B. TERRESTRIAL PHYSICS AND METEOROLOGY. 57 



since, if at the equator the water supplied from the south- 

 ward retains its cold temperature to so great an extent, the 

 bottom water of the North Atlantic, if supplied by the nearer 

 arctic, should be at least as cold ; but the temperature of the 

 lowest stratum increases decidedly as we pass north, and 

 completely cuts off the arctic water found by the Porcupine 

 at the bottom of the Faroe Channel from that discovered at 

 the equator by the Challenger, which reached the maximum 

 of 32 4'. 



He also remarks that the bottom water is colder on the 

 western side of the Atlantic, at all the stations south of the 

 Bermuda and Azores lines, than on the east; showing that 

 the antarctic cold current enters the North Atlantic, and runs 

 to the northwestward, through the channels between St. 

 Paul's rocks and the Brazilian coast, and gradually expends 

 itself, as it circles round to the northeastward, in the same 

 manner as the warm equatorial current does on the surface, 

 considering that current as including the Gulf Stream, which 

 Captain Nares thinks it helps to produce. This cold current 

 entering: the North Atlantic is found between 1700 fathoms 

 and the bottom, a total thickness of 700 fathoms. Thus the 

 heat-giving properties of the equatorial and northeast trade- 

 current, carrying, as they do, a continuous body of warmed 

 water toward the Caribbean Sea, can be traced by the rise in 

 temperature of the whole body of water at Sombrero, and 

 afterward at all the stations in the North Atlantic, but most 

 readily by the widening of the isotherms about 62, between 

 America and the Azores, forming an immense reservoir of 

 warmed water 1000 feet thick, and at least two millions of 

 square miles in extent. This change of temperature, or dis- 

 turbance, is greater and nearer the surface on the western 

 side of the Atlantic, the nearest point to the source of the 

 current, than at the eastern side, where it slowly but gradu- 

 ally expends itself, sinking as it expires. 



OCEAN CIRCULATION. 



According to Dr. William B. Carpenter, the researches of 

 the Challenger completely bear out the views presented by 

 him in regard to the general character and cause of the cir- 

 dilation in the ocean, in the range between 38 N". and 38 S., 

 this conclusion being based upon the facts ascertained in re- 



C2 



