IV SYNOPSIS. 



p. 28.8 and 289 ; volcanoes of Japan, p. 350 ; islands of Southern 

 Asia, p. 354-358); Java, p. 281-290. The Indian Ocean, p. 358- 

 363 ; the South Sea, p. 363-376. 



Probable number of volcanoes on the globe, and their distribution on the 

 continents and islands , Page 393-403 



Distance of volcanic activity from the sea, p. 279, 404, 405. Re- 

 gions of depression, p. 403-407; Maars, Mine funnels, p. 221, 222. 

 Different modes in which solid masses may reach the surface from 

 the interior of the earth, through a net-work of fissures in the cor- 

 rugated soil, without tjje upheaval or construction of conical or dome- 

 shaped piles (basalt, phonolite, and some layers of pearl-stone and 

 pumice, seem to owe their appearance above the surface, not to sum- 

 mit-craters, but to the effects of fissures). Even the effusions from 

 volcanic summits do not in some lava streams consist of a continuous 

 fluidity, but of loose scoriae, and even of a series of ejected blocks and 

 rubbish ; there are ejections of stones Avhich have not all been glow- 

 ing, p. 291, 311, 312-315, 322-326, note * (p. 289), note * (page 315). 



Mineralogical composition of the volcanic rock : generalization of 

 the term trachyte, p. 423 ; classification of the trachytes, according to 

 their essential ingredients, into six groups or divisions in conformity 

 with the definitions of Gustav Rose ; and geographical distribution of 

 these groups, p. 423-436; the designations andesite and andesine, 

 p. 422-437, note, 440. Along with the characteristic ingredients of 

 the trachyte formations there are also unessential ingredients, the 

 abundance or constant absence of which in volcanoes frequently very 

 near each other deserves great attention, p. 441 ; Mica, ibid. ; glassy 

 feldspar, p. 442; hornblende and augite, p. 443; leucite, p. 444; oli- 

 vin, p. 444 ; obsidian, and the difference of opinion on the formation 

 of pumice, p. 447 ; subterranean pumice-beds, remote from volcanoes, 

 at Zumbalica, in the Cordilleras of Quito, at Huichapa in the Mexican 

 Highland, and at Tschigem in the Caucasus, p. 320-324. Diversity 

 of the conditions under which the chemical processes of volcanicily 

 proceed in the formation of the simple minerals and their association 

 into trachytes, p. 440, 441, 451. 



