynclines and Geanticlines.

The fact that systems of folded strata lie along axes of especially thick sediments and that this implied subsidence during deposition was Hall’s contribution to geologic theory, but curiously enough he failed, as shown, to connect it with the subsequent nature of mountain folding. He did not see why such troughs should be weak to resist horizontal compression. The clear recognition of this relationship was the contribution of Le Conte, who in a paper on “A theory of the formation of the great features of the earth’s surface” (4, 345, 460, 1872), reached the conclusion that “mountain chains are formed by the mashing together and the up-swelling of sea bottoms where immense thicknesses of sediment have accumulated.”

As to the cause why mashing should take place along troughs of thick sediments Le Conte adopts the hypothesis of aqueo-igneous fusion proposed independently long before by Babbage and Herschel and elaborated into a theory of igneous rocks by Hunt. Under this view, as the older sediments became deeply buried, the heat of the earth’s interior ascended into them, and since they included the water of sedimentation a softening and metamorphism resulted. Dana had shown, however, six years previously (42, 252, 1866), as the following quotation will indicate, that metamorphism of sediments required more than deep burial and that no such weakening as was postulated by Herschel had occurred:

“The correctness of Herschel’s principle cannot be doubted. But the question of its actual agency in ordinary metamorphism must be decided by an appeal to facts; and on this point I would here present a few facts for consideration.

The numbers and boldness of the flexures in the rocks of most metamorphic regions have always seemed to me to bear against the view that the heat causing the change had ascended by the very quiet method recognized in this theory....

But there are other facts indicating a limited sufficiency to this means of metamorphism. These are afforded by the great faults and sections of strata open to examination. In the Appalachian region, both of Virginia and Pennsylvania, faults occur, as described by the Professors Rogers, and by Mr. J. P. Lesley, which afford us important data for conclusions. Mr. Lesley, an excellent geologist and geological observer, who has explored personally the regions referred to, states that at the great fault of Juniata and Blair Cos., Pennsylvania, the rocks of the Trenton period are brought up to a level with those of the Chemung, making a dislocation of at least 16,000, and probably of 20,000, feet. And yet the Trenton limestone and Hudson River shales are not metamorphic. Some local cases of alteration occur there, including patches of roofing slate; but the greater part of the shales are no harder than the ordinary shales of the Pennsylvania Coal formation.

At a depth of 16,000 feet the temperature of the earth’s crust, allowing an increase of 1° F. for 60 feet of descent, would be about 330° F.; or with 1° F. for 50 feet, about 380° F.—either of which temperatures is far above the boiling point of water; and with the thinner crust of Paleozoic time the temperature at this depth should have been still higher. But, notwithstanding this heat, and also the compression from so great an overlying mass, the limestones and shales are not crystalline. The change of parts of the shale to roofing slate is no evidence in favor of the efficiency of the alleged cause; for such a cause should act uniformly over great areas.”

The next contribution to the theory of orogeny was a series of papers published in 1873 by Dana, entitled “On some results of the earth’s contraction from cooling, including a discussion on the origin of mountains and the nature of the earth’s interior.”[^[88]] This contribution, viewed as a whole, ranks among the first half dozen papers on the science of mountains. The following quoted paragraphs give a view of the scope of this article:

“Kinds and Structure of Mountains.”

“While mountains and mountain chains all over the world, and low lands, also, have undergone uplifts, in the course of their long history, that are not explained on the idea that all mountain elevating is simply what may come from plication or crushing, the component parts of mountain chains, or those simple mountains or mountain ranges that are the product of one process of making—may have received, at the time of their original making, no elevation beyond that resulting from plication.

This leads us to a grand distinction in orography, hitherto neglected, which is fundamental and of the highest interest in dynamical geology; a distinction between—

1. A simple or individual mountain mass or range, which is the result of one process of making, like an individual in any process of evolution, and which may be distinguished as a monogenetic range, being one in genesis; and

2. A composite or polygenetic range or chain, made up of two or more monogenetic ranges combined.

The Appalachian chain—the mountain region along the Atlantic border of North America—is a polygenetic chain; it consists, like the Rocky and other mountain chains, of several monogenetic ranges, the more important of which are: 1. The Highland range (including the Blue Ridge or parts of it, and the Adirondacks also, if these belong to the same process of making) pre-Silurian in formation; 2. The Green Mountain range, in western New England and eastern New York, completed essentially after the Lower Silurian era or during its closing period; 3. The Alleghany range, extending from southern New York southwestward to Alabama, and completed immediately after the Carboniferous age.

The making of the Alleghany range was carried forward at first through a long-continued subsidence—a geosynclinal (not a true synclinal, since the rocks of the bending crust may have had in them many true or simple synclinals as well as anticlinals), and a consequent accumulation of sediments, which occupied the whole of Paleozoic time; and it was completed, finally, in great breakings, faultings and foldings or plications of the strata, along with other results of disturbance.

These examples exhibit the characteristics of a large class of mountain masses or ranges. A geosynclinal accompanied by sedimentary depositions, and ending in a catastrophe of plications and solidification, are the essential steps, while metamorphism and igneous ejections are incidental results. The process is one that produces final stability in the mass and its annexation generally to the more stable part of the continent, though not stable against future oscillations of level of wider range, nor against denudation.

It is apparent that in such a process of formation elevation by direct uplift of the underlying crust has no necessary place. The attending plications may make elevations on a vast scale and so also may the shoves upward along the lines of fracture, and crushing may sometimes add to the effect; but elevation from an upward movement of the downward bent crust is only an incidental concomitant, if it occur at all.

We perceive thus where the truth lies in Professor Le Conte’s important principle. It should have in view alone monogenetic mountains and these only at the time of their making. It will then read, plication and shovings along fractures being made more prominent than crushing:

Plication, shoving along fractures and crushing are the true sources of the elevation that takes place during the making of geosynclinal monogenetic mountains.

And the statement of Professor Hall may be made right if we recognize the same distinction, and, also, reverse the order and causal relation of the two events, accumulation and subsidence; and so make it read:

Regions of monogenetic mountains were, previous, and preparatory, to the making of the mountains, areas each of a slowly progressing geosynclinal, and, consequently, of thick accumulations of sediments.

The prominence and importance in orography of the mountain individualities described above as originating through a geosynclinal make it desirable that they should have a distinctive name; and I therefore propose to call a mountain range of this kind a synclinorium, from synclinal and the Greek ὄρος, mountain.

This brings us to another important distinction in orographic geology—that of a second kind of monogenetic mountain. The synclinoria were made through a progressing geosynclinal. Those of the second kind, here referred to, were produced by a progressing geanticlinal. They are simply the upward bendings in the oscillations of the earth’s crust—the geanticlinal waves, and hardly require a special name. Yet, if one is desired, the term anticlinorium, the correlate of synclinorium, would be appropriate. Many of them have disappeared in the course of the oscillations; and yet, some may have been for a time—perhaps millions of years—respectable mountains.

The geosynclinal ranges or synclinoria have experienced in almost all cases, since their completion, true elevation through great geanticlinal movements, but movements that embraced a wider range of crust than that concerned in the preceding geosynclinal movements, indeed a range of crust that comes strictly under the designation of a polygenetic mass.”

“The Condition of the Earth’s Interior.”

“The condition of the earth’s interior is not among the geological results of contraction from cooling. But these results offer an argument of great weight respecting the earth’s interior condition, and make it desirable that the subject should be discussed in this connection. Moreover, the facts throw additional light on the preceding topic—the origin of mountains.

It seems now to be demonstrated by astronomical and physical arguments—arguments that are independent, it should be noted, of direct geological observation—that the interior of our globe is essentially solid. But the great oscillations of the earth’s surface, which have seemed to demand for explanation a liquid interior, still remain facts, and present apparently a greater difficulty than ever to the geologist. Professor Le Conte’s views, in volume iv, were offered by him as a method of meeting this difficulty; yet, as he admits in his concluding remarks, the oscillations over the interior of a continent, and the fact of the greater movements on the borders of the larger ocean, were left by him unexplained. Yet these oscillations are not more real than the changes of level or greater oscillations which occurred along the sea border, where mountains were the final result; and this being a demonstrated truth, no less than the general solidity of the earth’s interior, the question comes up, how are the two truths compatible?

The geological argument on the subject (the only one within our present purpose) has often been presented. But it derives new force and gives clearer revelations when the facts are viewed in the light of the principles that have been explained in the preceding part of this memoir.

The Appalachian subsidence in the Alleghany region of 35,000 to 40,000 feet, going on through all the Paleozoic era, was due, as has been shown, to an actual sinking of the earth’s crust through lateral pressure, and not to local contraction in the strata themselves or the terranes underneath. But such a subsidence is not possible, unless seven miles—that is, seven miles in maximum depth and over a hundred in total breadth—unless seven miles of something were removed, in its progress, from the region beneath.

If the matter beneath was not aërial, then liquid or viscous rock was pushed aside. This being a fact, it would follow that there existed, underneath a crust of unascertained thickness, a sea or lake of mobile (viscous or plastic) rock, as large as the sinking region; and also that this great viscous sea continued in existence through the whole period of subsidence, or, in the case of the Alleghany region, through all Paleozoic time—an era estimated on a previous page to cover at least thirty-five millions of years, if time since the Silurian age began embraced fifty millions of years.

The facts thus sustain the statement that lateral pressure produced not only the subsidence of the Appalachian region through the Paleozoic, but also, cotemporaneously, and as its essential prerequisite, the rising of a sea-border elevation, or geanticlinal, parallel with it; and that both movements demanded the existence beneath of a great sea of mobile rock.”

The recognition of regional warping as a major factor in the larger structure of mountain systems, and the expression of that factor in the terms geosyncline and geanticline forms a notable advance in geologic thought. Subsequent folding on a regional scale results in the development of synclinoria and anticlinoria. Van Hise has given these latter terms wide currency, but apparently inadvertently has used synclinorium in a different sense than that in which Dana defined it. Dana gave the word to a mountain range made by the mashing and uplift of a geosyncline, Van Hise defines it as a downfold of a large order of magnitude, embracing anticlines and synclines within it; anticlinorium he uses for a corresponding up fold.[^[89]] Rice has called attention to this change of definition,[^[90]] but Van Hise’s usage is likely to prevail, since they are needed terms for the larger mountain structure and do not require a determination of the previous limits of upwarp and downwarp,—of original denudation and deposition. Furthermore, a geosyncline in mountain folding may have one side uplifted, the other side depressed and there are reasons for regarding the folds of Pennsylvania, Dana’s type synclinorium, as representing but the western and downfolded side of the Paleozoic geosyncline. Under that view the folded Appalachians of Pennsylvania constitute a synclinorium in both the sense of Dana and Van Hise.

The Ultimate Cause of Crustal Compression.

The next important advance in the theory of mountains was made by C. E. Dutton who in 1874 published in the Journal (8, 113–123) an article entitled “A criticism upon the contractional hypothesis.” Dutton gives reasons for holding that the amount of folding and shortening exhibited in mountain ranges, especially those of Tertiary date, is very much greater in magnitude and is different in nature and distribution from that which would be given by the surficial cooling of the globe. The following quotations cover the principal points in the argument:

“The argument for the contractional hypothesis presupposes that the earth-mass may be considered as consisting of two portions, a cooled exterior of undetermined (though probably comparatively small) depth, inclosing a hot nucleus.... The secular loss of heat, it is assumed, would be greater from the hot nucleus than from the exterior, and the greater consequent contraction of the nucleus would therefore gradually withdraw the support of the exterior, which would collapse. The resulting strains upon the exterior would be mainly tangential. Owing to considerable inequalities in the ability of different portions to resist the strains thus developed, the yielding would take place at the lines, or regions of least resistance, and the effects of the yielding would be manifested chiefly, or wholly, at those places, in the form of mountain chains, or belts of table lands, and in the disturbances of stratification. The primary division of the surface into areas of land and water are attributed to the assumed smaller conductivity of materials underlying the land, which have been left behind in the general convergence of the surface toward the center. Regarding these as the main and underlying premises of the contractional argument, it is considered unnecessary to state the various subsidiary propositions which have been advanced to explain the determination of this action to particular phenomena, since the main proposition upon which they are based is considered untenable.

There can be no reasonable doubt that the earth-mass consists of a cooled exterior inclosing a hot nucleus, and a necessary corollary to this must be secular cooling, probably accompanied by contraction of the cooling portions. But when we apply the known laws of thermal physics to ascertain the rate of this cooling, and its distribution through the mass, the objectionable character of the contractional hypothesis becomes obvious.

That Fourier’s theorem, under the general conditions given, expresses the normal law of cooling, is admitted by all mathematicians who have examined it. The only ground of controversy must be upon the values to be assigned to the constants. But there seem to be no values consistent with probability which can be of help to the contractional hypothesis. The application of the theorem shows that below 200 or 300 miles the cooling has, up to the present time, been extremely little.... At present, however, the unavoidable deduction from this theorem is that the greatest possible contraction due to secular cooling is insufficient in amount to account for the phenomena attributed to it by the contractional hypothesis.

The determination of plications to particular localities presents difficulties in the way of the contractional hypothesis which have been underrated. It has been assumed that if a contraction of the interior were to occur, the yielding of the outer crust would take place at localities of least resistance. But this could be true only on the assumption that the crust could have a horizontal movement in which the nucleus does not necessarily share. A vertical section through the Appalachian region and westward to the 100th meridian shows a surface highly disturbed for about two hundred and fifty miles, and comparatively undisturbed for more than a thousand. No one would seriously argue that the contraction of the nucleus had been confined to portions underlying the disturbed regions: yet if the contraction was general, there must have been a large amount of slip of some portion of the undisturbed segment over the nucleus. Such a proposition would be very difficult to defend, even if the premises were granted. It seems as if the friction and adhesion of the crust upon the nucleus had been overlooked. Nor could this be small, even though the crust rested upon liquid lava. The attempts which some eminent geologists have recently made to explain surface corrugation by this method clearly show a neglect on their part to analyze carefully the system of forces which a contraction of the nucleus would generate in the crust. Their discussions have been argumentative and not analytical. The latter method of examination would have shown them certain difficulties irreconcilable with their knowledge of facts. Adopting the argumentative mode, and in conformity with their view regarding the exterior as a shell of insufficient coherence to sustain itself when its support is sensibly diminished, the tendency of corrugation to occur mainly along certain belts, with series of parallel folds, is not explained by assuming that these localities are regions of weakness. For a shrinkage of the nucleus would throw each elementary portion of the crust into a state of strain by the action of forces in all directions within its own tangent plane. A relief by a horizontal yielding in one direction would by no means be a general relief.”

Dutton’s criticisms robbed the current hypothesis of mountain-making of its conventional basis without providing a new foundation. It was a quarter of a century in advance of its time, has been seldom cited, and seems to have had but little direct influence in shaping subsequent thought. It, however, gave direction to Dutton’s views, and his later papers were far-reaching in their influence.

If contraction from external cooling is not the cause of the compressive forces it is necessary to seek another cause. Two years later, in 1876, Dutton attempted to provide an answer to this open question.[^[91]] A review of this paper, evidently by J. D. Dana, is given in the Journal. The following explanations of Dutton’s theory and of Dana’s comments upon it are contained in a few paragraphs from this review (12, 142, 1876).

“Captain Dutton presents in this paper the views brought out in his article in volume viii of this Journal, with fuller illustrations, and adds explanations of his theory of the origin of mountains. The discussion should be read by all desiring to reach right conclusions, it presenting many arguments from physical considerations against the contraction-theory, or that of the uplifting and folding of strata through lateral pressure. There is much to be learned before any theory of mountain-making shall have a sufficient foundation in observed facts to demand full confidence, and Captain Dutton merits the thanks of geologists for the aid he has given them toward reaching right conclusions. His discussions are not free from misunderstandings of geological facts, and if they fail to be finally received it will be for this reason.

We here give in a brief form, and nearly in his own words, the principal points in his theory of mountain-making as explained in the later part of his memoir.

Accepting the proposition that there is a plastic condition of rock beneath the earth’s crust and that metamorphism is a ‘hydrothermal process,’ and believing that ‘the penetration of water to profound depths [in the earth’s crust] is a well sustained theory,’ he says that great pressure and a temperature approaching redness are essential conditions of metamorphism.... ‘The heaviest portion would sink into the lighter colloid mass underneath, protruding it laterally beneath the lighter portions where, by its lighter density, it tends to accumulate.’ He adds: ‘The resulting movements would be determined, first, by the amount of difference in the densities of the upper and lower masses, and, second, by inequalities in the thickness of the strata: the forces now become adequate to the building of mountains and the plication of strata, and their modes of operation agree with the classes of facts already set forth as the concomitants of those features.’

The views are next applied to a system of plications. ‘It has been indicated that plications occur where strata have rapidly accumulated in great volume and in elongated narrow belts; that the axes of plications are parallel to the axes of maximum deposit; and that the movements immediately followed the deposition’—the case of the Appalachians being an example in which the accumulations averaged 40,000 feet. He observes: ‘Wherever the load of sediments becomes heaviest, there they sink deepest, protruding the colloid magma beneath them to the adjoining areas, which are less heavily weighted, forming at once both synclinals and anticlinals.’

With regard to this new theory, we might reasonably question the existence of the colloid magma—a condition fundamental to the theory—and his evidence that water penetrates to profound depths in the earth’s crust sufficient to make hydrous rocks. We might ask for evidence that the rocks beneath the Cretaceous and Tertiary, and other underlying strata of the Uintahs, were in such a colloid state, and this so near the surface, that the ‘beds subsided by their gross weight as rapidly as they grew.’

Again, he says that the movements of mountain-making ‘immediately followed the deposition.’ ‘Immediately’ sounds quick to one who appreciates the slowness of geological changes. The Carboniferous age was very long; and somewhere in that part of geological time, either before the age had fully ended, or some time after its close, the epoch of catastrophe began.”

We see foreshadowed in this paper the theory of isostasy, or condition of vertical equilibrium in the crust which Dutton published in 1889. This theory has borne remarkable fruit, but Dutton attempted to link to it the horizontally compressive forces which have produced folding and overthrusting. Willis in 1907[^[92]] and Hayford in 1911, overlooking Dana’s objections, have attempted to make a lateral isostatic undertow the cause of all horizontal movements in the crust, adopting the mechanism of Dutton. The present writer, although accepting the principle of isostasy as an explanation of broad vertical movements, has published papers which go to show the inadequacy of this hypothesis of lateral pressure; inadequate in time relation, in amount, and in expression.[^[93]]

In 1903 it was determined by several physicists that the materials of the earth’s crust were radioactive and must generate throughout geologic time a quantity of heat which perhaps equalled that lost by radiation into space. By 1907 this had become demonstrated. The remarkable conclusion had been reached that the earth, although losing heat, is not a cooling globe. Dutton’s contentions against mountain growth through external cooling and contraction were thus unexpectedly, through a wholly new branch of knowledge, demonstrated to be true.

Nevertheless, all students of orogeny are agreed that profound compressive forces have been the chief agents in developing mountain structures. Chamberlin was the first to arrive at the idea that the shrinkage may originate in the deeper portions of the earth under the urgency of the enormous pressures, apparently by giving rise to slow recombinations of matter into denser forms.[^[94]]

The New Era in the Interpretation of Mountain Structures.

In the meantime, between 1874 and 1904, another advance in the knowledge of mountain structures was taking place in Europe. Suess studied the distribution of mountain arcs over the earth and dwelt upon the prevalence of overthrust structures; the backland being thrust toward and over the foreland, the rise of the mountain arc or geanticline depressing the foredeep or geosyncline. Bertrand and Lugeon from 1884 to 1900 were reinterpreting the Alpine structures on this basis. They showed that the whole mountain system had been overturned and overthrust from the south to an almost incredible degree. Enormous denudation had later dissevered the northern outlying portions and given rise to “mountains without roots,”—isolated outliers, consisting of overturned masses of strata which had accumulated as sediments far to the southward in another portion of the ancient geosyncline.

On a smaller scale similar phenomena are exhibited in the Appalachians. Willis showed that the deep subsidence of the center of the geosyncline gave an initial dip which determined the position of yielding under compression. Laboratory experiments brought out the weakness of the stratigraphic structure to resist horizontal compression. The nature of the stratigraphic series was shown to determine whether the yielding would be by mashing, competent folding, or breakage and overthrust. The problem of mountain structures was thus brought into the realm of mechanics. These results were published in three sources in 1893,—the Transactions of the American Institute of Mining Engineers, the thirteenth annual report of the United States Geological Survey, and the Journal (46, 257, 1893).

Finally should be noted the contributions of the Lake Superior school of geology, in which the work of Van Hise stands preeminent. Under the economic stimulus given by the discovery and development of enormously rich bodies of iron ore, hidden under Pleistocene drift and involved in the complex structures of vanished mountain systems of ancient date, structural geology and metamorphism have become exact sciences to be drawn upon in the search for mineral wealth and yielding also rich returns in a fuller knowledge of early periods of earth history.

Crust Movements as Revealed by Physiography.

During the last quarter of the nineteenth century another division of geology, dominantly American, was taking form and growth,—the science of land forms,—physiography. The history of that development is treated by Gregory in the preceding chapter but some of its bearings upon theory, in so far as they affect the subject of mountain origin, are necessarily given here.

Powell, Dutton, and Gilbert in their explorations of the West saw the stupendous work of denudation which had been carried to completion again and again during the progress of geologic time. The mountain relief consequently may be much younger than the folding of the rocks, and may be largely or even wholly due to recurrent plateau movement, a doctrine to which Dana had previously arrived. But the introduction of the idea of the peneplain opened up a new field for exploration in the nature and date of crust movements. Davis by this means began to study the later chapters of Appalachian history, the most important early paper being published in 1891.[^[95]] Since then Davis, Willis, and many others have found that, girdling the world, a large part of the mountainous relief is due to vertical elevatory forces acting over regions of previous folding and overthrust. In addition, great plateau areas of unfolded rocks have been bodily lifted one to two miles, or more, above their earlier levels. They may be broad geanticlinal arches or bounded by the walls of profound fractures.

The linear mountain systems made from deep troughs of sediments have come then to be recognized as but one of several classes of mountains. This class, from its clear development in the Appalachians, and the fact that many of the laws of mountain structure pertaining to it were first worked out there, has been called by Powell the Appalachian type (12, 414, 1876). A classification of mountain systems was proposed by him in which mountains are classified into two major divisions, those composed of sedimentary strata altered or unaltered, and those composed in whole or in part of extravasated material. The first class he subdivides into six sub-classes of which the folded Appalachians illustrate one. It appears to the writer that Powell’s classification gives disproportionate importance to certain types which he described; but nevertheless, the fact that such a classification was made, indicates the growth of a more comprehensive knowledge of mountains,—their origin, structure, and history.

Relations of Crust Movements to Density and Equilibrium.

A recent important development in the fields of geophysics and major crust movements consists in the incorporation into geology of the doctrine of isostasy. The evidence was developed in the middle of the nineteenth century by the geodetic survey of India which indicated that the Himalayas did not exert the gravitative influence that their volume called for. It was clear that the crust beneath that mountain system was less dense than beneath the plains of India and still less dense than the crust beneath the Indian Ocean. This relation between density and elevation indicated some approach to flotational equilibrium in the crust, comparable in its nature though not in delicacy of adjustment to the elevation of the surface of an iceberg above the ocean level owing to its depth and its density, less than that of the surrounding medium. This important geological conception was kept within the confines of astronomy and geodesy, however, until Dutton in 1876, but especially in 1889, brought it into the geologic field. A test of isostasy was made for the United States by Putnam and Gilbert in 1895 and much more elaborate investigations have since been made by Hayford and Bowie. These investigations demonstrate the importance and reality of broad warping forces acting vertically and related to the regional variations of density in the crust.

There are consequently two major and unrelated classes of forces involved in the making of mountain structures,—the irresistible horizontal compressive forces, arising apparently from condensation deep within the earth, and vertical forces originating in the outer envelopes and tending toward a hydrostatic equilibrium. In this latter field of investigation, America, since the initial paper by Dutton, has taken the lead.

Conclusion on Contributions of America to Theories of Orogeny.

The sciences arose in Europe, but those which treated of the earth were still in their infancy when transplanted to America. The first comprehensive ideas on the nature of mountain structures arose in Great Britain and France. These ideas served as a guide and stimulus to observation in the recognition of deformations in the strata of the Appalachian system. Since 1840, however, America has ceased to be a pupil in this field of research but has joined as an equal with the two older countries. New ideas have been contributed, new and striking illustrations cited, first by the scientists of one nation, next by those of another. The composite mass of knowledge has grown as a common possession. Nevertheless, a review of the progress since 1840 as measured by the contribution of new ideas shows on the whole America at least equal to its intellectual rivals, and at certain times actually the leader. This is true of the science of geology as a whole and also of the subdivision of orogeny.

Thus far no mention has been made of German geologists, with the exception of Suess, an Austrian. German geology is voluminous and the names of many well-known geologists could be cited. But this article has sought to trace the origin and growth of fundamental ideas. The Germans have been assiduous observers of detail; preeminent as systematizers and classifiers, seldom originators. Even petrology, which might be regarded as their especial field, was transplanted from Great Britain. In the science of mountains they have followed in their fundamental ideas especially the French.

Turning to the mediums of publication through which this progress of knowledge in earth structures has been recorded, the American Journal of Science stands foremost as the only continuous record for the whole century in American literature, fulfilling for this country what the Quarterly Journal of the Geological Society has done for Great Britain since 1845, and the Bulletin de la Société Géologique for France since 1830.

Notes.

[78]. H. D. Rogers, Geology of New Jersey, Final Report, p. 115, 1840.

[79]. H. D. Rogers, Geology of Pennsylvania, vol. 2, pt. II, pp. 761, 762, 1858.

[80]. Connecticut Academy of Arts and Sciences, 1810; quoted by G. P. Merrill in Contributions to the History of North American geology, Ann. Rpt. Smithsonian Institution for 1904, p. 216.

[81]. A Sketch of the geology, mineralogy, and scenery of the regions contiguous to the river Connecticut; with a geological map and drawings of organic remains; and occasional botanical notices, the Journal, 6, 1–86, 201–236, 1823; 7, 1–30, 1824.

[82]. Clarence King, U. S. Geol. Exploration of the Fortieth Parallel, vol. 1, pp. 16, 44–48, 1878.

[83]. Illustrations of the Huttonian Theory of the Earth, pp. 219–238, 1802.

[84]. Robert Jameson, Elements of Geognosy, pp. 55–57, 1808.

[85]. G. P. Merrill, Contributions to the History of American Geology. Report of the U. S. National Museum for 1904, p. 328.

[86]. H. D. Rogers, Geology of Pennsylvania, vol. 2, p. 916, 1858.

[87]. James Hall, Natural History of New York, Paleontology, vol. 3, pp. 51–73, 1859.

[88]. The Journal, 5, 423–443, 474, 475; 6, 6–14, 104–115, 161–172, 304, 381, 382, 1873.

[89]. C. R. Van Hise, Principles of North American Pre-Cambrian Geology, U. S. Geol. Surv., 16th Ann. Report, pt. I, pp. 607–612, 1896.

[90]. W. N. Rice, On the use of the words synclinorium and anticlinorium, Science, 23, 286, 287, 1906.

[91]. C. E. Dutton, Critical observations on theories of the earth’s physical evolution, The Penn Monthly, May and June, 1876.

[92]. B. Willis, Research in China, vol. 2, 1907.

[93]. Joseph Barrell, Science, 39, 259, 260, 1909; Jour. Geol., 22, 672–683, 1914.

[94]. T. C. Chamberlin, Geology, vol. 1, pp. 541, 542, 1904.

[95]. W. M. Davis, The geological dates of origin of certain topographic forms on the Atlantic slope of the United States, Geol. Soc. Am. Bull., 2, 541–542, 545–586, 1891.

V
A CENTURY OF GOVERNMENT GEOLOGICAL SURVEYS

By GEORGE OTIS SMITH

Director of the United States Geological Survey

Even a Federal Bureau must be considered a product of evolution: the past of the United States Geological Survey far antedates March 3, 1879. The scope of endeavor, the refinement of method, and especially the personnel of the newly created service of that day were largely inherited from pioneer organizations. Therefore a review of the country’s record of surveys under Government auspices becomes more than a grateful acknowledgment by the present generation of geologists of the credit due to those who blazed the way; it shows the sequence and progress in the contributions made by geologic science to industry.

The earlier stages in industrial evolution mentioned by Hess[^[96]]—exploitation, development, and maturity—determine a somewhat similar progressive development in geologic investigation, so that geographic exploration and geologic reconnaissance of the broadest type are the normal contribution of exact science whenever and wherever a nation is in the state of exploitation and initial development of its mineral and agricultural resources. The refinements of detailed surveys and quantitative examinations belong rather to the next stage of intensive utilization, or, indeed, they are the essentials preliminary to full use. Thus regrets that the results of present-day work were not available fifty years ago are largely vain: the fathers may not have been without the vision; they simply did the work as their day and generation needed it done.

Twenty years ago S. F. Emmons, in a presidential address before the Geological Society of Washington, divided the history of Governmental surveys in this country into two periods, separated in a general way by the Civil War. The first of these was the period of geographic exploration, the second that of geologic exploration. Mr. Emmons of course regarded this subdivision as not hard and fast, yet his dividing line seems logical, for not only did the military activities in the East necessarily suspend exploration in the West, but after the war national, political, and economic considerations led naturally to the demand for a more exact knowledge of the vast national domain in the West. Geography and geology are so closely related that Mr. Emmons’s distinction of the two periods is useful only with the limitations inferentially set by himself—namely, that while geologic investigation entered into most of the explorations of the earlier period, the geologist was regarded as only an accessory in these exploring expeditions; on the other hand, in the later surveys the topographic work was developed because it was essential to the geologic investigations.

The year 1818 was a notable one in American geology, first of all in the appearance of the American Journal of Science, itself so perfect a vehicle for geological thought that, as is so well stated by Dr. G. P. Merrill, “a perusal of the numbers from the date of issue down to the present time will alone afford a fair idea of the gradual progress of American geology.” The beginning of publications on New England geology appeared that year in Edward Hitchcock’s first paper on the Connecticut Valley (1, 105, 1818) and the Danas’ (S. L. and J. F.) detailed geologic and mineralogic description of Boston and vicinity; and the “Index” of Amos Eaton (noticed in this Journal, 1, 69) was the first of that long list of notable contributions to American stratigraphy that are to be credited to the New York geologists.

In the present discussion, too, the year 1918 can be regarded as in a way the centennial of Government geologic surveys, for it was in 1818 that Henry R. Schoolcraft began his trip to the Mississippi Valley—perhaps the first geologic reconnaissance into the West—and it was his work in the lead region which served to make him a member of the Cass expedition sent out by the Secretary of War in 1820 to examine the metallic wealth of the Lake Superior region. The earlier Government explorations of Lewis and Clark, in 1803–7, and of Pike, in 1805–7, were so exclusively geographic that geologic work under Federal auspices must be regarded as beginning with Schoolcraft and with Edwin James, the geologist of the expedition of Major Long in 1819–20 to the Rocky Mountains. Both these observers published reports that are valuable as contributions to the knowledge of littleknown regions.

Any description of geologic work under the Federal Government that included no reference to the State surveys would be inadequate, for in both date of execution and stage of development the work of the State geologists must be given precedence. In Merrill’s Contributions to the History of American Geology,[^[97]] whose modest title fails even to suggest that this work not only furnishes the most useful chronologic record of the progress of the science on the American continent but is in fact a very thesaurus of incidents touching the personal side of geology, the author by his division of his subject shows that four decades of the era of State surveys elapsed before the era of national surveys began.

Thus the geologic surveys of some of the Eastern States antedate by several decades any Federal organization of comparable geologic scope, and in investigations directed to local utilitarian problems these pioneer geologists working in the older settled States of the East were in fact already conducting work as detailed in type as much of that attempted by the Federal geologists of the later period. Even to-day it is true in a general way that the State geologist can and should attack many of his local problems with intensive methods and with detail of results that are neither practicable nor desirable for the larger interstate investigations or for examinations in newer territory. All this relation of State and Federal work must be looked upon as normal evolutionary development of geologic science in America.

One who reads the names of the Federal geologists of the early days, beginning with Jackson and Owen and following with such leaders in Federal work as Gilbert, Chamberlin, King, R. D. Irving, Pumpelly, Van Hise, and Walcott, may note that these were all connected in their earlier work with State surveys. Nor has the relation been one-sided, for among the State geologists Whitney, Blake, Mather, Newberry, J. G. Norwood, Purdue, Bain, Gregory, Ashley, Kirk, W. H. Emmons, DeWolf, Mathews, Brown, Landes, Moore, and Crider received their field training in part or wholly as members of a Federal Survey. Moreover, under the present plan of effective cooperation of several of the State surveys with the United States Geological Survey, it is often difficult to differentiate between the two in either personnel or results, for it even happens that the publishing organization may not have been the major contributor. The full record of American geology, past and present, can not be set forth in terms of Federal auspices alone.

The three decades preceding the Civil War, then, constitute the era of State surveys, well described by Merrill as at first characterized by a contagious enthusiasm for beginning geologic work, later by a more normal condition in which every available geologist seems to have been quietly at work, and finally by renewed activity in creating new organizations. The net result was that Louisiana and Oregon seem to have been the only States not having at least one geological survey.

From “Contributions to the History of American Geology”
by George P. Merrills.

The first specific appropriation by the Federal Government for geologic investigation appears to have been made in 1834, when a supplemental appropriation for surveys of roads and canals under the War Department, authorized in 1824, contained the item “of which sum five thousand dollars shall be appropriated and applied to geological and mineralogical survey and researches.” In July, 1834, Mr. G. W. Featherstonhaugh was appointed United States geologist and employed under Colonel Abert, U. S. Topographical Engineers, to “personally inspect the mineral and geological character” of the public lands of the Ozark Mountain region. Overlooking the incidental fact that this Englishman—a man of scientific attainment and large interest in public affairs—was never naturalized,[^[98]] it must be placed to the credit of this first of United States geologists that within seven months he completed his field work and returned to Washington, and on February 17, 1835, his report was transmitted to Congress. Two years earlier Featherstonhaugh had memorialized Congress for aid in the preparation of a geologic map of the whole territory of the United States, and in connection with this project he suggested that geology as an aid to military engineering should have a place in the curriculum at West Point. This first United States geologist also appears to have combined an appreciation of the practical worth of “the mineral riches of our country, their quality, quantity, and the facility of procuring them,” with an interest in the more scientific side of geology, though his hypotheses regarding both economic geology and stratigraphic and structural geology have not won the endorsement of all later workers in the same regions. In all these respects, however, Featherstonhaugh may stand as a fairly good prototype. His contributions to international affairs subsequent to his scientific service to the United States are of interest; he served as one of Her Majesty’s commissioners in the settlement of the Canadian-United States boundary question in 1839–40 and made an examination of the disputed area, and after the settlement of this controversy he was appointed British Consul for the Department of the Seine, France, where in 1848 he personally engineered the escape of Louis Philippe from Havre.

The Federal geologic work thus started was soon continued in surveys of wider scope and more thorough accomplishment. The position of the Government as the proprietor of mineral lands in the Upper Mississippi Valley led to their examination. These Government lands containing lead had been reserved from sale for lease since 1807, although no leases were issued until 1822. The amount of illegal entry and consequent refusal of smelters and miners to pay royalty after 1834 forced the issue upon the attention of Congress, and in 1839 President Van Buren was requested to present to Congress a plan for the sale of the public mineral lands. In carrying out this policy Dr. David Dale Owen was selected to make the necessary survey.

Owen had served as an assistant on the State Survey of Tennessee and as the first State geologist of Indiana, and he organized the new work promptly and effectively. Although suffering from the handicap unfortunately known by geologists of the present day—the receipt late in the season (August 17, 1839) of authority to begin work—within exactly a month he had his force of 139 assistants organized into 24 field parties, instructed in “such elementary principles of geology as were necessary to their performance of the duties required of them.” His plan of campaign provided for a northward drive at a predetermined rate of traverse for each party, with periodic reports to himself at appointed stations, “to receive which reports and to examine the country in person” he crossed the area under survey eleven times. The result of such masterful leadership was the completion of the exploration of all the lands comprehended in his orders in two months and six days, and his report on this great area—about 11,000 square miles—bears date of April 2, 1840.

Eight years later Doctor Owen made a survey of an even larger area, continuing his examination northward to Lake Superior. Again his report was published promptly, and he continued for several years his examination of the Northwest Territory, submitting his final report in 1851. It is interesting to note that in his earlier report Doctor Owen subscribed himself as “Principal Agent to explore the Mineral Lands of the United States,” but that in the later report he was “U. S. Geologist for Wisconsin.” The two surveys together covered 57,000 square miles.

During the same period similar surveys were being made in northern Michigan by Dr. Charles T. Jackson, 1847–48, and Foster and Whitney, 1849–51. These surveys also had been hastened by the “copper fever” of 1844–46, with wholesale issue of permits and leases, Congress in 1847 authorizing the sale of the mineral lands and a geological survey of the Lake Superior district. The execution of these surveys under Jackson and under Foster and Whitney and the prompt publication in 1851 of the maps of the whole region materially helped to establish copper mining on a more conservative basis. and the development of the Lake Superior region was rapid.[^[99]]

These land-classification surveys, with their definite purpose, represent the best geologic work of the time. The plan necessitated thoroughgoing field work with considerable detail and prompt publication of systematic reports, and in the working up of the results specialists like James Hall and Joseph Leidy contributed, while F. B. Meek was an assistant of Owen. It is worthy of note that had not Doctor Houghton, the State geologist of Michigan, met an untimely death in 1847, effective cooperation of the State Survey with the Federal officials would have combined geologic investigation with the execution of the linear surveys.[^[100]]

Belonging to the same period of geologic exploration was the service of J. D. Dana, as United States Geologist on the Wilkes Exploring Expedition, the disaster to which compelled his return from the Pacific Coast overland and resulted in his geologic observations on Oregon and northern California.

The military expeditions during the decade 1850–60 and the earlier expeditions of Fremont added to the geographic knowledge of the Western country and also contributed to geologic science, largely through collections of rocks and fossils, usually reported on by the specialists of the day. Thus the names of Hall, Conrad, Hitchcock, and Meek appear in the published reports on these explorations, while Marcou, Blake, Newberry, Gibbs, Evans, Hayden, Parry, Shumard, Schiel, Antisell, and Engelmann were geologists attached to the field expeditions. In 1852 geologic investigation was seemingly so popular as to necessitate the statutory prohibition “there shall be no further geological survey by the Government unless hereafter authorized by law.”

Certain of these explorations had a specific purpose: several of them sought a practical route for a transcontinental railroad; another a new wagon road across Utah and Nevada; and one under Colonel Pope, with G. G. Shumard as geologist, was sent out “for boring Artesian Wells along the line of the 32d Parallel” in New Mexico. The published reports varied greatly in scientific value and in carefulness of preparation, while the publication of at least two reports was delayed until long after the war, and the manuscript of another was lost. The report of the expedition of Major Emory contained a colored geologic map of the western half of the country, a pioneer publication, for the map prepared by Marcou extended only to the 106th meridian.

Thus in the first period of Government surveys, covering about forty years, the great West, with its wealth of public lands, was well traversed by exploratory surveys, which furnished, however, only general outlines for a comprehension of the stratigraphy and structure of mountain and valley, plain and plateau. To an even less degree was there any realization of the economic possibilities of the vast territory west of the Mississippi. President Jefferson, in planning the Lewis and Clark expedition, had stated his special interest in the mineral resources of the region to be traversed. Nearly forty years later Doctor Owen was strongly impressed with the commercial promise of the region he surveyed. His reports contain analyses of ores and statistics of production; he compared the lead output of Wisconsin, Iowa, and Illinois with that of Europe and foretold the value of the iron, copper, and zinc deposits of the area; he outlined the extent of the Illinois coal field; and he laid equal emphasis upon the agricultural possibilities of the region. Indeed, so optimistic were Owen’s general conclusions that he referred to his separate township plats, with their detailed descriptions, as the basis for his sanguine opinions, realizing that “the explorer is apt to become the special pleader.” With equal breadth of view and thoroughness of execution the surveys of Foster and Whitney laid the foundation for the development of the copper and iron resources of the Lake Superior region, and although these areas were largely wilderness and not adapted to rapid traverse or easy observation the reports on their explorations nevertheless compare most favorably with the contributions of geologists working in the more hospitable regions in the older States.

The period following the Civil War naturally became one of national expansion, the faces of many were turned westward, and exploration of the national domain for its industrial possibilities took on fresh interest. Home-seekers and miners largely made up this army of peaceful invasion, and the winning of the West began on a scale quite different from that of the days of the military path-finding expeditions of Fremont and other Army officers. Thus the nation was aroused to the task of investigating its public lands and Congress gave the support needed to make geologic exploration possible on a large scale.

Geologic surveys of a high order were continued in the older States, as shown by the contributions during this period of J. P. Lesley and G. H. Cook in the East, W. C. Kerr, E. W. Hilgard, and E. A. Smith in the South, and J. S. Newberry, C. A. White, Raphael Pumpelly, T. C. Chamberlin, Alexander Winchell, and T. B. Brooks in the Central States. To the north the Canadian Survey, organized in 1841 under Logan, had continued under the same sturdy leadership until 1869, when the experienced and talented Doctor Selwyn became Director. As contrasted with the short careers of most of the State Surveys and with the temporary character of all of the Federal undertakings in geologic investigation, the continuance of the Canadian Geological Survey for more than half a century under two directors gave opportunity for continuity of effort in making known to the people of the Dominion its resources and at the same time contributing to the world much pure science.

Passing with simple mention the two Government expeditions into the Black Hills, which afforded opportunity for geologic exploration by N. H. Winchell in 1874 and by Jenney and Newton in 1875, the record of geologic work under Government auspices in the period immediately following the Civil War groups itself around the names of four leaders—Hayden, King, Powell, and Wheeler. The four organizations, distinguished commonly by the names of these four masterful organizers, occupied the Western field more or less continuously from 1867 to 1878, and the sum total of their contributions to geography and geology was large indeed. In the words of Clarence King,[^[101]] “Eighteen hundred and sixty-seven, therefore, marks, in the history of national geological work, a turning point, when the science ceased to be dragged in the dust of rapid exploration and took a commanding position in the professional work of the country.” Together these four expeditions covered half a million square miles, or more than a third of the area of the United States west of the one-hundredth meridian, and the cost of all this work was approximately two million dollars, which was a small fraction of its value to the nation counting only the impetus given to settlement and utilization.

As viewed from a distance of nearly half a century, these four surveys differed much in plan of organization, scope of purpose, and success of execution, so that comparison would have little value except as possibly bearing upon the work of the larger organization which followed them and became the heir not only to much that had been attained by these pioneer surveys but also to the great task uncompleted by them. So, if in the earliest days of the present United States Geological Survey there may have been a certain partisanship in tracing derived characters in the new organization, it is even now worth while to recognize the real origin of much that is credited to present-day development.

Dr. F. V. Hayden was the first of these Survey leaders to engage in geological exploration. He visited the Badlands as early as 1853, and his connection with subsequent expeditions was interrupted only by his service as a surgeon in the Federal Army during the war. In 1867, however, Hayden resumed his geologic work as United States Geologist in Nebraska, operating under direction of the Commissioner of the General Land Office. In the following eleven years the activities of the Hayden Survey—the “Geological and Geographical Survey of the Territories”—extended into Wyoming, Colorado, New Mexico, Montana, and Idaho, covering with areal surveys 107,000 square miles. This Survey, as might be expected from the long experience of its leader, made large contributions to stratigraphy, which involved notable paleontologic work by Cope, Meek, and Lesquereux. Next in importance was the structural work of A. C. Peale, W. H. Holmes, Capt. C. E. Dutton, and Dr. Hayden himself, and the influence of these expeditions in popularizing geology should not be overlooked. The expedition of 1871 into the geyser region on the upper Yellowstone resulted in the creation of the first of the national parks. W. H. Holmes began his artistic contributions to geology in 1872 with this Survey. Topographic mapping was added to the geologic exploration, James T. Gardner and A. D. Wilson joining the Hayden Survey after earlier service on the King Survey and Henry Gannett being a member of parties, first as astronomer and later as topographer in charge. The accomplishment of the Hayden Survey itself and the later work of many of its members show that this organization possessed a corps of strong men.

The King Survey was a smaller organization, with Congressional authorization of definite scope and a systematic plan of operation. The beginning of construction of the Union Pacific terminated the period of the railroad surveys under the War Department and afforded opportunity for geologic work that would be more than exploratory: the opening up of the new country made investigation of its resources logical. This fact was recognized by Clarence King, who had traversed the same route as a member of an emigrant train with his friend James T. Gardner. His plan to make a geological cross section of the Cordilleras, with a study of the resources along the route of the Pacific railroads, won the support of Congress, and the “Geological Exploration of the Fortieth Parallel” was authorized in 1867, with Clarence King as geologist in charge, under the Chief of Engineers of the Army. Field work was begun in the summer of that year, and it is interesting to note that Mr. King and his small force of geological assistants—the two Hagues and S. F. Emmons—began at the western end of this cross section, and in this and subsequent years extended the survey from the east front of the Sierra Nevada to Cheyenne, covering a belt of territory about 100 miles in width. This comprehensive plan was carried out in the field operations, and the scientific and economic results were systematically worked up in the reports, which appeared in 1870–80. The only departure from this plan was a study of the volcanic mountains Shasta, Rainier, and Hood, in 1870, occasioned by an unexpected and unsolicited appropriation for field work, and that summer’s work resulted in the discovery of active glaciers, the first known within the United States.

The Fortieth Parallel Survey is to be credited with contributions to the knowledge of the stratigraphy of the West, the region traversed being remarkably representative of the stratigraphic column, to which was added the paleontologic work of Marsh, Meek, Hall, and Whitfield, while the attempt was made to interpret the sedimentary record in terms of Paleozoic, Mesozoic, and Tertiary geography. King’s plan of survey included large use of topographic mapping with astronomic base and triangulation control and contours based upon barometric elevations. The results were pronounced by an unfriendly critic[^[102]] as “very valuable, especially from a geological point of view,” but unfortunate in being the forerunner of work in which Government geologists “have presumed to arrogate the control of the fundamental operations of a topographic survey.” To the King Survey must be credited the introduction of systematic contour mapping and the use of contour maps for purposes of geology. In two other respects the King Survey contributed largely to future Government work: microscopical petrography in the United States may be said to have begun with the visit of Professor Zirkel to this country as a member of this Survey in 1875, and the report of J. D. Hague on “Mining Industry” was the fitting expression of the emphasis then put on the study of the mineral resources of this newly opened territory, a subject of investigation that was in large part the true basis of King’s project rather than simply “the immediate excuse for the Survey.” An earlier influence in the scientific study of ore deposits had come from Von Richthofen’s investigation of the Comstock Lode in 1865 and his subsequent work with Whitney in California. The incident of King’s relation to the diamond fraud in Arizona in 1872 furnished a precedent for public servants of a later day; he investigated the reported find from scientific interest but exposed it with all the zeal of a publicist and truth lover. In a word, the Fortieth Parallel Survey commands our admiration for its brilliant plan, thoroughgoing work in field and office, and high quality of personnel.

Major J. W. Powell began his large contribution to Government surveys with his exploration of the Grand Canyon in 1869, the Congressional recognition of his expedition being limited to an authorization for the issue of rations by the War Department. Small appropriations were made in the following years, and in 1874 full authorization was given for the continuance of his survey in Utah under the Secretary of the Interior and was followed by the adoption of the name “United States Geographical and Geological Survey of the Rocky Mountain Region.” This organization was the least pretentious of the four operating during this period—it covered less area, expended less public money, and published much less—but its contribution to American geology is not to be measured by miles or pages but by ideas. Its physical environment favored this survey, and in the work of Powell, Dutton, and Gilbert can be seen the beginnings of physiography on the heroic scale exemplified in the Grand Canyon and the High Plateaus. The first use of terms like “base-level of erosion,” “consequent and antecedent drainage,” and “laccolith” marked the introduction of new ideas in the interpretation of land sculpture and geologic structure. The daring boat trip of Powell was no less brilliant than his simple explanation of the Grand Canyon itself.

“The United States Geographical Surveys West of the 100th Meridian” was the title given to the explorations made under Lieut. G. M. Wheeler, of the Engineer Corps, which began with topographic reconnaissances in Nevada, Utah, and Arizona, specifically authorized by Congress in 1872. From the standpoint of American geology this could be better known as the Gilbert Survey, Mr. G. K. Gilbert serving for the three years 1871–73, the later part of the time with the title of chief geological assistant. Gilbert’s contributions included his description of Basin Range structure, his first account of old Lake Bonneville, and his discussion of the erosion phenomena of the desert country. J. J. Stevenson also served later as a geologist of this Survey, and A. R. Marvine, E. E. Howell, E. D. Cope, Jules Marcou, and I. C. Russell were connected with the field parties. Captain Wheeler’s own claim for the work of his Survey emphasized its geographic side, for he regarded the results as the partial completion of a systematic topographic survey of the country.

By 1878, when the Fortieth Parallel Survey had completed the work planned by its chief, three of these independent surveys still contended for Federal support and for scientific occupation of the most attractive portions of the Western country. Unrestrained competition of this kind, even in the public service, proves as wasteful as unregulated competition in private business,[^[103]] and Congress appealed to the National Academy of Sciences for a plan for Government surveys to “secure the best results at the least possible cost.” Under instructions by Congress the National Academy considered all the work relating to scientific surveys and reported to Congress a plan prepared by a special committee, whose membership included the illustrious names of Marsh, Dana, Rogers, Newberry, Trowbridge, Newcomb, and Agassiz. This report, which was adopted by the Academy with only one dissenting vote, grouped all surveys—geodetic, topographic, land parceling, and economic—under two distinct heads, surveys of mensuration and surveys of geology. At that time five independent organizations in three different departments were carrying on surveys of mensuration, and the Academy recommended that all such work be combined under the Coast and Geodetic Survey with the new name Coast and Interior Survey. For the investigation of the natural resources of the public domain and the classification of the public lands a new organization was proposed, the United States Geological Survey. The functions of these two surveys and of a third coordinate bureau in the Interior Department, the Land Office, were carefully defined and their interrelations fully recognized and provided for in the plan presented to Congress. Viewed in the light of 39 years of experience the National Academy plan would be indorsed by most of us as eminently practical, and the report stands as a splendid example of public service rendered by America’s leading scientists. The legislation which embodied the entire plan, however, failed of passage in Congress.

The natural activity behind the scenes of the conflicting interests represented by those connected with the several surveys may be seen in the legislative history of the moves leading up to the creation of the United States Geological Survey. In the last session of the 45th Congress the special legislation embodying the recommendations of the National Academy was included in the Legislative, Executive, and Judicial Appropriation bill as it passed the House of Representatives, while the Sundry Civil Appropriation bill carried an item simply making effective the longer section in the other appropriation bill. The item in the Legislative appropriation bill created the office of the Director of the Geological Survey, provided his salary, and defined his duties, as well as specifically terminating the operations of the three older organizations. The item in the Sundry Civil bill as it passed the House appropriated $100,000 for the new Geological Survey, but when this appropriation bill was reported to the Senate a committee amendment added the words “of the Territories,” and further amendments offered on the floor changed the item so as to provide specifically and exclusively for the continuation of the Hayden Survey. Other amendments provided small appropriations for the completion of the reports of the Powell and Wheeler surveys, and the bill passed the Senate in this form. The Legislative Appropriation bill was similarly pruned, while in the Senate, of all reference to the proposed new organization. This bill, however, died in conference, but in the last hours of the session the conferees on the Sundry Civil bill took unto themselves legislative powers and transferred from the dead bill to the pending measure all the language which constitutes the “organic act” of the United States Geological Survey. This action was denounced in the Senate as “a wide departure from the authority that is possessed by a conference committee,” and it was further stated in debate that the inserted provision which created a new office and discontinued the existing surveys was one “which neither the Committee of the Senate nor the Senate itself ever saw.” This assertion was perhaps parliamentarily sound in that the language was new to the Sundry Civil bill, yet actually the Senate had only two days before stricken the same proposed legislation from the pending Legislative Appropriation bill. However, the House conferees—Representatives Atkins of Tennessee, Hewett of New York, and Hale of Maine—had realized their tactical advantage, and the Senate, after a brief debate, voted on March 3 to concur in the report of the committee of conference, thus reversing all their earlier action, in which the friends of the Hayden and Wheeler organizations apparently had commanded more votes than the advocates of the National Academy plan.

Clarence King was appointed first Director of the United States Geological Survey on April 3, 1879, and began the work of organization. With his proven genius for administration, King promptly resolved the doubt as to the meaning of the term “national domain” in the language defining the duties of the Director by taking the conservative side and limiting the work of the new organization to the region west of the 102d meridian. This region was divided into four geological divisions, and for economy of time and money field headquarters were established for these divisions. The Division of the Rocky Mountains was placed under Mr. Emmons as geologist in charge, the Division of the Colorado under Captain Dutton, the Division of the Great Basin under Mr. Gilbert, and the Division of the Pacific under Arnold Hague. The Division of the Colorado was intended as merely temporary for the purpose of bringing to completion the scientific work of the Powell Survey. Similarly Dr. Hayden was given the opportunity to prepare a systematic digest of his scientific results. This organization of the work and the selection of geologists in charge showed the relation of the new and the old, and a glance at the personnel of the new Survey indicates the extent to which the geologic investigation of the Western country was to continue without interruption. Of the twenty-four geologists and topographers listed in the first administrative report, four had been connected with the Powell Survey, two with the Hayden, three with the Wheeler, and five with the King Survey.

In planning the initial work of the United States Geological Survey, the Director speaks of the “most important geological subjects” and “mining industries,” of “instructive geological structure” and “great bullion yield” in the same sentences, so that the intent was plain to make the geologic investigations both theoretical and practical.

It was expected that the field of operations of this Federal Survey would be at once extended by Congress over the whole United States, but the measure making this extension, which would simply carry out the intent of the framers of the legislation creating the new bureau, passed the House alone, and it was only by subsequent modification of the wording of appropriation items that the United States Geological Survey became national in scope as well as in name. The critical question of the effective coördination of State and Federal geologic surveys was met by Director King, who corrected an erroneous impression “industriously circulated” by stating his policy to be to urge the inauguration and continuance of State surveys.[^[104]] This was the initial step in the cooperation between State and Federal surveys which became effective on a large scale in subsequent years.

Though the Geological Survey has extended its operations over the whole United States, its largest activities have always been directed toward the exploration and development of the newer territory in the public-land States. All four of its directors had their field training in the West: the name of Major Powell, who succeeded King in 1880, is inseparably connected with scientific exploration; Charles D. Walcott, who was Director from 1894 to 1907, the period of the Survey’s greatest expansion, made the largest contribution to the Paleozoic stratigraphy and paleontology of the West; and the present Director spent seven field seasons in the Northern Cascades and one in a mining district in Utah. The scope of the activities both East and West as developed during the 39 years since the establishment of the new bureau can be best described, perhaps, in terms of its present functions as expressed in the organization of to-day.

The growth of the Survey is measured in the increase of annual appropriation from $106,000 in 1879–80 to the amount available for the current year—$1,925,520, not including half a million dollars from War Department appropriations being spent in the topographic work of the Survey. The corresponding increase in personnel has been from 39, listed in the first report, to 911 holding regular appointments at the present time, divided among the different branches as follows: A scientific force of 173 in the Geologic Branch, 169 in the Water Resources Branch, 71 in the Topographic Branch, and 15 in the Land Classification Board, with a clerical force of 168 divided among the same branches, and the remainder the technical and clerical employees of the publication and administrative branches. These personnel statistics are not expressive of normal conditions, since a large number of the topographic engineers are commissioned officers and thus are not included on the civilian roll, while, on the other hand, the classification of the stock-raising homestead lands makes the technical force of the Water Resources Branch unusually large this year.

The primary aim of the Geological Survey is geologic, whether directed by authority of law toward the “examination of the geological structure, mineral resources, and products of the national domain,” toward the preparation of the authorized “reports upon general and economic geology and paleontology,” of the “geologic map of the United States,” or of the “report on the mineral resources of the United States,” or toward the “continuation of the investigation of the mineral resources of Alaska” or “chemical and physical researches relating to the geology of the United States.” The spirit and the purpose of the Survey’s work in all these fields are not believed to have materially changed from those of the founders of the science in America. From time to time too much emphasis may have appeared to be laid upon applied geology as contrasted with pure science, yet the report of the National Academy to Congress in terms placed the stress upon economic resources and referred to paleontology as “necessarily connected” with general and economic geology. The practical purpose of geologic research under Government auspices must be recognized by the administrator, whether he be the paleontologist like Walcott, the philosopher like Powell, or the mining geologist like King. That the task of steering the true course is no new problem can be seen from the statement of Owen[^[105]] written 70 years ago, and these words describe conditions of Government geological work even to-day:

Scientific researches, which to some may seem purely speculative and curious, are essential as preliminaries to these practical results. Further than such necessity dictates, they have not been pushed, except as subordinate and incidental, and chiefly at such periods as, under the ordinary requirements of public service, might be regarded as leisure moments; so that the contributions to science thus incidentally afforded, and which a liberal policy forbade to neglect, may be considered, in a measure, a voluntary offering, tendered at little or no additional expense to the department.

The increased attention given to mineral resources has been a matter of gradual growth. Mr. King early organized a Division of Mining Geology with Messrs. Pumpelly, Emmons, and Becker as geologists in charge, to whom were assigned the collection of mineral statistics for the Tenth Census. These Survey geologists and Director King himself held appointments as special agents of the Census Bureau, and on the staff selected for this work appear the names of T. B. Brooks, Edward Orton, T. C. Chamberlin, Eugene A. Smith, George Little, J. R. Proctor, R. D. Irving, N. S. Shaler, John Hays Hammond, Bailey Willis, and G. H. Eldridge, indicating the extent to which the supervision of these inquiries was placed in the hands of economic geologists. This procedure was reverted to by Director Walcott and in the last ten years has become a well-established policy, the statistics of annual production of all the important mineral products being under the charge of geologists, as best qualified to comprehend the resources of the country. Another of these special assistants in 1880 was Albert Williams, Jr., who became the first chief of the Division of Mineral Resources, in 1882. The study of ore deposits, which may be said to have begun with the King Survey, was inspired by King’s own appreciation of the broad geologic relations of the distribution of mineral wealth and by the detailed studies of individual mining districts by his associates, “based upon facts accurately determined in the light of modern geology.”

Geological surveys have been prosecuted in Alaska since 1895, and in the last few years the annual appropriation for the work has been the same as that made for the expenses of the whole Survey in the first year of its history. The Division of Alaskan Mineral Resources is in fact a geological survey in itself, except that it shares in the administrative machinery of the larger organization and has the advantage of the cooperation of the scientific specialists of the Survey as they may be needed to supplement its own force. All the investigations in this distant part of the country represent the Geological Survey at its best, for here the organization’s long experience in the Western States can be applied to most effective and helpful work on the frontier, where the geologist and topographer in their exploration do not always follow the prospector but often precede him. Undoubtedly no greater factor has contributed to the development of Alaskan resources than this pioneer work of the Federal Survey, yet the work has also contributed notable additions to the sciences of geology and geography.

The first duty laid upon the Director of the Geological Survey in the law of 1879 was “the classification of the public lands,” and this phrase undoubtedly expressed the idea of the committee of the National Academy. The same legislation, however, contained provision for the further consideration by a commission of the classification and valuation of the public lands, as also recommended by the National Academy. Thus the decision of Director King that the classification intended by Congress was scientific and was intended for general information and not to aid the Land Office in the disposition of land by sale or otherwise was really based upon the deliberate opinion of the Public Lands Commission, of which he was a member, that classification would seriously impede rapid settlement of the unoccupied lands. Nearly forty years later those who are intrusted with the land-classification work of the Geological Survey recognize this familiar argument, which undoubtedly had much more force in that earlier stage of the utilization of the Nation’s resources of land.[^[106]] The conception of land classification as a business policy on the part of the Government as a landed proprietor belongs rather to this day of more intensive development. At present current public-land legislation calls for highest use, and hence official investigation of natural values and possibilities must precede disposition. This type of mineral and hydrographic classification of public lands has been in progress in increasing amount since 1906, so that now the Geological Survey is the kind of scientific adviser to the Secretary of the Interior and Commissioner of the General Land Office that may have been contemplated by the National Academy of Sciences in 1878. It is plain, however, to everyone at all conversant with Western conditions that the recent land-classification surveys in Wyoming, for instance—detailed geologic surveys which form the basis for the valuation of public coal lands in 40–acre units—would have possessed no utility in 1871, when the coal-land law was passed but when the demand for railroad fuel had just begun.

The land-classification idea is of course the basis of the National forest and irrigation movements. The laws of 1888 and 1896, which mark the beginning of active endorsement by Congress of these conservation movements, placed upon the Survey the duties of examining reservoir sites and forest reserves respectively. The earlier of these laws began the investigation of the water resources of the country, which is still an important phase of the Survey’s activity, and led to the creation of an independent organization—the Reclamation Service. It is easy to trace the beginnings of Federal reclamation of arid lands in the pioneer work of Powell, whose report in 1878 on the arid region of the United States was the first adequate statement of the problem of largest use of these lands in terms broader than those of individualistic endeavor. For years, however, Powell’s appeal for Congressional consideration of this National task was like the “voice of one crying in the wilderness.”

In a somewhat similar way the forestry surveys under the Geological Survey helped in the organization of a separate bureau—now the Forest Service. The other important Federal bureau tracing direct relationship to the Survey is the Bureau of Mines, established in 1910, which continued the investigations in mining technology specifically provided for by Congress for six years under the Geological Survey but in some degree begun in the early days of the Survey under Directors King and Powell.

Another equally important organization of a public nature, though not a Federal bureau, traces its beginnings to the Geological Survey: the Geophysical Laboratory of the Carnegie Institution, which now exercises so potent an influence over geologic investigation, had its origin in the official work of the Geological Survey’s Division of Chemical and Physical Research, and its personnel was at first largely recruited from the Survey. The highly original experimental work of this laboratory has extended far beyond the scope of the Survey’s work—at least far beyond the scope possible with the Federal funds available—yet most of the results of these investigations may eventually come under even a strict construction of the language used in the Survey’s appropriation “for chemical and physical researches relating to the geology of the United States.”

The topographic work of the present Survey continues with constant refinement of standards and economy of methods the work of the earlier organizations. The primary purpose of these topographic surveys is to provide the bases for geologic maps, yet these topographic maps, which cover 40 per cent of the area of the United States, are used in every type of civil engineering as well as by the public generally. The annual distribution by sale of half a million of these maps is an index of their value to the people.

The hot discussion that was waged for years on the question of military versus scientific administration of topographic surveys is in striking contrast with the present concentration of all the topographic mapping under the Geological Survey in those areas where it may best serve the needs of the Army. In 1916 Congress specifically recognized the possibility of greater cooperation of this kind, both in the appropriation made to the Geological Survey and in a special appropriation made to the War Department. For a number of years indeed special military information had been contributed to the Army by the Survey topographers, but since March 26, 1917, every Geological Survey topographer has worked exclusively on the program of military surveys laid down by the General Staff of the Army, and the places of some of the 44 Survey topographers now in France as engineer officers are filled by 34 other reserve engineer officers detailed by order of the Secretary of War to the Director of the Geological Survey to assist in this military mapping and to receive instruction fitting them in turn for topographic service in France.

The contribution of this civilian service to the military operations in the present emergency forms a fitting conclusion to this review of a century of Government surveys. At present 215 members of the Geological Survey are in uniform, 107 as engineer officers, two of whom are on the staff of the American Commanding General in France. In the war work carried on in the United States the Survey’s contribution is by no means limited to military mapping: the geologists are also mobilized for meeting war needs, assisting in developing new sources of the essential war minerals, in speeding up production of mineral products, in collecting information for the purchasing officers both of our own and of the Allied governments, in coöperating with the constructing quarter-masters in the location of gravel and sand for structural use and in both general and special examinations of underground water supply and of drainage possibilities at cantonment sites, and in supplying the Navy Department with similar technical data. A special contribution has been the application to aërial surveys of photogrammetric methods developed in the Alaskan topographic work and the perfection of a camera specially adapted to airplane use. The utilization of the Survey’s map engraving and printing plant for confidential and urgent work for both the Army and Navy has necessitated postponement of current work for the Geological Survey itself. Throughout the organization the records, the methods, and the personnel which represent the product of many years of scientific activity are all being utilized; thus is the experience of the past translated into special service in the present crisis.

Notes.

[96]. Hess, R. H., Foundations of National Prosperity, p. 100.

[97]. Report Nat’l Museum, 1904, pp. 189–733.

[98]. Featherstonhaugh, J. D., Am. Geol., 3, 220, 1889.

[99]. Whitney, Mineral Wealth of the United States, pp. 248–250.

[100]. Foster and Whitney, 31st Cong., 1st session, House Doc. 69, pp. 13–14, 1850.

[101]. First Annual Rept. U. S. Geol. Survey, p. 4.

[102]. Wheeler, Report 3d Internat’l Geog. Cong., p. 492, 1885.

[103]. The views of the writer on “natural monopolies” in the Government service are set forth in an address delivered at the centennial celebration of the U. S. Coast and Geodetic Survey, April 5, 1916. (See Science, vol. 43, pp. 659–665, May 12, 1916.)

[104]. For correspondence on this subject, see Minnesota Geol. Survey, Eighth Ann. Rept., 1880, p. 173.

[105]. Owen, D. D., 30th Cong., 1st sess., Senate Doc. No. 57, p. 7, 1848.

[106]. This essential difference between present-day requirements and the needs of earlier generations has been discussed by W. C. Mendenhall, the geologist in charge of the Land Classification Board of the Geological Survey: Proceedings 2d Pan-American Sci. Cong., 1915–16, 3, 761.

VI
ON THE DEVELOPMENT OF VERTEBRATE PALEONTOLOGY

By RICHARD SWANN LULL

Introduction.

Unlike its sister science of Invertebrate Paleontology, which has been approached so largely from the viewpoint of stratigraphic geology, that of the vertebrates is essentially a biologic science, having its inception in the masterly work of Cuvier, who is also to be regarded as the founder of comparative anatomy. For long decades, vertebrate paleontology was simply a branch of comparative anatomy or morphology in that it dealt almost exclusively with the form and other peculiarities of fossil bones and teeth, often in a more or less fragmentary condition, very little or no attention being paid to any other system of the creature’s anatomy. Distribution both in space and in time was recorded, but the value of vertebrates in stratigraphy was still to be appreciated and has hardly yet come into its own. It is readily seen, therefore, that the two departments of paleontology did not enlist the same workers or even the same type of investigators, for while the two sciences have much in common and should have more, the vertebratist must, above all else, be a morphologist, with a keen appreciation of form, and a mind capable of retaining endless structural details and of visualizing as a whole what may be known only in part. The initial work of the brilliant Cuvier set so high a standard of preparedness and mental equipment that as a consequence, the number of those engaged in vertebrate research has never been large as compared with the workers in some other branches of science, but the results achieved by the few who have consecrated their research to the fossil vertebrates has been in the main of a high order.

At first, as has been emphasized, this work was largely morphological, dealing both with the individual skeletal elements and later with the bony framework as a whole. Then came the endeavor to clothe the bones with sinews and with flesh—to imagine, in other words, the life-appearance of the ages-departed form—with such of its habits as could be deduced from structure of body, tooth, and limb. Next came the working out of systematic series of vertebrates and their marshalling into species, genera, and larger groups, and much time was thus spent, especially when rapid discovery brought a continual stream of new forms before the systematist, and hence some appreciation of the countless hosts of bygone creatures which peopled the world in the geologic past. This systematic work, however, was based upon the most painstaking morphologic comparisons and so the science was still within the scope of comparative anatomy.

In connection with taxonomic research came increasingly tangible evidence in favor of the law of evolution; investigators turned to the working out of phyletic series showing the actual record of the successive evolutionary changes that the various races had undergone. Coupled with this evolutionary evidence came an increased attention to the sequential occurrence in successive geologic strata, and the stratigraphic distribution of vertebrates became known with greater and greater detail. Then followed the assemblage of faunas, which brought the study of the fossil forms within the realm of historical geology, rather than being the mere phylogeny of a single race, and the value of vertebrate fossils as horizon markers became more and more appreciated by the stratigrapher. They serve to supplement the knowledge gained from the invertebrates, and in this connection are especially valuable in that they often give data concerning continental formations about which invertebrate paleontology is largely silent.

Rise of Vertebrate Paleontology in Europe.

To those who had been nurtured in the belief in a relatively recent creation covering in its entirety a period of but six days, and occurring but four millenniums before the time of Christ, the appearance of the remains of creatures in the rocks, the like of which no man ever saw alive, must have given scope to the wildest imaginings concerning their origin and significance; for many believed that not only had no new forms been added to the world’s fauna since the creation, except possibly by hybridizing, but that none had become extinct save a very few through the agency of human interference. The supposition was, therefore, that such creatures as were thus discovered were still extant in some more remote fastnesses of the world. Thus, our second president, Thomas Jefferson, who wrote one of the first papers on American fossil vertebrates, published in 1798, discussed therein the remains of a huge ground-sloth which has since borne the name Megalonyx jeffersoni. Jefferson, however, described the great claws as pertaining to a huge leonine animal which he firmly believed was yet living among the mountains of Virginia.

Cuvier (1769–1832) has been spoken of as the founder of our science. His opportunity lay in the profusion of bones buried in the gypsum deposits of Montmartre within the environs of the city of Paris. Cuvier’s studies of these remains, done in the light of his very broad anatomical knowledge, enabled him to prepare the first reconstructions of fossil vertebrates ever attempted and to bring before the eyes of his contemporaries a world peopled with forms which were utterly extinct. That these creatures were no longer living, none was a better judge than Cuvier, for his prominence was such that material was sent him from all parts of the world, to which must be added that which he saw in his visits to the various museums of Europe. He felt it safe, therefore, to affirm the unlikelihood of any further discovery of unknown forms among the great mammals of the present fauna of our globe, and few indeed have been the additions since his day. To Cuvier is due not alone the masterly contribution to the sister sciences of comparative anatomy and vertebrate paleontology—the Ossements Fossiles (1812)—but he also announced the presence in continental strata of a series of faunas which showed a gradual organic improvement from the earliest such assemblage to the most modern, an idea of the most fundamental importance and one with which he is rarely credited. He believed in the sudden and complete extinction of faunas, and the facts then known were in accord with this idea, as no common genera nor transitional forms connected the creatures of the Paris gypsum with the mastodons, elephants, and hippopotami which the later strata disclosed. It is not remarkable, therefore, that Cuvier advanced his theory of catastrophism to account for these extinctions. He should not, however, according to Depéret, be credited with the idea of successive re-creations, such as that held by D’Orbigny and others, but of repopulation by immigration from some area which the catastrophe, be it flood or other destructive agency, failed to reach.

Cuvier was followed in Europe by a number of illustrious men, none of whom, however, with the exception of Sir Richard Owen, possessed his breadth of knowledge of comparative anatomy upon which to base their researches among the prehistoric. The more notable of them may be enumerated before going on to a discussion of the American contributions to the science.

They were, first, Louis Agassiz, a pupil of Cuvier and later a resident of America, whose researches on the fossil fishes of Europe are a monumental work, the result of ten years of investigation in all of the larger museums of that continent, and which appeared in 1833–43, while he was yet a young man. The fishes were practically the only fossil vertebrates to come within the scope of his investigations, for his later time was consumed in the study of glaciers and of recent marine zoology. Another student of these most primitive vertebrates who left an enduring monument was Johannes Mϋller. Huxley, Traquair, and Jaekel also did masterly work upon this group, while Smith Woodward of the British Museum is considered the highest living authority upon fossil fishes.

Of the Amphibia, the most famous foreign students were Brongniart, Jaeger, Burmeister, Von Meyer, and Owen, although Owen’s claim to eminence lies rather in the investigations of fossil reptiles which he began in 1839 and continued over a period of fifty years of remarkable achievement. Not only did he describe the dinosaurs of Great Britain in a series of splendidly illustrated monographs, but extended his researches to the curious reptilian forms from the Karroo formation of South Africa. It was to him, moreover, that the establishment of the true position of the famous Archœopteryx as the earliest known bird and not a reptile is due. Von Meyer also enriched the literature of fossil reptiles, discussing exhaustively those occurring in Germany, while Huxley’s classic work on the crocodiles as well as on dinosaurs, and the labors of Buckland, Fraas, Koken, Von Huene, Gaudry, Hulke, Seeley, and Lydekker have added immensely to our knowledge of the group.

Of the birds, which at best are rare as fossils, our knowledge, especially of the huge flightless moas, is due largely again to Owen, and his realization of the systematic position of Archœopteryx has already been mentioned.

The mammals were, perhaps, the most prolific source of paleontological research during the nineteenth century, for, as Zittel has said, Cuvier’s famous investigations on the fossil bones, mentioned above, not only contain the principles of comparative osteology, but also show in a manner which has never been surpassed how fossil vertebrates ought to be studied, and what are the broad inductions which may be drawn from a series of methodical observations. Such was Cuvier’s influence that until Darwin began to interest himself in mammalian paleontology the study of these forms was conducted entirely along the lines indicated by the French savant. This was seen in a large work, Osteology of Recent and Fossil Mammalia, by De Blainville, which, although not up to the standard set by the master, is nevertheless a notable contribution, as was also the Osteology prepared by Pander and D’Alton. A summary of the knowledge of the fossil Mammalia up to the year 1847 is contained in Giebel’s Fauna der Vorwelt, and Lydekker has done for the mammals in the British Museum what Smith Woodward did for the fishes, producing vastly more than the mere catalogue which the title implies.

The first work wherein the fossil mammals were treated genealogically was Gaudry’s Enchaînements du Monde Animal, written in 1878. Other work on the fossil Mammalia was done by Kaup, who described those from the Mainz basin and from Epplesheim near Worms whence came one of the most famous of prehistoric horses, the Hipparion; this horse, together with the remarkable proboscidean Dinotherium, was described by Von Meyer. One of the most remarkable discoveries, ranking in importance, perhaps, next to Montmartre, was that of the Pliocene fauna of Pikermi near Athens, Greece, first made known through the publications of A. Wagner of Munich and later, and much more extensively, through that of Gaudry (1862–1867). H. von Meyer was Germany’s best authority on fossil Mammalia. After his death the work was carried on by Quenstedt, Oscar Fraas, Schlosser, Koken, and Pohlig, among others.

In France, rich deposits of fossil mammals were discovered in the Department of Puy-de-Dôme, the Rhone basin, Sansan, Quercy, and near Rheims. These were described by a number of writers, notably Croizet and Jobert, Pomel, Lartet, Filhol, and Lemoine.

Rütimeyer of Bâle was one of the most famous European writers on mammalian paleontology, and his researches were both comprehensive and clothed in such form as to give them a high place in paleontological literature. He studied comparatively the teeth of ungulates, discussed the genealogy of mammals, and the relationships of those of the Old and New Worlds. He was an exponent of the law of evolution as set forth by Darwin, and his “genealogical trees of the Mammalia show a complete knowledge of all the data concerning the different members in the succession, and are amongst the finest results hitherto obtained by means of strict scientific methods of investigation” (Zittel, History of Geology and Palæontology, 1901). The mammals of the Swiss Eocene have been studied in much detail by Stehlin.

For Great Britain, the most notable contributors were Buckland in his Reliquiæ Diluvianæ; Falconer, co-author with Cautley on the Tertiary mammals of India; Charles Murchison, who wrote on rhinoceroses and proboscideans; and more recently Bush, Flower, Lydekker, Boyd Dawkins, L. Adams, and C. W. Andrews. But by far the most commanding figure of all was Sir Richard Owen, who for half a century stood without a peer as the greatest of authorities on fossil mammals. It was the Natural History of the British Fossil Mammals and Birds, published in 1846, that established Sir Richard’s reputation.

Russia has produced much mammalian material, especially from the Tertiary of Odessa and Bessarabia, and from the Quaternary of northern Russia and Siberia. These have been described mainly by J. F. Brandt, A. von Nordmann, but especially by Mme. M. Pavlow of Moscow.

Forsyth-Major discovered in 1887 a fauna contemporaneous with that of Pikermi in the Island of Samos in the Mediterranean.

One of the most remarkable recent discoveries of fossil localities was that announced in 1901 by Mr. Hugh J. L. Beadnell of the Geological Survey of Egypt and Doctor C. W. Andrews of the British Museum of London, of numerous land and sea mammals of Upper Eocene and Lower Oligocene age in northern Egypt. The exposures lay about 80 miles southwest of Cairo in the Fayûm district and are the sediments of an ancient Tertiary lake, a relic of which, Birket-el-Qurun, yet remains. These beds contained ancient Hyracoidea, Sirenia, and Zeuglodontia, but above all, ancestral Proboscidea which, together with those known elsewhere, enabled Andrews to demonstrate the origin and evolutionary features of this most remarkable group of beasts. This discovery in the Fayûm lends color to the belief that Africa may have been the ancestral home of at least five of the mammalian orders, those mentioned above, together with the Embrithopoda, a group unknown elsewhere. This theory had been advanced independently by Tullberg, Stehlin, and Osborn, before the discovery in Egypt.

Another European worker of pre-eminence who wrote more broadly than the faunal studies mentioned above was W. Kowalewsky. He discussed especially the evolutionary changes of feet and teeth in ungulates, a line of research afterward developed in greater detail by the Americans, Cope and Osborn.

South America has yielded series of rich faunas which have been exploited by the great Argentinian, Florentino Ameghino, and by the Europeans, Owen, Gervais, Huxley, Von Meyer, and more recently by Burmeister and Lydekker. Later exploration and research by Hatcher and Scott of North America will be discussed further on in this paper.

Vertebrate Paleontology in America.

Early Writers.—Having thus summarized paleontological progress in the Old World, we can turn to a consideration of the work done in the New, especially in the United States, because while the Old World investigation has been invaluable, a science of vertebrate paleontology, very complete both as to its zoological and geological scope and in the extent and value of published results, could be built exclusively upon the discoveries and researches made by Americans. The science of vertebrate paleontology may be said to have had its beginnings in North America with the activities of Thomas Jefferson, who, like Franklin, felt so strong an interest in scientific pursuits that even the graver duties of the highest office in the gift of the American people could not deter him from them. When in 1797 Jefferson came to be inaugurated as vice-president of the United States, he brought with him to Philadelphia not only his manuscript but the actual fossil bones upon which it was based. Again in 1801 he was greatly interested in the Shawangunk mastodon, despite heavy cares of state, and in 1808 made part of the executive mansion in Washington serve as a paleontological laboratory, displaying therein for study the bones of proboscideans and their contemporaries which the Big Bone Lick of Kentucky had produced. Jefferson’s work would not, perhaps, have been epoch-making were it not for its unique chronological position in the annals of the science.

Jefferson was followed by another man—this time one whose diverging lines of interest led him not into the realm of political service, but of art, for Rembrandt Peale possessed an enviable reputation among the early painters of America. Peale published in 1802 an account of the skeleton of the “mammoth,” really the mastodon, M. americanus, speaking of it as a nondescript carnivorous animal of immense size found in America. It was because of the form of the molar teeth that Peale said of it: “If this animal was indeed carnivorous, which I believe cannot be doubted, though we may as philosophers regret it, as men we cannot but thank Heaven that its whole generation is probably extinct.”

With the work of these men as a beginning, it is not strange that the more conspicuous Pleistocene fossils of the East should have attracted the attention of many subsequent writers in the first part of the nineteenth century, nor that the early papers to appear in the Journal should pertain to proboscideans or to the huge edentate ground-sloths and the aberrant zeuglodons whose bones frequently came to light. Therefore a number of men such as Koch, both Sillimans, J. C. Warren, and others made these forms their chief concern.

Fossil Footprints.—Among the early writers who concerned themselves with these greater fossils was Edward Hitchcock, sometime president of Amherst College, and a geologist of high repute among his contemporaries. Hitchcock is, however, better and more widely known as the pioneer worker on a series of phenomena displayed as in no other place in the region in which he made his home. These are fossil footprints impressed upon the Triassic rocks of the Connecticut valley. It was in the Journal for the year 1836 (29, 307–340) that Hitchcock first called attention to the footmarks, although they had been known and discussed popularly for a number of years previous. James Deane, of Greenfield, was perhaps the first to appreciate the scientific interest of these phenomena, but deeming his own qualifications insufficient properly to describe them, he brought them to the attention of Hitchcock, and the interest of the latter never waned until his death in 1864. Hitchcock wrote paper after paper, publishing many of them in the Journal, again in his Final Report on the Geology of Massachusetts (1841), and later in quarto works, one in the Memoirs of the American Academy of Arts and Sciences and the two others under the authority of the Commonwealth, the Ichnology in 1858, and the Supplement in 1865, the last being a posthumous work edited by his son, Charles H. Hitchcock.

Hitchcock’s conception of the track-makers was more or less imperfect because of the fact that for a long time but a few fragmentary osseous remains were known, either directly or indirectly associated with the tracks, while on the other hand the bird-like character of many of the latter and the discovery of huge flightless birds elsewhere on the globe suggested a very close analogy if not a direct relationship. Hence “bird tracks” they were straightway called, a designation which it has been difficult to remove, even though in 1843 Owen called attention to the need of caution in assuming the existence of so highly organized birds at so early a period, especially when large reptiles were known which might readily form very similar tracks. The footprints are now believed to be very largely of dinosaurian origin, and dinosaurs whose feet corresponded in every detail with the footprints have actually come to light within the same geologic and geographic limitations. This of course refers to the bipedal, functionally three-toed tracks. Of the makers of certain of the obscurer of the quadrupedal trails we are as much in the dark to-day as were the first discoverers of a century ago, so far as demonstrable proof is concerned. We assume, however, that they were the tracks of amphibia and reptiles, beyond which we may not go with certainty.

Agassiz, writing in 1865 (Geological Sketches), says:

“To sum up my opinion respecting these footmarks, I believe that they were made by animals of a prophetic type, belonging to the class of reptiles, and exhibiting many synthetic characters. The more closely we study past creations, the more impressive and significant do the synthetic types, presenting features of the higher classes under the guise of the lower ones, become. They hold the promise of the future. As the opening overture of an opera contains all the musical elements to be therein developed, so this living prelude of the creative work comprises all the organic elements to be successively developed in the course of time.”

Of those whose work was contemporaneous with that of Hitchcock, but one, W. C. Redfield, wrote on Triassic phenomena, and he concerned himself mainly with the fossil fishes of that time, his first paper on this subject appearing in 1837 in the Journal (34, 201), and the last twenty years later.

Paleozoic Vertebrates.—Later the vertebrates of the Paleozoic began to attract attention, footprints from Pennsylvania being described by Isaac Lea, beginning in 1849, a notice of his first paper appearing in the Journal for that year (9, 124). Several papers followed on the reptile Clepsysaurus. Alfred King also wrote on the Carboniferous ichnites, his work slightly antedating that of Lea, but being less authoritative.

But by far the most illuminating of the mid-century writers on Paleozoic vertebrates was Sir William Dawson, a very large proportion of whose numerous papers relate to the Coal Measures of Nova Scotia and their contained plant and animal remains. In 1853 appeared Dawson’s first announcement, written in collaboration with Sir Charles Lyell, of the finding of the bones of vertebrates within the base of an upright fossil tree trunk at South Joggins. These bones were identified by Owen and Wyman as pertaining to a reptilian or amphibian to which the name Dendrerpeton acadianum was given. Following this were several papers published in the Quarterly Journal of the Geological Society, London, describing more vertebrates and associated terrestrial molluscs. In 1863 Dawson summarized his discoveries in the Journal (36, 430–432) under the title of “Air-breathers of the Coal Period,” a paper which was expanded and published under the same title in the Canadian Naturalist and Geologist for the same year. Dawson also printed in the same volume the first account of reptilian(?) footprints from the coal. Thus from time to time there emanated from his prolific pen the account of further discoveries, both in bones and footprints, his final synopsis of the air-breathing animals of the Paleozoic of Canada appearing in 1895. The only other group of vertebrates which claimed his attention were certain whales, on which he occasionally wrote.

Fishes.—The fossil fishes from the Devonian of Ohio found their first exponent in J. S. Newberry, appointed chief geologist of the second geological survey of Ohio, which was established in 1869. These fishes from the Devonian shales belonged for the greater part to the curious group of armored placoderms, the remains of which consist very largely of armor plates with little or no traces of internal skeleton. There was also found in association a shark, Cladoselache, of such marvelous preservation that from some of the Newberry specimens now in the American Museum of Natural History, New York, Bashford Dean has demonstrated the histology of muscle and visceral organs, in addition to the very complete skeletal remains.

Newberry’s work on these forms, begun in 1868, has been carried to further completion by Bashford Dean and his pupil L. Hussakof, as well as by C. R. Eastman. Newberry’s other paleontological work was with the Carboniferous fishes of Ohio, the Carboniferous and Triassic fishes of the region from Sante Fé to the Grand and Green rivers, Colorado, and on the fishes and plants of the Newark system of the Connecticut valley and New Jersey. He also discussed certain mastodon and mammoth remains, and those of the peccary of Ohio, Dicotyles.

Joseph Leidy (1823–1891).

We now come to a consideration of the work of Joseph Leidy, one of the three great pioneers in American vertebrate paleontology, for if we disregard the work of Hitchcock and others on the fossil footprints, few of the results thus far obtained were based upon the fruits of organized research. Leidy began his publication in 1847 and continued to issue papers and books from time to time until the year 1892, having published no fewer than 219 paleontological titles, and 553 all told. His earlier paleontological researches were exclusively on the Mammalia, which were then coming in from the newly discovered fossil localities of the West. The discovery of these forms, one of the most notable events in the history of our science, will bear re-telling.

The first announcement was made in 1847, when Hiram A. Prout of St. Louis published in the Journal (3, 248–250) the description of the maxillary bone of “Palæotherium” (= Titanotherium proutii)from near White River, Nebraska. This at once drew the attention of geologists and paleontologists to the Bad Lands, or Mauvaises Terres, which were to prove so highly productive of fossil forms. About the same time S. D. Culbertson of Chambersburg, Pennsylvania, submitted to the Academy of Natural Sciences at Philadelphia some fossils sent to him from Nebraska by Alexander Culbertson. These were afterward described by Leidy in the Proceedings of the Academy, together with the paleotheroid jaw, in addition to which three other collections which had been made were also placed at his disposal for study.

This aroused the interest of Doctor Spencer F. Baird of the Smithsonian Institution, who sent T. A. Culbertson to the Bad Lands to make further collections. The latter was successful in securing a valuable series of mammalian and chelonian remains. These, together with other specimens from the same locality, were sent to Leidy, for, as Baird remarked, Leidy, although only thirty years of age, was the only anatomist in the United States qualified to determine their nature. The outcome of Leidy’s study of this material was “The Ancient Fauna of Nebraska,” published in 1853, and constituting the most brilliant work which up to that time American paleontology had produced. Leidy’s determinations, which are in the main correct, are the more remarkable when it is realized that he had little recent osteological material for comparative study. The forms thus described by him were new to science, of a more generalized character than those now living, and yet their distinguished describer recognized, either at that time or a little later, their true relationship to the modern types. The extent of Leidy’s anatomical knowledge was almost Cuvierian, and Cuvier-like he established the fact of the presence of the rhinoceroses, then unheard of in the American fauna, from a few small fragments of molar teeth, an opinion shortly to be fully sustained through the finding of complete molars and the entire skull of the same individual animal.

Leidy next turned his attention to the huge edentates, which he studied exhaustively, publishing his results in the form of a memoir in 1855, two years after the appearance of the “Ancient Fauna.”

Extinct fishes of the Devonian of Illinois and Missouri and the Devonian and Carboniferous of Pennsylvania were made the subjects of his next researches, after which he described the peccaries of Ohio, and later, in a much larger and most important work, the Cretaceous reptiles of the United States (1865). Most of the fossils discussed in this last work are from the New Jersey Cretaceous marls and of them the most notable was the herbivorous dinosaur Hadrosaurus, the structure and habits of which, together with its affinities with the Old World iguanodons, Leidy described in detail. From Leidy’s descriptions and with his aid, Waterhouse Hawkins was enabled to restore a replica of the skeleton in a remarkably efficient way. This restoration for a long time graced the museum of the Philadelphia Academy of Natural Sciences and there was a plaster replica of it in the United States National Museum. These, together with plaster replicas of Iguanodon from the Royal College of Surgeons in London, gave to Americans their first real conceptions of members of this most remarkable group. The associated fossils from the New Jersey marls were chiefly crocodiles and turtles.

From 1853 to 1866 F. V. Hayden was carrying on a series of most energetic explorations in the West, especially in Nebraska and Dakota as then delimited, returning from each trip laden with fossils which were given to Leidy for determination. The results appeared in 1869 in Leidy’s Extinct Mammalian Fauna of Dakota and Nebraska, published as volume 7 of the Journal of the Philadelphia Academy. In this large volume no fewer than seventy genera and numerous species of forms, many of them new to science, were described, representing many of the principal mammalian orders; horses were, however, especially conspicuous. This last group led Leidy to the conclusion, afterward emphasized by Huxley, that North America was the home of the horse in geologic time, there being here a greater representation of different species than in any recent fauna of the world. Leidy’s interest in the horses, for the forwarding of which he made a large collection of recent material, extended over many years, as his first paper on the subject bears the date of 1847, the last that of 1890.

Next came the discovery of Eocene material from the vicinity of Fort Bridger, Wyoming, geologically older than the Nebraska and Dakota formations. This, together with specimens from the Green River and Sweetwater River deposits of Wyoming and the John Day River (Oligocene) of Oregon, was also referred to Leidy, and added yet more to the list of newly discovered species with which he had already become familiar in his earlier researches. The results of this study were published by the Hayden Survey in 1873, under the title “Contributions to the Extinct Vertebrate Fauna of the Western Territories.” This was the last of Leidy’s major works, but he continued up to the time of his death to report to the Academy concerning the various fossil forms that were submitted to him for identification. Of such reports the most important was one on the fossils of the phosphate beds of South Carolina, published in the Journal of the Academy in 1887.

As a paleontologist, Leidy ranks with Cope and Marsh high among those who enriched the American literature of the subject, but it must be remembered that this was but a single aspect of his many-sided scientific career, for he made many contributions of high order to botany, zoology, and general and comparative anatomy as well, nor did his knowledge and usefulness as an instructor of his fellow men keep within the limitations of these subjects.

Othniel Charles Marsh (1831–1899).

The sixth decade of the nineteenth century saw the beginning of the labors of several paleontologists who, like Leidy, were destined to raise the science of fossil vertebrates in America to the level of attainment of the Old World. They were, among others, Othniel Charles Marsh and Edward Drinker Cope. Of these the names of Marsh and Cope are linked together by the brilliance of their attainments, their contemporaneity, and the rivalry which the similarity of their pursuits unfortunately engendered. Marsh produced his first paleontological paper in 1862 (33, 278), Cope in 1864, but the latter died first, so that his life of research was shorter.

To Professor Marsh should be given credit for the first organized expedition designed exclusively for the collection of vertebrate remains, the results of which contain so much material that it has not yet entirely seen the light of scientific exposition. Marsh’s first trip to the West was in 1868, the first formal expedition being organized two years later. These expeditions, of which there were four, were privately financed except for the material and military escort furnished by the United States Government, and consisted of a personnel drawn entirely from the graduate or undergraduate body of Yale University. These parties explored Kansas, Nebraska, Wyoming, Utah, and Oregon, and returned laden with material from the Cretaceous and Tertiary formations of the West. Some of this is of necessity somewhat fragmentary, but type after type was secured which, with his exhaustive knowledge of comparative anatomy, enabled Marsh to announce discovery after discovery of species, genera, families, and even orders of mammals, birds, and reptiles which were unknown to science. The year 1873 saw the last of the student expeditions, and thereafter until the close of his life the work of collecting was done under Marsh’s supervision, but by paid explorers, many of whom had been his scouts and guides in the formal expeditions or had been especially trained by him in the East. In 1882, after fourteen years of the experience thus gained, Marsh was appointed vertebrate paleontologist to the United States Geological Survey, which relieved him in part of the personal expense connected with the collecting, although up to within a short time of his death his own fortune was very largely spent in enlarging his collections. After his connection with the Survey was established, Marsh had two main purposes in view in making the collections: (1) to determine the geological horizon of each locality where a large series of vertebrate fossils was found, and (2) to secure from these localities large collections of the more important forms sufficiently extensive to reveal, if possible, the life histories of each. Marsh believed that the material thus secured would serve as key or diagnostic fossils to all horizons of our western geology above the Paleozoic, a belief in which he was in advance of his time, for few of his contemporaries appreciated the value of vertebrates as horizon markers. The result of the fulfilment of his second purpose saw the accumulation of huge collections from all horizons above the Triassic and some Paleozoic and Triassic as well. These contained some very remarkable series, each of which Marsh hoped to make the basis of an elaborate monograph to be published under the auspices of the Survey. One can visualize the scope of his ambitions by the fact that no fewer than twenty-seven projected quarto volumes, to contain at least 850 lithographic plates, were listed by him in 1877. These covered, among other groups, the toothed birds (Odontornithes), Dinocerata, horses, brontotheres, pterodactyls, mosasaurs and plesiosaurs, monkeys, carnivores, perissodactyls and artiodactyls, crocodiles, lizards, dinosaurs, various birds, proboscideans, edentates and marsupials, brain evolution, and the Connecticut Valley footprints. Much was done towards the preparation of these memoirs, as evidenced by the long list of preliminary papers, admirably illustrated by woodcuts which were to form the text figures of the memoirs, which appeared with great regularity in the pages of the Journal for a period of thirty years. Of the actual memoirs, however, but two had been published at the time of Marsh’s death in 1899—the Odontornithes in 1880 and the Dinocerata in 1884. One must not overlook, however, the epoch-making Dinosaurs of North America, which was published by the Survey in 1896, although it was not in the form nor had it the scope of the proposed monographs. This was not due to lack of application, for Professor Marsh was an indefatigable worker, but rather to the fact that the program was of such magnitude as to necessitate a patriarchal life span for its consummation. As it is, Professor Marsh’s fame rests first upon his ability and intrepidity as a collector, ready himself to brave the very certain hardships and dangers which beset the field paleontologist in the pioneer days, and also by his judgment and command of men to secure the very adequate services of others and so to direct their endeavors that the results were of the highest value. The material witness to Marsh’s skill as a collector lies in the collections of the Peabody Museum at Yale and in the Marsh collection at the United States National Museum, the latter secured through the funds of the United States Geological Survey. Together they constitute what is possibly the greatest collection of fossil vertebrates in America, if not in the world; individually, they are second only to that of the American Museum in New York City, the result of the combined labors of Osborn and Cope and their very able corps of assistants.

As a scientist Marsh possessed in large measure that wide knowledge of comparative anatomy so necessary to the vertebrate paleontologist, and as a consequence was not only able to recognize affinities and classify unerringly, but also to recognize the salient diagnostic features of the form before him and in few words so to describe them as to render the recognition of the species by another worker relatively easy. The publication of hundreds of these specific diagnoses in the Journal constitutes a very large and valuable part of that periodical’s contribution to the advancement of our science. Marsh’s method of indicating forms by so brief a statement leaves much to be done, however, in the way of further description of his types, which in many instances were but partially prepared.

Yet another important service which Marsh rendered to science was the restoration of the creatures as a whole, made with the most painstaking care and precision through assembling the drawings of the individual bones. These restorations have become classic, embracing as they did a score or more of forms, of beast, bird, and reptile. They also were published first in the Journal, although they have subsequently been reproduced in text-books and other works the world over. Part of Marsh’s popular reputation, at least, which was second to that of no other American in his line, was due to his skill in attaining publicity, for his papers, of whatever extent, were carefully and methodically sent to correspondents in the uttermost parts of the earth, and thus the Marsh collection has reflected the fame of its maker.

Edward Drinker Cope (1840–1897).

The third great name in American vertebrate paleontology, that of Edward Drinker Cope, stands out in sharp contrast with the other two, although in the range of his interests he was probably more nearly comparable with Leidy than with Marsh. The beginning of Cope’s scientific labors dates from 1859, the year made famous in the annals of science by the appearance of Darwin’s Origin of Species. It is not surprising, therefore, that matters evolutional should have interested him to the very end of his career. Cope was not merely a paleontologist, but was interested in recent forms, especially the three lower classes of vertebrates, to such an extent that his work therewith is highly authoritative and in some respects epoch-making. Thirty-eight years of almost continual toil were his, and the mere mass of his literary productions is prodigious, especially when one realizes that, unlike those of a writer of fiction, they were based on painstaking research and philosophical thought. The greater part of Cope’s life was spent in or near Philadelphia except for his western explorations, and he is best known as professor of geology and paleontology in the University of Pennsylvania, although he served other institutions as well.

Cope’s early work was among the amphibia and reptiles, his first paleontological paper, the description of Amphibamus grandiceps, appearing in 1865. This year he also began his studies of the mammals, especially the Cetacea, both living and extinct, from the Atlantic seaboard. The next year saw the beginning of his work on the material from the Cretaceous marls of New Jersey, describing therefrom one of the first carnivorous dinosaurs, Lælaps, to be discovered in America. In 1868 Cope began to describe the vertebrates from the Kansas chalk and three years later made his first exploration of these beds. This led to his connection with the United States Geological Survey of the Territories under Hayden, and to continued exploration of Wyoming and Colorado in 1872 and 1873. The material thus gained, consisting of fishes, mosasaurs, dinosaurs, and other reptiles, was described in the Transactions of the American Philosophical Society as well as in the Survey Bulletins. In 1875 these results were summarized in a large quarto volume entitled “Vertebrata of the Cretaceous formations of the West.” Subsequent summers were spent in further exploration of the Bridger, Washakie, and Wasatch formations of Wyoming, the Puerco and Torrejon of New Mexico, and the Judith River of Montana. The material gathered in New Mexico proved particularly valuable, and led to the publication in 1877 of another notable volume entitled “Report upon the Extinct Vertebrata obtained in New Mexico by Parties of the Expedition of 1874.”

Material was now accumulating so fast as to necessitate the concentration of Cope’s own time on research, so that, while he continued to make brief journeys to the West, the real work of exploration was delegated to Charles H. Sternberg and J. L. Wortman, both of whom became subsequently very well known, the former as a collector whose active service has not yet ceased, the latter as an explorer and later an investigator of extremely high promise.

As early as 1865, Cope began no fewer than five separate lines of research which he pursued concurrently for the remainder of his career. On the fishes, he became a high authority in the larger classification, owing to his researches into their phylogeny, for which a knowledge of extinct forms is imperative. On amphibia, he wrote more voluminously than any other naturalist, discussing not only the morphology but the paleontology and taxonomy as well. In this connection must be mentioned not only Cope’s exploration and collections in the Permian of Ohio and Illinois, but especially the remains from the Texas Permian, first received in 1877, upon which some of his most brilliant results were based; these of course included reptilian as well as amphibian material. His third line of research, the Reptilia, is in part included in the foregoing, but also embraced the reptiles of the Bridger and other Tertiary deposits, those of the Kansas Cretaceous, and the Cretaceous dinosaurs.

Up to 1868 Leidy alone was engaged in research in the West, but that year saw the simultaneous entrance of Marsh and Cope into this new field of research, and their exploration and descriptions of similar regions and forms soon led to a rivalry which in turn developed into a most unfortunate series of controversies, mainly over the subject of priority. This resulted in a permanent rupture of friendship and the division of American workers into two opposing camps to the detriment of the progress of our science. This breach has now been happily healed, and for a number of years the degree of mutual good will and aid on the part of our workers has been of the highest sort.

The extent of the western fossil area, and particularly the explorations of three of Cope’s aids, Wortman in the Big Horn and Wasatch basins, Baldwin in the Puerco of New Mexico, and Cummins in the Permian of Texas, gave him so fruitful a field of endeavor that the occasion for jealous rivalry was largely removed. The most manifest result of Cope’s western work was the publication in 1883 of his Vertebrata of the Tertiary Formations of the West, which formed volume 3 of the quarto publications of the Hayden Survey. This huge book contains more than 1000 pages and 80 plates and has been facetiously called “Cope’s Bible.”

Cope’s philosophical contributions, which covered the domains of evolution, psychology, ethics, and metaphysics, began in 1868 with his paper on The Origin of Genera. In evolution he was a follower of Lamarck, and as such, with Hyatt, Ryder, and Packard, was one of the founders of the so-called Neo-Lamarckian School in America. Cope’s principal contribution, set forth in his Factors of Organic Evolution, is the idea of kinetogenesis or mechanical genesis, the principle that all structures are the direct outcome of the stresses and strains to which the organism is subjected. Weismann’s forcible attack on the transmission theory did not shake Cope’s faith in these doctrines, for he claimed that the paleontological evidence for the inheritance of such characters as are apparently the result of individual modification was too strong to be refuted. Cope was more like Lamarck than any other naturalist in his mental make-up as well as his ideas. He was also, like Haeckel, given to working out the phylogeny of whatever type lay before him, and in many instances arrived marvellously near the truth as we now see it.

Associated for a while with A. S. Packard, Cope soon became chief editor and proprietor of the American Naturalist, which was for many years his main means of publication and thus served our science in a way comparable to the Journal. As Osborn says by way of summation:

“Cope is not to be thought of merely as a specialist in Paleontology. After Huxley he was the last representative of the old broad-gauge school of anatomists and is only to be compared with members of that school. His life work bears marks of great genius, of solid and accurate observation, and at times of inaccuracy due to bad logic or haste and overpressure of work.... As a comparative anatomist he ranks both in the range and effectiveness of his knowledge and his ideas with Cuvier and Owen.... As a natural philosopher, while far less logical than Huxley, he was more creative and constructive, his metaphysics ending in theism rather than agnosticism.”

1870–1880.

The seventh decade was productive of comparatively few great names in the history of our science, but two, J. A. Ryder and Samuel W. Williston, being notable contributors. The former produced but few papers and those between 1877 and 1892, yet they were of note and such was their influence that he is named with Hyatt, Packard, and Cope as one of the founders of the Neo-Lamarckian School of evolutionists in America. Ryder was a particular friend and a colleague of Cope, as they were both concerned with the back-boned animals, while the other two were invertebratists. Ryder wrote on mechanical genesis of tooth forms and on scales of fishes, also on the morphology and evolution of the tails of fishes, cetaceans, and sirenians, and of the other fins of aquatic types. He did, on the other hand, practically no systematic or descriptive work.

Williston, on the contrary, has had a long and varied career as an investigator and as an educator. Trained at Yale, he prepared for medicine, and much of his teaching has been of human anatomy, both at Yale and at the University of Kansas where he served for a number of years as dean of the Medical School. He is also a student of flies, and as such not only the foremost but indeed almost the only dipterologist in the United States. But it is with his work as a vertebrate paleontologist that we are chiefly concerned, and here again he stands among the foremost. His initial work and training in this department of science were with Marsh, for whom he spent many months in field work, collecting largely in the Niobrara Cretaceous of Kansas. He did, however, no research while with Marsh, owing to the latter’s disinclination to foster such work on the part of his associates. Williston began his publications in 1878 and has continued them until the present, working mainly with Cretaceous mosasaurs, plesiosaurs, and pterodactyls. Of late, since his transference to the University of Chicago, where as professor of paleontology and director of the Walker Museum he has served since 1902, his interest has lain mainly among the Paleozoic reptiles and amphibia. Williston’s more notable works are American Permian Vertebrates and Water Reptiles of the Past and Present, wherein he sets forth his views of the phylogenesis and taxonomy of the reptilian class. He is at present at work on the evolution of the reptiles, a volume which is eagerly awaited by his colleagues. It is in morphology that Williston’s greatest strength lies and some of his most effective work on the mosasaurs has appeared in the Journal.

1880–1900.

The next decade, that of 1880–1890, saw a number of notable additions to the workers in vertebrate paleontology: Henry F. Osborn, W. B. Scott, R. W. Shufeldt, J. L. Wortman, George Baur, F. A. Lucas, and F. W. True. Shufeldt is our highest authority on the osteology of birds, both recent and extinct, having recently described all of the extinct forms contained in the Marsh collection; True wrote of Cetacea; Lucas of marine and Pleistocene mammals and birds, and has also written popular books on prehistoric life. Lucas’s greatest service, however, lies in the museums, where he has manifested a genius second to none in the installation of mute evidences of living and past organisms. Wortman was for a time associated with Cope, later with Osborn in the American Museum, again at the Carnegie Museum at Pittsburgh, and finally at Yale in research on the Bridger Eocene portion of the Marsh collection. His work has been chiefly the perfection of field methods in vertebrate paleontology, and as a special investigator of Tertiary Mammalia, treating the latter largely from the morphologic and taxonomic standpoints. Wortman’s Yale results on the carnivores and primates of the Eocene, as yet unfinished, were published in the Journal in 1901–1904.

William B. Scott is a graduate of Princeton, and has spent thirty-four years in her service as Blair Professor of Geology and Paleontology. His first publication, in 1878, issued in conjunction with Osborn and Speir, described material collected by them in the Eocene formations of the West, and since that time Scott’s research has been entirely with the mammals, on which he is one of our highest authorities. His most notable works have been a History of Land Mammals of the Western Hemisphere, 1913, and the results of the Patagonian expeditions by Hatcher, which are published in a quarto series in conjunction with W. J. Sinclair, although they are the authors of separate volumes, Scott’s work being mainly on the carnivores and edentates of the Santa Cruz formation. It is as a systematist in research and as an educator that Scott has attained his highest usefulness.

The man who, next to the three pioneers, has attained the highest reputation in vertebrate paleontologic research, is Henry Fairfield Osborn. Graduate of Princeton in the same class that produced Scott, Osborn served for a time as professor of comparative anatomy in that institution, and in 1891 was called to New York to organize the department of zoology in Columbia University and that of vertebrate paleontology in the American Museum of Natural History. He had, early in his career, gone west in company with Professor Scott, and had collected material from the Eocene formation of Wyoming, upon which they based their first joint paper in 1878, Osborn’s first independent production, a memoir on two genera of Dinocerata, appearing in 1881. A number of papers followed, on the Mesozoic Mammalia, on Cope’s tritubercular theory, and on certain apparent evidences for the transmission of acquired characters. It was, however, with his acceptance of the New York responsibilities, especially at the American Museum, that Osborn’s most significant work began. Aided first by Wortman and Earle, later by W. D. Matthew and others, he has built up the greatest and most complete collection of fossil vertebrates extant; its value, however, was largely enhanced through the purchase of the private collection of Professor Cope, which of course included a large number of types. The American Museum collection thus contains not only a vast series of representative specimens from every class and order of vertebrates, secured by purchase or expedition from nearly all the great localities of the world, but an exhibition series of skulls and partial and entire skeletons and restorations which no other institution can hope to equal. Based upon this wonderful material is a large amount of research, filling many volumes, published for the greater part in the bulletin and memoirs of the Museum. This research is not only the product of the staff, including Walter Granger, Barnum Brown, W. D. Matthew, and W. K. Gregory, but also of a number of other American and some foreign paleontologists as well.

Professor Osborn’s own work has been voluminous, his bibliography from 1877 to 1916 containing no fewer than 441 titles, ranging over the fields of paleontology,—which of course includes the greater number—geology, correlation and paleogeography, evolutionary principles exemplified in the Mammalia, man, neurology and embryology, biographies, and the theory of education.

In paleontology, Osborn’s researches have been largely with the Reptilia and Mammalia, partly morphological, but also taxonomic and evolutional. Faunistic studies have also been made of the mammals. Of his published volumes the most important are, first, the Age of Mammals (1910), in which he treats not of evolutionary series of phylogenies, but of faunas and their origin, migrations, and extinctions, and of the correlation of Old and New World Tertiary deposits and their contents. Men of the Old Stone Age (1916) is an exhaustive treatise and is the first full and authoritative American presentation of what has been discovered up to the present time throughout the world in regard to human prehistory. In his latest volume, The Origin and Evolution of Life (1917), Osborn presents a new energy conception of evolution and heredity as against the prevailing matter and form conceptions. In this volume there is summed up the whole story of the origin and evolution of life on earth up to the appearance of man. This last book is novel in its conceptions, but it is too early as yet to judge of the acceptance of Osborn’s theses by his fellow workers in science.

Since the death of Professor Marsh, Osborn has served as vertebrate paleontologist to the United States Geological Survey, and has in charge the carrying through to completion of the many monographs proposed by his distinguished predecessor. One of these, that on the horned dinosaurs, has been completed by Hatcher and Lull (1907), another on the stegosaurian dinosaurs has been carried forward by C. W. Gilmore of the United States National Museum, while under Osborn’s own hand are the memoirs on the titanotheres (aided by W. K. Gregory), the horses, and the sauropod dinosaurs. Of these, the first, when it shall have been completed, promises to be the most monumental and exhaustive study of a group of fossil organisms ever undertaken.

As a leader in science, a teacher and administrator, Professor Osborn’s rank is high among the leading vertebratists. He is remarkably successful in his choice of assistants and in stimulating them in their productiveness so that their combined results form a very considerable share of the later literature in America.

The ninth decade ushered in the work of a valuable group of students, of whom John Bell Hatcher should be mentioned in particular, as his work is done. Graduate of Yale in 1884, he spent a number of years assisting his teacher, Professor Marsh, mainly in the field, collecting during that time, either for Yale or for the United States Geological Survey, an enormous amount of very fine material, especially from the West, although he also collected in the older Tertiary and Potomac beds near Washington. In the West he secured no fewer than 105 titanothere skulls, explored the Tertiary, Judith River, and Lance formations, collected and in fact virtually discovered the remains of the Cretaceous mammals and of the horned dinosaurs which he was later privileged to describe. He then (1893) went to Princeton, which he served for seven years, his principal work being explorations in Patagonia for the E. and M. Museum, one direct result of which was the publication of a large quarto on the narrative of the expedition and the geography and ethnography of the region. Going to the Carnegie Museum in Pittsburgh in 1900, Hatcher carried forward the work of exploration and collecting begun for that institution by Wortman, and as a partial result prepared many papers, the principal ones being memoirs on the dinosaurs Haplocanthosaurus and Diplodocus. In 1903, with T. W. Stanton of the United States Geological Survey, Hatcher explored the Judith River beds and together they settled the vexatious problem of their age, the published results appearing in 1905, after Hatcher’s death. His last piece of research, begun in 1902 and continued until his death in 1904, was an elaborate monograph on the Ceratopsia, one of the many projected by Marsh. Of this memoir Hatcher had completed some 150 printed quarto pages, giving a rare insight into the anatomy of these strange forms. The final chapters, however, which were based very largely upon Hatcher’s own opinions, had to be prepared by another hand.

Despite his early death, therefore, Hatcher rendered a very signal service to American paleontology—in exploration, stratigraphy, morphology, and systematic revision—and his activity in planning new fields of research, such, for instance, as the exploration of the Antarctic continent, gave promise of further high attainment, when his hand was arrested by death.

Summary.

It is not surprising that American vertebrate paleontology has arisen to so high a plane, when one considers the material at its disposal. Having a vast and virgin field for exploration, a sufficient number of collectors, some of whom have devoted much of their lives to the work, and a refinement of technique that permitted the preservation of the fragmental and ill conserved as well as the finer specimens, the results could hardly have been otherwise. Thus it has been possible to secure material almost unique throughout the world for extent, for completeness, and for variety. To this must be added a certain American daring in the matter of the restoration of missing portions, both of the individual bones and of the skeleton as a whole, such as European conservatism will not as a rule permit. This work has for the most part been done after the most painstaking comparison and research and is highly justified in the accuracy of the results, which render the fabric of the skeleton much more intelligible, both to the scientist and to the layman. Material once secured and prepared is then mounted, and here again American ingenuity has accomplished some remarkable results. Some of the specimens thus mounted are so small and delicate as to require holding devices comparable to those for the display of jewels; yet others—huge dinosaurs the bones of which are enormously heavy, but so brittle that they will not bear even the weight of a process unsupported—require a carefully designed and skilfully worked out series of supports of steel or iron which must be perfectly secure and at the same time as inconspicuous as possible. And of late the lifelike pose of the individual skeleton has been augmented by the preparation of groups of several animals which collectively exhibit sex, size, or other individual variations and the full mechanics of the skeleton under the varying poses assumed by the creature during life.

The work of further restoration has been rendered possible through comparative anatomical study, enabling us to essay restorations in entirety by means of models and drawings, clothing the bones with sinews and with flesh and the flesh with skin and hair, if such the creature bore; while the laws of faunal coloration have permitted the coloring of the restoration in a way which if not the actual hue of life is a very reasonable possibility.

Thus the American paleontologists have blazed a trail which has been followed to good effect by certain of their Old World colleagues.

With such means and methods and such material available, it is again not surprising that American paleontology has furnished more and more of the evidences of evolution, and disclosed to the eyes of scientists animal relationships which were undreamed of by the systematist whose research dealt only with the existing. It has also explained some vexatious problems of animal distribution and of extinction, and has connected up cause and effect in the great evolutionary movements which are recorded.

The results of systematic research have added hosts of new genera and species and of families, but of orders there are relatively few. Nevertheless a number, especially among reptiles and mammals, have come to light as the fruits of American discovery. But aside from the dry cataloguing of such groups, the American systematists have worked out some very remarkable phylogenies and have thus clarified our vision of animal relationships in a way which the recent zoologist could never have done. In this connection, the Permian vertebrates, which have been collected and studied with amazing success, principally by Williston and Case, should be mentioned, although the work is yet incomplete. Some of these forms are amphibian, others reptilian, yet others of such character as to link the two classes as transitional forms. Of the Mesozoic reptiles, a very remarkable assemblage has come to light, in a degree of perfection unknown elsewhere. These are dinosaurs, of which several phyla are now known; carnivores both great and small, some of the latter being actually toothless; Sauropoda, whose perfection and dimensions are incomparable except for those found in East Africa; and predentates, armored, unarmored, and horned, the last exclusively American. The unarmored trachodonts are now known in their entirety, for not only has our West produced articulated skeletons but mummified carcasses whose skin and other portions of their soft anatomy are represented, and which are thus far without a parallel elsewhere in the world. Other reptilian groups are well known, notably the Triassic ichthyosaurs, and the mosasaurs and plesiosaurs of the Kansas chalk. The last formation has also produced toothed birds, Hesperornis and Ichthyornis, which again are absolutely unique.

But it is in the mammalian class that the phylogenies become so highly complete and of such great importance as evolutionary evidences, for nowhere else than in our own West have such series been found as the Dinocerata and creodonts among archaic forms, the primitive primates from the Eocene, the carnivores such as the dogs and cats and mustellids, but especially the hoofed orders such as the horses. Of these hoofed orders, the classic American series of horses is complete, that of the camels probably no less so, while much is known of the deer and oreodonts, the last showing several parallel phyla, and of the proboscideans, which while having their pristine home in the Old World nevertheless soon sought the new where their remains are found from the Miocene until their final and apparently very recent extinction. These creatures show increase of bulk, perfection of feet and teeth, development of various weapons, horns and antlers, which may be studied in their relationship with the other organs to make the evolving whole, or their evolution may be traced as individual structures which have their rise, culmination, and sometimes their senile atrophy in a way comparable to that of the representatives of the order as a whole. Thus, for example, Osborn has traced the evolution of the molar teeth, and Cope of the feet, while Marsh has shown that brain development runs a similar course and that its degree of perfection within a group is a potent factor for survival.

As a student of evolution, the paleontologist sees things in a very different light from the zoologist. The latter is concerned largely with matters of detail—with the inheritance of color or of the minor and more superficial characteristics of animals—and the period of observation of such phenomena is of necessity brief because of the mortality of the observer. Whereas the paleontologist has a perspective which the other lacks, since for him time means little in the terms of his own life, and he can look into the past and see the great and fundamental changes which evolution has wrought, the rise of phyla, of classes, of orders, and he alone can see the orderliness of the process and sense the majesty of the laws which govern it.

Influence of the American Journal of Science.

The influence of the American Journal of Science as a medium for the dissemination of the results of vertebrate research has been in evidence throughout this discussion, but it were well, perhaps, to emphasize that service more fully. The Journal was, as we have seen, the chief outlet for Professor Marsh’s research, for there were published in it during his lifetime no fewer than 175 papers descriptive of the forms which he studied, as well as a great part of the material in the published monographs. As Marsh left very few manuscript notes, the importance of these frequent publications in thus setting forth much that he thought and learned concerning the material is very great indeed. The combined titles of all other authors in the Journal in this line of research for the century of its life fall far short of the number produced by Marsh alone, as they include 136 all told, but the range of subjects is highly representative of the entire field of vertebrate research. It should be borne in mind, moreover, that Leidy, Cope, and Osborn each had another medium of publication, which of course is true of other workers in the great museums such as the American, National, and Carnegie, all of which issue bulletins and quarto publications for the purpose of disseminating the work of their staff. Many of the earlier announcements of the discovery of vertebrate relics appeared in the Journal, as did practically all the literature of the science of fossil footprints (ichnology), except of course the larger quartos of Hitchcock and Deane. Of the footprint papers by Hitchcock, Deane, and others, there were no fewer than thirty-two, with a number of additional communications on attendant phenomena bones and plants.

Up to 1847, except for a few foreign announcements, the Journal published almost exclusively on eastern American paleontology, the only exception being a notice of bones from Oregon by Perkins in 1842. In 1847 came the announcement of a western “Palæothere” by Prout, which marked the beginning of the researches of Leidy and others in the Bad Lands of the great Nebraska plains. The Journal thenceforth published paper after paper on forms from all over North America, and on all aspects of our science: discovery, systematic description, faunal relationships, evolutionary evidences—thus showing that breadth and catholicity which has made it so great a power in the advancement of science.

VII
THE RISE OF PETROLOGY AS A SCIENCE

By LOUIS V. PIRSSON

This chapter is intended to present a brief sketch of the progress of the science of petrology from its early beginnings down to the present time. The field to be covered is so large that this can be done only in broadest outline, and it has therefore been restricted chiefly to what has been accomplished in America. Although the period covered by the life of the Journal extends backward for a century it is, however, practically only within the last fifty years that the rocks of the earth’s crust have been made the subject of such systematic investigation by minute and delicately accurate methods of research as to give rise to a distinct branch of geologic science. It is not intended of course to affirm by this statement that the broader features of the rocks, especially those which may be observed in the field and which concern their relations as geologic masses, had not been made the object of inquiry before this time, since this is the very foundation of geology itself. Moreover, a certain amount of investigation of rocks, as to the minerals of which they were composed, the significance of their textures, and their chemical composition, had been carried out, concomitant with the growth from early times of geology and mineralogy. Thus, in 1815, Cordier by a process of washing separated the components of a basalt and by chemical tests determined the constituent minerals. At the time the Journal was founded, and for many years following, the genesis of rocks, especially of igneous rocks, was a subject of inquiry and of prolonged discussion. The aid of the rapidly growing science of chemistry was invoked by the geologists and analyses of rocks were made in the attempt to throw light on important questions. It is remarkable, also, how keen were the observations that the geologists of those days made upon the rocks, as to their component minerals and structures, aided only by the pocket lens. Many ideas were put forward, the essentials of which have persisted to the present day and have become interwoven into the science, whereas others gave rise to contentions which have not yet been settled to the satisfaction of all. At times in these earlier days the microscope was called into use to help in solving questions regarding the finer grained rocks, but this employment, as Zirkel has shown, was merely incidental, and no definite technique or purpose for the instrument was established.

On the other hand, the fact that up to the middle of the last century a large store of information relating to the occurrence of rocks, and to the mineral composition of those of coarser grain, and somewhat in respect to their structure, had been accumulated, caused attempts in one way or another to find means of coördinating these data and to produce classifications, such as those of Von Cotta and Cordier. The history of these attempts at classification, before the revelations made by the use of the microscope had become general, has been admirably reviewed by Whitman Cross[^[107]] and need not be further enlarged upon here.

That a considerable amount of work was done along chemical lines also is testified to by the publication of Roth’s Tabellen in 1861, in which all published analyses of rocks up to that date were collected. What was accomplished during this period was done chiefly on the continent of Europe, and little attention had been paid to the subject of rocks either in America or in Great Britain—even so late as 1870 Geikie remarks, as referred to by Cross,[^[108]] that there was no good English treatise on petrography, or the classification and description of rocks. In this country still less had been accomplished, interest being almost wholly confined to the vigorous and growing sciences of geology and mineralogy. This was natural, for mineralogy is the chief buttress on which the structure of petrology rests and must naturally develop first, especially in a relatively new and unexplored region, whose mineral resources first attract attention. The geologists in carrying out their studies also observed the rocks as they saw them in the field and made incidental reference to them, but investigations of the rocks themselves was very little attempted. An inspection of the first two series of the Journal shows relatively little of importance in petrology published in this country; a few analyses of rocks, occasional mention of mineral composition, of weathering properties, and notices of methods of classification proposed by French and German geologists nearly exhaust the list.

Introduction of the Microscope.

The beginnings of a particular branch of science are generally obscure and rooted so imperceptibly in the foundations on which it rests that it is difficult to point to any particular place in its development and say that this is the start. There are exceptions of course, like the remarkable work of Willard Gibbs in physical chemistry, and it may chance that the happy inspiration of a single worker may give such direction to methods of investigation as to open the gates into a whole new realm of research, and to thus create a separate scientific field, as happened in Radiochemistry.

This is what occurred in petrology when Sorby in England, in 1858,[^[109]] pointed out the value of the microscope as an instrument of research in geologic investigations, and demonstrated that its employment in the study of thin sections of rocks would yield information of the highest value. Others beside Sorby had made use of the microscope, as pointed out by Zirkel,[^[110]] but, as he indicates, no one before him had recognized its value. During the next ten years or so, however, its recognition was very slow and the papers published by Sorby himself were mainly concerned in settling very special matters.

As Williams[^[111]] has suggested, the greatest service of Sorby was, perhaps, his instructing Zirkel in his ideas and methods, for the latter threw himself whole-heartedly into the study of rocks by the aid of the microscope and his discoveries stimulated other workers in this field in Germany, his native country, until the dawning science of petrology began to assume form. A further step forward was taken in 1873 in the appearance of the text-books of Zirkel[^[112]] and Rosenbusch[^[113]] which collated the knowledge which had been gained and furnished the investigator more precise methods of work. It is difficult for the student of to-day to realize how much had been learned in the interval and, for that matter, how much has been gained since 1873, without an inspection of these now obsolete texts. In 1863, Zirkel, who was then at the beginning of his work, said in his first paper presented to the Vienna Academy of Sciences[^[114]] that if he confined himself chiefly to the structure of the rocks investigated and of their component minerals, and stated little as to what these minerals were, the reason for that was because “although the microscope serves splendidly for the investigation of the former relations, it promises very little help for the latter. Labradorite, oligoclase and orthoclase, augite and hornblende, minerals whose recognition offers the most important problems in petrography, in most cases cannot be distinguished from one another under the microscope.” How little could Zirkel have foreseen, at this time, less than forty years later, that not only could labradorite be accurately determined in a rock-section, but that in a few minutes by the making of two or three measurements on a properly selected section, its chemical composition and the crystallographic orientation of the section itself could be determined!

The Thin Section.

Before going further we may pause here a moment to consider the origin and development of the thin section, without which no progress could have been made in this field of research. When we reflect upon the matter, it seems a marvelous thing indeed that the densest, blackest rock can be made to yield a section of the ¹⁄₁₀₀₀ of an inch in thickness, so thin and transparent that fine printing can be easily read through it, and transmitting light so clearly that the most high-powered objectives of the microscope can be used to discern and study the minutest structures it presents with the same capacity that they can be employed upon sections of organic material prepared by the microtome. This is no small achievement.

The first thin sections appear to have been prepared in 1828 by William Nicol of Edinburgh, to whom we owe the prism which carries his name. He undertook the making of sections from fossil wood for the purpose of studying its structure. The method he developed was in principle the same as that employed to-day, where machinery is not used; that is, he ground a flat smooth surface upon one side of a chip of his petrified wood, then cemented this to a bit of glass plate with Canada balsam, and ground down the other side until the section was sufficiently thin. This method was used by others for the study of fossil woods, coal, etc., but it was not applied to rocks until 1850, when Sorby used it for investigating a calcareous grit. Oschatz, in Germany, also about this time independently discovered the same method. A further advance was made in melting the cement, floating off the slice, and transferring it to a suitable object-glass with cover, a process still employed by many; though most operators now cement the first prepared surface of the rock chip directly to the object-glass, and mount the section without transferring it.

Next came the use of machinery to save labor in grinding, and another step was made in the introduction of the saw, a circular disk of sheet iron whose edge was furnished with embedded diamond dust. This makes it possible to cut relatively thin slices with comparative rapidity, but the final grinding which requires experience and skill must still be done by hand. Carborundum has also largely replaced emery. The skill and technique of preparers has reached a point where sections of rocks of the desired thinness (0·001 inch), and four or five inches square have been exhibited.

The Era of Petrography.

In these earlier days of the science, as noted above, great difficulty was at first experienced in the recognition of the minerals as they were encountered in the study of rocks under the microscope. At that time the chemical composition and outward crystal form of minerals were relatively much better known than their physical and, especially, their optical properties and constants. Some beginnings in this had been made by Brewster, Nicol, and other physicists, and the mineralogists had commenced to study minerals from this viewpoint. Especially Des Cloiseaux had devoted himself to determining the optical properties of many minerals, and the writer, when a student in the laboratory of Rosenbusch in 1890, well recalls the tribute that he paid to the work of Des Cloiseaux for the aid which it had afforded him in his earlier researches in petrography.

The twenty years following the publication of the texts of Rosenbusch and Zirkel may be characterized as the era of microscopical petrography. A distinction is drawn here between the latter word and petrology, a distinction often overlooked, for petrography means literally the description of rocks, whereas petrology denotes the science of rocks. As time passed the broader and more fundamental features of rocks, especially of igneous and metamorphic rocks, in addition to their mineral constitution, were more studied and gained greater recognition, petrography gradually became a department of the larger field of petrology—the science of to-day.

The use of the microscope, as soon as the method became more generally understood, opened up so vast a field for investigation that at first the study and description of the rocks seemed of prime importance. This was natural, for hitherto the finer grained rocks had for the most part defied any adequate elucidation and here was a key which enabled one to read the cipher. A flood of literature upon the composition, structure, and other characters of rocks from all parts of the world began to appear in ever increasing volume. The demands of the petrographers for a greater and more accurate knowledge of the physical and optical constants of minerals stimulated this side of mineralogy, and increasing attention was given to investigations in this direction. No definite line between the two closely related sciences could be drawn, and a large part of the work published under the heading of petrography could perhaps be as well, or better, described under the title of micro-mineralogy. To some, in truth, the rocks presented themselves simply as aggregates of minerals, occurring in fine grains.

The work of the German petrographers attracted attention and drew students from all parts of the world to their laboratories, especially to those of Zirkel and Rosenbusch. The great opportunities, facilities, and freedom for work which the German universities had long offered to foreign students of science naturally encouraged this. In France a brilliant school of petrologists, under the able leadership of Michel-Lévy and Fouqué, had arisen whose work has been continued by Barrois, Lacroix and others, but the rigid structure of the French universities at that period did not permit of the offering of great inducements for the attendance of foreign students. The work of the French petrographers will be noticed in another connection.

In Great Britain, the home of Sorby, the new science progressed at first slowly, until it was taken up by Allport, Bonney, Judd, Rutley, and others. In 1885 the evidence of the advance that had been made and of the firm basis on which the new science was now placed appeared in Teall’s great work, “British Petrography,” which marked an epoch in that country in petrographic publication. This work was of importance also in another direction than that of descriptive petrography, in that it contains valuable suggestions for the application of the principles of modern physical chemistry in solving the problems of the origin of igneous rocks. In it, as in the publications of Lagorio, we see the passage of the petrographic into the petrologic phase of the science.

The earliest publication in America of the results of microscopic investigation of rocks that the writer has been able to find is by A. A. Julien and C. E. Wright, chiefly on greenstones and chloritic schists from the iron-bearing regions of upper Michigan.[^[115]] Naturally, it was of a brief and elementary character. In 1874 E. S. Dana read a paper before the American Association for the Advancement of Science on the result of his studies on the “Trap-rocks of the Connecticut valley,” an abstract of which was published in this Journal.[^[116]] Meanwhile Clarence King, in charge of the 40th Parallel survey, feeling the need of a systematic study of the crystalline rocks which had been encountered, and finding no one in this country prepared to undertake it, had induced Zirkel to give his attention to this task. The result of this labor appeared in 1876 in a fine volume[^[117]] which attracted great attention. In the same year appeared also petrographical papers by J. H. Caswell,[^[118]] E. S. Dana[^[119]] and G. W. Hawes.[^[120]] The latter devoted himself almost entirely to this field of research and may thus, perhaps, be termed the earliest of the petrographers in this country. His work, “The Mineralogy and Lithology of New Hampshire,” issued in 1878 as one of the reports of the State Survey under Prof. C. H. Hitchcock, was the first considerable memoir by an American. This was followed by various papers, one on the “Albany Granite and its contact phenomena,”[^[121]] being of especial interest as one of the earliest studies of a contact zone, and in the fullness of methods employed in attacking the problem forecasting the change to the petrology era.

During the ten years following, or from 1880 to 1890, the new science of petrography flourished and grew exceedingly. Many young geologists abroad devoted themselves to this field of research and the store of accumulated knowledge concerning rocks from all parts of the world, and their relations grew apace. The work of Teall has been noticed and among others might be mentioned the name of Brögger, whose first contribution[^[122]] in this field gave evidence that his publications would become classics in the science.

In America there appeared in this period a number of eager workers, trained in part in the laboratories of Rosenbusch and Zirkel, whose researches were destined to place the science on the secure footing in this country which it occupies to-day. Among the earlier of these may be mentioned Whitman Cross, R. D. Irving, J. P. Iddings, G. H. Williams, J. F. Kemp, J. S. Diller, B. K. Emerson, M. E. Wadsworth, G. P. Merrill, N. H. Winchell, and F. D. Adams in Canada. Others were added yearly to this group. As a result of their work a constantly growing volume of information about the rocks of America became available, and one has only to examine the files of the Journal and other periodicals and the listed publications of the National and State Surveys to appreciate this.

In the Journal, for example, we may refer to papers[^[123]] by Emerson on the Deerfield dike and its minerals, and on the occurrence of nephelite syenite at Beemersville, N. J.; to various interesting articles by Cross on lavas from Colorado and the pneumatolytic and other minerals associated with them; to important papers by Iddings on the rocks of the volcanoes of the Northwest, and those of the Great Basin, to primary quartz in basalt, and the origin of lithophysæ; to the results of researches by G. H. Williams on the rocks of the Cortlandt series, and on peridotite near Syracuse, N. Y.; to papers by Diller on the peridotites of Kentucky, and recent volcanic eruptions in California; to articles by R. D. Irving on the copper-bearing and other rocks of the Lake Superior region, and to Kemp on dikes and other eruptives in southern New York and northern New Jersey. Other publications would greatly extend this list.

The Petrologic Era.

As the chief facts regarding rocks, especially igneous rocks, as to their mineral and chemical composition, their structure and texture and the limits within which these are enclosed, became better known; and the relations, which these bear to the associations of rocks and their modes of occurrence, began to be perceived, the science assumed a broader aspect. The perception that rocks were no longer to be regarded merely as interesting assemblages of minerals, but as entities whose characters and associations had a meaning, increased. More and better rock analyses stimulated interest on the chemical side and this and the genesis of their minerals led to a consideration of the magmas and their functions in rock-making. The fact that the different kinds of rocks were not scattered indiscriminately, but that different regions exhibited certain groupings with common characters, was noticed. These features led to attempts to classify igneous rocks on different lines from those hitherto employed, and to account for their origin on broad principles. In other words, the descriptive science of petrography merged into the broader one of petrology. No exact time can be set which marks this passage, since the evolution was gradual. Yet for this country, in reviewing the literature, for which the successive issues of the “Bibliography of North American Geology” published by the U. S. Geological Survey has been of the greatest value; the writer has been struck by the fact that in the first volume containing the index of papers down to and including 1891, the articles on subjects of this nature are listed under the heading of petrography, whereas in the second volume (1892–1900) they are grouped under petrology and the former heading is omitted. A justification for this is found in examining the list of publications and noting their character. With some reason, therefore, the beginning of this period may be placed as in the early years of this decade. Furthermore, it was at this time that the great work of Zirkel[^[124]] began to appear, which sums up so completely the results of the petrographic era. Rosenbusch[^[125]] was formulating more definitely his views on the division of rocks into magmatic groups, as displayed by their associations in the field, and using this in classification; an idea which, appearing first in the second edition of his “Physiographie der massigen Gesteine,” finds fuller development in the third and last editions of this work. In this country Iddings[^[126]] published an important paper, in which the family relationships of igneous rocks and the derivation of diverse groups from a common magma by differentiation are clearly brought out. The fundamental problems underlying the genesis of igneous rocks had now been clearly recognized, and with this recognition the science passed into the petrologic phase. Brögger[^[127]] also had ascribed to the alkalic rocks of South Norway a common parentage and had pointed out their regional peculiarities.

From this time forward an attempt may be noted to find an analogy between rocks and the forms of organic life and to apply those principles of evolution and descent, which have proved so fruitful in the advancement of the biological sciences, to the genesis and classification of igneous rocks. This, perhaps, has on the whole been more apparent than real, in the constant borrowing of terms from those sciences to express certain features and relationships observed, or imagined, to obtain among rocks. Nevertheless, the perception of certain relations which we owe so largely to Rosenbusch and to Brögger[^[128]] has proved of undoubted value in furnishing a stimulus for the investigation of new regions, and in affording indications of what the petrologist should anticipate in his work.

Thus, the labors of the men previously mentioned, with those of Bayley, Bascom, Cushing, Daly, Lane, Lawson, Lindgren, Pirsson, J. F. Williams, Washington, and others, have thrown a flood of light upon the igneous rocks of this continent, and has made it possible to draw many broad generalizations concerning their origin and distribution. Thus, the differentiated laccoliths of Montana[^[129]] have been of service in affording clear examples of the process of local differentiation. Many papers published in the Journal during the last twenty years show this evolution and growth of petrological ideas. The contributions from American sources during this later period, and of which those in the Journal form a considerable fraction, have indeed been of great weight in shaping the development and future of the science.

By referring to the files of the Journal, it will be seen that they cover a continually widening range of subjects concerning rocks, and articles of theoretical interest are more and more in evidence, along with those of a purely descriptive character.[^[130]] Thus we find discussions by Becker on the physical constants of rocks, on fractional crystallization, and on differentiation; by Cross on classification; by Adams on the physical properties of rocks; by Daly on the methods of igneous intrusion; by Wright on schistosity; by Fenner on the crystallization of basaltic magma; by Bowen on differentiation by crystallization; by the writer on complementary rocks and on the origin of phenocrysts; by Smyth on the origin of alkalic rocks; by Murgoci on the genesis of riebeckite rocks; and by Barrell on contact-metamorphism. These may serve as examples, selected almost at random, from the files of the Journal, and we find with them articles descriptive of the petrology of many particular regions, which often contain also matter of general interest and importance, such as papers by Lindgren on the granodiorite and related rocks of the Sierra Nevada; by Ransome on latite; by Cross on the Leucite Hills; by Hague on the lavas of the Yellowstone Park; by Pogue on ancient volcanic rocks from North Carolina; by Warren on peridotites from Cumberland, R. I.; on sandstone from Texas by Goldman; and on the petrology of various localities in central New Hampshire by Washington and the writer. Such a list could of course be much extended and other papers of importance be cited, but enough has been said to indicate how important a repository of the results of petrologic research the Journal has been and continues to be.

In thus looking backward over the list of active workers we are involuntarily led to pause and reflect how great a loss American petrology has sustained in the premature death of some of its most brilliant and promising exponents; it is only necessary to recall the names of R. D. Irving, G. H. Williams, G. W. Hawes, J. F. Williams and Carville Lewis, to appreciate this.

The store of material gathered during these years has led to the publication of extensive memoirs, in which the science is treated not from the older descriptive side, but from the theoretical standpoint and of classification.[^[131]] In these works strong divergencies of views and opinions are observed, which is a healthy sign in a developing science.

It should be also noted that along with this evolution on the theoretical side there has been a constant improvement in the technique of investigating rocks. It is only necessary to compare the older handbooks of Zirkel and Rosenbusch with the many modern treatises on petrographic methods to be assured of this.[^[132]] It is due on the one hand to the vast amount of careful work which has been done in accurately determining the physical constants of rock-minerals[^[133]] and in arranging these for their determination microscopically, as in the remarkable studies on the feldspars by Michel-Lévy, and on the other in researches on the apparatus employed, and in consequent improvements in them and in ways of using them, as exemplified in the delicately accurate methods introduced by Wright.[^[134]] The development of the microscope itself as an instrument of research in this field and in mineralogy deserves a further word in this connection. The first step toward making the ordinary microscope of special use in this way was taken by Henry Fox Talbot of England, when he introduced in 1834 the employment of the recently invented nicol prisms for testing objects in polarized light. The modern instrument may be said to date from the design offered by Rosenbusch in 1876. Since that time there have been constant improvements, almost year by year, until the instrument has become one of great precision and convenience, remarkably well adapted for the work it is called upon to perform, with special designs for various kinds of use, and an almost endless number of accessory appliances for research in different branches of mineralogy and crystallography, as well as in petrography proper.[^[135]] This also calls to mind the fact that for the convenience of those who are not able to use the microscope special manuals of petrology have been prepared in which rocks are treated from the megascopic standpoint.[^[136]]

Metamorphic Rocks.

In this connection the metamorphic rocks should not be forgotten. They afford indeed the most difficult problems with which the geologist has to deal; every branch of geological science may in turn be called upon to furnish its quota for help in solving them. Under the attack of careful, accurate and persistent work in the field, under the microscope and in the chemical laboratory, with the aid of the garnered knowledge in petrology, stratigraphy, physiography, and other fields of geologic science, their mystery has in large part given way. The inaugural work of Lehmann, Lossen, Barrois, Bonney, Teall, and other European geologists, was paralleled in America by that of R. D. Irving, owing to whose efforts the Lake Superior region became the chief place of study of the metamorphic rocks in this country. Irving soon obtained the assistance of G. H. Williams, who had been engaged in the study of such rocks, and the latter published a memoir on the greenstone schist areas of Menominee and Marquette in Michigan[^[137]] which will always remain one of the classics in the literature of metamorphic rocks. Irving’s own contributions to petrology, though valuable, were cut short by his untimely death, but the study of this region under the direction of his associate and successor, C. R. Van Hise, with his co-laborers, has yielded a mass of information of fundamental importance in our understanding of metamorphism and the crystalline schists. Its fruitage appears in the memoir by Van Hise[^[138]] which is the authoritative work of reference on metamorphism, and in various publications by him and his assistants, Bayley, Clements, Leith, and others. The work of the Canadian geologists, and of Kemp, Cushing, Smyth and Miller in the Adirondack region, should also be mentioned in connection with this field of petrology.

Chemical Analyses of Rocks.

It has been previously pointed out that, as the science of petrology grew, chemical investigations of rocks in bulk were undertaken. The object of such analyses was to obtain on the one hand a better control over the mineral composition and on the other to gain an idea of the nature of the magmas from which igneous rocks had formed. The earliest analysis of an American rock of which I can find record is of a “wacke” by J. W. Webster given in the first volume of the Journal, page 296, 1818.

During the next 40 years a few occasional analyses were undertaken by American chemists, by C. T. Jackson, T. Sterry Hunt, and others. In 1861, Justus Roth published the first edition of his Tabellen, in which he included all analyses which had been made to that date and which he considered were worthy of preservation. Although, naturally, from the status of analytical chemistry up to that time, most of these would now be considered rather crude, the publication of the work was of great service and marked an epoch in geochemistry. In these tables Roth lists four analyses of American igneous rocks, two from the Lake Superior region by Jackson and J. D. Whitney and two by European chemists, one of whom was Bunsen. The material of the last two was a “dolerite” and the same locality is given for each—“Sierra Nevada between 38° and 41°” which was probably considered quite precise for western America in those days.

From these feeble beginnings the forward progress of petrology on the chemical side in this country has been a steady one until its development has reached the point which will be indicated in what follows.

The collection of material by the various State surveys and by those initiated by the National Government led to an increasing number of rocks being analyzed during the petrographic period. These became also increasingly good in quality, like those published by G. W. Hawes in his papers. When, however, chemists were appointed to definite positions on the staffs of the Government surveys and especially when, after the organization of the U. S. Geological Survey in 1879, a general central laboratory was founded in 1883 with F. W. Clarke in charge, then a new era in the chemical investigation of rocks may be said to have started. In this connection should be mentioned the work of W. F. Hillebrand, who set a standard of accuracy and detail in rock analysis which had not hitherto been attempted. As a consequence of his accurate and thorough methods and results the mass of analyses performed by him and his fellow chemists in this laboratory affords us the greatest single contribution to chemical petrology which has been made. Up to January, 1914, the report of Clarke[^[139]] lists some 8000 analyses of various kinds made in this laboratory for geologic purposes. Nearly everywhere also a great improvement in the quality of rock-analyses is to be noted, and in the manuals of Hillebrand[^[140]] and Washington[^[141]] the rock analyst has now at his command the methods of a greatly perfected technique which should insure him the best results.

Roth’s Tabellen have been previously mentioned; several supplements were published, but after his death a long interval elapsed before this convenient and useful work was again taken up by Washington[^[142]] and Osann.[^[143]] A new edition of Washington’s Tables has recently been published, listing some 8600 analyses of igneous rocks made up to the close of 1913.[^[144]]

On the theoretical side also, where petrology passes into geology, the investigator of to-day will find a mass of most useful and accurate data well discussed in the modern representative of Bischof’s Chemical Geology—Clarke’s Data of Geochemistry.[^[145]] The advance on the chemical side, therefore, has been quite commensurate with that in the microscope as an instrument, and in the results obtained by it.

Physico-Chemical Work.

The study of geological results by experimental methods, which should gain information concerning the processes by which those results are caused, and the conditions under which they operate, has been from the earliest days of the developing science recognized as most important, and the record of the literature shows considerable was done in this direction. Experimental work in modern petrology may, however, be considered to date from 1882 when Fouqué and Michel-Lévy[^[146]] published the results of their extensive researches on the synthesis of minerals and rocks by pyrogenous methods. The brilliant experiments of the French petrologists at once attracted attention, and since that time a considerable volume of valuable work has been done in this field by a number of men, among whom may be mentioned Morozewicz,[^[147]] Doelter,[^[148]] Tamman,[^[149]] and Meunier.[^[150]] As this work continued the results of the rapid advances made in physical chemistry began to be applied in this field with increasing value. To J. H. L. Vogt we owe a valuable series of papers,[^[151]] in which the formation of minerals and rocks from magmas is treated from this standpoint. Most important of all for the future of petrology has been the founding in Washington of the splendid research institution, the Carnegie Geophysical Laboratory, under the leadership of Dr. A. L. Day with its corps of trained physicists, chemists and petrologists, devoted to the solving of the problems which the progress of geological science raises. The publications of this institution (many of them published in the Journal) are too numerous to be mentioned here; many of them treat successfully of matters of the greatest importance in petrology. This is an earnest of what we may hope in the future. The accumulation of the exact physical and chemical data, which is its aim, will serve as a necessary check to hypothetical speculation and bring petrology, and especially petrogenesis, in line with the other more exact sciences by furnishing quantitative foundations for its structure of theory to rest upon.

While the achievements of this great organization seem to minimize the work of the individual investigator in this field, he may take heart by observing the important results on the strength of rocks under various conditions which have been obtained by Adams in recent years, data of wide application in theoretical geology. In this field also a special text has appeared in which the principles and acquired data are given.[^[152]]

Summary.

In this brief retrospect, giving only the barest outlines and omitting from necessity much of importance, we have seen petrology grow from occasional crude experiments into a fully organized science in the last half century. It has to-day a well-perfected technique, a large volume of literature, texts treating of general principles, of methods of work, descriptive handbooks on the morphological side, and has attained general recognition as a field, which, though not large, is worthy of the concentration of intellectual endeavor. Like other healthy growing organisms it has given rise to offshoots, and the sciences of metallography and of the micro-study of ore deposits, which are rapidly assuming form, have branched from it.

What of the future? The old days of mostly descriptive work, and of theorizing purely from observed results, have passed. The science has entered upon the stage where work and theory must be continually brought into agreement with chemical, physical and mathematical laws and data, and in the application of these new problems present themselves. As we climb, in fact, new horizons open to our view indicating fresh regions for exploration, for acquiring human knowledge and for our satisfaction.

Bibliography.

[107]. W. Cross, Jour. Geology, 10, 451, 1902.

[108]. Ibid., p. 45.

[109]. Sorby, Quart. Jour. Geol. Soc., 14, 453, 1858.

[110]. Zirkel, Einführung des Mikroskops in das mineralogisch-geologische Studium, 1881.

[111]. Williams, G. H., Modern Petrography, 1886.

[112]. Zirkel, Mikroskopische Beschaffenheit der Mineralien und Gesteine.

[113]. Rosenbusch, Mikroskopische Physiographie der petrographisch wichtigen Mineralien.

[114]. Zirkel, Mikroskopische Gesteinstudien, Sitzung vom 12 März, 1863.

[115]. Julien and Wright, Geol. Surv. of Michigan, 2, 1873. Appendices A and C.

[116]. Dana, E. S., the Journal, 8, 390–392, 1874.

[117]. Zirkel, Geological Exploration of the 40th Parallel; vol. VI, Microscopical Petrography.

[118]. Caswell, Microscopical Petrography of the Black Hills. U. S. Geog. and Geol. Surv. Rocky Mts. Rep. on Black Hills of Dakota, 469–527. The separate copies issued bear the imprint 1876; the complete report 1880.

[119]. Dana, E. S., Igneous Rocks in the Judith Mts. Rep. of Reconnaissance Carroll, Mont., to Yellowstone Park in 1875. Col. Wm. Ludlow, War Dept., Washington, 105–106.

[120]. Hawes, G. W., Rocks of the Chlorite Formation, etc., the Journal, 11, 122–126, 1876. Greenstones of New Hampshire, etc, ibid., 12, 129–137, 1876.

[121]. Hawes, G. W., the Journal, 21, 21–32, 1881.

[122]. Brögger, Die silurischen Etagen 2 und 3, Kristiania, 1882.

[123]. The references for the papers alluded to, all of them in the Journal, are as follows:

Emerson, 24, 195–202, 270–278, 349–359, 1882;

——, 23, 302–308, 1882.

Cross, 27, 94–96, 1884; 31, 432–438, 1886; 39, 359–370, 1890; 41, 466–475, 1891; 23, 452–458, 1882.

Iddings, 26, 222–235, 1883;

——, 27, 453–463, 1884;

——, 36, 208–221, 1888;

——, 33, 36–45, 1887.

Williams, 31, 26–41, 1886; 33, 135–144, 191–199, 1887; 35, 433–448, 1888; 36, 254–259, 1888.

——, 34, 137–145, 1887.

Diller, 32, 121–125, 1886; 37, 219–220, 1889;

——, 33, 45–50, 1887.

Irving (26, 27–32, 321–322, 27, 130–134, 1883; 29, 358–359, 1885).

Kemp (35, 331–332, 1888; 36, 247–253, 1888; 38, 130–134, 1889).

[124]. Zirkel, Lehrbuch der Petrographie, 2d ed., 1893.

[125]. Hunter and Rosenbusch, Ueber Monchiquit, etc., Min. petr. Mitth., 11, 445, 1890. Rosenbusch, Ueber Structur und Class. der Eruptivgesteine, ibid., 12, 351, 1891.

[126]. Iddings, Origin of Igneous Rocks, Bull. Phil, Soc. Washington, 12, 89–213, 1892.

[127]. Brögger, Mineralien der Syenit-pegmatit-gànge, etc., Zs. Kryst., 16, 1890.

[128]. ——, Basic Eruptive Rocks of Gran, Quart. Jour. Geol. Soc., 50, 15, 1894; Grorudit-Tinguait-Serie, Vidensk. Skrift. 1 Math. nat. Kl., No. 4, 1894.

[129]. Weed and Pirsson, e. g. Shonkin Sag, the Journal, 12, 1–17, 1901.

[130]. The references for the articles mentioned (all in the Journal) are as follows:

Becker, 46, 1893; 4, 257, 1897; 3, 21–40, 1897.

Cross, 39, 657–661, 1915.

Adams, 22, 95–123, 1906; 29, 465–487, 1910.

Daly, 22, 195–216, 1906; 26, 17–50, 1908.

Wright, 22, 224–230, 1906.

Fenner, 29, 217–234, 1910.

Bowen, 39, 175–191; 40, 161–185, 1915.

Pirsson, 50, 116–121, 1895; 7, 271–280, 1899.

Smyth, 36, 33–46, 1913.

Murgoci, 20, 133–145, 1905.

Barrell, 13, 279–296, 1902.

Lindgren, 3, 301–314, 1897; 9, 269–282, 1900.

Ransome, 5, 355–375, 1898.

Cross, 4, 115–141, 1897.

Hague, 1, 445–457, 1896.

Pogue, 28, 218–238, 1909.

Warren, 25, 12–36, 1908.

Goldman, 39, 261–288, 1915.

Washington and Pirsson, Belknap Mts., 20, 344–353, 1905; 22, 439–457, 493–515, 1906.

——, Red Hill, 23, 257–276, 433–447, 1907.

——, Tripyramid Mt., 31, 405–431, 1911.

[131]. Quantitative Classification of Igneous Rocks, Cross, Iddings, Pirsson and Washington, Chicago, 1903.

Petrogenesis, C. Doelter, Braunschweig, 1906.

Igneous Rocks, vols. 1 and 2, J. P. Iddings, New York, 1909 and 1913.

Problem of Volcanism, Iddings, New Haven, 1914.

Natural History of Igneous Rocks, Alfred Harker, London, 1909.

Igneous Rocks and their Origin, R. A. Daly, New York, 1914.

[132]. Among these may be mentioned:

Rosenbusch u. Wülfing, Physiog. der petrog. wicht. Min., Stuttgart, 1905.

Iddings, J. P., Rock-Minerals, 1st ed., New York, 1906.

Johannsen, A., Manual of Petrographic Methods, New York, 1914.

Winchell, N. H. and A. N., Elements of Optical Mineralogy, New York, 1909.

[133]. We may mention here, for example, the work in mineralogy of Penfield, noticed in the accompanying chapter on mineralogy. In addition to the accurate determination of the composition and constants of many minerals, some of which have importance from the petrographic standpoint, we owe to him more than anyone the recognition of fluorine and hydroxyl in a variety of species, and thereby the perception of their pneumatolytic origin. His papers have been published almost entirely in the Journal.

[134]. Wright, Methods of Petrographic-Microscopic Research, Carnegie Inst., Washington, 1911, and various papers; many in the Journal.

[135]. Conf. Wright’s work quoted above and the various manuals previously mentioned.

[136]. Kemp, Hand-book of Rocks, 3d ed., New York, 1904. Pirsson, Rocks and Rock-Minerals, New York, 1910.

[137]. Williams, G. H., U. S. Geol. Surv., Bull. 62, Washington, 1890.

[138]. Van Hise, Treatise on Metamorphism, U. S. Geol. Surv., Monograph 17.

[139]. F. W. Clarke, U. S. Geol. Surv., Bull. 591, 1915.

[140]. Hillebrand, Analysis of Silicate and Carbonate Rocks, U. S. Geol. Surv., Bull. 422, 1910.

[141]. Washington, Chemical Analysis of Rocks, pp. 200, New York, 1910.

[142]. Id., Chemical Analyses of Igneous Rocks (1884–1900), U. S. Geol. Surv., Prof. Paper, No. 14, 1903.

[143]. Osann, Beitr. zu chem. Petrogr., II Teil. Anal. d. Eruptivgest., 1884–1900, Stuttgart, 1905.

[144]. Washington, ibid., 2d ed., U. S. Geol. Surv., Prof. Paper 99, pp. 1216, 1917.

[145]. Clarke, U. S. Geol. Surv., Bull. 616, 1916.

[146]. Fouqué and Michel-Lévy, Synthese des Mineraux et des Roches, Paris, 1882.

[147]. Morozewicz, Exper. Untersuch. u. Bildung der Min. im Magma, Min. petr. Mitt., 18, 1898.

[148]. Doelter, Synthetische Studien, N. Jahrb. Min. 1897, 1, 1–26. Allg. chem. Mineralogie, etc.

[149]. Tamman, Krystallisieren und Schmelzen, 1903.

[150]. St. Meunier, Les Méthodes de Synthèse en Minéralogie, Paris, 1891.

[151]. Vogt, Mineralbildung in Smelzmassen, Christiania, 1892; Silikatschmelzlösungen, 1 and 2, 1903, 1904, and various other papers, esp. in Min. petr. Mitt., vols. 24 and 25, 1906.

[152]. H. E. Boeke, Grundlagen der physikalisch-chemischen Petrographie, Berlin, 1915.

VIII
THE GROWTH OF MINERALOGY FROM 1818 TO 1918

By WILLIAM E. FORD

Mineralogy to-day would certainly be generally considered one of the minor members of the group of the Geological Sciences. We commonly look upon it in the light of an useful handmaiden, whose chief function is to serve the other branches, and we are inclined to forget that, in reality, mineralogy was the first to be recognized and, with considerable truth, might be claimed as the mother of all the others. Minerals, because of their frequent beauty of color and form, and their uses as gems and as ornamental stones, were the first inorganic objects to excite wonder and comment and we find many of them named and described in very early writings. Theophrastus (368–284 B. C.), a famous pupil of Aristotle, wrote a treatise “On Stones” in which he collected a large amount of information about minerals and fossils. The elder Pliny (23–79 A. D.), more than three centuries later, in his Natural History, described and named many of the commoner minerals. At this time it was natural that no clear distinction should be drawn between minerals and rocks, or even between minerals and fossils. As long as all study of the materials of the earth’s crust was concerned with their superficial characters, it was logical to include everything under the single head. There were some writers in the early centuries of the Christian era, however, who believed that fossils had been derived from living animals but the majority considered them to be only strange and unusual forms of minerals. During many succeeding centuries little was added to the general store of geological knowledge and it was not until the beginning of the sixteenth century, that any further notable progress was made. Agricola (1494–1555) was a physician, who, for a time, lived in the mining district of Joachimstal. He studied and described the minerals that he collected there. He was the first to give careful and critical descriptions of minerals, of their crystals and general physical properties. Unfortunately, he also did not realize the fundamental distinction between fossils and minerals, and probably because of his influence this error persisted, even until the middle of the eighteenth century. But, naturally, as the number of scientific students increased, the number of those who rejected this conclusion grew, until at last, the true character of fossils was established. The keen interest in minerals and fossils which was aroused by this controversy, together with the rapid extension of mining operations, drew the attention of scientific men to other features of the earth’s surface and led to a more extended investigation of its characters and thus to the development of geology proper. It is interesting to note also that mineralogy was the first of the Geological Sciences to be officially recognized and taught by the universities.

Although, as has been shown, the beginnings of mineralogy lie in the remote past, the science, as we know it to-day, can be said to have had practically its whole growth during the last one hundred years. Of the more than one thousand mineral species that may now be considered as definitely established hardly more than two hundred were known in the year 1800 and these were only partially described or understood. It is true that Haüy, the “father of crystallography,” had before this date discovered and formulated the laws of crystal symmetry, and had shown that rational relations existed between the intercepts upon the axes of the different faces of a crystal. It was not until 1809, however, that Wollaston described the first form of a reflecting goniometer, and thus made possible the beginning of exact investigation of crystals. The distinctions between the different crystal groups were developed by Bernhardi, Weiss and Mohs between the years 1807 and 1820, while the Naumann system of crystal symbols was not proposed until 1826. The fact that doubly refracting minerals also polarize light was discovered by Malus in 1808, and in 1813 Brewster first recognized the optical differences between uniaxial and biaxial minerals. The modern science of chemistry was also just beginning to develop at this period, enabling mineralogists to make analyses more and more accurately and thus by chemical means to establish the true character of minerals, and to properly classify them.

Franz von Kobell, on page 372 of his “Geschichte der Mineralogie,” somewhat poetically describes the condition of the science at this period as follows: “With the end of the eighteenth and the commencement of the nineteenth centuries exact investigations in mineralogy first began. The mineralogist was no longer content with approximate descriptions of minerals, but strove rather to separate the essential facts from those that were accidental, to discover definite laws, and to learn the relations between the physical and chemical characters of a mineral. The use of mathematics gave a new aspect to crystallography, and the development of the optical relationships opened a magnificent field of wonderful phenomena which can be described as a garden gay with flowers of light, charming in themselves and interesting in their relations to the forces which guide and govern the regular structure of matter.”

In the Medical Repository (vol. 2, p. 114, New York, 1799), there occurs the following notice: “Since the publication of the last number of the Repository an Association has been formed in the city of New York ‘for the investigation of the Mineral and Fossil bodies which compose the fabric of the Globe; and, more especially, for the Natural and Chemical History of the Minerals and Fossils of the United States,’ by the name and style of The American Mineralogical Society.” With this announcement is given an advertisement in which the society “earnestly solicits the citizens of the United States to communicate to them, on all mineralogical subjects, but especially on the following: 1, concerning stones suitable for gun flints; 2, concerning native brimstone or sulphur; 3, concerning salt-petre; 4, concerning mines and ores of lead.” Further the society asks “that specimens of all kinds be sent to it for examination and determination.”

This marks apparently the beginning of the serious study of the science of mineralogy in the United States. From this time on, articles on mineralogical topics appeared with increasing frequency in the Medical Repository. Most of these were brief and were largely concerned with the description of the general characters and modes of occurrence of various minerals. Nothing of much moment from the scientific point of view appeared until many years later, but the growing interest in things mineralogical was clearly manifest. An important stimulus to this increasing knowledge and discussion was furnished by Col. George Gibbs who, about the year 1808, brought to this country a large and notable mineral collection. In the Medical Repository (vol. 11, p. 213, 1808), is found a notice of this collection, a portion of which is reproduced below: