346 Mr. smeaton’s Fundamental Experiments 
circumftances obferved the laws of collifion of non-elaftic foft 
bodies, then it would be proved, that one half of the mecha- 
nical power, redding bn the ftriking body, would be loft in the 
action of colhiion ; becaufe the impnlfive force or power of the 
fpring in its reftitution being cut off, or fufpended from a&ing, 
which is equal to the impuHive force or power to bend it (and 
which alone lias been employed to communicate motion from 
one body to the other), it would make it evident, that one half of 
th e impuifive force is loft in the a£hon, as the other half remains 
locked np in the fp rings. It alio follows, as a collateral circum - 
Jlance , that be the impuifive power of the fprings what it 
may from firft to laft, yet as one half of the time of the 
action is by this means cut off, in this fenfe alfo it will fol- 
low, that one half of the mechanic power is deftroyed ; or 
rather, in this cafe, remains locked up in the fprings, capable 
of being re- exerted whenever they are fet at liberty, and of 
producing a frefh mechanical effedt, equivalent to the motion 
or mechanical power of the two non-elaftic foft bodies after 
their collifion. 
Hence we muft infer, that the quantity of mechanical power 
expended in difplacing the parts of non-elaftic foft bodies in 
collilion, is exaftly the fame as that expended in ' bending the 
fprings of perfectly elaftic bodies ; but the difference in the 
ultimate effect is, that in the non-elaftic foft bodies, the power 
taken to difplace the parts will be totally loft and deftroyed, as 
it would require an equal mechanic power to be raifed a-frefh, 
and exerted in a contrary direction to reftore the parts back 
again to their former places ; whereas, in the cafe of the elaftic 
bodies, the operation of half the mechanic power is, as obferved 
already, only locked up and fufpended, and capable of being 
re-exerted without a further original accellion. 
4 
Thefe 
