The information it contains is, indeed, nothing decisive as to the existence of the human species, contemporaneously with those great extinct animals whose remains are found fossilized in the earth's strata. But, as relating to the first instance of the discovery of human bones in a fossil state, it is of some interest. After mentioning that, up to the date of his letter, he had discovered in 200 chalk caves of Brazil, 115 species of mammalia, of which not more than 88 are now known to exist there, the writer proceeds :

"In the midst of these numerous proofs of an order of things quite different from the present, I yet have never found the slightest trace of the existence of man. I supposed, therefore, that this question was decided, that human bones nowhere occur, when unexpectedly, after six years toil, I had the good fortune to find these bones; and, indeed, under circumstances which admit of speaking with some certainty in favour of their occurring again. These bones I fell upon in a cave, mingled with the bones of decidedly extinct animals, as, for example, of the Platyonyx Bucklandii, Chlamydotherium Humboldtii, C. Majus, Dasypus sulcatus, Hydrochorus sulcidens, &c., which directed my whole attention to these remarkable remains. Besides, they all bore the stamp of genuine fossil bones, inasmuch as they were partly converted to stone, and partly impregnated with small particles of the oxide of iron, which not only gave them an extraordinary weight, but even to some of them a metallic glistening. As to the great age of these bones no doubt can exist; but whether they date from the times of those animals, with the bones of which they were found lying together, in company, is a question which does not admit of being determined with equal certainty, since the cave is on the edge of a lake, by which the waters are yearly driven into it in the rainy season. Not only, therefore, might animal remains by degrees come there, but those brought there by the flowing of the water at later periods might also mingle with the earlier. This supposition has, in fact, received confirmation, in that, among the bones of extinct animals, there are also those of races still living. The condition of the latter, too, of which some appear to differ little from fresh bones, leads to this view, while others have reached the half metallic

state spoken of, and between the two sorts a third and more numerous variety is distinguishable, which has reached a middle state in decomposition. A similar difference was observed also in the human bones, by which their varying gradations of age are clearly manifested. Yet all are so altered, as well in their constituent parts as in the joining, that one cannot deny them a high antiquity; and even should they not have come there contemporaneously with the bones of extinct animal races, still they have a sufficient interest in this respect. From the investigations of European students of nature, it results, that no land animal, of which the bones appear in a truly fossil state, has lived within our historical period, and that they, consequently, mount up over 3000 years. If this conclusion is applied also to the human bones existing in a like state, they too are of a like antiquity. Since, however, the process of fossilization is as yet little known, especially if the time necessary to this transformation comes into question; and, if it is true that this time varies according to circumstances, we can attain only to a very indefinite approximation. Be it nevertheless as it may, in any case these bones must have a high antiquity, not only far outreaching the discovery of America, but even surpassing all historical documents of our race, since up to this time no fossilized human bones have been before met with. But hence it results, that Brazil was peopled at a very remote period, and probably before our historical era; and the inquiries which therefore urge themselves upon us are these: Who were these oldest inhabitants? from what race were they descended? and what was their manner of life, and their natural quality of mind. Happily, these questions may be easily solved. Being in possession of several more or less perfect skulls, I was able to define the position which they have occupied in the anthropological system; and, in fact, the narrow head, the prominent cheek-bones, the angle of the face, the formation of the jaw and of the cavities of the eyes, shew that those skulls belong to the American race. The Mongolian tribes come, as is well known, the nearest to it, and the most striking difference between the two is the greater flattening of the head in the former species. In this point the discovered skulls not only accord with those of the American tribes, but some

of them are to such a degree pressed in, that the forehead almost entirely disappears. It is known, that the human figures which were sculptured upon the ancient Mexican monuments are of a wholly peculiar conformation, and that the eranium, retreating backwards, was made to disappear immediately above the eyes. This anomaly, which in general is ascribed either to an artificial disfiguring of the head, or to the taste of the artists, thus receives a natural explanation, since it is proved that a race of men lived in these regions which possessed this conformation of the head.* The skeletons found belonged to both sexes, and were of ordinary size, though two male skeletons shewed a larger size. After these brief observations on the corporeal constitution of the primitive inhabitants of Brazil, we will also take into consideration their probable mental condition, and the degree of their cultivation. Since now it is proved that the development of the mental powers stands in direct relation to that of the brain, it follows, from the formation of the skulls found, that the intellectual life of their possessors must have played a very inferior part, and that their progress in arts and crafts must have been in the highest degree meagre. This inference is confirmed by the discovery of an utensil of the most imperfect make, which lay buried alongside of the skeletons. It was a semi-spherical hornstone of ten inches in circumference, which was worn smooth on the flat side, and evidently must have served to bruise seeds and other hard substances. As it cannot be my object, on this occasion, to make a thorough exposition of the present subject, a labour which I give over to abler hands, I have merely to observe farther, that I have found human fossil bones in two other caves also, which were almost without any gelatinous part, and therefore easily friable, and shewed a white fracture. Unfortunately, however, they did not occur with other animal bones, so that the question of chief importance, in respect to the longer existence of the human race on this earth, remains still undecided."

* It is still probable, however, that this configuration of cranium was the result of artificial causes. (Professor Silliman.)

Report on M. Alcide d'Orbigny's Memoir, entitled General Considerations on the Geology of South America. By M. ELIE DE BEAUMONT.

Regarded as a whole, the portion of the American Continent situated to the south of the equator, exhibits a great variety of orographical configuration. On the east we have an immense group of low mountains, forming a mass whose branches extend from some degrees south of the Line as far as the mouth of La Plata; while on the west, we have the Cordillera, whose elevated summits commence near the Straits of Magellan, and extend into Columbia, forming a ridge which follows different directions, and from which rise the highest peaks of the New World. Between these two great systems, commencing from the south of Patagonia, a nearly level plain skirts the Cordillera, occupies the intervening space comprised between that important chain and the mountain mass of Brazil, passes from the basin of the Plata into that of the Amazon, afterwards expands to the east, and embraces to a long distance the two banks of that vast river.

Gneiss Formation.-In South America, as over the surface of the whole globe, the rocks which constitute the first formations of the series of stratified rocks are crystalline; they are chiefly gneiss. These rocks are especially developed in the eastern part of the Continent, where the modern geological products are less prevalent than in the western. All geologists who have visited Rio Janeiro have pointed out the gneiss formation. Messrs Clausen and Pissis have ascertained its existence over the greater part of the surface comprised between the course of the Rio San-Francisco and the sea, from the 16th to the 27th degree of southern latitude. M. d'Orbigny has found it again at Maldonado, at Monte-Video, and in the Banda Orientale. M. Parchappe recognised it in the chain of the Tandil. M. d'Orbigny discovered an immense belt of the same rock, occupying a mean breadth of half a degree, having a length of upwards of 340 English miles, and traversing the whole province of Chiquitos.

The old rocks are almost every where composed of the same elements; and these are, at Rio-Janeiro and in the pro

vince of Chiquitos, porphyritic or granitoidal gneisses, which are superimposed on granite, and form the support of fine grained gneisses, or of mica-slates containing garnets and gnenatites; at Monte-Video, and at Maldonado, there are blackish and finely laminated gneisses; and at Tandil, according to the determination of M. Cordier, there are tabular varieties of petrosilex.

In Brazil, and in the east of the province of Chiquitos, the gneiss everywhere supports transition clay-slates. But when the latter are awanting, the gneiss is succeeded by formations of a much more modern date; for at Conception, at San Ignacio, and at Santa Anna de Chiquitos, portions of the Patagonian territory formation repose on the gneiss. M. Pissio has pointed out tertiary deposits, resembling the molasse of Europe, reposing on the gneiss of the environs of Bahia. At Monte-Video, and in the Pampas, the gneiss is surrounded by the Pampian tertiary formation; and, lastly, at Chiquitos, it is covered by the recent alluvia.

Silurian System.-The most ancient beds which M. d'Orbigny has found superimposed on the rocks of a decidedly crystalline character in South America, present, wherever he has seen them, a very uniform composition. They are, in their lower portions, coarse clay-slates (des phyllades schistoides), having a blue colour, and often containing chiastolite; and they pass in their middle portions into fine grained clayslates (des phyllades satinés), having a rose colour. These two series of beds, which are the most developed, possessing frequently a thickness of several hundred yards, do not contain any traces of organized beings. Above these there are sandstone flags (des phyllades grésiformes), or very micaceous slaty sandstones (grès phylladifères très micacés), whose thickness is upwards of 160 feet.

In these last mentioned beds, M. d'Orbigny has collected fossils, which, however, are rare, and which belong to the genera Cruziana, Orthis, Lingula, Calymene, Asaphus, and Graptolithus. Of ten species of these genera, eight are extremely analogous to the species of the silurian strata of Europe, and three, viz., Calymene macrophthalma, Cruziana rugosa, and Graptolithus dentatus, are even identical with