88 volcanoes; earthquakes. 



stances cannot escape through the upward outlets 

 so quickly as it is supplied, the formation of 

 vapour ceases, the temperature of the water 

 rises, and with it the elasticity of the steam, If, 

 now, the conditions are such, that the resulting 

 pressure can be transmitted downwards as far as 

 to the red-hot molten masses in the bowels of the 

 earth, some of this latter must be set in motion, 

 and, if there are any available channels in the 

 strata, must be forced up to the surface, just as 

 certainly, and just in the same manner, as springs 

 of water are raised by weaker forces acting at less 

 depths. Naturalists seem at present very gene- 

 rally in favour of the view that volcanic outbursts 

 owe their origin to forces of this kind. 



This belief is strongly supported by the nume- 

 rous hot springs and steam-jets that are met with 

 in the neighbourhood of nearly all volcanoes, and 

 by the fact that volcanic discharges are always 

 accompanied by enormous quantities of steam, 

 which force their way through the liquid masses of 

 lava, and take the form of clouds, which, over- 

 hanging the crater, often give rise to sudden storms 

 and floods of rain. 



Even the smoke of volcanoes, during their state 

 of rest, consists in great part of steam, which, 

 according to the less or greater difficulty which it 

 finds in making its escape, sometimes puffs out 

 quietly, sometimes hurls up stones and earth, as is 



