92 Evolution of the Earth. 



left Aviiere they are now found by the subsiding waters of 

 Xoah's deluge. The great mind of Leonardo da Vinci was 

 the first in the later Christian times to propound the true 

 scientific theory of their origin; and he and later 

 scholars of the Italian renaissance were the real fathers of 

 the modern science of geology. 



Continents and islands are even now gradually rising 

 from the ocean ; mountain ranges have been differentiated 

 and integrated by processes of gradual elevation. Else- 

 where the solid land is yielding to the encroachments of 

 the sea. We all realize the ver}^ visible effect of this de- 

 structive action of the waves, as it goes on from year to 

 year at Coney Island. It is said that Montauk Point, at the 

 eastern end of Long Island, is two or three miles west of 

 where it formerly was, as indicated by indisputable geolog- 

 ical evidence. The coast around New York, in many places, 

 is washed away at the rate of two or three feet a year ; and 

 in the Eastern part of the continent the encroachment of 

 the sea progresses at a much more rapid rate. The rate 

 varies in different localities according to the conditions of 

 exposure, and the hard or yielding character of the rock 

 which constitutes the substratum of the soil. The sand, 

 which forms the beaches so attractive to the seaside visitor 

 in summer, has all been made by the gradual grinding down 

 of the silicate rock by the attrition of the waves, and by 

 other natural processes. On the other hand, the rivers are all 

 the time at work carrying material into the sea, and thus 

 gradually raising its level. If no other agencies than the 

 destructive ones were at work, it has been estimated that 

 the sea, in time, would wear its way to the center of the 

 largest continents. I have said that continents and islands 

 were gradually rising from the sea, at the same time that 

 these destructive forces are operating elsewhere. I did not 

 refer exclusively to those slow processes of elevation, of the 

 operation of which we are scarcely aware, though careful 

 experiment has determined that they are still in progress ; 

 but also to the even more wonderful work of the coral 

 polyps, which is proceeding in the warmer parts of the 

 globe. The southern end of our Florida peninsula, for ex- 

 ample, is the product of these little creatures. In the South 

 Pacific ocean, coral reefs and islands have already risen 

 above the level of the sea, and are crowned with luxuriant 



