4 BULLETIN OF THE NATURAL HISTORY SOCIETY. 



very earliest periods of which geology has cognizance by 

 mean of organic remains, and of terrestrial climate in the 

 later, Devonian age. 



To illustrate the past, let us take a brief survey of some 

 peculiarities of existing climates by contrasting tropical 

 marine life with the living beings of the northern seas ; and 

 also by observing the kinds of animals that characterize 

 the shores as contrasted with those found in deep water. 



We will thus learn what kind of creatures are suited to 

 warm water ; and on the other hand what other kinds prefer 

 to live in the cold seas, and if we can prove by the distribution 

 of the sea-animals in ancient times that there were areas of 

 cold water, and others of warm water on the surface of the 

 globe, we have shown the existence of varying climates on 

 the land as well as in the sea; for I have only to call your 

 attention to the well-known influence of the Gulf Stream on 

 the climate of Western Europe, to show what effect warm 

 currents in the ocean will produce on the neighboring land. 



Certain broad features in which tropical marine life differs 

 from that of northern seas are of a kind that might have left 

 their impress on the animals of former geological ages, had 

 these animals been constituted then, as their descendents are 

 now. Such creatures, for instance, as the corals and the 

 shell-fish (shelled molluscs), whose skeletons are composed of 

 stony matter, would have left imperishable memorials of their 

 existence, to show where these animals had flourished, and 

 also to certify us of the particular kinds which had once 

 existed on the earth. 



In regard to the reef-building corals, you will notice that 

 they are confined to tropical seas, and that even in such seas 

 the reef builders are found at work only where the water is 

 pure, as well as warm ; thus while coral reefs skirt the eastern 

 shores of Brazil, they are wanting off the mouth of the 

 Amazons, and only re-appear where the Windward Islands 

 rise abruptly from the profound depths of the Atlantic. 

 And further, it has been found that the "coral animal" does 

 not flourish at great depths in the ocean, but only where 

 rocky reefs approach the surface of the sea. 



