364 CORALS AND CORAL ISLANDS. 



The absence from the American coast of the Atlantic, 

 of any coral reefs in the Cretaceous beds, and of any reef corals, 

 seem to show that the oceanic temperature off this coast was 

 not favorable for such corals; and if so, then the line of 68° 

 F. extended at least 20° farther north on the European side 

 of the ocean, than on the Atlantic — an inequality to be ac- 

 counted for only by the existence of the Gulf Stream. But, 

 in addition, the whole range of life in the European Creta- 

 ceous, and its vastly greater variety of species, leave no doubt 

 as to the higher temperature of the ocean along its European 

 border ; so that the idea of a Cretaceous Gulf Stream must be 

 accepted. Alid that of a Tertiary is demonstrated by similar 

 facts. 



If the Gulf Stream had its present position and force in 

 Oolitic, Cretaceous and Tertiary times, then the ocean had, 

 throughout these eras, its present extension and oceanic char- 

 acter ; and, further, no barrier of land extended across from 

 South America to the Canaries and Africa, dividing the South 

 from the North Atlantic, but all was one great ocean. 

 Such a barrier would not annul entirely the flow of the Gulf 

 Stream ; yet the North Atlantic is so small an ocean, that if 

 left to itself, its system of currents would be very feeble. 



XIV. THE OCEANIC CORAL ISLAND SUBSIDENCE. 



Coral islands have been shown to be literally monuments 

 erected over departed lands ; and, through the evidence from 

 such records, it is discovered that the Pacific has its deep-water 

 mountain chains, or lines of volcanic summits, not merely 

 hundreds, but thousands of miles in length. Some of the 

 ranges of high islands are proved by such records to have an 

 under- water prolongation, longer than that above water : the 

 Hawaian Islands for example, which have a length of only 



