Holy THE EVOLUTION OF CONTINENTS. 
the facts of the extensive foldings of the strata by 
lateral thrust into hills and mountains, as being irrel- 
evant to the question. So far as the more recent up- 
lifts are concerned, such as those of the Rocky moun- 
tains, this would be doubtless true. But the considera- 
tion of the extensive folding of the very lowest founda- 
tion-strata of the continent, in the very early ages of the 
growth of continents, cannot properly be left out; that 
is, the folding of the Archean rocks. There is nota 
spot on our continent, where this universally underly- 
ing stratum is not folded up. In mountainous regions, 
the lateral compression has been estimated by Prof. Le- 
"Conte to be in the proportion of five to two; that is, 
what was originally five miles in breadth is now re- 
duced to two miles in breadth. Supposing the average 
contraction in breadth by the universal folding of the 
Archeean to be much less, say one half of the above 
ratio, it would indicate an enormous action of forces in 
modifying the shape of the entire continent. 
Now the theory advanced supposes, for instance, that 
the Atlantic coast lines of North and South America re- 
tain corresponding shapes to those of the Atlantic coast 
lines of Europe and Africa from which they broke away 
when the entire American continent floated to its 
present position. If we may suppose this great raft of 
floating rock to have navigated unbroken for three 
thousand miles and more, and then to have become per- 
manently anchored, then it is absolutely necessary for 
us to assume that the folding of these foundation strata 
must have been done by two vast forces acting exactly 
in parallelism to the two great trends of the coast lines. 
- Otherwise the original form of the continent could not 
have been preserved, as the present theory supposes. 
But if we find it necessary to suppose these two great 
forces acting thus at right angles to each other and 
parallel each to each to the Atlantic and Pacific coasts, 
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