68 Mr. H. H. Howortii on 



the deflection of ocean currents must affect temperature."' 

 {Climate and Time, 15). With this general postulate I 

 have no quarrel. It seems to me to be sound, and to be 

 supported by abundant evidence. So it seems to me is the 

 following more concrete corollary which he draws from it. 



Applying himself especially to the Gulf Stream, he 

 calculates that the quantity of water it conveys is prob- 

 ably equal to that of a stream fifty miles broad and 

 1,000 feet deep, flowing at the rate of four miles an hour, and 

 that its mean temperature on leaving the Gulf of Mexico is 

 not less than 65 °. This is one-half only of the volume of the 

 stream as calculated by Maury, Herschell, and others. 

 Taking its speed at only two miles an hour, and the average 

 temperature of the return stream at 40 , showing 

 a loss of 25 of heat, Dr. Croll argues that the quantity 

 of heat which is transferred daily by the Gulf Stream 

 is 77,479,650,000,000,000,000 foot-pounds, and that the 

 quantity conveyed by it in one year is equal to the heat 

 which falls on an average on 3,436,900 square miles of the 

 arctic regions. As the frigid zone or arctic regions contain 

 8,130,000 square miles, there is therefore nearly one half as 

 much heat transferred from tropical regions by the Gulf 

 Stream as is received from the sun by the entire arctic 

 regions, the proportion being nearly as 2 to 5 (id., 24-27), and 

 this without taking into calculation the greater amount of heat 

 absorbed by the air in the Arctic regions in consequence of 

 the obliquity of the sun's rays, which in the article "Climate " 

 in the E. B. is calculated to be 75 per cent. Comparing 

 the quantity of heat conveyed by the Gulf Stream with that 

 conveyed by aerial currents, he argues that it would require 

 a current of air 31,234 times the volume of the Gulf Stream 

 at the same temperature to convey the same heat, and he 

 concludes that the quantity of heat conveyed by the Gulf 

 Stream alone from the tropical to the temperate and arctic 

 regions is probably greater than by all the aerial currents 



