236 WINDS; CLIMATE. 



capacity for vapour, that is, its power of retaining 

 the whole quantity of vapour taken up, is lessened, 

 it is, therefore, always losing some of its charge of 

 vapour and continually letting it fall in the form of 

 water. Hence come the rains which, in some parts 

 of Europe, often last for days and weeks; these soften 

 the cold of winter, and bring coolness in summer, 

 because the thick layer of clouds, from which they 

 fall, weakens the direct action of the sun. 



The air from the south, when it has come down 

 into the lower regions, and is passing over the sea, 

 cannot be far from its dew point (the point of full 

 charge of moisture). But as it passes farther up 

 over the continents, its charge of water is lessened, 

 and it becomes less able to recover, by fresh sup- 

 plies of water, its losses by the continual fall. The 

 south-west winds, therefore, if they reach as far as 

 the inner parts of the continents, bring usually but 

 little moisture thither. But in the east of Europe, 

 and in the midland parts of Asia, as I have already 

 told you, north-east winds prevail. They carry 

 the cold of the north to lower latitudes, and are, 

 therefore, probably the chief, if not the only, causes 

 of the low mean temperature of Russia and Siberia. 

 This northern current, as it gradually moves 

 onward into lower latitudes, is continually gaining 

 in temperature, and consequently in capacity for 

 vapour. It becomes a drying wind, and by 

 keeping the sky clear during the long summer 



