TEMPERATURE OF THE HYDROSPHERE 185 



arate consideration, we must first note the principal sources of the 

 hot and cold waters of the three great oceans, and then note their 

 distribution. It need scarcely be repeated that the chief source of 

 warm waters is the sinking warm surface water of the tropical 

 regions of the ocean. The chief source of the cold waters, especially 

 in the deeper parts, must be sought in the antarctic extensions of the 

 three great oceans, though the cold waters of the Arctic Ocean to 

 a considerable extent modify the surface layers of the North Atlan- 

 tic and North Pacific. 



The cooling of the surface waters of the antarctic extensions and 

 the formation of ice, with the corresponding extrusion of the salts, 

 greatly increase the density of the water, which will sink and carry 

 the low surface temperatures with it. The following temperatures 

 have been recorded for the antarctic extensions of the three great 

 oceans, showing in each case a mesothermal arrangement. In the 

 Atlantic at 61° S. latitude off the coast of South America (63° W. 

 long.) the Belgica found surface temperatures of +3.2° C, which at 

 75 meters depth had fallen to — i°.o and at 125 meters to the cool- 

 est, — 1.4° C. Rising beyond this the temperature reached +0.4° C. 

 at 175 meters, +1.9° between 500 and 1,000 meters, and then fell 

 again to +0.6° C. at the bottom, 3,690 meters. At the other side 

 of the Atlantic, in 70° 30' south latitude, off the South African 

 coast (94° W. long.), the same vessel found surface temperatures of 

 — 1.8° C, which increased downward more or less regularly to 

 -|-o.3° at 175 meters, and to +1.7° C. at 400 meters, after which 

 it decreased to the bottom (1,750 meters), where it was -[-0-8° C. 

 In the antarctic extension of the Indian Ocean the Gauss found at 

 6sy2° S. lat., 855^° E. long, surface temperatures of —1.80° C, 

 increasing to — 1-75° C. at 75 meters, and then decreasing again to 

 — 1.90° C. between 175 and 200 meters. This is followed by an 

 increase to +0.35° at 1,000 meters, and a decrease to — 0.20° at the 

 bottom of 2,821 meters. At 62° S. lat. and 56° E. long, the 

 Valdivia found surface temperatures of — 1.0° decreasing to — 1.6° 

 at 75 meters depth, and rising again more or less regularly to +1.7° 

 C. at 300 m. After this a decrease with some irregularity to — 0.4° 

 C. at 4,636" meters occurs. For the Pacific, the Belgica found at 

 61° S. lat. and 63° W. long, surface temperatures of — 1.8° C, in- 

 creasing downward, though with some irregularity, to +i-7° C. at 

 400 meters, after which a slow decrease followed to -f-o.8° C. at the 

 bottom, of 1.750 meters. 



Turning, now, to the intercontinental portion of the three great 

 oceans, we find that the temperature distribution in the upper 100 

 meters is largely affected by the seasonal variations, which for the 



