370 SEE— THE NEW THEORY OF EARTHQUAKES [November 15, 



Accordingly if we are able to give concrete and convincing illus- 

 trations of the processes now at work in the depths of the sea, they 

 will prove the new theory beyond doubt for certain cases ; and then 

 Newton's rule of continuity can be invoked to show that a cause 

 conclusively established in certain cases must be held to be general 

 for all cases whatsoever, where the phenomena are similar. To 

 prove the general physical cause of earthquakes, therefore, we need 

 certain illustrations which admit of but one interpretation, and where 

 there can be no possible doubt about the true nature of the process. 

 If this can be established for a few typical cases we may feel sure 

 that all world-shaking earthquakes and mountain-forming processes 

 depend upon the same physical cause; and that the smaller earth- 

 quakes, which are very numerous, depend upon the larger ones and 

 upon the gradual settlement of the crust where for any reason it 

 has become unstable. To unite the small with the large earthquakes, 

 in the hope of finding from the whole body of phenomena, when com- 

 bined indiscriminately, their general cause, would be to labor in vain ; 

 for in the case of the large world-shaking earthquakes there is 

 movement of molten rock beneath the earth's crust, while in the 

 case of small earthquakes the tremors are due to a variety of causes, 

 but more especially to any kind of instability which may give rise to 

 a small movement of the ground. As the earth's crust is thick and 

 the true nature of the underlying movement hidden from our view 

 by the depth at which it occurs, the process involved can not be 

 recognized without excluding from consideration the small earth- 

 quakes, and dealing exclusively with those great world-shaking dis- 

 turbances, in which the effects are so large that the nature of the 

 hidden process can be discovered. The disturbances which show 

 the underlying process most clearly are beneath the oceans, or along 

 the coast of deep seas, where there is expulsion of lava from beneath 

 the sea under the land. We shall now consider some particular 

 cases in which the meaning is unmistakable, and which have only 

 been alluded to in the former papers. 



§ 2. The great earthquakes now occurring in the sea near the 

 Aleutian Islands are developing a high submarine mountain range, 

 of which only a few peaks rise above the water. — It is generally 



