THE GEYSERS OF MONTANA. 289 
Iceland palagonite, and palagonitic tufas, with fifty per cent. of 
silica, are considered as the material acted upon and lixiviated by 
the hot water. By the gradual cooling of the volcanic rocks under 
the surface of the earth in the course of centuries the hot springs 
also will gradually disappear; for they too are but a transient 
phenomenon in the eternal change of everything created.” — (Hoch- 
stetter’s ‘ New Zealand,” English translation, p. 432.) 
Bischof in his “ Researches into the internal heat of the globe,” 
thus discourses on the origin of the Geysers of Iceland :— 
“ No doubt can be entertained respecting the nature of the agent 
by which the waters of the geyser, the Strokr, and other less con- 
siderable springs, are thrown to such an immense height. It is, 
as in volcanoes, a gaseous body, principally aqueous vapor. We 
may, therefore, very fairly agree with Krug Von Nidda, and con- 
sider volcanoes in the same light as intermittent springs, with this 
difference only, that instead of water, they throw out melted 
matters 
“ He takes it for granted that these hot springs derive their 
temperature from aqueous vapors rising from below. en these 
vapors are able to rise freely in a continual column, the water at 
the different depths must have a constant temperature, equal to 
that at which water would boil under the pressure existing at the 
respective depths ; hence the constant ebullition of the permanent 
springs and their boiling heat. If, on the other hand, the vapors 
be prevented by the complicated windings of its channels from ris- 
ing to the surface ; if, for example, they be arrested in caverns, the 
temperature in the upper layers of water must necessarily become 
reduced, because a large quantity of it is lost by evaporation at 
the surface, which cannot be replaced from below. And any cir- 
