MEASURE OF MOVING FORCE. 139 
‘“‘ Suppose a ball of clay to be suspended at 
rest, having two similar and equal pegs slightly 
inserted into its opposite sides ; and let two other 
bodies A and B, whose weights are as 2 to 1, 
strike at the same instant against the opposite 
pegs, with velocities which are in the proportion 
of 1 to 2. In this case the ball of clay would not 
be moved from its place to either side; neverthe- 
less, the peg impelled by the smaller body B, 
which has the double velocity, would be found 
to have penetrated twice as far into the clay as 
the peg impelled by the larger body 4.” 
The results of this experiment were admitted 
by both parties; but they reasoned upon them 
differently. |The party termed Newtonians 
asserted that as the clay is not moved, it isa 
proof that the forces of impact of the two balls 
were equal; as they would infer from the mo- 
menta being equal. Their opponents, on the 
other hand, maintained with equal confidence that 
the unequal depths to which the pegs had been 
driven was a proof that the causes of these dif- 
ferent effects were unequal; as might be inferred 
from considering the forces as proportional to the 
squares of the velocities. One party drew their 
conclusions from the fact that equal momenta can 
