16 PROCEEDINGS OF THE WASHINGTON MEETING 



In the summer of 1871 he went to Brazil with Hartt again, this time 

 visiting the Amazon Valley and making an important collection of Car- 

 boniferous fossils from the limestones at Itaituba, on the lower Tapajos 

 River. 



In the interval between 1871 and 1873 he was occupied with his 

 studies, and in 1873 he graduated at Cornell University; the year follow- 

 ing he continued his geological work for the master's degree, which he 

 received in June, 1874. His thesis was "On the Carboniferous brachio- 

 poda of Itaituba., Rio Tapajos," and was published as number 2 of Volume 

 I of the Bulletin of Cornell University, Ithaca, 1874. That was Derhy's 

 first publication on the geology of Brazil, and it is not only a valuable 

 paper in itself, but it is especially interesting in view of subsequent de- 

 velopments. The Itaituba fossils were in compact limestone, but as they 

 were silicified, they could be obtained in satisfactory form only by dis- 

 solving away the surrounding rock — a long and tedious process which 

 would have thoroughly discouraged most young men of Derby's age. 



In 1873 Derby was appointed instructor in geology in Cornell, and in 

 the summer of 1874 Professor Hartt made arrangements to go to Brazil 

 again. Leave of absence was obtained, Derby was placed in charge of 

 the work of instruction in the department, and in September, 1874, Hartt 

 went to Brazil again, taking Branner with him as his only assistant. 



Arriving in Rio de Janeiro, Hartt at once devoted all his energies to 

 interesting the leading men in a geological survey of the empire, and by 

 the end of a year the survey was provided for, and 0. A. Derby, Richard 

 Rathbun, and E. F. Pacheco Jordao were named as assistants of the new 

 "Commissao Geologica do Imperio do Brasil." In December, 1875, Derby 

 reached Rio de Janeiro and began his work under the government. He 

 held this position less than two years, for, through a change of ministry, 

 the survey was abolished in 1877, and Hartt died in Rio that same year. 

 Shortly after the extinction of the survey, however, Derby was given a 

 position in the National Museum at Rio as curator in charge of geology. 

 He remained in the museum until 1886, when he was made State Geologist 

 of the Brazilian State of Sao Paulo. 



The establishment of the Sao Paulo Survey was a step of great impor- 

 tance to geological science in Brazil, for Derby's knowledge of and interest 

 in the geology of the country as a whole enabled him to grasp more firmly 

 the geological problems of that particular State, and at the same time lie 

 became and remained the leading authority on the geology of Brazil. He 

 was State Geologist of Sao Paulo until 1904, when he resigned. 



In January, 1907, a new federal geological survey was provided for 

 under Dr. Miguel Calmon, who was then minister of public works, arid 



