426 PHYSICAL GEOGRAPHY OF THE SEA, AND ITS METEOROLOGY. 



is stretched out in continental masses, upon the thirsty bosom of 

 which, when the air drops do"\vn its load of moisture, only a portion 

 of it can be 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 replenishes 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-pouit prevails. The rivers to 

 the north of 40°, I reckon, could not, if they were all converted 

 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 m the other hemisphere. 



827. On the polar side of 40° S., near Cape Horn, the gauge of 

 The rain-fall of Cape Captaius King and Fitzroy showed a rain-fall of 

 po^iij'i'e!"^ ^"^' 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 m 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 

 impossibihty that there should be a region of such precipitation as 

 King and Fitzroy found on the western 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 North Atlantic, water smface 

 enough to afford vapour for such an amount of precipitation. In 

 the North Pacific the water sm-face 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 fi'om the sea. More- 

 over, if the westerly ^wls 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 abruptly out of the 

 sea, or separated from it only by lowlands — that seems to be neces- 



