230 On the Force of Percussion. 
a name given by Newton to the multiple of the velocity of 
a body simply taken into its quantity of matter. 
It cannot be expected that at this time any new experi- 
ment should be thought of by which the controversy can be 
decided, since the most simple experiments that have already 
been appealed to by either party have received different in- 
terpretations from their opponents, although the facts were 
admitted. 
My object in the present ‘lecture is to consider which of 
these opinions respecting the force exerted by moving bodies 
is most conformable to the usual meaning of that word, and 
to show that the explanation given by Newton of the third 
law of motion is in no respect favourable to those who in 
their view of this question have been called Newtonians. 
If bodies were made to act upon each other under the cir- 
cumstances which I am about to describe, the leading phee- 
nomena would occur, which afford the grounds of reasoning 
on either side, 
Let a ball of clay or of any other soft and wholly inelastic 
substance be suspended at rest, but free to move in any di- 
rection with the slightest impulse; and let there be two 
pegs, similar and equal in every respect, inserted slightly 
into its opposite sides. Let there be also two other bodies, 
A and B, of any magnitude, which are to each other in the 
proportion of 2 to 1, suspended in such a position, that 
when perfectly at rest they shall be in contact with the ex 
tremities of the opposite pegs without pressing against them, 
Now if these hodies were made to swing with motions sa 
adapted that in falling from heights in the proportion of J 
to 4, they might strike at the same instant against the pegs 
opposite to them, the ball of clay would not be moved from 
its place to either side; nevertheless the peg, impelicd by 
the smaller body B, which has the double velocity, would 
be found to have penetrated twice as far as the peg impelled 
by A. 
Tt is unnecessary to make the experiment precisely as 
here stated, since the results are admitted as facts by both 
parties ; but upon these facts they reason differently. 
Ong 
