154 



DYNAMICAL GEOLOGY. 



the boiling-point is reached and a large quantity of steam 

 is formed first, at some point deep below. The water 

 above is immediately ejected, and the fountain continues 



FIG. 83. Old Faithful geyser in action. (After Hayden.) 



to play until all the steam escapes and the water is some- 

 what cooled. Then all is quiet until the water again 

 heats up to the boiling-point. 



SECTION IT. EARTHQUAKES. 



When we consider the suddenness with which earth- 

 quakes occur, the terror they inspire, and the place of 

 their origin, deep in the interior of the earth, and hidden 

 from observation, it is not surprising that we know so 



