230 COSMOS. 



of the upheaved mountain were least ahle, from their configu- 

 ration and position, to offer any resistance. Cones of eruption 

 are sometimes uplifted on these fissures ; the .larger ones, which 

 are erroneously termed iieiv volcmioes, are ranged together in a 

 line marking the direction of a fissure, which is soon reclosed, 

 while the smaller ones are grouped together, covering a whole 

 district with their dome-like or hive-shaped forms. To the 

 latter belong the homitos de Jorullo,^ the cone of Vesuvius 

 erupted in October, 1822, that of Awatscba, according to Pos- 

 tels, and those of the lava-field mentioned by Erman, near the 

 Baidar Mountains, in the peninsula of Kamtschatka. 



When volcanoes are not isolated in a plain, but surrounded, 

 as in the double chain of the Andes of Quito, by a table-land 

 having an elevation from nine to thirteen thousand feet, this 

 circumstance may probably explain the cause why no lava 

 streams are formedf during the most dreadful eruption of ig- 

 nited scoriae accompanied by detonations heard at a distance 

 of more than a hundred miles. Such are the volcanoes of Po- 

 payan , those of the elevated plateau of Los Pastes and of the 

 Andes of Quito, with the exception, perhaps, in the case of 

 the latter, of the volcano of Antisana. The height of the cone 

 of cinders, and the size and form of the crater, are elements 

 of configuration which yield an especial and individual char- 

 acter to volcanoes, although the cone of cinders and the crater 

 are both wholly independent of the dimensions of the mount- 

 ain. Vesuvius is more than three times lower than the Peak 

 of Tenerifle ; its cone of cinders rises to one third of the height 

 of the whole mountain, while the cone of cinders of the Peak 

 is only -^-^di of its altitude. | In a much higher volcano than 

 that of Teneriffe, the Rucu Pichincha, other relations occur 



* See my drawing of the volcano of .Torullo, of its homitos, and of the 

 uplifted malpays, in my Viies de Cordilleres, pi. xliii., p. 239. 



[Burckhardt states that during the twenty-four years that have inter- 

 vened since Baron Humboldt's visit to Jorullo, the homitos have either 

 wholly disappeared or completely changed their forms. See Aufenthalt 

 und Reisen in Mexico in 1825 und 1834.] — Tr. 



\ Humboldt, £ssai sur la Giogr. desPtantes et Tableau Phys. des R6- 

 gions Equinoxiales, 1807, p. 130, and Essai Geogn. snr le Gisement des 

 Roches, p. 321. Most of the volcanoes in Java demonstrate that the 

 cause of the perfect absence of lava streams in volcanoes of incessant 

 activity is not alone to be sought for in their form, position, and height. 

 Leop. von Buch, Descr. Phys. des lies Canaries, p. 419 ; Reinwardt and 

 Hoffmann, in Poggend., Annalen., bd. xii., s. C07. 



\ [It may be remarked in general, although the rule is liable to ex- 

 ceptions, that the dimensions of a crater are in an inverse ratio to the 

 elevation of the mountain. Daubeuey, op. cit., p. 444.] — Tr. 



