If cm never recover its force when it is resisted, where* 

 us gravity can. Therefore the constant bending of its 

 ction, which must be equal to a constant proportion- 

 able resistance, must uniformly and perpetually weaken 

 its power, and strengthen that of gravitation; so that 

 the direction of motion must necessarily sink more and 

 more, and at last fail wholly into the direction of gravi- 

 tation. It follows that no power acting upon an orb 

 which gravitates towards its centre of motion, can pos- 

 sibly maintain its projectile motion, in the direction of a 

 circle. 



5. Even on supposition that projection and gravita- 

 tion equally retained their propensity to motion though 

 resisted, yet those powers could not move the planets in 

 ellipsis, because in the same proportion as the one pre- 

 vailed over the other, in the same proportion it must 

 alter the tendency of motion towards its own direction. 

 And none can explain how, when a quantity of motion 

 and also of inclination is gained by gravitation over pro- 

 jection, the orb will, while these remain unchanged, leave 

 at any point the direction of the moving power that pre- 

 vails, and recede into the direction of the weaker power, 

 or e contra, 



6. Again : from the proportions of the forces required 

 between gravitation and projection, in order to move the 

 orbs and circles, it is evident that these two powers can- 

 not be the cause of their motions. For by comparing 

 the forces of these it appears, that the force of gravita- 

 tion is not such in proportion to that of projection, as to 

 bend the direction of the projected body sensibly from 

 the right line. 



7.. The motion of the moon along with tfce earth, 

 cannot be owing to her gravitating towards it, nor to a 

 projection impressed upon her, in common with the 

 earth : because she has a projection of her own round 

 the earth. And she cannot be so projected as to move 

 \i\ two different orbits at one and the same time, by the 



