228 THE GEYSER. 



Great part of Iceland is volcanic, and there is 

 no doubt that there are many curious caverns that 

 have been formed below ground, as there are in 

 all volcanic countries. The Geyser appears to have 

 a boiler, which opens downward into the well or 

 pit that supplies the water; and, whatever the 

 heating cause is, whether warm air or warm earth, 

 it converts the water in that boiler into steam. 

 The steam is confined by the pressure of the 

 column of water in the pit or well, which is open 

 to the air. But when the steam reaches a certain 

 heat, the pressure of the column can no longer 

 resist it, and it forces the water up in a high and 

 powerful jet. The steam, and most likely also 

 heated air, escapes along with the water, and 

 the water is cooled, so that it sinks down in the 

 pit, and again enters the boiler, so as to shut the 

 opening till the steam be sufficiently powerful to 

 drive up the column of water. 



