500 DR MUERAy ON THE MARINE FAUNA OF THE GREAT SOUTHERN OCEAN. 



Explanation of the Map showing the Temperature of the Ocean at 1000 

 Fathoms and at the Bottoji in greater depths. 



The accompanying Map has been constructed from materials in Dr Buchan's 

 Challenger Eeport on Oceanic Circulation, and shows the temperature of the ocean at 

 1000 fathoms as well as the temperature at the bottom of the ocean in depths greater 

 than 1000 fathoms. The different shades of red and blue within the different isotherms 

 show the temperature in different areas at the uniform level of 1000 fathoms. For the 

 depths below 1000 fathoms the actual observations are given. The red figures, on the one 

 side of the dot marking the position, give the depth in hundreds of fathoms ; thus 28 in red 

 figures stands for 2800 fathoms ; 11 for 1100 fathoms, etc. The hlue figures on the other 

 side of the dot, plus 30, give the temperature at the depth indicated by the red figures ; 

 thus 35 in hlue figures must be read 33°*5 F. and 64 must be read 36°'4 F., etc. Where 

 the temperature is below 30° F. or above 40° F., the temperature has l^een entered in full 

 to the first decimal place, and in all such cases there are three figures instead of two ; for 

 instance, in the Arctic Ocean 292 signifies 29°'2 F., in the Mediterranean 565 signifies 

 56°"5 F., and in the Sulu Sea 505 signifies 50°'5 F. 



At a depth of 1000 fathoms the lowest temperature recorded is 29° F. ( — 1°"7 C.) in 

 the Arctic Ocean, and the highest in the open ocean is about 41° F. (5° C.) between the 

 Canaries and Madeira, the total range at this depth being about 12° F. (6° "7 C). It will 

 be noticed that at the depth of 1000 fathoms the North Atlantic is much the warmest 

 ocean, and that the whole of the Atlantic and Indian Oceans is above the average at 

 this depth (36°"5 F.), while the greater part of the Pacific is below this average. The 

 same general features persist to the bottom in each ocean with some slight deviations due 

 to local conditions. The thirty-seven deep-water Challenger stations south of the 

 southern tropic, specially referred to in this paper, are indicated by a circle in black. 



