Moving Force. 171, 
rectilinear force. That inconsistency (stated 
in case 3d) is overlooked in the usual demon- 
strations respecting rotatory motion; it is 
nevertheless one of considerable importance, 
and it requires explanation. I have already 
endeavoured to show (p. 139.) that the expla- 
nation, which refers us to the properties of the 
lever, is by no means sufficient. If, however, 
the product of the mass into the square of its 
velocity, be taken as the proper measure of 
the force of a body in motion, the explanation 
is obvious. | . 
The case of the balance beams (case 4th.) 
has been adduced by many authors in proof of 
the moving forces being as the masses multi- 
plied into their velocities. There is no doubt 
that after they have been put in motion, the 
weights will balance each other the same as 
when they were at rest ; but the question is, 
whether or not the motion of x can be gene- 
rated by a moving force no greater than that 
which generates the motion of m? If these 
two quantities of motion can be generated by 
equal forces, the same forces should generate 
equal quantities of motion in o and p; bat 
equal pressures applied to A and C will not 
produce, in equal times, equal quantities of 
motion in the respective weights. - Mr. Emer- 
son, by neglecting this circumstance, appears 
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