‘PHYSICAL Anp LITERARY. 10% 
_ deed only by experience that we learn the 
Jaws of the communication of motion. For 
_ who’ever fuppofed, that either the general or 
particular properties of matter could be dif- 
covered in any other way? How could it be 
known, whether body was penetrable or im- 
penetrable, divifible or indivifible, elaftic or 
non-elaftic, animated or inanimated, but by 
trial? Suppofing, however, that we were in-. 
formed before hand, that the body at reft 
‘was impenetrable, utterly inactive and foft, 
and had neither impediment nor tendency to 
motion; what would hinder us to foretell 
exactly every circumftance that’ happens, 
when another body of the ae kind ftrikes 
upon it*? 
~ Wuen a body in motion ftrikes upon ano- . 
ther at reft ; the one lofes as much motion, as 
the other gains, in the fame direction. This 
is ordinarily faid to proceed from a reaétion 
of the body that acquires the motion. The 
4 effet is indeed the fame upon the percutient 
: ‘body; there is the fame change of its ftate, 
as if it had adtually received an impulfe in 
the contrary direction. This, for the fake of 
: : fhortnefs 
: 
4 
"4 
= 
., | 
ae 
f __ * Philof- Effays. 
