STUDIES IN NATURE 



then, it is natural that a south-west wind should 

 bring mild weather. It is equally natural that 

 a north-east wind, coming from the frozen plains 

 of Russia, should bring cold and frost. 



As yet we have said nothing about the effect 

 of the sun in England ; during the winter season 

 the temperature does not depend much on the 

 sunshine. The sun is low in the sky, and the 

 direct effect of his rays in heating the ground 

 is very small. The result of the changes in the 

 wind, and the differences produced by its coming 

 from warm moist regions and from cold dry ones, 

 are so much greater than any effect of more or 

 less direct sunshine, that the influence of the sun's 

 direct heat may be neglected. In the middle of 

 a great continent, however, this is not so, and in 

 central Europe or Asia the absence of much 

 sun in winter produces extreme cold ; for there 

 are no warm oceanic regions near to warm the 

 winds coming from any direction. 



In summer the sun is much higher in the 

 heavens, and the land of our islands gets heated 

 by its direct rays. Thus a clear sky in summer 

 usually means heat, while in winter it often 

 brings frost, since, as we have seen, the warmth 

 can then escape into space. On large conti- 

 nental areas this effect is much increased ; the 

 influence of the sun is not masked by the in- 

 fluence of neighbouring oceans, and clear weather 

 in winter means extreme cold, and in summer 

 extreme heat Thus the dry north-east winds 



(64) 



