82 THE HISTORY OF THE NORTH ATLANTIC 



cauldron, and pouring through the mouth of this in the 

 Bahama channel, forms the gulf stream, which, widening out like 

 a fan, forms a vast expanse of warm water, from which the pre- 

 vailing westerly winds of the North Atlantic waft a constant 

 supply of heated moist air to the western coasts of Europe, 

 giving them a much more warm and uniform climate than that 

 which prevails in similar latitudes in Eastern America, where 

 the cold Arctic currents hug the shore, and bring down ice from 

 Baffin's Bay. Now all this might be differently arranged. We 

 shall find that there were times, when the Isthmus of Panama 

 being broken through, there was no Gulf Stream, and Norway 

 and England were reduced to the conditions of Greenland 

 and Labrador, and when refrigeration was still further increased 

 by subsidence of northern lands affording freer sweep to the 

 Arctic currents. On the other hand, there were times when 

 the Gulf of Mexico extended much farther north than at 

 present, and formed an additional surface of warm water to 

 heat all the interior of America, as well as the Atlantic. Geo- 

 graphical changes of these kinds, have probably given us the 

 glacial period in very recent times, and at an earlier era those 

 warm climates which permitted temperate vegetation to flourish 

 as far north as Greenland. These are, however, great topics, 

 which must form the subject of other chapters. 



I am old enough to remember the sensation caused by the 

 delightful revelations of Edward Forbes respecting the zones 

 of animal life in the sea, and the vast insight which they gave 

 into the significance of the work on minute organisms pre- 

 viously done by Ehrenberg, Lonsdale and Williamson, and 

 into the meaning of fossil remains. A little later the sound- 

 ings for the Atlantic cable revealed the chalky foraminiferal 

 ooze of the abyssal ocean. Still more recently, the wealth of 

 facts disclosed by the Challenger voyage, which naturalists 

 have scarcely yet had time to digest, have opened up to us 

 new worlds of deep-sea life. 



