either to New Brunswick or Nova Scotia, to continue his explorations, in the course of which he would often lecture in the different towns to obtain means of paying his field expenses. In 1864 Mr. Hartt was employed, with Profs. Bailey and Matthews, on the geological survey of New Brunswick, and, while engaged in this work, obtained the first full proof of the existence of primordial strata in that province. Many of his discoveries in Nova Scotia and New Brunswick were published in the Provincial Government reports, and also in Dr. Dawson's "Acadian Geology." Hartt's constitution, though well able to withstand the severest kind of fatigue in exploration, was not proof against the damp, chilly atmosphere of his native land, and from this cause he often suffered much; so it was probably fortunate for him that just about this time his attention was attracted toward a new field.
Upon the organization of the Thayer Expedition to Brazil, by Prof. Agassiz in 1865, he was appointed one of its geologists, and henceforth to the time of his death he was ever a most devoted investigator of South American natural history. As a member of Prof. Agassiz's party he explored the neighborhood of the coast from Rio de Janeiro to Bahia, and ascended many of the rivers, making large zoological collections, but finding little of interest in the geology. Aided by New York friends he returned to Brazil alone in 1867, this time examining with the greatest care the reefs of the Abrolhos Islands, and those of the coast, as well as the geology of a part of Bahia and Sergipe. With the material thus far collected he began the work of writing up his geological reports in the capacity of geologist to the Thayer Expedition. This report was to have been included along with those of his chief, but under Hartt's hands it grew to such size that it was published separately in 1870 as the "Geology and Physical Geography of Brazil." In addition to the account of Hartt's researches, it included the best results of all who had ever published on the geology of the country.
After his return from the Thayer Expedition, the time he spent in this country until 1868 was devoted mostly to scientific teaching and lecturing in and around New York City, where he attained much success and made many warm friends. Early in 1868 he was elected Professor of Natural History in Vassar College, a position he resigned in the fall of the same year, to accept the chair of Geology in Cornell University. Shortly after assuming his duties at Cornell, he was married to Miss Lucy Lynde, of Buffalo, New York, who is now left with two children. In 1869 he was made General Secretary of the American Association for the Advancement of Science, to serve at the meeting of 1870; but a third expedition to Brazil, which he had been planning, called him away before the Association met. This trip was made in company with Prof. Prentice and eleven students of Cornell University, and was the largest of his own organizations from the United States. With this party he entered what was really a new region for