252 



colossal summits of the Andes, Cptopaxi, and 

 Tungurahua, scarcely have an eruption once in 

 a century. We might say, that in active vol- 

 canoes the frequency of the eruptions is in the 

 inverse ratio of the height and the mass. The 

 Peak also had seemed extinguished during nine- 

 ty-two years, when, in 1798, it made it's last 

 eruption by a lateral opening formed in the 

 mountain of Chahorra. In this interval Vesu- 

 vius had sixteen eruptions. 



I have observed in another place*, that the 

 whole of the mountainous part of the kingdom 

 of Quito may be considered as an immense vol- 

 cano, occupying more than seven hundred square 

 leagues of surface, and throwing out flames by 

 different cones, known under the particular de- 

 nominations of Cotopaxi, Tungurahua, and Pi- 

 chincha. In like manner, the whole group of 

 the Canary islands is placed, as it were, on the 

 same submarine volcano. The fire makes it's 

 way sometimes by one and sometimes by another 

 of these islands. Teneriffe alone contains in it's 

 centre an immense pyramid terminated by a 

 crater, and throwing out from one century to 

 another, lava by it's flanks. In the other islands, 

 the different eruptions have taken place in va- 

 rious parts ; and we no where find those isolated 

 mountains, to which the volcanic effects are re- 

 strained. The basaltic crust, formed by ancient 



* G€ograph. Veget. p. 130. 



