FOOTNOTES:
[37] The latitude of the Great Salt Lake was taken from about the centre of the north side of it, where the party were encamped.
In 1786 Don Pablo Zisur, a lieutenant in the Spanish navy, had fixed the north-east angle of the lake in lat. 37° 10´, and 4° 36´ west of the meridian of Luxan (Guardia); according to him the lake of Cabeza del Buey is in lat. 36° 8´, and the Guardia de Luxan in 34° 36´. Azara fixed it in 34° 38´ 36".
[38] In the life of the Carreras, given in the Appendix to Mrs. Graham's account of Chile, there is an account of some of these Indian forays in conjunction with Carrera's troops, particularly of their surprisal of the town of Salto, and the carrying off from thence of 250 women and children, after butchering all the men, in spite of every effort of their unnatural allies to prevent it.
[39] Villariño found the Indians in the Cordillera opposite to Valdivia calling themselves Aucases.
[40] Garcia seems to have believed that the language and origin of this people was different from the other Indians he fell in with. There is no proof, however, adduced of the difference of language, and I suspect they were only a further-removed branch of the Araucanian family, as were the Indians Viedma found at San Julian's in 1782.
[41] Captain Fitzroy determined it to be 3350 feet above the level of the sea, from which its true distance is 45 miles.
[42] At Buenos Ayres the variation in 1708 was 16° 45´ east; in 1789 it was 16° 30´; and in 1818 it was 12½ east.
[43] A collection of the birds of those regions would form a most interesting addition to any museum. A large proportion of them are, I believe, quite unknown in Europe.
[44] An accident to the barometer prevented the officers making a series of observations with that instrument, which would have been of considerable interest. They made, however, good use of the thermometer, of which a daily register was preserved.
[45] I understand, however, that General Ramos has expressed his opinion that it is not navigable for more than forty leagues from its mouth.
CHAPTER X.
GEOLOGY OF THE PAMPAS.
Geological Features of the Southern compared with those of the Northern Shore of the Plata. The Pampa Formation, probably derived from the Alluvial Process now going on, as exhibited in the Beds of the Plata itself and other Rivers. Fossil remains of land Animals found in it, above Marine Shells. Such Shells where met with, and of what Species. Mr. Bland's Theory of the Upheaval of the Pampas from the Sea, founded on the Deposits of Salt in them:—The presence of such Salt may be otherwise accounted for. Account of the Discovery of the Gigantic Fossil remains sent to England by the Author.
I cannot leave the pampas without a few words upon their geological features, and upon the remarkable contrast exhibited in the appearance of the country on the northern and on the southern shores of the Plata. On the north side the formation is of clay-slate, gneiss, and granite, of which the islands in the river above Buenos Ayres are also composed, particularly Sola, Las Hermanas, and Martin Garcia, where the granite is quarried for the pavement of the city. On the southern side every trace of rock is entirely lost, and for hundreds of miles inland not even the smallest pebble is to be met with.
As far as we are yet acquainted with it, the whole of that vast level called the pampas, reaching from the eastern terminations of the Andes to the shores of the Plata, appears to be one immense bed of alluvium tranquilly deposited during the imperceptible lapse of ages; the delta perhaps, not of one, but of numerous rivers, originating in a once more general diffusion of the waters from the Andes before their courses were defined by their present channels. Some such process of formation appears still to be going on in many parts of the pampas, where muddy streams and streamlets, the collections from the mountains in the south and of the rainy seasons, too sluggish to force a way through the level country, inundate the plains, and gradually deposit the alluvial sediment, together with a prodigious quantity of decomposed vegetable matter, in the swamps and morasses, until accumulations of fresh soil take place in sufficient quantity to throw off the waters again in some other direction. The bed of the Plata, itself the reservoir of a hundred rivers, is, from all I could learn, gradually silting up, and, wide as it is at the present day, along its shores, and particularly above Buenos Ayres, may be distinctly traced the evidences of the waters having once occupied a bed of infinitely greater extent. Every observation tends to the inference that this now mighty estuary may, centuries hence, be reduced to similar bounds and rules to those which govern the outlets of the Amazons, the Mississippi, the Nile, and the Ganges. Nor will this require, perhaps, so long a period as might at first be imagined.[46] If we except the narrow channel between the Chico and Ortiz banks, below Buenos Ayres, the average depth of the river between that city and Monte Video does not exceed twenty feet. The prodigious quantity of mud and detritus brought down by it is well known,—the whole river, wide as it is, is at times discoloured by it. Now, if but enough of this sediment is deposited to cause the small annual increase of only half an inch in the bed of the river, it will not require 500 years to form a delta, which, in the language of the country, will be nothing more or less than an extension of the existing pampas.
Such, I conceive, may have been the origin of the far spread formation of the present pampas or plains, throughout which are to be found the fossil remains of gigantic animals of long lost species, such as the megatherium and mastodon, and other monsters yet unnamed, which in former ages may have grazed upon the abundant pastures produced in the rich loamy lands saved from the waters; whilst beneath, in strata of marine shells, are no less incontestable evidences of the ancient bed of the ocean.
It cannot be expected that, in a country so uniformly level as the pampas, sections of sufficient depth will frequently occur to exhibit the underlying strata. They must be looked for at the outlying extremities of the formation, where the upper bed thins out,—to use a geological term. Now there is nothing that I know of to interrupt the uniformity of the stratum between the southern shore of the Plata on the one side, and the eastern base of the Andes on the other, and at both these extremes marine remains are strikingly exhibited.
General Cruz, in his journey from Antuco to Buenos Ayres (noticed in chapter viii.), in passing through the valleys in the lower ranges of the Cordillera, immediately before reaching the pampas, was exceedingly struck with the abundance of marine remains thereabouts. He says, in his diary, "In all the hills and valleys under the Cordillera, as far as the river Chadileubu, a great quantity of marine remains are met with, some of them constituting a sort of limestone. Not only may these remains be observed upon the surface, but also at great depths below it, in the sections formed by the torrents as they descend from the mountains: there can, therefore, be no doubt that the waters of the sea once occupied the place of the land in those parts."
Proceeding eastward, by the base of the mountain ranges of San Luis and Cordova, which bound the pampas to the north, we have the testimony of water-worn rocks and beds of shells in that direction, from Schmitmeyer, Helms, and other travellers, at Portezuela and on the banks of the Tercero; and beyond the Sierra de Cordova, on the great river Paranã, near Santa Fé, Mr. Darwin found in the cliff which skirts the river a stratum of marine shells distinctly exposed a little above the level of the water, and with the alluvial bed over it, forty or fifty feet thick, containing bones of extinct mammalia.
Here, then, I think, we may trace, all but continuously, the northern and western shores of a gulf, which must have been nearly as large as that of Mexico, and not very unlike it, perhaps, in general outline. Travelling south from Santa Fé, along the shores of the Plata, which bounds these pampas on the east, we find, at distances varying from one to six leagues inland from the river, and from fifty to one hundred and fifty miles from the sea, large beds of marine shells, which the people of those parts quarry for lime. From these deposits I have myself specimens of Voluta Colocynthis, Voluta Angulata, Buccinum Globulosum, Buccinum Nov. Spe., Oliva Patula; Cytheræa Flexuosa? Mactra? Venus Flexuosa, Ostrea, &c. In some places these shells are so compact as to form a sort of limestone, easily worked when first dug out, and hardening afterwards on exposure to the air. The church of Magdalena upon the coast is built of this material. They are generally in good preservation, and some of the species appear almost identical with those found upon the coasts of Brazil; others, on the contrary, found with them are not known. There is one, found generally by itself, unmixed with others, which is particularly interesting on this question, as strikingly proving the gradual growth of the pampas; it is the small mya, named potamo-mya by Sowerby, usually found in estuaries at the junction of the fresh and salt water, and the existing type of which is now to be met with at the mouth of the Plata; but the bed from which my fossil specimens were taken is at the Calera de Arriola, to the north of Buenos Ayres, nearly 150 miles from its present habitat; and there (I think manifestly proved by these little shells) must have been once the mouth of the mighty estuary, which is now more than 150 miles below it.
I must not omit to state that all these marine deposits are found in situations more or less above the present level of the ocean; this, in the neighbourhood of the Cordillera, which is so continually liable to volcanic disturbances, may be accounted for; but it leads to other speculations in the flat alluvial plains towards the Plata, where the phenomenon of an earthquake is utterly unknown, and where the apparently perfect horizontality of the strata would seem to negative the idea of any violent action by which it might have been upheaved.
Mr. Bland, one of the North American Commissioners sent to Buenos Ayres in 1818, reasoning upon the quantity of saline matter found in the pampas, hazards, as he says, the conjecture that the pampa formation "may have been gently lifted just above the level of the ocean, and left with a surface so unbroken and flat as not yet to have been sufficiently purified of its salt and acrid matter, either by filtration or washing:" and undoubtedly such saline matter does exist very extensively over this formation. Many of the running waters, as their names denote, are rendered brackish by it; and lakes which have no outlet become saturated with it, and deposit it in regular beds, where in the dry season it may be collected in any quantity. But it does not necessarily follow that it has been left there by the ocean: we know that salt abounds in the Andes, and that extensive beds of it occur, particularly in those parts of them from which we may conjecture that the greater part of the waters of the pampas are derived; and if for a moment we can suppose the pampas themselves to have originated in sedimentary deposits from those mountain chains, we must I think equally admit that the alluvial soil washed down can hardly fail to be impregnated with so soluble a substance as the salt which abounds in them. In a country of more varied surface we might expect the briny particles to be carried off by the streams and lost in the sea; but in the dead levels of the pampas the greater part of the streams themselves are lost long ere they reach the ocean. The waters deposit their sediment over the surface, and the salt is left to amalgamate with the mire of the marshes, until perhaps again the rains collect it, and either partially carry it off in brackish streams, or deposit it in the basins of the inland lakes, in which it is so abundantly found. That it is a superficial deposit I think is proved by the fact that (as elsewhere noticed) in the immediate vicinity of some of the saline lakes and rivers in the pampas, and where the surface of all the surrounding country appears to be incrusted with salt, the people dig wells, and find perfectly fresh and potable water, as I understand, at a depth of from twenty to fifty feet. The same may be said to occur throughout the city of Buenos Ayres, where all the wells which do not penetrate the tosca produce water more or less brackish, whilst those which go below it are sweet. Some of the best water I ever tasted was from a well sunk in the sandy stratum below the clay at Mr. Brittain's quinta outside the city. Further, I imagine that the discovery of the remains of land animals so generally throughout this formation is in itself conclusive of its deposition subsequently to the existence of the ocean in those parts, the ancient bed of which it must very considerably overlie.
To speak of the megatherium alone, its remains have been found in all parts of the pampas, from the river Carcaraña, in the province of Santa Fé, to the south of the Salado, a distance of nearly 300 miles in a direct line, and in all the intermediate country. Such remains are much more common than is supposed, and I am satisfied might frequently be met with if searched for during the dry season, or after long droughts, either in the banks of the rivers, or in the beds of some of the numerous lakes which are then dried up. All the remains I sent home were so discovered, and so were those sent to Madrid by the Marquis of Loreto, which were found in the bed of the river Luxan, a short distance to the north of the city of Buenos Ayres. The great skeleton I obtained was discovered in the river Salado, to the south of Buenos Ayres, after a drought of unusually long continuance, by a peon in the service of the Sosa family, who, attempting to cross the river at an unfrequented spot, was struck by the appearance of a large mass of something standing above the surface of the water, and which, supposing at first to be some part of the trunk of a tree, he determined to get out if possible: in this he was assisted by some of his brother peons, who, throwing their lassoes over it, succeeded in dragging it out, fortunately without injury, for it proved to be nearly the entire pelvis of the megatherium: with it were also brought up several of the other bones, and amongst them some of the vertebræ. To the peons the pelvis luckily appeared to be useless: turn it which way they would, they all agreed that it did not make half so comfortable a seat as either a bullock's or a horse's head; but the vertebræ did not so easily escape, and in a place where not a stone is to be seen, were eagerly seized upon as excellent substitutes to boil their camp-kettles upon. The smaller ones being best suited to the purpose were the first to disappear, which may account for the deficiency of all the cervical vertebræ as well as of many of the smaller bones of the feet and other parts. After a time it was suggested that the pelvis and some of the largest bones should be sent as curiosities to the owner of the estancia on which they were found, Don Hilario Sosa, at whose house in Buenos Ayres I first saw them. He was good enough, seeing my great anxiety to obtain possession of them, after exhibiting them to his friends, to place them at my disposal, and to allow me to send people to his estancia to search for the remainder of the skeleton: by their exertions many other portions of it were saved; and but for the destruction of some by the country-people, as described, and of others which, having been taken out in the first instance, had remained exposed for some months to the sun, and had become so brittle in consequence as not to bear removal, the skeleton would have been tolerably perfect. As it is, it was very fortunate that amongst the parts preserved were some of those which are wanting in the skeleton at Madrid, especially the bones of the tail, which singularly corroborate the anticipations of Cuvier, whose description of this remarkable monster was drawn from a representation of that specimen, the only one known to exist till mine reached Europe.
M. Cuvier was not I believe aware of the grounds which now exist for supposing that the animal was covered with a coat of mail, like the armadillo, which has led other comparative anatomists to ally it to that family. There were no remains of such a shell appertaining to the specimen at Madrid, neither were any found with the bones which I have spoken of as discovered in the Salado. Portions, however, of a shelly covering in a fossil state, which must have belonged to some gigantic animal, had been at various times dug up in the pampas, which had excited the attention and speculations of the curious. Even father Falkner in his account of the country speaks of them:—he says, that he himself found the shell of an animal composed of little hexagonal bones, each bone an inch in diameter at least, and the whole shell nearly three yards over: it seemed to him to be in all respects, except its size, the upper part of the shell of an armadillo.
The researches I set on foot after finding the skeleton in the Salado led to fresh discoveries, which, if they do not identify these shells with the megatherium, must lead us to conclude that these regions were once inhabited by other gigantic animals no less extraordinary. When the country-people saw the eagerness with which the big bones from the Salado were sought for, they were not backward in speaking of other places where similar remains had been met with, and were still, as they believed, to be found. Upon this information I once more despatched my agent to the south of the Salado, and the governor, Don Manuel Rosas, taking an interest in the matter, was good enough to furnish him with a letter of recommendation to the local authorities, desiring them to give him not only protection, but every assistance he might need to ensure his success. In little less than three weeks we were repaid by the discovery of two more enormous skeletons on the estancias of the governor himself, called Villanueva and Las Averias, and in both instances with the novelty of their being encased in a thick coating or shell resembling that of the armadillo. The first, found at Villanueva, though still of gigantic proportions, appears to have been very much smaller than that which had been taken out of the Salado: it was discovered in the bed of a small rivulet, and upon exposure to the air nearly all crumbled to dust. The only portions it was possible to preserve being part of a scapula, a small portion of the jaw with one small but perfect tooth remaining in it, and a fragment of a hind leg, with some of the feet bones. The shell lay, as Mr. Oakley, my agent, described it, a little below the principal mass of the bones, looking like the section of a huge cask; the form of it when first discovered appeared natural and perfect, but it would not bear to be lifted out of its bed, and broke into small pieces and crumbled away immediately.
From the account given by Mr. Oakley, and the apparent resemblance of the remains of this specimen to those previously discovered, although of a much smaller size, I was induced to believe that they belonged to a younger animal of the same species; other persons, however, who have since had an opportunity of comparing them with recent specimens of the dasypus family, have suggested that it is more probable that they belonged to a gigantic armadillo. Such is the belief entertained, I am told, at Paris, where casts of the bones in question have been sent. The other skeleton, found at Las Averias, was described to be as large as that of the megatherium. It lay in a bed of hard clay, on the side of the lake of Las Averias, partly exposed to view by the action of the water against it in stormy weather. Here a large portion of the shell appeared in a perfect state, and the country people, who took Mr. Oakley to the spot, assured him that, when first discovered, it was at least twelve feet in length, and from four to six in depth. It was very hard, but could not be got out whole. Mr. Oakley, however, brought away some considerable portions of it, which, in this instance, became harder the longer they were exposed to the external air. Not so the bones within, which, like those at Villanueva, almost immediately mouldered away on being taken out of the earth. A very imperfect fragment of the pelvis only reached Buenos Ayres.
On my return to England I exhibited these remains at the Geological Society, and afterwards made them over to the Royal College of Surgeons, whose collection of comparative anatomy is by far the finest in this country. Mr. Clift, the curator of that collection, undertook to describe them, and his paper upon them will be found in the "Transactions of the Geological Society for 1835." Casts of them, which were made at my desire, were also deposited in other museums, abroad as well as at home. Sir Francis Chantrey was kind enough to superintend the making of them, and to a simple suggestion of his, a solution of linseed-oil and litharge,[47] with which they were very thoroughly saturated, may be ascribed their restoration to a state hardly to be distinguished from that of the most recent bone.
Dr. Buckland, the learned professor of geology at Oxford, has since made the megatherium the subject of a chapter in his "Bridgewater Treatise," wherein he has fully described the remarkable peculiarities of its structure, in which, as he observes, it exceeds its nearest living congeners in a greater degree than any other known fossil animal. With the head and shoulders of a sloth, it combined, in its legs and feet, an admixture of the characters of the ant-eater, the armadillo, and the chlamyphorus: the latter it probably still further resembled in being cased with a bony coat of armour. Measuring the bones only, its haunches were more than five feet wide;[48] its thigh bone was twice the thickness of that of the largest elephant; the fore foot was a yard in length, and terminated by a gigantic claw; the tail, the width of the upper part of which was at least two feet, and which was probably clad in armour, must have been infinitely larger than that of any other known beast, amongst extinct or living mammalia. The whole body, according to the learned professor's calculations, was about eight feet in height, and twelve in length.[49] The annexed plate, carefully drawn from the original bones, under Mr. Clift's superintendence, will serve not only to give a general idea of the strange structure of this extraordinary monster, but to show the parts which are still wanting to make up the specimen. I will only add that, if any of those parts should fall into the hands of a casual collector, he will render a service to science by transmitting them to the curator of the College of Surgeons in London.
MEGATHERIUM.
Note: The Parts uncoloured are wanting.
Scale of 3 feet 3/8 of an Inch to a foot.