150 DISCUSSIONS IN CLIMATOLOGY. 



water within the Arctic circle during the sunless winter, if 

 air contributed none of it. Just think of a current of three- 

 quarters of a nautical mile per hour, or 70 miles per four 

 days flowing towards the pole across the Arctic circle. The 

 area of the Arctic circle is 700 square miles for each mile of 

 its circumference. Hence 40 fathoms deep of such a current 

 would carry in, per twenty-four hours, a little more than 

 water enough to cover the whole area to a depth of 1 fathom; 

 and this, if 7°*1 Cent, above the freezing point, would bring in 

 just enough of heat to prevent freezing, if in twenty-four 

 hours as much heat were radiated away as taken from a tenth 

 of a fathom of ice-cold water would leave it ice at the freez- 

 ing-point. This is no doubt much more than the actual 

 amount of radiation, and the supposed current is probably 

 much less than it would be if the water were ice-cold at the 

 pole and 7 o, Cent, at the Arctic circle. Hence, without any 

 assistance from air, we find in the convection of heat by 

 water alone a sufficiently powerful influence to prevent any 

 freezing-up in polar regions at any time of year." * 



That an amount of warm water flowing into the 

 Arctic Ocean, equal to that assumed by Sir William 

 Thomson, along with the effects of clouds, wind, dew, 

 and other agencies to which he refers, would wholly 

 prevent the existence of permanent ice in those regions, 

 is a conclusion which, I think, can hardly be doubted. 

 It is with the greatest deference that I venture to differ 

 from so eminent a physicist; but I am unable to 

 believe that such a transference of water from inter- 

 tropical and temperate regions could be effected by the 

 agency to which he attributes it. Certainly the 

 amount of heat conveyed by means of a circulation 

 resulting from difference of specific gravity, produced 

 by difference of temperature, must be trifling when 

 compared with that of ocean-currents produced by the 



* Trans, of the Geol. Soc. of Glasgow, 22nd February, 1877. 



