56 ESSAYS awn OBSERVATIONS 
tion, yet it isnot always the fame. It keeps 
pace with the impreffed force, and is very dif- 
ferent, according to the different forces with 
which bodies are put in motion. In a word, 
fince effects muft always correfpond with 
their caufes, the gradual increafe of the force 
of a falling body, muft infer the gradual in- 
creafe of the power of gravity, which‘is the 
caufe of the motion. Or rather, confidering 
the matter in a different light, perhaps more 
accurately, the tendency or m/us of a body 
towards the center of the earth, which is 
greater in motion than at reft, and which 
gradually increafes with the velocity of the 
motion, being nothing elfe but the exertion 
of its power of gravity, makes it evident 
that the power of gravity is continually in- 
creafing from the beginning, to the end of 
the motion. 
In accounting for this phcenomenon, I 
have neglected the v7s infita, tho’ it may pro- 
bably a& in conjunction with gravity in the 
defcent of bodies towards the center of the 
earth, as well as in the curvilinear motion of 
the planets. For, if the force of gravity be 
fuppofed invariable, the addition of the wis 
infita, which is alfo an invariable force, will 
only 
