of his many other duties, he was soon obliged to resign that position. The results of his researches may be briefly summed up as follows: Before he went to Brazil on his second trip, in 1867, scarcely anything was known of fossiliferous deposits there, and thus no material existed toward the study of the systematic geology of the country. A few Cretaceous fossils had been recorded from Bahia; the Danish naturalist Luns had very fully described the bone-caverns of Lagoa Santa in Minas Gerães, and we knew of coal-plants from Rio Grande do Sul; but beyond this the paleontology of Brazil was a perfect blank. Hartt's greatest achievement in Brazil was probably his solution of the structure of the Amazonian Valley. It was founded on the best of paleontological evidence which proves the existence of an immense palæozoic basin lying between the metamorphic plateau of Guiana on the north, and that of Central Brazil on the south, and through which flows the river Amazonas. Silurian, Devonian, and carboniferous rocks, make up the series in regular succession, and in many localities are highly fossiliferous. He has explained the character of the isolated Cretaceous deposits, mostly discovered by himself, existing along the coast from Pará, to Bahia, and of the Carboniferous and other regions south of Rio. He has shown us the manner in which the rocky structure of Brazil was built up, and has done much toward solving the relations of the crystalline rocks which compose by far the larger portion of its surface. He has explored the shell-heaps, burial-mounds, and other relic-localities of the prehistoric tribes from far up the Amazonas to the southernmost coast province. We owe to him also the first real satisfactory explanation of the reefs of Brazil, which he distinctly shows to be of two kinds—sandstone and coral. He spent much time in studying the customs and languages of the modern Indian tribes of the Amazonas and Bahia, and collected very much material toward a grammar and dictionary of the Tupé Indian language in several of its dialects. But to attempt a complete account of Prof. Hartt's Brazilian explorations and discoveries would require a longer article than we can give here. In connection with the Geological Commission of Brazil he founded a large museum in Rio de Janeiro, which will always bear testimony to his great final undertaking. His field-parties made very extensive collections of rock-specimens and fossils, and in the explorations of the reefs they gathered a large collection of marine invertebrate animals of all kinds. About a year ago, when the members of his survey were mostly recalled to Rio for the purpose of writing up their reports and of studying the material they had collected, it was found that some six hundred cases had been sent in from the field, and were awaiting suitable quarters. A large building was obtained, and in the course of several months there appeared a museum of geology and marine zoölogy that would have done credit to a much larger commission working a much longer time. It contained fossils, minerals, and rocks, from nearly every known geological locality in Brazil, and
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THE POPULAR SCIENCE MONTHLY.