442 niYSICAL GEOGRArHY OF THE SEA, AND ITS 3IETE0I10L0GY. 



down its load of moisture, only a portion of it can Lo taken up 

 again ; the rest is absorbed by the earth to feed the springs. On 

 the polar side of 40^ S. we have a water instead of a land surface, 

 and as fast as precipitation takes place there, the ocean re- 

 plenishes the air with moisture again. It may consequently be 

 assumed that a high dew-point, — at least one as high as the 

 ocean can maintain in contact with winds blowing over it, and 

 going from warmer to cooler latitudes all the time — is the 

 normal condition of the air on the polar side of 40^ S., whereas 

 on the polar side of 40° N. a low dew-point prevails. The rivers 

 to the north of 40°, I reckon, could not, if they were all con- 

 verted into steam, supply vapour enough to make up this 

 average difference of dew-point between the two hemispheres. 

 The symmetry of the rain and storm curves on the polar side of 

 40° S. suggests that it is the condensation of this vapour which, 

 with the liberation of its latent heat, gives such activity and 

 regularity to the circulation of the atmosphere in the other 

 hemisphere. 



827. The rain-fall of Cape Horn and Cherraponjie. — On the polar 

 side of 40° S., near Cape Horn, the gauge of Captains King and 

 Fitzroy showed a rain-fall of 153.75 inches in 41 days. There 

 is no other place except Cherraponjie where the precipitation 

 approaches this in amount. Cherraponjie (§ 299) is, it has 

 already been stated, a mountain station in India, 4500 feet high, 

 which, in latitude 25° N., acts as a condenser for the monsoons 

 fresh from the sea. But on the polar side of latitude 45°, in the 

 northern hemisphere, it is, except along the American shores of 

 the North Pacific, a physical impossibility that there should be a 

 region of such precipitation as King and Fitzroy found on the 

 Avestern slopes of Patagonia — a physical impossibility, because 

 that peculiar combination of conditions required to produce a 

 Patagonian rain-fall is wanting on the polar side of 45° N. 

 There is in the Korth Atlantic, water surface enough to afford 

 vapour for such an amount of precipitation. In the North 

 Pacific the water surface may be broad and ample enough to 

 afford the vapour, but in neither of these two northern sheets of 

 water are the winds continuous enough from the westward to 

 bring in the requisite quantities of vapour from the sea. More- 

 over, if the westerly winds of the extra-tropical north were as 

 steady and as strong as are those of the south, there is lacking in 

 the north that continental relief — mountain ranges rising ab- 



