ii4 



Galapagos Archipelago. 



PAET I. 



formerly have occupied the hollow of the crater, but is 

 now attached only to a few of the circumferential hills, 

 consists of a tuff, intermediate in character between 

 that with a resin-like, and that with an earthy fracture. 

 This mass contains white calcareous matter in small 

 patches. The second crater (520 feet in height) must 

 have existed until the eruption of a recent, great stream 

 of lava, as a separate islet ; a fine section, worn by the 

 sea, shows a grand funnel-shaped mass of basalt, sur- 

 rounded by steep, sloping flanks of tuff, having in parts 

 an earthy, and in others, a semi-resinous fracture. The 

 tuff is traversed by several broad, vertical dikes, with 

 smooth and parallel sides, which I did not doubt were 

 formed of basalt, until I actually broke off fragments. 

 These dikes, however, consist of tuff like that of the 

 surrounding strata, but more compact, and with a 

 smoother fracture; hence we must conclude, that 



No. 12. 



The Kicker Eock. 400 feet high. 



fissures were formed and filled up with the finer mud 

 or tuff from the crater, before its interior was occupied, 

 as it now is, by a solidified pool of basalt. Other 

 fissures have been subsequently formed, parallel to 

 these singular dikes, and are merely filled with loose 

 rubbish. The change from, ordinary scoriaceous parti- 

 cles to the substance with a semi-resinous fracture, 



