85 



io the centrifugal, which makes them roll in circles 

 at a distance. 



7. We have seen, that the ancients attribute to the 

 celestial bodies, a tendency towards one common 

 centre, and a reciprocal attractive power. Lucretius 

 well perceived this truth, though he deduced from 

 it a very strange consequence, that the universe had 

 no common centre, but that infinite space was filled 

 with an infinity of worlds like ours, for, says he, if 

 the celestial bodies were all of them carried to wards 

 one common centre, and not restrained from that 

 tendency by some exterior active force, they must 

 needs soon diverge towards one another, by virtue of 

 their attractive power, and like bodies tumbling from 

 on high, re-unite at the common centre of gravity 3 and 

 coalesce into one infinite inactive mass. 



8. It appears also, that the ancients knew, as well 

 as the moderns, the cause of gravitation, which at- 

 tracted all things, did not reside solely in the centre 

 of the earth. Their ideas were more philosophic : 

 that this power was diffused through every particle 

 of the terrestrial globe, and compounded of the va- 

 rious energy residing in each. 



9. It remains to inquire whether the ancients knew 

 the law by which gravity acts upon the celestial 

 bodies : that it was in an inverse proportion of their 

 quantity of matter, and the square of their distance. 

 Certain it is, that the ancients were not ignoranj^ 

 that the planets in their courses, observed a con. 

 stant and invariable proportion, and that they had 

 different opinions respecting this proportion. Some 

 sought for it in the difference of the quantity of 

 matter contained in the masses, of which they were 

 composed ; and others in the difference of their dis- 

 tances. Lucretius, after Democritus and Aristotle, 

 thought that the gravity of bodies was in proportion, 

 to the quantity of matter of which they were com- 



