Williams — Petrography of Fernando de Noronha. 179 



tuff containing fragments of basalt and palagonite, from both 

 Platform and Rat Islands. At the Aberdeen meeting of the 

 British Association in 1885, Renard made a further verbal com- 

 munication on the Fernando rocks, and the complete results of 

 his researches will be published in the Challenger reports. 



The collection of Fernando rocks placed in my hands for 

 examination numbers thirty-four specimens. They were se- 

 lected as a representative suite from a much larger collection 

 made by Professor Branner in 1876 and now deposited in the 

 National Museum at Rio de Janeiro. Specimens from this 

 same collection were also sent by Professor Derby to Professor 

 Rosenbusch who mentions the following types : nephelinoid 

 phonolite with inclusion of eleolite-syenite, nepheline basanite, 

 nephelinite, and augitite.* 



Mr. A. C. Gill, Fellow of the Johns Hopkins University, 

 made a preliminary examination of the collection here de- 

 scribed, identifying the following species : phonolite, nepheline- 

 basanite, nepheline-basalt, nephelinite, basalt-glass and tuff.f 



Another large collection of specimens appears to have been 

 made by a party from the British Museum, who spent six 

 weeks on the island of Fernando de Noronha in 1887, and from 

 whom still further petrographical descriptions may be ex- 

 pected.;}: 



Of the thirty-four specimens in Professor Branner's collec- 

 tion, one (66) is travertine, and three others (18, 20 and 118), 

 on account of their extremely altered and friable condition, 

 were not particularly studied. In most of the remaining thirty 

 nepheline is present, although in certain of the lightest colored 

 and most acid rocks its presence could not be established, while 

 in the more glassy of the basalts, if the requisite constituents 

 for its formation exist in the base, they have not come to act- 

 ual crystallization. 



The specimens may be assigned to the following petrographi- 

 cal types : — 



I. Trachytes and Andesites. 



Hornblende trachyte 10,121, and 129. 



Hyalotrachyte 19. 



Hornblende andesite 131. 



II. Phonolite. 1, 5, 9, 35, 40, 41, 43, 51, 52, 88, 137. 



*Die massigen Gesteine, 2d ed. 1887, pp. 91, 518, 624, 628, 769, 785, 802, 821. 



f Petrographical notes on a rock collection from Fernando Noronha (preliminary 

 notice) Johns Hopkins University Circulars, VII, p. 71, No. 65. April, 1888. 



% Rev. T. S. Lea : The island of Fernando de Noronha in 1887. Proc. Roy. 

 Geogr. Soc, x. 424, 1888. 



