OF THE GREAT VALLEY OR BASIN OF THE MISSISSIPPI
This vast region, embracing more than twenty degrees of latitude and about thirty of longitude, although it has been explored in various directions by men of intelligence, is yet but imperfectly known; and probably no country in the world affords a more ample or interesting field for philosophic investigation. A thorough acquaintance with its geological character would in all probability lead to the most important conclusions in forming a correct theory of the earth, while a knowledge of its vegetable and mineral productions may be conducive to the comforts and enjoyments of a large portion of the human family. All we shall presume to offer under this copious head, will be a few general remarks relative to the position and conformation of the valley, grounded almost exclusively upon the hydrography of the country, so far as it has come under our observation.
The valley is bounded on the west by the Rocky Mountains, on the east and south-east by the Alleghanies, and on the south by the Gulf of Mexico. To the northward, no precise limits can be assigned as its boundary. Although many have supposed that the waters of the Mississippi are separated from those running north-westwardly into the Pacific Ocean, and north-eastwardly into the Atlantic, by a mountainous range of country, yet, from the best information that can be had on the subject, the fact is quite otherwise. The old and almost forgotten statement of savage origin, viz. that "four of the largest rivers on the continent have their sources in the same plain," is entitled to far more {262} credit. The rivers alluded to are the Mississippi, the St. Lawrence, the Saskashawin, and the Oregon or M'Kenzie's river. Agreeably to the accounts of Colonel Dixon and others who have traversed the country situated between the Missouri and the Assinaboin, a branch of Red river of Hudson's Bay, no elevated ridge is to be met with; but, on the contrary, tributaries to both these streams take their rise in the same champaign, and wind their way in various directions to their far distant estuaries. Judging from the maps that have been given of the country near the sources of the Mississippi, and of the region generally situated northwardly of the great lakes, as also from the accounts of various travellers who have penetrated many parts of those countries, the same remarks appear equally applicable to a large portion of the whole. The watercourses are represented as chains of lakes of various magnitudes, while lakes and stagnant pools are scattered in almost every direction, without ridges or perceptible declivities to show the direction in which they are drained. But we forbear to enlarge on this subject, and beg leave that reference may be had to Bouchette's map of the region of which we have just been treating, as a document containing ample illustrations of our opinion. Hence it will be inferred that the valley of the Mississippi is merely a portion of an immense region of valley or flat country, extending from the Gulf of Mexico north-eastwardly to the Atlantic, and north-westwardly to the Pacific Ocean.
Within the valley or region drained by the Mississippi, are situated no less than three distinct ranges of mountainous country, the localities of which we will attempt to point out. The first and most considerable is a range of mountains commencing within the Spanish province of Texas, and stretching in a north-eastward direction, till it is terminated by the high lands on the lower part of the Missouri river. To this range we have given the name of the Ozark {263} Mountains, an appellation by which the Arkansa river was formerly distinguished, as also the tribe of Indians, since denominated the Quapaws, inhabiting near that river. Its direction is nearly parallel to that of the Alleghanies. Its peaks and ridges are less elevated than those of the latter, and do not present the same regularity in their arrangement. The second is denominated the Black Hills, commencing on the South or Padouca fork of the river Platte, at the distance of about one hundred miles eastward of the Rocky Mountains, and stretching north-eastwardly towards the great northerly bend of the Missouri. Of this range very little is yet known; and the fact that there is such a range is partially substantiated by the concurrent testimony of the traders and hunters of the Missouri, with whom it is a noted landmark, but it is more fully corroborated by the hydrography of the country, as may be shown by the map.
The third is a range of hilly and broken country, commencing on the Wisconsan near the Portage, and extending northwardly to Lake Superior. To this range we have taken the liberty to give the name of the Wisconsan Hills. The Ocooch and Smokey Mountains before mentioned, are connected with this range. In its geological character, and more especially in its metallic productions, so far as our inquiry will enable us to decide, it appears nearly allied to the Ozark Mountains, and circumstances are not wanting to induce the opinion, that they were once the same continuous range. Dr. James is decidedly of opinion, that the metalliferous region of the Mississippi, which extends from Red river to Lake Superior in the direction of these two ranges, strongly indicates that a continuous range, as just hinted, once had an existence.
The Mississippi river may be regarded as occupying the lowest part of the valley, from its great estuary, the Gulf of Mexico, to its confluence with the Missouri and Illinois. Thence to Lake Michigan, {264} the immediate valley of the Illinois is to be viewed as the lowest part of the great valley under consideration. This conclusion necessarily results from an attentive consideration of the characters of the three rivers just mentioned. If the inclinations of the plains down which these rivers respectively flow, be in any degree proportionate to the velocities of their currents, the plain of the Illinois will be found to have far the least inclination, inasmuch as the velocity of its current is not more than one-fourth of that of either of the others. But in order to have a more distinct view of the matter, let us assume the parallel of latitude intersecting the Illinois at its head, or point of confluence of the Kankakee and Des Plaines rivers, and suppose a vertical section cut in the direction of the parallel. Such a section would intersect the Missouri at the distance of nearly seven hundred miles from its mouth, the Mississippi at about two hundred and sixty, and the Illinois at two hundred and fifty from the same point. Hence, allowing that the plains of each have the same inclination, the point of intersection on the Missouri would be at a greater elevation than that on the Mississippi, and that on the Illinois would be less elevated than either. But the difference of inclination in these plains is manifest, not only from the comparative velocities of the several streams alluded to, but from the circumstance, that the Illinois is destitute of any considerable rapids throughout its whole course, whereas the Mississippi, in addition to a current uniformly more rapid, is hurried down the De Moyen rapids, eleven miles in length; and the Missouri, without a perversion of terms, may be denominated a rapid throughout the distance above specified. By a similar course of reasoning it may also be made to appear, that the assumed point of intersection on the Illinois is less elevated than any other point in the same parallel of latitude between that river and Lake Erie, and even that it is somewhat lower than the surface of {265} the lake itself; for the aggregate descent, from the surface of Lake Michigan to the point under consideration, is evidently greater than from the surface of the same lake to that of Lake Erie; or, in other words, the descent of the Des Plaines, from Chicago to its confluence with the Kankakee, is greater by a few feet than that of the stream uniting Lakes Huron and Erie.
This view of the subject affords us a clue whereby to ascertain, with some degree of precision, the aggregate fall of the water, from the head of the Illinois, to the Gulf of Mexico. Agreeably to the surveys of the Great Canal of New York, the elevation of Lake Erie above tide-water is found to be 564 feet. Hence we may assume, in round numbers, 450 feet as the altitude of the head of the Illinois above the ocean.
Of the conformation of the valley in other respects, no other ideas can be advanced but such as are suggested by a general view of the topography of the country, and especially of the courses of the principal rivers, as exhibited in the map of the country drained by the Mississippi. We will only add, that the inclined plain constituting the western side of the valley, or, in other words, the great slope down which the Red, Canadian, Arkansa, Konzas, Platte, and other large rivers have their courses, has probably a greater general inclination than any other side of the valley. In forming an estimate of the aggregate descent of this slope, commencing at tide-water, and extending to the base of the Rocky Mountains, Pike allows 8000 feet, which probably exceeds the truth by more than one-half. We would substitute 3000 feet as the aggregate elevation of the base of the mountains above the ocean, and are of opinion, that this amount rather exceeds the truth. This altitude, added to that of James's Peak as before stated, would give for the height of that Peak above the ocean, 11,500 feet; comparing this altitude with that of the "inferior {266} limit of perpetual snow," as estimated by M. De Humboldt for the latitude of 40 degrees, viz. 9846 feet above the ocean, we find the summit of the Peak 1654 feet higher than that elevation; and judging from appearances, this difference of altitude seemed sufficiently well marked by the distance to which the snow extended from the summit downward, upon the sides of the Peak, to authenticate in a good degree the calculation above stated.
The foregoing report is intended as a civil rather than a military description of the country. For a partial description of its military features, I beg leave to refer to my report of the 12th May, 1818, to Brigadier General T. A. Smith, on file in the War Department.
In the performance of topographical duties I have been aided by Lieutenants Graham and Swift, who have rendered essential service in these and other operations. The former of these gentlemen is at present occupied in completing the calculations upon the various astronomical and other observations we took in connexion with our duties; the latter is engaged in delineating the surveys made in behalf of the expedition.
The services of Captain Bell are to be recognized as highly important and useful to the expedition, in keeping a journal of our proceedings, and conducting detached parties whenever an occasion required. He is now busily engaged in revising his journal, a copy of which will soon be in readiness to be disposed of agreeably to your instructions.
The duties in the various departments of natural science were discharged with zeal and ability by Mr. Say and Dr. James, assisted by Mr. Peale, who was active and industrious in the collection and preservation of such rare specimens of animals, &c. as came under our observation. The vessel on board of which most of these specimens were shipped {267} from New Orleans, has very lately arrived in this port, and discharged our packages in good order. I take this opportunity to express my acknowledgements of the politeness of her owners, Messrs. Price and Morgan, who have kindly franked the transportation of the collections. A catalogue, embracing the zoology of the country explored by us, is shortly expected from Mr. Say, and shall be forwarded by the earliest opportunity. Dr. James has been instructed also to furnish a mineralogical and botanical catalogue, which is daily expected. Both of these are intended as accompaniments to this report.
Mr. Seymour has taken numerous landscape views, exhibiting the characteristic features of various parts of the country, besides many others of detached scenery.
A map of the country situated between the meridian of Washington City and the Rocky Mountains, shall be reported as soon as the necessary elements and data can be compiled and the drawings executed.
I have the honour to be, Sir,
most respectfully,
Your obedient and humble Servant,
S. H. LONG,
Major U. S. Engineers.
Honourable J. C. Calhoun,
Secretary of War.
[OBSERVATIONS ON THE MINERALOGY AND GEOLOGY OF A PART OF THE UNITED STATES WEST OF THE MISSISSIPPI.]
Extracted from a Report to Major Long[79]
The following remarks are designed to give a summary and connected view of the facts and observations collected during the progress of the exploring expedition, relative to the geology and mineralogy of the several regions traversed by the party, more particularly of the Rocky Mountains, and the western portions of the great valley of the Mississippi. In an attempt of this kind, some difficulty arises from the unsettled and progressive condition of geognostic science. A nomenclature, constructed upon principles applicable to the other branches of natural history, has been extended to this. Attempts have been made to define classes, orders, genera, and species of rocks; while it must be acknowledged, that the inventors of systems have hitherto failed to point out such infallible foundations for distinction of character as exist in the animal and vegetable kingdoms. Among minerals, from one extreme of the series to the other, there is a constant transition of approximating aggregates into each other. The particles of unorganized matter, being exempt from the influence of those peculiar laws which regulate the forms and characters of living {272} beings, and moving in obedience only to the impulses of attraction and affinity, arrange themselves together not always in an invariable order, and after a permanent and unalterable type, but are variously intermixed and confounded, as circumstances may have variously influenced their aggregation. Definitions, it must be acknowledged, have been constructed, strictly applicable to particular portions of matter, which may occur under similar circumstances in remote quarters of the globe. Fragments of granite may be found in the Rocky Mountains of America which could not be distinguished from the granite of Egypt, such as is seen in our collections. These definitions, then, may be sufficient for the purposes of the naturalist who confines his inquiries to his cabinet; but when examinations are extended, when we approach the imaginary limits of these artificial divisions, we not uncommonly find ourselves deserted by our boasted distinctions and definitions. It must be evident to any person in the slightest degree familiarized to the examination of the rocky materials composing the earth's surface, that between any two of the contiguous artificial divisions there is often-times no definite and discoverable boundary. Granite must consist essentially of felspar, quartz, and mica; so must gneiss and mica-slate; and between the two former, it is often extremely difficult to point out the line which shall be considered as marking the termination of the one and the commencement of the other. It will, we think, be acknowledged, that not one of the names applied to rocks, as constituting extensive strata, conveys of itself a definite and satisfactory idea. Hence the necessity which is felt, in attempting to give a detailed account of the rock formations of any particular district, to define the names in almost every instance of their application. If the following remarks should on this account seem faulty, by a certain monotony and appearance of {273} repetition, we hope there are a few, who, for the sake of the facts detailed, will excuse any want of precision in the language which may have necessarily resulted from the unsettled condition of the nomenclature.
[VERTICAL SECTION on the PARALLEL of LATITUDE 41 degrees North]
![[VERTICAL SECTION on the PARALLEL of LATITUDE 41 degrees North]](#5969309679840097903_illo_185.jpg.id-4555957255211491182.wrap-0.html.html){kind=link}
intended as a continuation of MACLURE'S third Section from the sea-shore to the summit of the Alleghenies.
[VERTICAL SECTION on the PARALLEL of LATITUDE 35 degrees North]
![[VERTICAL SECTION on the PARALLEL of LATITUDE 35 degrees North]](#5969309679840097903_illo_185.jpg.id-271442487988594103.wrap-0.html.html){kind=link}
intended as a continuation of MACLURE'S fifth Section.
No part of the earth, it is probable, presents a greater degree of simplicity and uniformity in the structure and conformation of its surface than North America. The mountain ranges are here distinct, forming each its own particular system, and preserving severally, through their whole extent, a similarity in external appearance, as well as in the structure and aggregation of the various rocks of which they are composed.
The outlines of a physical delineation of the continent of North America would present, first, the great chain of the Rocky Mountains, evidently a continuation of the Andes of the southern hemisphere, stretching parallel to the direction of the western coast from the isthmus of Panama to the northern ocean. Their summits penetrating far into the regions of perpetual winter, look down upon the vast plains of the Mississippi and its tributaries; in which we distinguish a comparatively inconsiderable range of rocky hills, commencing near the confluence of the Missouri and Mississippi, and running south-west of the Gulf of Mexico, near the estuary of the Rio del Norte. Beyond these, the surface subsides to a plain, stretching eastward to the commencement of the great chain of the Alleghanies. The range of the Alleghanies, far less elevated and alpine than that of the Rocky Mountains, traverses the continent in a direction nearly parallel to the Atlantic ocean, from the Gulf of St. Lawrence, on the north-east, to the confluence of the Alabama and Tombigbee rivers, in the south-west. Compared to the Rocky Mountains, this range is without summits, presenting, instead of conic peaks, long and level ridges, rising in no point to the inferior limit of perpetual frost, and scarce in any instance reaching that degree of {274} elevation which is incompatible with the growth of forests.
In many particulars there is a manifest resemblance between the Alleghanies, and the comparatively inconsiderable group known by the name of the Ozark mountains. They are parallel in direction, making an angle of about forty degrees with the great range of the Andes. They agree in having their most elevated portions made up of rocks of recent formation. It is well known, that, from the highly primitive gneiss rock at Philadelphia, there is a gradual ascent, across strata more and more recent, to the rocks of the coal formation, about the summit of the Alleghanies. Whether the same thing happens in every part of the range, our examinations have not yet been extensive enough to decide. We know that some of the granitic mountains of New England are far surpassed in elevation by the neighbouring hills and ridges of mica slate, talcose rocks, or even more recent aggregates.
In the Ozark mountains, as far as they have been hitherto explored, the granites and more ancient rocks are found at the lowest parts, being surmounted by those of a more recent date, the newest horizontal sandstone, and strata of compact limestone, forming the highest summits. What we wish to remark is, that the reverse of this being the case with the Rocky Mountains, the granite there far surpassing, both in extent and elevation, all the other aggregates forming the central and higher portions of all the ridges, that range has a character very distinct from the Ozark or Alleghany mountains.
It has been suggested by Major Long, that the hydrography of the upper portion of the Missouri seems to indicate the existence of a mountain range, approaching that river from the south-west, near the great northern bend, in the country of the Mandans. From Lewis and Clarke we have also some accounts tending to the confirmation of this opinion. Further {275} examination may perhaps prove this third range, called the Black hills, to resemble in direction and general character the Alleghany and Ozark mountains. The Rocky Mountains have not inaptly been called the backbone of the continent: these three lateral ranges, going off at an angle of about forty degrees, may with equal propriety be called the ribs. In latitude 38° north, the eastern base of the Rocky Mountains is found to be in about 106° west longitude: following the same parallel of latitude eastward, you arrive at the base of the Ozark mountains, nearly in longitude 94°. The intervening space, occupying the extent of near twelve degrees of longitude, is a wide and desolate plain, destitute of timber; scorched in summer by the reverberation of the rays of the sun, howled over in winter by the frozen west winds from the Rocky Mountains.
Though we have assumed twelve degrees of longitude as the medium width of this great plain, it is to be remarked, that to many parts of it our examinations have not been extended. In the latitude of 41°, no mountain, and scarce an elevation deserving the name of a hill, occurs between the western range of the Alleghanies and the Rocky Mountains. But at no great distance north of this parallel, low ranges of hills begin to appear in the region south-west of Lake Michigan; and though too inconsiderable in point of elevation to deserve particular notice, still they exhibit peculiar characters, which seem to designate an intimate connection with the Ozark mountains, south of the Missouri. The same succession of strata, the same alternation of crystalline beds, with those of mechanical deposition, and similar depositories of metallic ores, are observed here, as in the regions about the Merameg and St. Francis. A marked difference is also, as we think, to be discovered between the rocks and soils on the different sides of this range. Of this we shall speak more {276} particularly in another place. For our present purpose, it is sufficient to assume as a boundary of the region we propose first to consider, a line running from the confluence of the Arkansa and Canadian rivers on the south-west, to the junction of the Mississippi and Wisconsan, on the north-east. Assuming this as the direction of the range of the Ozark mountains, it will be perceived, by examining the map, that to the north-west of this line spreads an extensive plain, reaching to the base of the Rocky Mountains. This plain has been crossed in three different places by the exploring party, as already detailed in our narrative; once in ascending by the River Platte, between latitude 40° and 41° 30´; again, in descending the Arkansa, in 38°; and, thirdly, by the route of the Canadian, in 34°. To the information collected in these journeys, we have added a little from other sources; but the greater part of this extensive region yet remains unknown.
Of the Great Desert at the base of the Rocky Mountains
The portion of country which we design to consider under this division has an average width of five or six hundred miles, extending along the base of the Rocky Mountains from north to south: as far as we have any acquaintance with that range, consisting entirely of granitic sands, or of secondary aggregates made up of the detritus of that great chain of primitive mountains, there seems to be a degree of propriety in designating it by some name recognising relation to those mountains. It has been mentioned as the "Mexican desert;" a name sufficiently applicable, perhaps, to some portions of it, but one by no means to be extended to every part alike, as there can be little doubt of its occupying an extensive {277} portion of the interior of North America. That a similar desert region exists on the western side of the mountains, we have sufficient evidence; but whether as uninterrupted and as extensive, we have not the means of determining.
The Jesuit Venegas, speaking of the early history of California, says "Father Kino and his companions, after travelling thirty leagues from San. Marcelo, came to a small rancheria (Indian village); and leaving on the north the great mountain of Santa Clara, whose sides, for the length of a league, are covered with pumice-stone, they arrived at the Sandy Waste, on the 19th of March." Our information is, however, too limited to justify an attempt to fix the boundaries of this desert; we will, therefore, content ourselves with communicating the observations our opportunities have enabled us to make.
The channel of the Missouri, near the mouth of the Platte, discloses here and there rocks of horizontal limestone; which, from their peculiar character, we are disposed to consider as belonging rather to the Ozarks, than having any connection with the Rocky Mountains. These rocks appear at the lowest parts of the valleys, and are usually surmounted by extensive beds of soil, consisting principally of flinty sand in the most minute state of division, but variously intermixed with the remains of organized beings, and sometimes with calcareous and aluminous earth. Proceeding westward, the sand becomes deeper and more unmixed; not a rock or a stone, in place or out of place, is to be met with for some hundreds of miles. It is believed that no rocky bluffs appear along the valley of the Platte, within three hundred miles of its mouth, though a small part of this distance, on the lower portion of the river, has not hitherto been explored. The surface is not an absolute plain, but is varied with gentle undulations, such {278} as the draining of water, from an immense table of a light arenaceous earth, for a succession of centuries, may be supposed to have occasioned. The gradual intermixture of the exuviæ of animals and vegetables, with what was formerly a pure siliceous sand, has at length produced a soil capable of supporting a scanty growth of grasses; now almost the only covering of these desolate regions. Scales of mica, little particles of brownish felspar, and minute fragments of hornblende, may here be detected in the soil.
About four hundred miles west of the mouth of the Platte, a low range of sandstone hills crosses the country from south-west to north-east. The strata composing these hills have no perceptible inclination, and present appearances which indicate their deposition to have been nearly contemporaneous to that of many of our coal formations. It has already been suggested that this range may probably be a continuation of the Cotes Noir, or Black hills, said to contain the sources of the Shienne, the Little Missouri, and some branches of the Yellow Stone.[80]
These inconsiderable hills being passed, the surface again subsides nearly to a plain. The fine and comparatively fertile sand which prevailed to the east of the ranges, is exchanged for a gravel made up of rounded granitic fragments, varying in dimensions from the size of a six-pound shot to finish sand. This great mass of granitic fragments, evidently brought down by the agency of water from the sides and summits of the Andes, slopes gradually from their base, appearing, as far as examinations have extended, to correspond in some measure, in magnitude, to the elevation and extent of that part of the mountains opposite which it is placed. The minute particles derived from the quartzy portions of the primitive aggregates, being least liable to decomposition, have been carried to the greatest distance, {279} and now form the almost unmixed soil of the eastern margin of the great sandy desert. The central portions are of a coarser sand, with which some particles of felspar and mica are intermixed: nearer the mountains, pebbles and boulders become frequent, and at length almost cover the surface of the country.
The opinion above advanced, that the great sandy desert has resulted from the wearing down of the mountains, both before and since the retiring of the ocean, should, perhaps, be received with some caution. We have no foundation for the belief, but in the examinations which enabled us to discover that the materials composing both regions are similar in kind; that the granitic soils of the plain are precisely such as would result from the disintegration of the rocks now existing in the mountains; and that the numerous deep ravines and water-worn valleys traversing the mountains in various directions, indicate the change here supposed to have happened.
It is probable many parts of this extensive desert may differ from that traversed by the Platte, in having the surface more or less covered with horizontal strata of sandstone and conglomerate, instead of loose sand and pebbles. Indeed, there are many appearances indicating that a formation of this kind formerly extended down the Platte much farther than at present. From the minute account given in the narrative of the expedition, of the particular features of this region, it will be perceived that its eastern portions bear a manifest resemblance to the deserts of Siberia. The soils, and I believe the rocks, wherever any occur, are saline: plants allied to chenopodium and salsola are peculiarly abundant, as are the astragali and other herbaceous leguminæ; while trees and forests are almost unknown.
The surface of the sandy plain rises perceptibly towards the base of the mountains; and becoming constantly more and more undulating, is at length broken, disclosing some cliffs and ledges of micaceous {280} sandstone. Near the Platte this sandstone occurs in horizontal strata, sometimes divided by the beds of the streams, and forming low ridges parallel to the Rocky Mountains. Whether they continue in an uninterrupted line along the base of the mountains, we have not been able to ascertain. They are separated from the first range of primitive, by more elevated cliffs of a similar sandstone, having its strata in a highly inclined position. Behind these, occur lofty but uninterrupted ranges of naked rocks, destitute of any covering of earthy or vegetable matter, and standing nearly perpendicular. At a distant view, they present to the eye the forms of walls, towers, pyramids, and columns, seeming rather the effects of the most laborious efforts of art, than the productions of nature. When surveyed from the more elevated summits of the first granitic range, these immense strata of sandstone standing on edge, and sometimes inclining at various angles towards the primitive, resemble the plates of ice often seen thrown into a vertical position in the eddies and along the banks of rivers.
Climbing to the summits of such of these elevations as are accessible, and crossing their stratifications towards the primitive, we observe appearances similar to those found in the valleys, when circumstances enable us to push our inquiries to a corresponding extent below the surface. Having crossed the upturned margin of the whole secondary formation which occupies the plain, and arriving at the primitive, we find these highly inclined strata of sandstone reposing immediately against the granite. We search in vain for any traces of those rocks distinguished by the Wernerians as rocks of the transition period. We also observe an entire deficiency of all those primitive strata which the doctrine of universal formations may have taught us to look for in approaching the granite.
The sandstone along the base of the mountains, {281} though apparently not very recent, contains the remains of marine animals and plants, and embraces some extensive beds of puddingstone. It may be remarked that the sand and gravel composing these aggregates have in general the same close resemblance to the materials of the granitic mountains, as we have already observed in the un-cemented materials of the plain. Indeed, it does not seem easy to determine whether the sands, gravel-stones, and pebbles, now loosely strewed over the extensive plains of the desert, have been brought down immediately from the granitic mountains whence they were originally derived, or have resulted from the disintegration of the stratified sandstone and conglomerates deposited during a long series of ages, while the waters of the ocean rested upon the great plain, and washed the bases of the Rocky Mountains. The very wide and equal distribution of these sands, in other words, the very gradual slope of the débris of the mountain, would seem to countenance the latter supposition.
The position of the strata of sandstone varies in the distance of a few miles from nearly horizontal to an inclination of more than sixty degrees, and that without any very manifest change of character, or the interposition of any other stratum. The laminæ most distant from the primitive, occupying the eastern sides of the first elevations, though lowest in actual elevation, may with propriety be considered the uppermost, as resting on those beyond. At the level of the surface of the great plain, they sink beneath the alluvial; and in the neighbourhood of the river Platte, they are no more seen. The uppermost are of a yellowish-gray colour; moderately fine; compact and hard; constantly varying, however, at different points, in colour as well as most other characters. The light-coloured varieties usually contain small round masses about the size of a musket-ball, which are more friable than the rock itself, {282} from which they are easily detached, leaving cavities corresponding to their own shape and dimensions. They are commonly of a dark-brown colour, and of a coarser sand than that which constitutes the rock itself. Where these are found, I could never discover any of those remains of shellfish so distinctly seen in many of the secondary rocks in this neighbourhood.
Passing downwards, or in other words, proceeding towards the primitive, crossing the edge of the secondary, the sandstone becomes more coarse and friable, its colour inclining more to several shades of brown and red. This variety contains numerous masses of iron ore, and does not appear to abound in the remains or impressions of organized beings. It is also less distinctly stratified than that just mentioned; and it often becomes exceedingly coarse, with angular fragments intermixed, being in no respect different from the rock denominated breccia, and by some geologists considered a distinct stratum.
This tract of sandstone, which skirts the eastern boundary of the Rocky Mountains, and appears to belong to that immense secondary formation which occupies the valley of the Mississippi, abounds in scenery of a grand and interesting character. The angle of inclination of the strata often approaches 90°, and is very rarely less than 45°. That side of the ridges next the primitive appears to have been broken off from a part of the stratum beyond; and is usually an abrupt and perpendicular precipice, sometimes even overhanging and sheltering a considerable extent of surface. The face of the stratum is usually smooth and hard, and both sides are alike destitute of soil and verdure. Elevations of this description are met with, varying from twenty to several thousand feet in thickness; neither are they by any means uniform in height. Some of them rise, probably, three hundred or four hundred feet; and considering their singular character, would appear {283} high, were they not subjected to an immediate and disadvantageous comparison with the stupendous Andes, at whose feet they are placed. Their summits in some instances are regular and horizontal, and are crowned with a scanty growth of cedar and pine. Where the cement and most of the materials of the sandstone are siliceous, the rock evinces a tendency to break into fragments of a rhombic form; and in this case the elevated edge presents an irregularly notched or serrated surface.
Sandstones consisting of silex, with the least intermixture of foreign ingredients, are the most durable. But in the region of which we speak, the variations in the composition, cement, and characters of the sandstone, are innumerable. Clay and oxide of iron entering into its composition in certain proportions, seem to render it unfit to withstand the attacks of the various agents, whose effect is to hasten dissolution and decay. Highly elevated rocks of this description may well be supposed in a state of rapid and perceptible change. The sharp angles and asperities of surface which they may have originally presented, are soon worn away; the matter constantly removed by the agency of water from their sides and summits is deposited at their feet; their elevation gradually diminishes, and even the inclination of their strata becomes at length obscure or wholly undiscoverable. This appears to have been a part of the process by which numerous conic hills and mounds have been interspersed among the highly inclined naked rocks above mentioned. These hills, often clothed with considerable verdure to their summits, add greatly to the beauty of the surrounding scenery. The contrast of colours in this rude but majestic region, is often seen to produce the most brilliant and grateful effects. The deep green of the small and almost procumbent cedars and junipers, with the less intense colours of various species of deciduous foliage, acquires new beauty from being {284} placed as a margin to the glowing red and yellow seen in the surfaces of many of the rocks.
Of the Sandstones of the Rocky Mountains
Having commenced our account of the Rocky Mountains with the consideration of that vast accumulation of rounded fragments constituting the Great Desert, which may be reckoned the most recent formation connected with that great range of mountains, we proceed to speak of the sandstones, the next member in the inverted order we have adopted; and here we take occasion to remark the peculiar grandeur and simplicity of features which distinguish the mineral geography of this part of our continent. We have here a stupendous chain of granitic mountains, many hundred miles in extent, and with no stratified rocks resting about their sides, except a few sandstones, equally granitic, and almost equally primitive. We discover here comparatively few traces of that magnificent profusion of animal and vegetable life, which in other parts of the globe has reared mountains of limestone, clay-slate, and those other aggregates, which if not entirely, are often in a great measure, made up of the exuviæ of living beings. We shall not here be understood to contradict the assertion we have before made, that the sandstones along the base of the Rocky Mountains contain organized remains, and bear abundant evidence of having been at a comparatively recent period deposited gradually from the waters of the ocean. The particular we wish to remark as distinguishing these mountains most strikingly from the Alleghanies, and many other ranges, is the entire want of the aggregates referred by the Wernerians to the transition period, as well as nearly all the stratified primitive rocks, and the limestones of the secondary formations.[81] This great range, as far as hitherto known to us, lies nearly from north to south. Considered {285} topographically, the sandstone formation belongs both to the mountains and the plains, sloping down from the sides of the granite, and disappearing under the sands of the Great Desert.
The western boundary of this formation of sandstone, as far as our examinations have searched, appears to be defined, and corresponds to the side of the easternmost granitic ranges. From the Platte towards the south, the sandstone increases in width, and on the Canadian it extends more than half the distance from the sources of that river to its confluence with the Arkansa. This sandstone formation we consider as consisting essentially of two members.
1st. Red sandstone.—This rock, which is the lowest of the horizontal or fletz rocks met with in this part of the country, is very abundant in all the region immediately subjacent to the Rocky Mountains. We have never met with a similar rock in the eastern part of the valley of the Mississippi. It occurs at intervals along the base of the mountain, reposing against the primitive rocks, in an erect or highly inclined position. It varies in colour from bright brick red, to dark brown; and is sometimes found exhibiting various shades of yellow and gray. It is, however, almost invariably ferruginous; and the predominance of red in the colouring certainly entitles it to the distinctive appellation of red sandstone. The lowest part of the stratum has frequently least colour, and is also the most compact and hard. This is not, however, invariably the case; for in the neighbourhood of the Platte, that part of it which lies immediately upon the granite is white, and contains beds of coarse conglomerate or puddingstone. At the lowest points we have been able to examine, are found embodied large oval or irregular masses of hornstone, usually of a yellowish-white, or bluish colour; and near the surface of these masses are found the few well-marked organic relics the stratum can be said to contain. Higher {286} up the rock becomes much softer, and usually of a browner colour. It is disposed in immense horizontal laminæ or strata, which, when broken transversely, exhibit some tendency to separate into fragments of a rhombic form. Near the upper part of the stratum are frequently seen broad belts of a lighter colour, conspicuously marked with reticulating yellowish veins. The cross fracture of the stone is even and earthy, except in the conservatories. When divided in a direction parallel to that of the strata, small scales of mica are seen; but this is usual only in those parts of the stone where natural seams or fissures existed. Small specimens from many parts of this stratum could not be distinguished from the red sandstone quarried at Nyae in New Jersey, and used in great quantities in the cities of New York, Albany, &c. for building. The character which most particularly distinguishes this rock from "the old red sandstone of Werner," pointed out by Maclure in New York and New Jersey, appears to be the constant accompaniment of gypsum, and muriate of soda; the colour of the stratum is also in general of a brighter red, approaching vermilion, and is more copiously imparted to such streams of water as traverse it.
2d. Argillaceous or gray sandstone.—Immediately above the red sandstone, we have invariably found, where any rock rests upon it, a grayish or yellowish-white sandstone, which we distinguish as the second variety. It most frequently contains a large proportion of argillaceous earth in the cement, and has a more or less slaty structure. Hence it may with propriety be denominated argillaceous sandstone, though it may in some respects differ from the rock known to many by that name. This variety being uppermost in actual position, is perhaps more frequently seen than the other, while at the same time it is probably less abundant. The line of separation betwixt the two is often manifest and well defined; and in other instances, they pass by imperceptible gradations into each other. {287} The upper, or gray sandstone, is usually more compact and homogenous than the red; it breaks like the other, though more rarely, into large cubic or rhombic masses, which, on account of the more compact texture of the stone, retain their form longer than those of the other variety. The precipices formed by both are often lofty and perpendicular; but the projections and angles of the red are more worn and rounded than those of the gray. The narrow defiles and ravines which the streams of water have excavated, are less tortuous when they are made entirely in the gray sandstone, than in other instances. The springs of water flowing from it are more free of mineral impregnations, than such as are found in the other variety. It sometimes consists of glittering crystalline particles, but does not in this case appear to be a chymical deposit. In fine, it appears under an endless variety of characters, of which it would be in vain to attempt the enumeration. Although the gray sandstone is not invariably distinguished by the presence of an argillaceous ingredient, yet it is constantly found accompanying soft clay-slate, or bituminous shale and coal, wherever these last are met with.
If this formation of sandstone, consisting of the two varieties just mentioned, ever extended across the valley of the Mississippi to the Alleghany mountains, as some might be disposed to believe, we cannot pretend to determine what was its position relative to the immense masses of fletz, limestone, and other rocks now found in that valley. But as the red variety is still extensively disseminated, and usually accompanied by those valuable substances, salt and plaister, it may not be amiss to trace, as far as our examinations have enabled us to do it, the outline of the region which it occupies. As we have before mentioned, it is found in the vicinity of the river Platte, in a highly inclined position, covering a narrow margin immediately at the foot of the Rocky Mountains. {288} From the accounts of Lewis and Clarke, we are induced to believe that it exists under similar circumstances, near the falls of the Missouri. On the Canadian it is constantly met with, from the sources of that river on the borders of New Mexico, near Santa Fé, 106° west, until you arrive within a short distance of its confluence with the Arkansa, in long. 97° west. The waters of the Canadian, from flowing over the sandstone in question, acquire an intense red colour, and are so impregnated with muriate of soda and other soluble salts as to be unfit for use. This, we are credibly informed, is also the case with the waters of three small rivers tributary to the Arkansa, above the Canadian, on the same side; also with the waters of Red river. Hence the conclusion appears to be justified, that this rock extends from near the Arkansa on the north, to a point beyond Red river on the south; and from near the mouth of the Canadian, an unknown distance to the west. It is not unlikely it may exist about the sources and upper branches of the Rio Colorado of California, the Red river of Santa Fé, and the other Red rivers of New Mexico. Near the mountains, and for a great distance to the south and east of the High Peak, it is covered by the gray sandstone already mentioned. This gray sandstone is the uppermost of those horizontally stratified rocks which are seen in this region, possessing convincing evidence of their being the deposition of an ocean or lake of salt water.
Perhaps the most striking feature of this formation of sandstone, is the great and abrupt change in the inclination of the strata in the parts near the granite. We have already described this in a manner sufficiently explicit, as we suppose, to convince most of our readers that since the deposition of the sandstones, a signal change must have happened in the elevation of the secondary aggregates as compared with the granite. The appearances are precisely {289} such as we must suppose would have ensued, had the sudden emerging of the granite broken off, and thrown into an inclined or vertical position the margin of the horizontally stratified rocks of the plains. We are conscious that inclined strata of sandstone are by no means infrequent about the declivities of lofty mountains, but we are not well assured that the same strata being traced to a little distance, are often found in a horizontal position in the plains, as is the case in the instance under consideration.
It may perhaps be thought possible that the gradual wearing away, by the agency of rivers, of some portions of the sandstone, may have been sufficiently extensive to have occasioned that change of elevation of which we speak; and that those rocks now found in an inclined position, are insulated portions of what was formerly the upper part of the stratum, which having been undermined on their eastern side, and supported by the granite on their western, have fallen into their present situation.
This supposition, however, seems incompatible with the vast magnitude and extent of these rocks, and entirely irreconcilable to the fact that they dip to a great and indefinite extent below the present level of any of the beds of the river.
The position of this formation in relation to the granite is similar to that of the sandstone of Guachaco, in South America, observed by Humboldt; also to that spoken of by Mr. Burkhardt, at the entrance of Nubia, superimposed upon the granite of Syene, and to that mentioned by Mr. Schoolcraft, as found near Lake Superior, but it does not appear that those formations have the same peculiarities in regard to inclination.