360 THE HISTORY OF CREATION. 
separated and far distant chains of mountains? It is diffi- 
cult to believe, and in many cases quite inconceivable, that 
these inhabitants of fresh water should have in any way, 
actively or passively, migrated over the land lying between 
the Jakes, or that the inhabitants of mountains in any 
way, actively or passively, crossed the plains lying between 
their mountain homes. But here geology comes to our help, 
as a mighty ally, and completely solves these difficult pro- 
blems for us. 
The history of the earth’s development shows us that the 
distribution of land and water on its surface is ever and 
continually changing. In consequence of geological changes 
of the earth’s crust, elevations and depressions of the ground 
take place everywhere, sometimes more strongly marked in 
one place, sometimes in another. Even if they happen so 
slowly that in the course of centuries the seashore rises or 
sinks only a few inches, or even only a few lines, still they 
nevertheless effect great results in the course of long periods 
of time. And long—immeasurably long—periods of time 
have not been wanting in the earth’s history. During the 
course of many millions of years, ever since organic life ex- 
isted on the earth, land and water have perpetually struggled 
for supremacy. Continents and islands have sunk into the 
sea, and new ones have arisen out of its bosom. Lakes and 
seas have slowly been raised and dried up, and new water 
basins have arisen by the sinking of the ground. Peninsulas 
have become islands by the narrow neck of land which con- 
nected them with the mainland sinking into the water. 
The islands of an archipelago have become the peaks of a 
continuous chain of mountains by the whole floor of their 
sea being considerably raised. 
