148 J. C. Branner — Geology of Fernando de Noronha. 



mens. The results of these endeavors are to be seen in the 

 map published herewith — which does not differ materially from 

 the French map published in 1873 — and in the petrographic 

 work kindly done by Dr. George H. Williams. The drawings 

 are made from sketches and photographs taken by the writer. 

 Unfortunately the dry, sensitive plates so universally and suc- 

 cessfully used nowadays for photography were not then to be 

 had, and the clumsy apparatus I was obliged to use prevented 

 my obtaining some very desirable views. 



The work which has hitherto been done upon the rocks of 

 Fernando will be referred to by Dr. Williams in his part of the 

 present paper. 1 wish to add, however, that the statement 

 made by Dr. Alexander Rattray* to the effect that granite 

 forms part of the peak and of " other hills, headlands and 

 rocks " is erroneous. There is no granite on the island, so far 

 as I was able to discover. 



Amphibole-trachyte occurs at the base of Atalaia Grande 

 and to the west of it. The beds from which the specimen 

 (No. 10) was taken are soft and appear to be decaying rapidly. 

 The exposure has a northeast and southwest trend at this place. 

 The same kind of rock £No. 121) occurs on the east side and 

 about the base of the Morro Francez where it is traversed by 

 dykes of hornblende-augite trachyte (?) (No. 129). The soft 

 whitish and cream-colored amphi bole-trachyte which occurs at 

 the bases of some of the hills and notably about Atalaia Grande 

 is called taud by many of the inhabitants. This is a Tupi word 

 however, meaning clay, and is the one given on the Brazilian 

 mainland to clays of any kind, and is doubtless applied to these 

 soft rocks on account of their slight resemblance to hard clays. 



Hyalotrachyte occurs in several places. The principal locali- 

 ties are between the mouth of the stream flowing into the 

 Bahia do Sueste and the old Fortaleza dos Leoes. The rock 

 (No. 19) is white and almost as soft as chalk, and breaks into 

 irregular lumps. Here and there through the mass are lead- 

 colored patches. It is supposed by the people on the island to 

 be kaolin, and samples of it are said to have been taken to 

 Europe to be tested for the manufacture of porcelain. 



Phonolite. — Most of the isolated topographic prominences in 

 the eastern portion of the island, with the exception of the 

 Morro Francez, are composed either wholly or principally of 

 phonolite, while its lower elevations are of some variety of 

 basalt, loose fragments of nepheline-dolerite being of frequent 

 occurrence about the fields on the plateau above the village. 

 These prominences are the Peak and the southwestern j)rolong- 

 ation of the hill from which it rises, the Pedra da Conceicao, 



* Jour. Roy. Geog. Soc, vol. xlii, 1872, p. 43. 



