TIME AND CHANGE 
hundred thousand times as long, this preceding 
period, or great fall, was probably equally long 
— so long that the whole of recorded human history 
would form but a small fraction of it. It may easily 
be, I think, that we are now living in the spring of the 
great cycle of geologic seasons. The great ice-sheet 
has withdrawn into the Far North like snowbanks 
that linger in our wood in late spring, where it still 
covers Greenland as it once covered this country. 
When the season of summer is reached, some hun- 
dreds of thousands of years hence, it may be that 
tropical life, both animal and vegetable, will again 
flourish on the shores of the Arctic Ocean, as it did 
in Tertiary times. And all this change will come 
about so quietly and so slowly that nobody will 
suspect it. 
That the crust of the earth is becoming more and 
more stable seems a natural conclusion, but that all 
folding and shearing and disruption of the strata 
are at an end, is a conclusion we cannot reach in the 
face of the theory that the earth is shrinking as it 
cools. 
The earth cools and contracts with almost infinite 
slowness, and the great crustal changes that take 
place go on, for the most part, so quietly and gently 
that we should not suspect them were we present on 
the spot, and long generations would not suspect 
them. Elevations have taken place across the beds 
of rivers without deflecting the course of the river; 
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