228 



cone of Vesuvius erupted in October, 1822, that of Awatscha, 

 according to Postels, and those of the lava-field mentioned by 

 Erman, neai 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 formed* during the most dreadful eruption of 

 ignited scoria3 accompanied by detonations heard at a distance 

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

 Popayan, 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 ele- 

 ments of configuration which yield an especial and individual 

 character to volcanoes, although the cone of cinders and the 

 crater are both wholly independent of the dimensions of the 

 mountain. Vesuvius is more than three times lower than the 

 jcT'-k of Teneriffe ; its cone of cinders rises to one-third of the 

 hei ft ftt of the whole mountain, whilst the cone of cinders of 

 the Peak is only -^\ of its altitude. f In a much higher vol- 

 cano than that of Teneriffe, the Rucu-Pichincha, other rela- 

 tions occur which approach more nearly to that of Vesuvius. 

 Amongst all the volcanoes that I have seen in the two hemi- 

 spheres, the conical form of Cotopaxi is the most beautifully 

 regular. A sudden fusion of the snow at its cone of cinders 

 announces the proximity of the eruption. Before the smoke is 

 visible in the rarefied strata of air surrounding the summit and 

 the opening of the crater, the walls of the cone of cinders are 

 sometimes in a state of glowing heat, when the whole moun- 

 tain presents an appearance of the most fearful and portentous 



* Humboldt, Essai sur la GeogT. des Plantes et Tableau Phys. des 

 Hegions Equinoxiales, 1807, p. 130, and Essai Geogn. sar 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. 607. 



f [It may be remarked in general, although the rule is liable to excej* 

 tions, that the dimensions of a crater are in an inverse ratio to t>* 

 elevation of the mountain. Baubeney, op. cit., p. 444.1 Tr t 



