Moving Force. 175 
motion cannot be considered greater or less 
according to the manner in which it has been 
produced, and when we see a body in motion, 
if its mass and velocity be given, we never ask 
by what kind of lever it has been produced in 
order that we may judge of its force. 
The case of a balance beam was noticed 
by Sir Isaac Newton, near the end of his 
scholium to the laws of motion ; but it is not 
clear that he considered that case in the same 
light in which it has since been. taken by 
Desaguliers and other authors, to prove that 
the moving forces of the weights are not as the 
squares of their velocities. It may, I appre- 
hend, with greater consistency, be inferred, 
that he noticed that case merely to show, that 
the pressures of the weights balance each 
other when they are in motion, the same as 
when they are at rest. It will be seen, when 
we come to examine the 14th case, that Sir 
Isaac Newton did not consider quantities of 
motion to be in all cases in the ratio of the 
forces by which they are produced. 
The 5th case belongs to that class of the 
effects of force which are considered by Mr. 
Atwood to be disproportionate to the forces by 
which they are produced, which ever way 
they may be estimated, whether by the mass 
into its velocity, or by the mass ‘into the 
