820 THE POPULAR SCIENCE MONTHLY. 



received the generic name of geyser, from the Icelandic word signify- 

 ing to spout. One of the most remarkable geyser regions in the world 

 is in the Avcstern part of the United States, near the borders of 

 Wyoming Territory, where are grouped together more than two thou- 

 sand very hot springs, which we might imagine to have been engen- 

 dered by some vast steam-furnace. 



Waters may also acquire a high temperature by borrowing from 

 eruptive rocks which have been thrown up from greater depths and 

 still retain a part of their primitive heat. They generally rise by the 

 force of hydrostatic pressure, as in the artesian wells, while the expan- 

 sive force of vapor is sometimes the elevating agent. Volcanoes, the 

 eruptions of which suggest only the idea of fire, constitute, in fact, 

 gigantic intermittent springs of water, the temperature of which sur- 

 passes everything that we can comprehend. 



Thus, the vapor of water not only forms the most abundant and 

 most constant product of eruptions, but it seems even to be, through 

 its enormous tension, the mother of them. From the very beginning 

 of the crisis it bursts out in enormous spurts, dragging matter of every 

 kind up the subterranean conduit. This vapor produces a vertical 

 column which spreads out in the upper regions of the atmosphere in 

 the shape which in Italy Pliny has compared to that of a pine-tree. 

 It is sometimes blackened, especially at the beginning of an eruption, 

 by solid dejections of cinders or lapilli. The watery column may 

 reach a considerable height if it is not carried away or dissolved by 

 aerial currents. Torrential rains frequently fall from the clouds en- 

 gendered by these exhalations. 



Impossible as it may appear, water is incorporated in fused and in- 

 candescent lavas, and consequently participates in a temperature ex- 

 ceeding 1,000° ; but when it is vaporized its temperature falls at once 

 to the boiling-point. 



The water expelled from volcanoes gives only a very limited idea of 

 the importance of the domain of that fluid in the depths of the earth. 

 When we consider how many opportunities it finds to penetrate by 

 capillarity and other means into interior regions of a very high tem- 

 perature, we can not doubt that these regions contain superheated 

 water. Imprisoned within rocky walls that offer an enormous resist- 

 ance, it acquires a tension which recent experiments show to be of 

 marvelous power. 



Water also contributes invisibly to mechanical actions. In view 

 of the immense force it exhibits in eruptions, we have a right to sup- 

 pose that in regions where it has no outlet it may, under the force 

 of its enormous pressure, be also an effective cause of the most for- 

 midable earthquakes, which are simply volcanic eruptions without 

 outlet. These agitations are produced more especially in countries 

 the ground of which is dislocated and has most recently acquired its 

 present relief. Such a geological constitution, which is recognized as 



