ON ITS EXTERIOR. VOLCANOES. 219 



Where volcanoes are not isolated in the midst of 

 plains, but are surrounded, as in the double chain of the 

 Andes of Quito, by a table land from nine to twelve thou- 

 sand feet high, this circumstance may very probably 

 account for the non-production of streams of lava during 

 the most dreadful eruptions of ignited scorise, which are some- 

 times accompanied by detonations heard at distances of more 

 than four hundred miles. ( 218 ) Such are the volcanoes of 

 Popayan, of the table land of los Pastes, and of the Andes 

 of Quito; the volcano of Antisana may possibly form an 

 exception. 



The height of the cone of cinders, and the magnitude and 

 form of the crater, which are the principal elements of the 

 individual character of volcanoes, are independent of the 

 dimensions of the mountain itself. In Vesuvius, which is 

 only a third of the height of the Peak of Teneriffe, the cone 

 of ashes rises to a third of the height of the whole mountain, 

 while the cone of the Peak amounts to only l-22d part of 

 its altitude ; in the case of the Kucu-Pichincha, a volcano 

 much loftier than Teneriffe, the proportions much more 

 nearly resemble those of Vesuvius. Among all the volcanoes 

 which I have had an opportunity of seeing in both hemi- 

 spheres, the conical form of Cotopaxi is at once the most 

 regular and the most picturesque. A sudden melting of the 

 snow on its cone of cinders announces the near approach 

 of an eruption ; even before smoke is seen to ascend 

 through the rarefied atmosphere which surrounds the sum- 

 mit and the crater, the walls of the cone of cinders some- 

 times become glowing, and the mass of the mountain itself 

 then assumes an aspect of awful and portentous blackness. 

 The crater which, except iu very rare instances, always 



