482 ■ Proceedings. 



We thus see that Croll's argument is based on two facts, which he 

 considers placed beyond all doubt — that winds are the impelling cause of ocean 

 currents, and that the ocean currents are the great agents employed in 

 distributing over the globe the excess of heat received by the sea in intertropical 

 regions. 



The majestic flow of waters from the Gulf of Mexico — that "mighty 

 river," as Maury terms it — equals in magnitude a current of at least forty 

 miles broad and 1000 feet deep, flowing at the rate of two miles an hour, and 

 conveys a quantity of heat equal — to use the philosophic slang of the day — to 

 77,479,650,000,000,000,000 foot-pounds. That he has not overestimated 

 either the temperature or the volume of the Gulf Stream is shown by the 

 important results obtained during the "Challenger" expedition. Between 

 Bermuda and Sandy Hook the stream is sixty miles broad and 600 feet deep, 

 with a maximum velocity of from three and a half to four miles an hour; 

 while the observations made between St. Thomas and Sandy Hook reveal 

 the existence of an immense flow of warm water 2300 feet deep, coming 

 either from the Gulf of Mexico or from the Caribbean Sea. At Sandy Hook 

 it extends 1200 feet deeper than the Gulf Stream itself. This^mass of water, 

 after travelling northwards for about 1000 miles, crosses the Atlantic in the 

 direction of the Azores, where it appears to thin out. 



CroU then goes on to argue that any cause which will greatly afiect the 

 currents, or greatly change their paths and mode of distribution, will of 

 necessity greatly afiect the climatic condition of the globe. But, as the 

 existence of these currents depends on the winds, any cause which will greatly 

 affect the winds will also greatly affect the currents, and consequently will 

 influence the climatic conditions of the globe. Again, as the existence of the 

 winds depends mainly on the difference of temperature between equatorial 

 and polar regions, any cause which will greatly affect this diffierence of 

 temperature will likewise greatly affect the winds. That is, should any cause 

 increase the difference of temperature between the equator and the pole on the 

 one hemisphere, and decrease that difference on the other hemisphere, it 

 would effect a change in the distribution of the aerial currents, which change 

 would in turn produce a corresponding change in the distribution of ocean 

 currents. 



Now, an increase in the eccentricity of the earth's orbit tends to lower the 

 temperature of one hemisphere and to raise the temperature of the other. Let 

 us imagine the eccentricity at its superior limit to be -07775, and the winter 

 solstice of the northern hemisi)here, instead of in jjerihelio as at present, to be 

 in ajyhelio. The midwinter temperature, owing to the increased distance of 

 the sun, would bo lowered enormously ; and the effect of this would be to 

 cause all the moisture which now falls as rain during winter in temperate 



