XVI INTRODUCTION 



generally ; but the steady, hardly-varying set of a body 

 of water in the ocean in any given direction is fraught 

 with incalculable consequences to the people inhabit- 

 ing the land upon which that current impinges. Chief 

 among all these oceanic rivers, both in size and ns 

 regards its influence upon the human race, is the 

 Gulf Stream, without which Great Britain and, indeed, 

 Northern Europe generally would be a desert. I have 

 endeavoured to bring this fact prominently forward in 

 the chapter on currents, for I feel strongly that we 

 should know how it is that this little group of islands 

 of ours is kept so habitable, so perennially green, while, 

 in the same latitude, or at the same distance from the 

 North Pole, in other parts of the earth the land for 

 half the year, at any rate, is covered with a mask of 

 ice. This wonderful natural method of preventing 

 great vicissitudes of temperature is not the least of the 

 great blessings we British folk owe to the ocean, but 

 it is one which the bulk of us most thoughtlessly 

 accept without ever dreaming of what would be our fate 

 could any cosmic calamity divert the course of this 

 mighty river of warm water, so that, instead of coming 

 straight to us from the Gulf of Mexico, it should waste 

 itself upon the already overheated coast of Africa, or, 

 by the submergence of the isthmus of Panama, find its 

 way into the Pacific, a possibility fraught with such 

 terrible consequence to civilization that it hardly bears 

 thinking of at all. 



I have glanced briefly, too, at the working of the 

 other well-known and reliable ocean currents and 

 the work they do, which, though not comparable in 

 its direct effect upon civilized humanity to that per- 

 formed by the Gulf Stream, is still of tremendous, 



