AMERICA THE OLD WORLD. 
11 
on as before, a new set of animals and plants 
were introduced, and a time of building up and 
renewing followed the time of destruction. These 
Periods of revolution are naturally more difficult 
to decipher than the periods of rest ; for they 
have so torn and shattered the beds they up- 
lifted, disturbing them from their natural rela- 
tions to each other, that it is not easy to recon- 
stiuct the parts and give them coherence and 
completeness again. But within the last half- 
century this work has been accomplished in many 
parts of the world with an amazing degree of 
accuracy, considering the disconnected character 
of the phenomena to be studied ; and I think J 
shall be able to convince my readers that the 
modern results of geological investigation are 
perfectly sound logical inferences from well-estab- 
lished facts. In this, as in so many other things, 
we are but “ children of a larger growth.” The 
world is the geologist’s great puzzle-box ; he 
stands before it like the child to whom the sepa- 
rate pieces of his puzzle remain a mystery till he 
detects their relation and sees where they fit, and 
then his fragments grow at once into a connected 
picture beneath his hand. 
It is a curious fact in the history of progress, 
that, by a kind of intuitive insight, the earlier 
observers seem to have had a wider, more com- 
prehensive recognition of natural phenomena as 
