PHYSICAL AND LITERARY. 105 



make an impreffion fourfold of what it 

 makes with a velocity as i ; becaufe it 

 continues likewife for double the time. 

 In uniform motions, a double velocity 

 and a double time rauft always give a 

 fourfold fpace: And the fame thing muft 

 obtain in equably retarded motions ; the 

 fpaces defcribed being exadlly the half 

 of what would have been defcribed by the 

 uniform motions. But, though the im- 

 preffion be fourfold, the real effect, by 

 which the force ought to be meafured, is 

 only double ; for it has only undergone 

 a double refiftance* For the fame reafon, 

 triple the velocity makes a ninefold im- 

 preffion. And, in general, the fmall im- 

 preffions made upon the furface of foft 

 clay (or even upon marble) by bodies 

 flriking upon it, muft, caeteris paribus^ be 

 as the fquares of the velocities. Thefe 

 impreffions, made in oppoffiion to the u- 

 niform reliftance of cohefion, are no bet- 

 ter meafures of forces, than the, heights 

 to which bodies are thrown near the 

 tarth, in oppofition to the uniform power 

 of gravity. The heights are known to 

 be as the fquares of the velocities. When 

 Vol. L O the 



