J. C. Branner — Geology of Fernando de Noronha. 149 



a small peninsula northeast of the village, the Sella a Gineta,* 

 the summit and southeast face of Atalaia Grande down to the 

 water's edge, and to all appearances the Alatainha or Atalaia 

 Piquena, and the Morro do Sueste. No phonolite was found 

 in the western portion of the island. In all cases, excepting 

 that of the Pedra da Conceicao, these phonolites have the 

 appearance of having been injected as dykes into older rocks. 



Phonolite columns of Atalaia Grande. 



They seem to have cooled irregularly, but for the mostjpart, 

 from the sides. The older and more soluble surrounding rocks 

 have, of course, been removed by denudation. Mr. Darwin 

 says of such masses of phonolite that they have probably been 

 formed by "the injection of fluid feldspathic lava into yielding 

 strata."f In all the cases mentioned above, the rocks have a 



*This island was not visited by the writer. As seen from Ilha Raza and Ilha 

 Rapta, its rock had the appearance of phonolite and was so regarded. The exam- 

 ples collected by the Challenger party show beyond question that this supposition 

 was correct. 



f Geological Observations, second edition p. 27. 



