1879.] 1 °5 [Derby. 



Curators. 



Hector Tyndale, Charles M. Cresson, Daniel G. Brinton. 



Treasurer. 



J. Sergeant Price. 



Pending nominations 871, 872, 873 were read. 

 Mr. Lesley was nominated as Librarian ; and the meeting 

 was adjourned. 



A Contribution to the Geology of the Lower Amazonas.* 



By Orvii/le A. Derby, M. S. 



(Read before the American Philosophical Society, Feb. 21, 1879.) 



In the following sketch of the geology of the region of the Lower Ama- 

 zonas I have attempted to give a resume of the most important results of the 

 studies made by, and under the direction of, the late Prof. Ch. Fred. Hartt, 

 in whom Science mourns the loss of one of its brightest ornaments in 

 North America, and of its chief and ablest expounder in the southern con- 

 tinent. It is, for the most part, condensed from an extensive report, pre- 

 pared by Prof. Hartt as chief of the Geological Commission of the Empire 

 of Brazil, the publication of which has been delayed, in consequence of the 

 financial condition of the Empire and of the untimely death of the chief 

 of the Commission. 



The history of the explorations on which this sketch is based is briefly 

 as follows : In 1870, Prof. Hartt, with a party of students, visited the 

 Amazonas, ascending the Tocantins and the Tapajos to among their lower 

 rapids, and examining the high lands of the vicinity of Santarem, Monte 

 Alegre aud Erere. In the following year he returned, accompanied by 

 myself, re-examined the Erere and Tapajos regions and explored the table- 

 topped mountains between Prainha and Monte Alegre, sending me, in the 

 meanwhile, to Obydos and afterwards to the island of Marajo. These ex- 

 plorations gave rise to a number of special papers, published in the Ameri- 

 can scientific journals. On assuming direction of the Brazilian Geological 

 Survey, Prof. Hartt engaged Mr. Herbert II. Smith, a member of the party 

 of 1870, who was then on the Amazonas, to continue the geological ex- 

 ploration, and he afterwards sent me, with Dr. Francisco Jose de Freitas, 

 to the same region. Together with these two gentlemen I re-examined 

 the Erere region, and ascended the Maecuru (Gurupatuba of the maps), 

 as far as the fall called Pancada Grande. After this exploration, Mr. 

 Smith continued the examination, which he had already begun, of the 



* A Portuguese version of this report is also being published in the Archivos 

 do Museu National of Rio de Janeiro, Vol. If, ls78. 



