196 PHYSICAL SCIENCE BK. v 



then a breeze springs up ; the particles have got 

 more room now, and the thickly packed crowd of 

 them is broken up. 



IV 



1 BUT how, you will say, are winds then formed, for 

 you won't deny that they are formed ? Not in any 

 single way, I reply. Sometimes the earth herself 

 emits a great quantity of air, which she breathes out 

 of her hidden recesses. At other times a great 

 and long -continued evaporation drives the emis- 

 sions from the depths up on high, where the ,change 

 which the mixed breath undergoes issues in ^ wind. 

 A suggestion has been made which I cannot make 

 up my mind to believe, and yet I cannot pass over 

 without mention. In our bodies food produces 

 flatulence, the emission of which causes great 

 offence to one's nasal susceptibilities ; sometimes a 

 report accompanies the relief of the stomach, some- 



2 times there is a more polite smothering of it. In 

 like manner it is supposed the great frame of things 

 when assimilating its nourishment emits air. It is 

 a lucky thing for us that nature's digestion is good, 

 else we might apprehend some less agreeable con- 

 sequences. Is it not, then, nearer the truth to say 

 that numerous particles are constantly borne up 

 from every part of the world ; and when they are 

 accumulated and subsequently begin to be rarefied 

 by the sun, wind starts up ? It is a general prin- 

 ciple that anything contained in a narrow space 

 when it expands tries to get more room. 



