INTRODUCTION. 21 



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 



