408 SEE— THE CAUSE OF EARTHQUAKES. [October 19, 



The way in which several different classes of phenomena find 

 explanation by the most simple of causes may be considered not the 

 least remarkable result of the present investigation. In the minds 

 of those who follow Newton's first rule of philosophy, *' to admit 

 no more causes of natural things than are both true and sufficient 

 to explain their appearances," this will probably tell strongly in 

 favor of the truth of an hypothesis which explains easily and natur- 

 ally such diversified phenomena as earthquakes and volcanoes, the 

 formation of mountains and the deficiency in their attractions, the 

 origin of cordilleras from the ocean trenches near continents, and of 

 the great sea waves which frequently accompany violent earthquakes. 

 But there will doubtless be others who will prefer a variety of 

 causes, and will be slow to believe that the laws and order of nature 

 ire so simple. 



In an investigation of such considerable extent it would not 

 be surprising if many difficulties should require further elucidation 

 than they have received in this imperfect outline ; for the writer has 

 not the geological learning required for the full treatment of many 

 of the great problems of the earth's crust. But if, on the one hand, 

 some defects or omissions should be found, and no doubt many of 

 them will appear in special branches of the extensive lines of 

 thought here traversed, may it not be thought, on the other, that the 

 harmony established with geodetical measurements on the attrac- 

 tions of mountains and the deviations of the plumb line, combined 

 with the explanation of the equilibrium of the terrestrial spheroid 

 between the land and water hemispheres, is not wholly without a 

 certain degree of compensation to those interested in the numerous 

 and related problems of the physics of the earth? 



That the existing theory of earthquakes and volcanoes and 

 mountain formation is embarrassed by many difficulties has often 

 been frankly admitted. While the theory here suggested may re- 

 quire extension or modification, one may confidently submit the 

 question whether it is really possible to doubt its essential truth. ^ 



^ The sinking of the sea bottom after great earthquakes have heaved up 

 the coast, as along the west shore of South America, furnishes a truly- 

 remarkable criterion for unraveling the unseen processes of nature, hidden 

 beneath the earth's crust. The sea bottom could not sink unless it was in 

 some way undermined, and the adjacent coast could not be upraised unless 



