i9o6.] SEE— THE CAUSE OF EARTHQUAKES. 301 



exhibited by the shores of the Pacific Ocean, and their mode of at- 

 tack has been to show that the volcanoes around the Pacific are not 

 a continuous " girdle of fire," but are bunched here and there, with 

 large spaces between; and that while the earthquakes are also dis- 

 tributed with some irregularity, there is no visible connection be- 

 tween them and the volcanoes. 



But if steam forming in the earth's crust from sea water leaking 

 down is the common cause of both earthquakes and volcanoes, should 

 there really be any immediate connection between the two classes 

 of phenomena? Would not volcanoes develop chiefly where the 

 force of the steam was sufiiciently powerful and suddenly exerted 

 to break through the crust or mountains, and therefore chiefly in 

 the mountains along the seashore, where the crust is greatly frac- 

 tured, and enables the violent explosions of steam to blow open an 

 outlet by raising a mountain which would burst into a volcano? 

 It is along such shores also that the leakage would be greatest and 

 most volcanoes should exist, provided the crust becomes badly 

 fractured. 



If, on the other hand, the crust is not much broken and ex- 

 plosions of steam cannot break through, would there not result a 

 great many earthquakes of the class now called tectonic because not 

 visibly connected with volcanoes and supposed to be due to slipping 

 of rocks or faults? When the crust is wholly unbroken, it would 

 naturally be very difficult, even for deep-seated forces of enormous 

 magnitude, to raise up a mountain that would become a volcano, 

 because all the overlying strata would have to be violently broken in 

 such a way as to radiate from a point like a star, and ordinarily the 

 strain of the imprisoned steam is much more easily released by an 

 earthquake which merely shakes up the crust in such a way that a 

 neighboring fault moves and the internal pressure is relieved and 

 equalized by scattering, without breaking through all the overlying 

 strata at one time. 



This indeed appears to be the process of nature, and if we 

 consider it in relation to volcanoes and earthquakes we shall per- 

 ceive, in accordance with observation, that the former should be the 

 more special, the latter the more general phenomena. Also both 

 phenomena should occur under the sea, and along the shores of the 



