98 Mr. J. Croll on Ocean- currents in relation to 



but the reverse is the case. In the Atlantic, for example, the 

 41° isothermal line of mean annual temperature reaches to lati- 

 tude 65° 30', while in the Pacific it nowhere goes beyond latitude 

 57°. The 27° isothermal of mean annual temperature reaches 

 to latitude 75° in the Atlantic, but in the Pacific it does not 

 pass beyond 64°. And the 14° isothermnl reaches the north of 

 Spitzbergen in latitude 80°, whereas on the Pacific side of the 

 arctic regions it does not reach to latitude 72°. 



On no point of the earth's surface does the mean annual tem- 

 perature rise so high above the normal as in the northern Atlan- 

 tic, just at the arctic circle, at a spot believed to be in the middle 

 of the Gulf-stream. This place is no less than 22°*5 above the 

 normal, while in the northern Pacific the temperature does not 

 anywhere rise more than 9° above the normal. These facts 

 prove that the warm current passes up the Atlantic into the 

 arctic regions and not up the Pacific, or at least that the larger 

 amount of warm water must pass into the arctic regions through 

 the Atlantic. In other words, the Gulf-stream is the warm 

 compensating current. Not only must there be a warm stream, 

 but one of very considerable magnitude, in order to compen- 

 sate for the great amount of cold water that is constantly flow- 

 ing from the arctic regions, and also to maintain the tempe- 

 rature of those regions so much above the temperature of space 

 as they actually are. 



No doubt, when the results of the late dredging expedition 

 in the North Sea are published, they will cast much additional 

 light on the direction and character of the currents forming the 

 north-eastern branch of the Gulf-stream. 



The average quantity of heat received by the arctic regions as 

 a whole per unit surface to that received at the equator, as we 

 have already seen, is as 5"45 to 12, assuming that the percentage 

 of rays cut off by the atmosphere is the same at both places. 

 In this case the mean annual temperature of the arctic regions, 

 taken as a whole, would be about — 69°, did those regions de- 

 pend alone for their temperature upon the heat received directly 

 from the sun. But the temperature would not even reach to 

 this; for the percentage of rays cut off by the atmosphere in 

 arctic regions is generally believed to be greater than at the 

 equator, and consequently the actual mean quantity of heat 

 received by the arctic regions will be less than ^^ of what is 

 received at the equator. 



In the article on " Climate " in the Encyclopaedia Britannica 

 there is a Table calculated upon the principle that the quantity 

 of heat cut off is proportionate to the number of aerial particles 

 that the rays have to encounter before reaching the surface of 

 the earth — that, as a general rule, if the tracts of the rays fol- 



