xvi AIR NOURISHES THE UNIVERSE 245 



his course so close to us, many times larger than 

 the whole circuit of the earth all these draw 

 their nourishment from materials of earth which 

 they share among them, and are sustained, of 

 course, by nothing else than the breath of the 3 

 earth. This is their nourishment, this their pas- 

 turage. Now the earth would be unable to nourish 

 so many bodies of such size, larger even than 

 itself, unless it were full of breath, which it exhales 

 from every part of it day and night. For there 

 must be a large reserve of that from which so 

 much is sought and taken ; in fact, the supply to be 

 drawn from it is created for the occasion. The 4 

 earth would not possess a perennial supply of 

 air sufficient for the wants of so many heavenly 

 bodies, unless the elements issued and returned 

 alternately and were transmutable into one another. 

 But apart from this, it is necessary that the earth 

 be abundantly filled with it, and be able to draw 

 it forth from her hidden store. There is no 

 doubt then that a great quantity of air lurks 

 in the interstices of the earth, and a widely 

 diffused atmosphere occupies the hidden spaces 

 underground. If that is true, of necessity the 

 earth must often be moved, since it is full of a most 

 movable substance. No one, I suppose, can doubt 

 that there is nothing so restless, so capricious, so 

 fond of disturbance as air. 



XVII 



IT follows,' therefore, that air should obey the law of i 

 its being ; what is wont to be moved will sometimes 

 move other things. And when ? Whenever its free 

 course is checked. As long as it is not hindered it 



