FIRST let us examine the earth, whose situation is in the middle 

 of the universe solid, round, and conglobular by its natural 

 tendency. 



. . . What is most wonderful is that the world is so durable, and 

 so perfectly made for lasting that it is not to be impaired by time ; 

 for all its parts tend equally to the centre, and are bound together 

 by a sort of chain, which surrounds the elements ; this chain is 

 nature, which being diffused through the universe, and performing 

 all things with judgment and reason, attracts the extremities to the 

 centre. 



If, then, the world is round, and if on that account all its 

 parts, being of equal dimensions and relative proportions, mutually 

 support and are supported by one another, it must follow that, as 

 all the parts incline to the centre (for that is the lowest place of a 

 globe), there is nothing whatever which can put a stop to that pro- 

 pensity, in the case of such great weights. For the same reason, 

 though the sea is higher than the earth, yet because it has the like 

 tendency, it is collected everywhere, equally concentres, and never 

 overflows, and is never wasted. 



The stars have their revolutions in the sky, and are continued 

 by the tendency of all parts towards the centre ; their duration is 

 perpetuated by their form and figure, for they are round ; which 

 form, as I think has been before observed, is the least liable to 

 injury. 



CICERO, Nature of the Gods. 



