GEOLOGICAL CONCLUSIONS. 313 



the world accompanying this volume, has approximately the 

 course which that of 68^ F. probably had in Oolitic times. It 

 should have a little less northing, and the loop to the north 

 should lean more to the eastward. The latter would have been 

 a consequence of the submerged condition at the time of most 

 of the European continent. 



The ocean's waters seem to have cooled somewhat before 

 the next period — the Cretaceous — began, since evidence fails 

 of any Cretaceous coral reefs in the British seas ; but such 

 reefs prevailed then in central and southern Europe, so that 

 the amount of cooling in the interval since the Oolitic era had 

 not been large ; a,nd as late as the Miocene Tertiary there 

 were reef corals in the seas of Northern Italy, above latitude 

 45° N., or that of Montreal, in Canada. 



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 favourable 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 in part by the existence of the Gulf Stream.^ But, 

 in addition, the whole range of life in the European Cretaceous, 

 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. 

 And 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 cha- 

 racter; 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. 



' The influence of oceanic currents on the isothermal lines of the ocean 

 is Liijfly stated on pages 255, 256. 



