Mr. J. Croll on the Physical Cause of Ocean-currents. 257 



of the heat received from the sun, we remove 405 parts from 

 every 975 received from the sun, and consequently only 570 parts 

 per unit surface remain. 



It has been already shown that the quantity of heat conveyed 

 by the Gulf- stream from the equatorial regions into the tempe- 

 rate regions is equal to |^| of all the heat received by the At- 

 lantic in temperate regions*. But according to the theory under 

 consideration the quantity removed is double this, or equal to 

 i^-| of all the heat received from the sun. But the quantity 

 received from the sun is equal to 757 parts per unit surface ; 

 add then to this |^| of 757, or 367, and we have 1124 parts 

 of heat per unit surface as the amount possessed by the At- 

 lantic in temperate regions. The Atlantic should in this case 

 be much warmer in temperate regions than in tropical ; for in 

 temperate regions it possesses 1124 parts of heat per unit sur- 

 face, whereas in tropical regions it possesses only 570 parts per 

 unit surface. Of course the heat conveyed from tropical regions 

 does not all remain in temperate regions ; a very considerable 

 portion of it must pass into the arctic regions. Let us, then, as- 

 sume that one half goes to warm the Arctic Ocean, and the other 

 half remains in the temperate regions. In this case 183*5 parts 

 would remain, and consequently 757 + 183*5 = 940*5 parts 

 would be the quantity possessed by the Atlantic in temperate 

 regions, a quantity which still exceeds by no less than 370*5 

 parts the heat possessed by the Atlantic in tropical regions. 



As one half of the amount of heat conveyed from the tropical 

 regions is assumed to go into the Arctic Ocean, the quantity 

 passing into that ocean would therefore be equal to what passes 

 through the Straits of Florida, which amount we have already 

 found to be equal to all the heat received from the sun by 

 6,873,800 square miles of the arctic regions-]-. But taking the 

 volume of the Gulf-stream, as already stated, at one half our 

 original estimate, the quantity of heat passing into the Arctic 

 Ocean would therefore be equal to all the heat received by 

 3,436,900 square miles of the Arctic Ocean. The entire area 

 covered by sea beyond the arctic circle is under 5,000,000 square 

 miles; but taking the Arctic Ocean in round numbers at 5,000,000 

 square miles, the quantity of heat conveyed into it by currents 

 to that received from the sun would therefore be as 3,436,900 

 to 5,000,000. 



The amount received on the unit surface of the arctic regions 

 we have seen to be 454 parts. The amount received from the 

 currents would therefore be 312 parts. This gives 766 parts of 

 heat per unit surface as the quantity possessed by the Arctic 



* Phil. Mag. S. 4,vol. xxxix. p. 90. 

 t Ibid. p. 84. 



