182 THE FITXESS OF THE ENVIRONMENT 



west to east ; in the north a current flows 

 from east to west, from the Siberian coast 

 to Northeast Greenland and thence along the 

 east coast ; another flows from Baffin's Bay 

 along the east coast of North America. 



Of all ocean currents, the Gulf Stream, a 

 branch of the northern equatorial current, 

 has been most carefully studied. Its maxi- 

 mum velocity is 220 kilometers per day, 

 greater therefore than that of the Rhine at 

 Coblentz ; the mean about 134 kilometers a 

 day. In the Straits of Yucatan the Gulf 

 Stream carries 0.2 cubic kilometer (200,000,- 

 000 tons) per second. If all this water were 

 to be cooled to the temperature of the polar 

 ocean this would be equivalent to the trans- 

 port of about 5,000,000,000,000,000 gram 

 calories per second. The magnitude of this 

 quantity, of course, depends upon the specific 

 heat of water. 



In this manner vast quantities of water, 

 carrying enormous stores of heat, are constantly 

 in motion all over the globe. The result is 

 that homogeneity of the ocean which has been 

 discussed above, — constancy of concentra- 

 tion, of composition, of temperature, of alka- 

 linity, and of osmotic pressure. 



