352 COSMOS. 



and 112). In Madeira, 48 the two highest mountains, the 

 conical Pico Huivo, 6060 feet in height, and the Pico de 

 Torres, which is but little known, covered on their steep 

 declivities with scoriaceous lavas, cannot be regarded as the 

 central point of the former volcanic activity on the whole 

 island, as in many parts of the latter, especially towards the 

 coasts, eruptive-orifices and even a large crater, that of the 

 Lagoa, near Machico, are met with. The lavas, thickened 

 by confluence, cannot be traced far as separate streams. 

 Remains of ancient Dicotyledonous and .Fern -like vegeta- 

 tion, carefully investigated by Charles Bunbury, are found 

 buried in upheaved strata of volcanic tufa and loam, some- 

 times covered by more recent basalt. Fernando de Noronha, 

 lat. 3 50' S. and 2 27' to the east of Pernambuco : a group 

 of very small islands ; phonolitic rocks containing horn- 

 blende, no crater, but vein-fissures filled with trachyte 

 and basaltic amygdaloid, penetrating white tufa layers. 49 

 The island of Ascension ; highest summit 2868 feet ; basal- 

 tic lavas with more glassy felspar than olivine sprinkled 

 through them, and well bounded streams traceable up to the 

 eruptive cone of trachyte. The latter rock of light colours, 

 often broken up like tufa, predominates in the interior and 

 south-east of the island. The masses of scoriae thrown out 

 from Green Mountain, inclose immersed angular fragments 60 

 containing syenite and granite, which remind one of the 

 lavas of Jorullo. To the westward of Green Mountain, 

 there is a large open crater. Volcanic bombs, partly hollow, 

 of as much as 10 inches in diameter lie scattered about in 

 innumerable quantities, together with large masses of obsi- 

 dian. Saint Helena : the whole island volcanic, the beds ol 

 lava in the interior rather felspathic ; basaltic towards the 

 coast, penetrated by innumerable dykes as at Flagstaff Hill. 

 Between Diana Peak and JS"estlodge, in the central series of 

 mountains, is the curved and crescentic shaped fragments 

 of a wider, destroyed crater full of scoriae and cellular lava 



48 Results of the observations upon Madeira by Sir Charles Lyell and 

 Hartung in the Manual of Geology 1855, pp. 515 525. 



49 Darwin, Volcanic Islands 1844, p. 23, and Lieutenant Lee, Cruise 

 of the U.S. Brig Dolphin, 1 854, p. 80. 



50 See the admirable description of Ascension in Darwin's Volcanic 

 Islands, pp. 40 and 41. 



