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of any one familiar with similar facts alluded are unquestionably drift pheobserved in other parts of the world, nomena, they present in their wider exthat this is one of the many forms of tension, and especially in the northern drift connected with glacial action. I part of Brazil, as will hereafter be seen, was, however, far from anticipating,
some phases of glacial action hitherto when I first met it in the neighborhood unobserved. Just as the investigation of Rio, that I should afterwards find it of the ice period in the United States
has shown us that ice-fields may move spreading over the surface of the country, from north to south and from east
over open level plains, as well as along to west, with a continuity which gives the slopes of mountain valleys, so does legible connection to the whole geologi- a study of the same class of facts in cal history of the continent.
South America reveal new and unIt is true that the extensive decom- looked-for features in the history of the position of the underlying rock, pene- ice period. Some will
say, that the trating sometimes to a considerable fact of the advance of ice-fields over depth, makes it often difficult to distin
an open country is by no means estabguish between it and the drift ; and the lished, inasmuch as many geologists problem is made still more puzzling by believe all the so-called glacial traces, the fact that the surface of the drift, viz. striæ, furrows, polish, etc., found in when baked by exposure to the hot the United States, to have been made sun, often assumes the appearance of by floating icebergs at a time when the decomposed rock, so that great care continent was submerged. To this I is required for a correct interpretation can only answer, that in the State of of the facts. A little practice, how
Maine I have followed, compass in ever, trains the eye to read these ap- hand, the same set of furrows, running pearances aright, and I may say that I
from north to south in one unvarying have learned to recognize everywhere line, over a surface of one hundred and the limit between the two formations. thirty miles from the Katahdin Iron There is indeed one safe guide, namely, Range to the sea-shore. These furthe undulating line, reminding one of rows follow all the inequalities of the roches moutonnées," and marking the country, ascending ranges of hills varyirregular surface of the rock on which ing from twelve to fifteen hundred feet the drift was accumulated ; whatever in height, and descending into the inmodifications the one or the other may tervening valleys only two or three hunhave undergone, this line seems never dred feet above the sea, or sometimes to disappear. Another deceptive fea- even on a level with it. I take it to be ture, arising from the frequent disinte impossible that a floating mass of ice gration of the rocks and from the brittle should travel onward in one rectilinear character of some of them, is the pres- direction, turning neither to the right nor ence of loose fragments, which simulate to the left, for such a distance. Equally erratic boulders, but are in fact only de- impossible would it be for a detached tached masses of the rock in place. A mass of ice, swimming on the surface careful examination of their structure, of the water, or even with its base sunk however, will at once show the geolo- considerably below it, to furrow in a gist whether they belong where they straight line the summits and sides of are found, or have been brought from a the hills, and the beds of the valleys. It distance to their present resting-place. would be carried over the depressions But while the features to which I have without touching bottom. Instead of
ascending the mountains, it would re* The name consecrated by De Saussure to desig
main stranded against any elevation nate certain rocks in Switzerland, which have had their surfaces rounded under the action of the gla- which rose greatly above its own basis, ciers. Their gently swelling outlines are thought to and, if caught between two parallel resemble sheep resting on the ground, and for this reason the people in the Alps call them roches ridges, would float up and down be
tween them. Moreover, the action of
solid, unbroken ice, moving over the abrupt ascents; as, for instance, on ground in immediate contact with it, is the Corcovado, along the path leading so different from that of floating ice- up the mountain, are some very fine rafts or icebergs, that, though the latter banks of drift, — the more striking have unquestionably dropped erratic from the contrast of their deep red boulders, and made furrows and striæ color with the surrounding vegetation. on the surface where they happened I have myself followed this sheet of to be grounded, these phenomena will drift from Rio de Janeiro to the top of easily be distinguished from the more the Serra do Mar, where, just outside connected traces of glaciers, or ex the pretty town of Petropolis, the river tensive sheets of ice, resting directly Piabanha may be seen flowing beupon the face of the country and ad tween banks of drift, in which it has exvancing over it.
cavated its bed ; thence I have traced it There seems thus far to be an inex- along the beautiful macadamized road tricable confusion, in the ideas of many leading to Juiz de Fora in the province geologists, as to the respective action of Minas Geraes, and beyond this to of currents, icebergs, and glaciers. It the farther side of the Serra da Babyis time they should learn to distin- lonia. Throughout this whole tract of guish between classes of facts so dif- country, in the greater part of which ferent from each other, and so easily travelling is easy and delightful, — an recognized after the discrimination has admirable line of diligences, over one once been made. As to the south- of the finest roads in the world, being ward movement of an immense field established as far as Juiz de Fora, — the of ice, extending over the whole north, drift may be seen along the roadside, in it seems inevitable, the moment we ad- immediate contact with the native crysmit that snow may accumulate around talline rock. The fertility of the land, the pole in such quantities as to initi. also, is a guide to the presence of drift. ate a pressure radiating in every direc- Wherever it lies thickest over the surtion. Snow, alternately thawing and face, there are the most fourishing coffreezing, must, like water, find its level fee-plantations; and I believe that a at last. A sheet of snow ten or fifteen more systematic regard to this fact thousand feet in thickness, extending would have a most beneficial influence all over the northern and southern upon the agricultural interests of the portions of the globe, must necessarily country. No doubt the fertility arises lead, in the end, to the formation of a from the great variety of chemical elenorthern and southern cap of ice, mov ments contained in the drift, and the ing toward the equator.
kneading process it has undergone beI have spoken of Tijuca and the Dom neath the gigantic ice-plough,
a proPedro Railroad as favorable localities cess which makes glacial drift everyfor studying the peculiar southern drift; where the most fertile soil. Since my but one meets it in every direction. A return from the Amazons, my impression sheet of drift, consisting of the same as to the general distribution of these homogeneous, unstratified paste, and phenomena has been confirmed by the containing loose materials of all sorts reports of some of my assistants, who and sizes, covers the country. It is have been travelling in other parts of of very uneven thickness, - sometimes the country. Mr. Frederick C. Hartt, acthrown into relief, as it were, by the sur- companied by Mr. Copeland, one of the rounding denudations, and rising into volunteer aids of the expedition, has hills
, -- sometimes reduced to a thin been making collections and geological layer, — sometimes, as, for instance, on
observations in the province of Spiritu steep slopes, washed entirely away, Santo, in the valley of the Rio Doce, leaving the bare face of the rock ex and afterwards in the valley of the Muposed. It has, however, remained com cury.
He informs me that he has paratively undisturbed on some very found everywhere the same sheet of
red, unstratified clay, with pebbles and ited, although he had never thought occasional boulders, overlying the rock of referring it to so recent a period. -in place. Mr. Orestes St. John, who, And here let me interrupt the course taking the road through the interior, of my remarks to say, that the facts rehas visited, with the same objects in corded in this article are by no means view, the valleys of the Rio San Fran- exclusively the result of my own incisco and the Rio das Velhas, and also vestigations. They are in great part the valley of Piauly, gives the same
due to this able and intelligent young account, with the exception that he Brazilian, a member of the government found no erratic boulders in these more corps of engineers, who, by the kindness northern regions. The rarity of erratic of the Emperor, was associated with me boulders, not only in the deposits of the in my Amazonian expedition. I can Amazons proper, but in those of the truly say that he has been my good whole region which may be consid- genius throughout the whole journey, ered as the Amazonian basin, is ac- saving me, by his previous knowledge counted for, as we shall see hereafter, of the ground, from the futile and misby the mode of their formation. The directed expenditure of means and observations of Mr. Hartt and Mr. St. time often inevitable in a new country, John are the more valuable, because I where one is imperfectly acquainted had employed them both, on our first both with the people and their lanarrival in Rio, in making geological sur- guage. We have worked together in veys of different sections on the Dom this investigation ; my only advantage Pedro Railroad, so that they had a over him being my greater familiarity great familiarity with those formations with like phenomena in Europe and before starting on their separate jour- North America, and consequent readineys. Recently, Mr. St. John and my ness in the practical handling of the self having met at Pará on returning facts, and in perceiving their connecfrom our respective journeys, I have tion. Major Coutinho's assertion, that had an opportunity of comparing on the on the banks of the Amazons I should spot his geological sections from the find the same red, unstratified clay as valley of the Piauhy with the Amazoni- in Rio and along the southern coast, an deposits. There can be no doubt of seemed to me at first almost incredible, the absolute identity of the formations impressed as I was with the generally in these valleys.
received notions as to the ancient charHaving arranged the work of my as acter of the Amazonian deposits, resistants, and sent several of them to ferred by Humboldt to the Devonian, collect and make geological examina- and by Martins to the Triassic period, tions in other directions, I myself, and considered by all travellers to be with the rest of my companions, pro- at least as old as the Tertiaries. The ceeded up the coast to Pará. I was result, however, confirmed his report, surprised to find at every step of my at least so far as the component materiprogress the same geological phenom- als of the formation are concerned; but, ena which had met me at Rio. As the as will be seen hereafter, the mode of steamer stops for a number of hours, their deposition, and the time at which or sometimes for a day or two, at Bahia, it took place, have not been the same at Maceio, Pernambuco, Parahiba, Natal, the north and south ; and this differCeara, and Maranham, I had many ence of circumstances has modified the opportunities for observation. It was aspect of a formation essentially the my friend Major Coutinho, already an same throughout. At first sight, it experienced Amazonian traveller, who would indeed appear that this formation, first told me that this formation con as it exists in the valley of the Amatinued through the whole valley of the zons, is identical with that of Rio; but Amazons, and was also to be found on it differs from it in the rarity of its all of its affluents which he had vis- boulders, and in showing occasional
signs of stratification. It is also every Major Coutinho has found palæozoic dewhere underlaid by coarse, well-strati- posits, with characteristic shells, in the fied deposits, resembling somewhat the valley of the Rio Tapajos, at the first recife of Bahia and Pernambuco; where- cascade, and carboniferous deposits as the unstratified drift of the south have been noticed along the Rio Guarests immediately upon the undulating pore and the Rio Mamore. But the first surface of whatever rock happens to chapter in the valley's geological histomake the foundation of the country, ry about which we have connected and whether stratified or crystalline. The trustworthy data is that of the cretapeculiar sandstone on which the Ama- ceous period. It seems certain, that, zonian clay rests exists nowhere else. at the close of the secondary age, the Before proceeding, however, to describe whole Amazonian basin became lined the Amazonian deposits in detail, I with a cretaceous deposit, the margins ought to say something of the nature of which crop out at various localities on and origin of the valley itself.
its borders. They have been observed The Valley of the Amazons was first along its southern limits, on its western sketched out by the elevation of two outskirts along the Andes, in Venezuetracts of land; namely, the plateau of Gui- la along the shore-line of mountains, ana or the north, and the central plateau and also in certain localities near its of Brazil on the south. It is probable eastern edge. I well remember that that, at the time these two table-lands one of the first things which awakened were lifted above the sea-level, the An- my interest in the geology of the Amades did not exist, and the ocean flowed zonian Valley was the sight of some between them through an open strait. cretaceous fossil fishes from the provIt would seem (and this is a curious re- ince of Ceara. These fossil fishes were sult of modern geological investigations) collected by Mr. George Gardner, to that the portions of the earth's surface whom science is indebted for the most earliest raised above the ocean have extensive information yet obtained retrended from east to west. The first specting the geology of that part of tract of land lifted above the waters in Brazil. In this connection, let me say North America was also a long conti- that here and elsewhere I shall speak nental island, running from Newfound- of the provinces of Ceara, Piauhy, and land almost to the present base of the Maranham as belonging geologically to Rocky Mountains. This tendency may the Valley of the Amazons, though be attributed to various causes, - to the their shore is bathed by the ocean, rotation of the earth, the consequent de- and their rivers empty directly into the pression of its poles, and the breaking Atlantic. But I entertain no doubt, and of its crust along the lines of greatest I hope I may hereafter be able to show, tension thus produced. At a later pe- that, at an earlier period, the northeastriod, the upheaval of the Andes took ern coast of Brazil stretched much farplace, closing the western side of this ther seaward than in our day; so far, strait, and thus transforming it into a indeed, that in those times the rivers gulf, open only toward the east. Little of all these provinces must have been or nothing is known of the earlier strati- tributaries of the Amazon in its eastfied deposits resting against the crystal- ward course. The evidence for this line masses first uplifted in the Amazo- conclusion is substantially derived from nian Valley. There is here no sequence, the identity of the deposits in the val23 in North America, of Azoic, Siluri- leys belonging to these provinces with an, Devonian, and Carboniferous forma- those of the valleys through which the tions, shored up against each other by actual tributaries of the Amazons flow; the gradual upheaval of the continent, as, for instance, the Tocantins, the although unquestionably older palæo Xingu, the Tapajos, the Madura, etc. zoic and secondary beds underlie, here Besides the fossils above alluded to and there, the later formations. Indeed, from the eastern borders of this an-cient basin, I have had recently anoth- South America, run along the western er evidence of its cretaceous character coast; both have a great eastern promfrom its southern region. Mr. William ontory, — Newfoundland in the northern Chandless, on his return from a late continent, and Cape St. Roque in the journey on the Rio Purus, presented southern ;-and though the resemblance me with a series of fossil remains of between the inland elevations is perthe highest interest, and undoubtedly haps less striking, yet the Canadian belonging to the cretaceous period. range, the White Mountains, and the They were collected by himself on the Alleghanies may very fairly be comRio Aquiry, an affluent of the Rio Purus. pared to the table-lands of Guiana and Most of them were found in place be- Brazil, and the Serra do Mar. Similar tween the tenth and eleventh degrees of correspondences may be traced among south latitude, and the sixty-seventh the river systems. The Amazons and and sixty-ninth degrees of west longi- the St. Lawrence, though so different in tude from Greenwich, in localities vary- dimensions, remind us of each other by ing from 430 to 650 feet above the sea- their trend and geographical position; level. There are among them remains and while the one is fed by the largest of Mososaurus, and of fishes closely al- river system in the world, the other lied to those already represented by drains the most extensive lake surfaces Faujas in his description of Maestricht, known to exist in immediate contiguity. and characteristic, as is well known to The Orinoco, with its bay, recalls Hudgeological students, of the most recent son's Bay and its many tributaries, and cretaceous period.
the Rio Magdalena may be said to be Thus in its main features the Valley the South American Mackenzie ; while of the Amazons, like that of the Mis- the Rio de la Plata represents geosissippi, is a cretaceous basin. This graphically our Mississippi, and the Paresemblance suggests a further compar- raguay recalls the Missouri. The Paison between the twin continents of rana may be compared to the Ohio; the North and South America. Not only Pilcomayo, Vermejo, and Salado rivers, is their general form the same, but to the River Platte, the Arkansas, and the their framework as we may call it, that Red River in the United States; while is, the lay of their great mountain-chains the rivers farther south, emptying into and of their table-lands, with the ex- the Gulf of Mexico, represent the rivers tensive intervening depressions, pre- of Patagonia and the southern parts of sents a striking similarity. Indeed, a the Argentine Republic. Not only is zoologist, accustomed to trace a like there this general correspondence bestructure under variously modified an- tween the mountain elevations and the imal forms, cannot but have his homo- river systems, but as the larger river logical studies recalled to his mind by basins of North America — those of the the coincidence between certain phys- St. Lawrence, the Mississippi, and the ical features in the northern and south- Mackenzie – meet in the low tracts ern parts of the Western hemisphere. extending along the foot of the Rocky And yet here, as'throughout all nature, Mountains, so do the basins of the Amthese correspondences are combined azons, the Rio de la Plata, and the Oriwith a distinctness of individualization, noco join each other along the eastern which leaves its respective character slope of the Andes. not only to each continent as a whole, But while in geographical homola but also to the different regions cir- gy the Amazons compare with the St. cumscribed within its borders. In Lawrence, and the Mississippi with the bath, however, the highest mountain Rio de la Plata, the Mississippi and .chains, the Rocky Mountains and Coast the Amazons, as has been said, resemRange with their wide intervening table- ble each other in their local geological land in North America, and the chain character. They have both received of the Andes with its lesser plateaus in a substratum of cretaceous beds, above