Crosby.] 466 [November 7, 



50,000 feet in central Europe, and a subsidence in the Rocky- 

 Mountain region, according to King, of 60,000 feet, etc., hold 

 that it is extremely improbable that any part of the floor of the 

 deep sea ever has been or will be elevated to form dry land ? 



Again, what is the basis for the view that all extensive upward 

 movements are confined to the land areas ? It certainly is a 

 strange doctrine that, while the stable continental crust is sub- 

 ject to repeated up and down movements of from one to ten 

 miles, the (according to Professor Dana) comparatively flexible 

 oceanic crust is only susceptible of slight oscillations, in addition 

 to a slowly progressing subsidence covering the whole of geologi- 

 cal time. As Professor Dana has shown, however, the coral 

 islands testify that a large part of the floor of the Pacific has 

 subsided from 3,000 to at least 10,000 feet in quite recent geolog- 

 ical times. He also insists that this subsidence is a true down- 

 ward bending of the crust, being due mainly to pressure and not 

 to contraction, that the ocean-floor moves as a unit, and that the 

 entire crust of the of the earth is involved in the movement. But 

 10,000 feet subtracted from the depth of the Pacific would make 

 it a very shallow ocean ; and its islands would be vastly more 

 numerous and larger than they are now. 



In fact, the Central Pacific, before the subsidence began, was 

 probably as continental as the major portions of Europe and Asia 

 during the early Tertiary epochs. Now, since this coral island- 

 subsidence is not the result of contraction, what large element 

 of improbability is there in the supposition that it may some 

 day be reversed to the extent of 10,000 or even 20,000 feet ? 

 Nearly all the land bordering on the Pacific is rising, and rising 

 probably (as Dana has suggested) as a joint and complementary 

 effect of the same great cause that produces the oceanic subsi- 

 dence. It is safe to assume, however, that these continental 

 movements will, sooner or later, be reversed; and when that 

 happens will not the Pacific subsidence be almost necessarily- 

 reversed too? 



The formation of extensive deposits of sediments requires a 

 continent as well as an ocean. So far as our present purpose is 

 concerned we may say that the continents are composed entirely 

 of stratified rocks, there being no igneous rocks except such as 

 have come up through the stratified series. In other words, no part 



