INTRODUCTION. PA | 
stable earth, as we usually call it, is more changeable even 
than the sea. We speak of the everlasting hills, but we 
know that there was a time when the mountains had not 
been brought forth,—that many of our own mountains bear 
the strongest internal evidence that they have been upheaved 
from the depths of the sea; and we know also that the 
same power that thus brought them forth could again easily 
submerge them in the watery deep. On a small scale, 
there was an exemplification of this not long ago in the 
Mediterranean, where what was called Graham’s Island 
arose in the sea, but after being visited by many as a new 
island, again hid itself in the dark profound. On the coast 
of South America, some thirty years ago it is well known 
that the shore for several miles was considerably elevated, 
leaving the seaweeds to wither and the fish to perish on dry 
land; while on other places of the coast there were depres- 
sions, the sea gaining upon the land. Many of the peaked 
islands in the Pacific are evidently of volcanic origin; and 
it is on this interchange of upheaval and depression, but 
more especially of gradual and long-continued submer- 
gence, that Darwin’s theory proceeds. 
Let us take, then, one of these peaked volcanic islands, 
that has been elevated to the height of 6000 feet above 
