38 DOMAIN 1. SIDEROUJ* 



of those which compose the substance of traps, 

 and not of the large grains or glands which form 

 amygdaloids, these little grains, I say, are of 

 quartz, felspar, sometimes of hornblende, and of 

 that substance I have called granular chusite, 

 1944*." 



volcanoes. According to the present classification, ge- 

 nuine basalt, that of the ancients, must be omit- 

 ted in the dispute between the Neptunists and 

 Volcanists, which only regards basaltin. The 

 common trap of the Swedes and Germans is 

 always a basaltin ; and when stratified is allowed 

 even by Faujas not to be volcanic. The contest 

 therefore chiefly relates to the columnar basaltin* 

 which the French mineralogists infer to be always 

 of a volcanic origin ; while, as already observed, 

 it seems rather to arise from a phenomenon still 

 more grand and rare. The great chain of vol- 

 canoes in the Andes is chiefly argillaceous, or 

 clay porphyry ; and their most dangerous ejec- 

 tions are torrents of mud. In New Spain, where 

 the mountains are chiefly of clay- slate, a vol- 



* Sauss. vii. 203. For the chusite of Saussure, see his Journey 

 to the extinct volcanoes of Brisgaw, Journ. de Ph. 17Q4, p. 325. 



See also his account of pierres de corne, Q5 : most of them may 

 be scratched by the nail. He says, 103, that trap is a compact 

 pierre de corne, which not being a production of fire, is very different 

 from basalt. In 1525, Saussure doubts if the basaltin of the 

 extinct volcano of Beaulieu be volcanic. 



