<_< 
Moving Force. 141 
conclusions, and we have only to regret that 
he has not pursued the subject farther. 
If the amount of the force could be encreased 
or diminished by any variation of the length of 
the lever, we might expect to find its measure 
to be of that indefinite kind which might be 
estimated by the product of the mass into any 
function of its velocity. Such a conclusion, 
however, is quite inconsistent with experience ; 
for under every variation of the proportions 
of the lever, the effect, if measured by the mass 
into the square of its velocity, is uniformly 
found to be in proportion to the moving force 
by which it is produced; if that force be 
measured by the pressure multiplied into the 
space through which it acts. But if we 
multiply the mass into any other. function than 
the square of its velocity, no such general cor- 
respondence between the force and its effects 
is to be found. 
Mr. Smeaton has well illustrated this prin- 
ciple by many valuable experiments on the 
more complicated cases of the action of water 
on mill-wheels, and on force generating: rota- 
tory motion in masses of matter about fixed 
axes. * 
The Edinburgh reviewers of Dr. Wollaston’s 
lecture on the force of percussion, have urged 
* See Philos. Trans. for 1759 and 1776, 
1 
