ON ITS EXTERIOR. VOLCANOES. 217 



Although volcanoes are justly termed in many languages 

 w fire-emitting mountains/' they are not formed by the 

 gradual accumulation of erupted streams of lava ; they ap- 

 pear, on the contrary, to originate generally in a sudden eleva- 

 tion of masses of trachyte or augitic rock in a softened state. 

 The degree of intensity of the upheaving force is shewn by 

 the height of the volcano, which varies from that of a mere hill 

 such as the volcano of Cosima, one of the Japanese Kurile 

 islands, to that of a cone of above 18000 feet of elevation. 

 It has appeared to me that the height of volcanoes exercises a 

 great influence on the frequency of eruptions, which are far more 

 numerous in the lower than in loftier volcanoes. As instances 

 I may place in a series, Stromboli (2175 Trench, or 2318 

 English feet) : Guacamayo, in the province of Quiros, whence 

 detonations are heard almost daily; (I have often heard 

 them myself at Chillo, near Quito, at a distance of 88 miles:) 

 Vesuvius (3637 French, or 3876 English feet) : Etna 

 (10200 French, or 10870 English feet) : the Peak of 

 Teneriffe (31424 French, or 12175 English feet): and 

 Cotopaxi (17892 French, or 19070 English feet). If we 

 suppose the seat of action to be at an equal depth below 

 the general surface of the earth in the case of all these 

 volcanoes, it must require a greater force to raise the 

 molten masses in the case of the higher mountains. It is 

 not therefore surprising that the one whose elevation is 

 least considerable, Stromboli (Strongyle), should have been 

 in a state of constant activity from the Homeric times, 

 and should still serve as a flaming beacon to mariners who 

 navigate the Tyrrhenian Sea, whilst the loftier volcanoes are 

 characterised by longer intervals of repose. Thus also we see 

 the eruptions of most of the colossal summits which crown 



