geological exploration—the Amazonian Valley—hoping there to discover, at the falls of the different tributaries of the Amazonas, other fossiliferous formations than the Cretaceous, which latter alone he had found along the coast. He was well rewarded, and returned to the United States with large collections of fossils of the Palæozoic age, and sufficient other evidence to allow of his giving us a very accurate though general idea of the formation of the Amazonian Valley. His results were strongly opposed to the theory of Prof. Agassiz, of its glacial origin. Not entirely satisfied with the amount of material obtained on this last expedition, he returned again to the Amazonas in 1871 with Mr. O. A. Derby, who had accompanied him on the former trip. Together they carefully reëxplored the same regions gone over before, adding much to the stores already brought to the United States, and also examining the ancient Indian mounds and shell-heaps of numerous localities. The two Amazonian trips of Prof. Hartt were rendered possible through the liberality of Mr. Edward Morgan, of Aurora, New York, in whose honor they have been called the "Morgan Expeditions."
Returning from Brazil once more, he remained at Cornell University about three years, quietly working up the results of his later trips, and publishing his reports upon them; but his active spirit would not allow him to remain in this condition long. He conceived the idea of systematically exploring the entire empire of Brazil, a country possessing an area almost as great as the United States. In August of 1874, by request of the Brazilian Minister of Agriculture, he went to Rio de Janeiro to submit his plans for the organization of a Geological Commission of Brazil. He first suggested the forming of a very large party similar to those engaged in our own national explorations; but it was found that the existing appropriations would not suffice for so grand an undertaking, and he was forced to begin on a more modest scale, the commission dating from May 1, 1875. In addition to the chief, there were never more than five or six assistants at any one time, comprising two assistant geologists, one topographer, and two other assistants, and at times a photographer or other specialist. His former experiences in Brazil aided him in rapidly attaining good and important results. He took the old grounds which he had already examined as starting-points for his new explorations, and worked outward from them in all directions, quickly but carefully enlarging the known area of fossiliferous and other rocks. This kind of work he was, of course, able to carry out only on the Amazonas and in the northern coast provinces; but to the south of Rio he had everything to begin, and in those localities his examinations were more hasty, bearing the character of preliminary surveys; but they were also productive of valuable results.
On the reorganization of the National Museum at Rio, in 1876, Hartt became director of its department of Geology; but, on account