TRUE VOLCANOES. 433 



tain of no great height, and whose distance from the coast 

 must have been 160 miles. The Mexican volcano of Jorullo, 

 which was elevated above the surface in September, 1759, is 

 84 miles from the nearest point of the sea-shore (see above, 

 pp. 314-321) ; the volcano of Popocatepetl is 132 miles; an 

 extinct volcano in the eastern Cordilleras of Bolivia, near S. 

 Pedro de Cacha, in the vale of Yucay (see above, p. 295), 

 is upwards of 180 miles ; the volcanoes of the Siebenge- 

 birge, near Bonn, and of the Eifel (see above, p. 231 238), 

 are from 132 to 152 miles; those of Auvergne, Velay, and 

 Vivarais, 43 distributing them into three separate groups (the 

 group of the Puy de Dome, near Clermont, with the Mont 

 Dore, the group of the Cantal. and the group of the Puy and 

 Mezenc), are severally 148, 116, and 84 miles distant from 

 the sea. The extinct volcanoes of Olofc, south of the Pyrenees, 

 west of Gerona, with their distinct and sometimes divided 

 lava-streams, are distant only 28 miles from the Catalonian 

 shores of the Mediterranean, while, on the other hand, the 

 undoubted, and to all appearances very lately extinct, vol- 

 canoes in the long chain of the Rocky Mountains, in the 

 north-vest of America, are situated at a distance of from 600 

 to 680 miles from the shore of the Pacific. 



A very abnormal phenomenon in the geographical distri- 

 bution of volcanoes is the existence in historical times of 

 active, and partially, perhaps, even of burning volcanoes in 

 the mountain-chain of the Thian-shan (the Celestial Moun- 

 tains), between the two parallel chains of the Altai and the 

 Kueii-lun. The existence of these volcanoes was first made 

 known by Abel-Rernusat and Klaproth, and I have been 

 enabled, by the aid of the able and laborious investigations of 



42 In these three groups which, according to the old geographical 

 nomenclature, belong to Auvergne, the Vivarais, and the Velay, the 

 distances given in the text are those of the northernmost parts of each 

 group as taken from the Mediterranean Sea (between the Golfe d'Aigues 

 Mortes and Cette). In the first group, that of the Puy de Dome, a 

 crater erupted in the granite near Man/at, called Le Gour de Tazena, 

 is taken as the most northerly point (Rozet. in the Mem. de la Societe 

 Geol. de France, t. i, 1844, p. 119). Farther south than the group of 

 the Cantal, and therefore nearest the sea-shore, lies the small volcanic 

 district of la Guiolle near the Monts d'Aubrac, norta-west of Chirac, 

 and distant scarcely 72 geographical miles from the sea. Compare tL 

 Carte Geotoyique de la France, 1841. 



VOL. V. 2 F 



