170 J. D. Dana— Results of the Earth's Contraction. 
es have been chief among the regions of the earth’s crust that 
have used the pent-up force in the contracting sphere to carry 
forward the continental developments. 3 
If this was true of the North American continent, the same in 
principle was law for all continents. 
CONCLUSION. 
I here close this reconsideration of the views brought out in 
my papers of 1847. Of the principles then presented, and 
> 
avoided in my early papers any expression of opinion as to the 
nature of the earth’s interior keene had Hopkins’s argument 
of 1839-1842 in view) and hence there is nothing on this point 
g 
e views on mountain-making now sustained suppose the 
existence, through a large part of geological time, of a thin 
crust, and of liquid rock beneath that crust so as to make its 
oscillation possible, and refers the chief oscillations, whether of 
elevation or of subsidence, to lateral pressure ftom the contrac: 
tion of that crust; and this accords with my former view, 4? 
with that earlier presented by the clear-sighted French geolog}sh 
révost. 
I hold also, as before. that the prevailing position of moun 
tains on the borders of the continents, with the like location of 
* Introduced in Part I, y, 431, and Part II, vi, 12, 13 
opkins, 
he physical and mathematical side. This it has recently had through the writing® 
of Sir William Thomson and others. 
