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and sandstone of the second region, and above this a bed, 100 metres or more in thickness, of amygdaloidal and porphyritic trap, apparently a kind of trachyte. The amygdaloid is full of beautiful agates. This second escarpment is the beginning of the third geological region, the topographi cal features of which are very similar to those of the second or Campos Geraes region, that is, produced by denudation on horizontal beds. The escarpment extends entirely across the province, in a north-south direction, and into the province of São Paulo, where I have recognized the same rock, in the margin of the plateau, west of the Piracicaba river. South of the river Iguassú, I am informed by Mr. Luis Cleve, a very competent observer, that it bends eastward, under the name of Serra de Espigão, and extends as far as the Serra do Mar. Prof. Hartt had already observed that the Serra do Mar, in Santa Catharina, is capped by phorphyritic trap. It is probable, therefore, that these rocks cover the greater part of the interior of that province, as well as the neighboring portion of Rio Grande do Sul, in which agatiferous trap is common. A portion of the Republic of Uruguay probably belongs to the same formation. To the west the country is unexplored, but from the scanty information I could obtain, it seems probable that the trap formation extends to the river Paraná.

The surface of this region is, in general, a heavily wooded plain, but has several extensive campos, the most important ones being those of Guarapuava, which unite, to the south, with the extensive campos of Rio Grande do Sul. There appears to be a slight inclination towards the Paraná, and the river valleys being deep, present high steep slopes, that have been dignified by geographers, as well as the common people, as mountains. In point of fact, no true mountains exist in the province, outside of the metamorphic area.

No very definite data exists for determining the geological age of this enormous outflow of trap. It is certainly later than the Devonian, and is most probably Mesozoic. In lithological characters both the trap and the red sandstone, which appears to be associated with it, and to be distinct from the underlying Devonian series, resemble in a striking manner the Triassic rocks of eastern North America.

The drainage of the province is determined by the above described topographical features, and is principally toward the Paraná, only one large river, the Ribeira, flowing directly to the Atlantic. This river rises north of Curityba, in the mountainous Assunguy region, and flows northward, into the province of São Paulo, breaking through the Serra do Mar, above the city of Iguape. Some of its tributaries flow down the slope of the Serrinha, and have cut ravines, indenting the margin of the sandstone region, but can hardly be said to drain any part of the Campos Geraes. In the same metamorphic region, between the Serra do Mar and the Serrinha, rises the principal river of the province, the Iguassú, which flows first southward and then westward, traversing the second and third regions, to empty into the Paraná. Passing over several almost unknown rivers, belonging exclusively to the third region, we come to the Ivahy,

which rises in the wooded western portion of the second region, flows for some distance northward, skirting the base of the Serra de Esperança, and finally turns westward, entering the third region, and traversing it to the Paraná. In the north, forming a part of the northern boundary of the province, is the large river Paranapanema, which, like the Iguassú, rises in the metamorphic region and traverses the two others, receiving from the province the Itararí, Rio de Cinzas and Tibagy. The latter is, par excellence, the river of the Campos Geraes, in which it rises and flows, to within a short distance of its mouth, where it enters the third region. It receives from the north the Pitanguí and Yapo, both of which rise in the metamorphic region, about Castro, and enter the sandstone region by deep cañons.

The diamantiferous region is principally in the valley of the Tibagy. Its tributaries, the Yapo and Pitanguí, also contain the gems, but are supposed to be less rich than the main river, perhaps because of insufficient examination. Fine diamonds are also said to have been found in the Rio de Cinzas. As far as I was able to learn, they have never been found in the Iguassú or Ivahy, although I see no reason why they should not occur, at least in the former river.

The gems occur in the sands of the river, in the numerous pot-holes, and also in gravel banks, known as dry washings, situated in the campos, at a greater or less elevation above the river. Near the village of Tibagy, are two of these dry washings. One is in a depression of the Devonian shale, in the valley of a small stream, and is only a few metres above the level of the river. It may therefore be supposed to have been deposited by the river, or by the stream that now cuts through the deposit. The section presents below a very irregular deposit of pebbles and sand, a few centimetres in thickness, which is the part washed. Above this are three or four metres of coarse, variegated sand, with pebbles scattered irregularly through the bed, which shows very irregular lines of deposition, as if deposited in an eddy. Portions of this bed have been cemented by oxide of iron, forming curious, corrugated sheets, globes, and irregular masses, of extravagant form. On top is about a metre and a half of dark-red, structureless clay. The other washing is on a hill side, near the top, at an elevation of about twenty metres above the bed of a small stream, which flows along the base of the hill, and empties into the river, at an elevation of about 100 metres below the mine. The deposit has evidently been laid down under water, but it can scarcely be attributed to any of the present streams. It also rests on Devonian shale, fragments of which are scattered abundantly through it, and consists of a bed, about three metres thick, of sand and pebbles, in which diamonds are irregularly distributed. Above this are about six metres of structureless, red clay, like that of the first washing.

The pebbles in both these washings are well rounded, and consist mainly of quartz and of quartzose rocks, with pebbles of gneiss, and of various other metamorphic and igneous rocks. The red clay continues nearly to the top of the hill, which is a long ridge, with moderate slopes, and extends for a

considerable distance horizontally, but whether it is everywhere underlaid by the diamantiferous gravel or not, I cannot state. Other washings have been opened, some twelve or fifteen miles below Tibagy, and it is probable that there are many other localities in which diamonds may be found.

As I saw no work in progress, I could form no idea of the richness of these mines. The diamonds are said to be rare, and small and poor, in comparison with those found in the river. The workings have been conducted on a very small scale and very carelessly, so that, although the mines are certainly not extremely rich, it is impossible to affirm that they would not repay better, and more systematic management. A small quantity of gold also occurs in these washings, and this metal is quite generally distributed throughout the region.

In the river, the best stones are found in the deposits in the pot-holes, which contain gravel, firmly cemented by ferruginous matter. Rarely potholes are found with a very hard, bluish cement, and these are reported to contain the most diamonds, which are of the best quality both as regards size and perfection. Not having seen this cement, I can form no idea of its character. The miners note as a curious fact, that in a group of pot-holes close together, one may have the bluish cement, while all the rest have the ferruginous, the pebbles of the one being quite different from those of the others.

Many of the stones shown me were broken and worn, but a fair proportion were perfect crystals. The largest ones I saw were about the size of a small grain of corn, but were irregular and broken. The most valuable stone found here, of which I could obtain an authentic account, was sold for a conto of reis ($500). The stones are in general of good color and brilliancy.

Coming now to the question of the origin of the diamonds, it seems to me to be very evident that they are washed out of the Devonian sandstone. As already remarked, the Tibagy is almost exclusively a river of the Devonian plain. The lower portion, in the trap region, is not known to be diamantiferous, and if it is, since the stones occur throughout the whole course of the river, before it enters the trap formation, the latter may be eliminated from the problem. There remain then the Devonian rocks and the diorite. Having passed around the head of the river, and crossed it at three different places, I have become satisfied that these are the only rocks that come to the surface, to the eastward of Tibagy, that is to say, in the diamantiferous region. It is of course possible that the river may have cut down, in certain places, to the underlying metamorphic rocks, but of this there is no evidence, and it is not probable that any considerable area of such rocks are exposed, or if so exposed that it could have furnished diamonds to so wide-spread a region. Two considerable tributaries, the Yapo and the Pitanguí, flow from the metamorphic region, and might be supposed to have brought the diamonds from the rocks cut through in that region, but I was unable to obtain any notice of diamonds, found in those rivers, before entering the sandstone district, and the Tibagy is diamantiferous above, as well as below, its confluence with them.

PROC. AMER. PHILOS. SOC. XVIII. 103. 2G.

PRINTED JUNE 10, 1879.

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[May 16, The diorite can scarcely be supposed to have furnished the gems, not alone on account of the nature of the rock, but because in the upper part of the valley, where diamonds are not uncommon, diorite is extremely rare, if it occurs at all, and because the pebbles which always accompany the gems, certainly do not come from the diorite. This last has most probably furnished, by decomposition, the red clay, above the gravel at Tibagy. The only other rocks which, as far as I observed, could have given such a clay, are those about Castro; but it would be difficult to account for its transportation from there to Tibagy, while large dykes of diorite are common near the latter place.

The secondary origin of the gravel is not far to seek. The sandstone is everywhere full of pebbles, and on every slope where this rock is exposed the surface is strewn with gravel, set free by disintegration. The primary origin of the pebbles is equally clear; they, in common with all the material of the Devonian beds, are derived from the metamorphic series. That the diamonds have the same primary origin can hardly be doubted, as they cannot be supposed to have been produced in the sandstone, which does not show the slightest sign of metamorphism or of crystallization of any kind. That the diamond must have originated in some series rich in crystals is evident from the fact, that it is always accompanied by a variety of crystals, called by the miners informations. I have not had an opportunity of determining those of Tibagy, which do not differ materially from those already described from Bahia and Minas Geraes.

It may then be regarded as extremely probable, if not absolutely certain, that the diamonds originated in the metamorphic series; that, during the Devonian age, they were washed out and redeposited in the sandstone, from which they have been again extracted, to find their third resting place in the sand banks and pot-holes of the river, and in the gravel deposits of the campos. May we not suppose that the rare patches of gravel, with blue cement, are nests formed in the sandstone and laid bare by the formation of pot-holes?

As to what portion of the extensive metamorphic series constituted the original matrix of the diamond, I could obtain no data in Paraná. The evidence on the subject, which is being slowly accumulated, tends apparently to the confirmation of the old idea, that it belongs to some part of the itacolumite series.

After my studies in Paraná, it seems to me probable that the extensive high sandstone plateaus of Central Brazil, which we have been accustomed to consider of Tertiary age, are in reality much older, and probably Palæozoic. It is yet too early to form a decided opinion respecting them, but if my suspicion regarding their age proves correct, we can explain the course of geological events in Brazil much more satisfactorily than at present.

The lower plateaus, of almost precisely similar topographical and litho logical character, along the coast and on the Amazonas, are certainly later than the Cretaceous; but none of those, whose age can be positively determined, rise much above 1000 metres, and the higher plateaus of the interior have been referred to the Tertiary, solely on resemblances in lithological characters which, in Brazil, are peculiarly deceptive and untrustworthy.

Obituary Notice of the late Isaac Hays, M.D. By Daniel G. Brinton, M.D.

(Read before the American Philosophical Society, May 16, 1879.)

The subject of the present memoir, Dr. Isaac Hays, had been at the time of his death, a member of this Society for very nearly fifty years, his name first appearing upon its rolls in 1830. For many years he was also one of its most active members, and in the published volumes of our Proceedings which embrace the period previous to 1850, his name frequently recurs. Most of the subjects which he brought before the Society, related to medical science, and especially those portions of it connected with the physiology of vision and ophthalmic surgery. But he did not confine himself to professional topics. I find, on looking over the earlier numbers of our Proceedings that he took considerable interest in geology, particularly in the remains of the gigantic mammals preserved from the post-tertiary period. About 1840, a number of such remains were collected in Missouri by Dr. Koch, and subsequently exhibited in this city and London. An active d'scussion arose among palæontologists as to their classification. Besides, the mastodon, the Elephas primogenius, and the mammoth, they distinctly proved, so one party maintained, the former existence of another species of mastodontoid animals belonging to the class Proboscida, to which was given the name Tetracaulodon. Dr. Hays sided with this party, and in addition to many verbal statements embodied in the Proceedings, he published in the Transactions a paper on the teeth of the mastodon, evincing in its preparation a most careful study of his theme. That later investigations have disproved his position, detracts but little from its merit; for the abstract correctness of a scientific theory is of less importance than the honesty and ability with which it is advocated. At various periods Dr. Hays served on the Committee of Publication, and the Council, and was Curator.

At the time Dr. Hays was elected to this Society, he was thirty-four years of age. He was born July 5, 1796, in this city, his father residing at that time on Chestnut street below Third. His education had been first at the Grammar school kept in those days by Samuel Wylie, next at the University of Pennsylvania, whence he was graduated, A. M., in 1916; and finally as a medical student in the same institution whence he received the degree of M. D., in 1820. His preceptor was the eminent Dr. Nathaniel Chapman, celebrated not less for his wit than for his professional skill.

In early life Dr. Hays was much interested in natural science, and even before his graduation in medicine, he joined, in 1818, the Academy of Natu ral Sciences. With its history and success, he was identified for more than half a century. From 1865 to 1869 he was its President, and in many other official capacities actively aided its progress and influence.

His sympathies with the advance of general science led him to unite with others in the organization of the Franklin Institute. He was one of its original members, and for a number of years its Corresponding Secretary.