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.