168 THE MEANING OF EVOLUTION 
ican continent, with its developing animals and plants, 
is tied up with the gradual shrinkage of this interior 
sea. Slowly across the Canadian district, the Eastern 
and Western lands became connected with each other, 
while the waters progressively were pushed down the 
continent, which was steadily growing from the east 
and from the north, though less slowly from the west, 
into this internal sea. To-day only the Gulf of Mex- 
ico remains as evidence of the broad stretch that once 
extended through to the Arctic Ocean and west be- 
yond the present position of the Rocky Mountains. 
How this great Eastern backbone of the continent 
was produced, what sort of animals lived while these 
rocks were being formed, or whether this preceded 
entirely the existence of life upon the earth, no man 
to-day may surely say. In the oldest of the rocks 
there are beds of graphite, from which lead pencils 
are made. This substance is believed by the geolo- 
gists to be, like coal, the remains of vegetable life. 
But these early rocks have been so heated and baked, 
so twisted and bent, that whatever forms of life they 
once held are now obliterated, or so altered as to give 
us no idea of what may have been their character. 
So far as anyone can now see, this past history is 
wiped out forever and it will be impossible for men 
ever to demonstrate the character of this early life. 
Speculations, more or less certain, will arise. They 
