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.

FOOTNOTES:

[46] With respect _to the past_, it is, I fear, useless to look for any very positive data as to the state of the river previously to the last century:--the only allusion to it which I can find is in the 'Argentina,' an historical poem by Barco Centenera, who went out in 1572 with the Adelantado Zarate, and who, speaking of its depth between Buenos Ayres and San Gabriel, off Colonia, on the opposite shore, says:--

"De ancho nueve leguas ó mas tiene El rio por aqui, _y muy hondable_. La nave hasta aqui segura viene Que como el ancho mar es navigable."

The river's here nine leagues or more, _And very deep_, twixt shore and shore; _So far the navigation's free, As tho' twere on the open sea_.

ARGENTINA, CANTO II.

And although, perhaps, a poet's authority to not the very best for a geological fact, I have the less hesitation in quoting his couplet, as it is, to a certain extent, corroborated by the circumstance that, amongst all the dangers and disasters recorded with so much minuteness by the historians of the first discoveries of those parts, there is no instance, that I am aware of, mentioned by them of a shipwreck in the river below San Gabriel, the port to which all vessels at that time directed their course after entering it:--from this I think any one who knows the dangers of the navigation of that part of the river now, will be disposed to infer that it really must have been in former times as Centenera describes it, much more free and safe than it is at the present day:--it is probable that the Ortiz bank especially has very much increased.

[47] In the proportion of an ounce of litharge to a quart of oil.

[48] The following comparative measurements of the bones of the megatherium and of an elephant eleven feet high, are furnished by Mr. Clift:--

ELEPHANT. MEGATHERIUM. Ft. In. Ft. In.

The expansion of the ossa ilia 3 8 5 1 Breadth of the largest caudal vertebra 0 7 1 9 Circumference of middle of femur 1 0 2 2 Length of the os calcis 0 7-1/2 1 5

[49] Mr. Clift quotes a MS. memorandum in his possession, stating the measurement of the skeleton at Madrid to be, from the front of the nasal bones to the setting on of the tail, thirteen feet seven inches, and he is of opinion that, of the two, the specimen I brought home was the older and somewhat larger individual.