Moving Force. 189 
can have been spent in no other way than in 
compressing the particles together, or in over- 
coming their tenacity. To take a familiar 
example.—If a quantity of corn is to be 
ground, a considerable quantity of motion 
must, no doubt, be produced before that can 
be effected ;—but after it is ground, there is 
no more motion in the flour than there was in 
the corn before it was ground, and the whole 
force employed must have been expended in 
overcoming the tenacity or cohesion of the 
particles of the corn. 
In answer to the very common objection, 
that the quantity of force expended in pro- 
ducing an effect of this kind, cannot be 
precisely ascertained, it may be observed, that 
in real practice, such quantities of force are 
estimated with quite as much precision as the 
force necessary to generate a given velocity in 
a given mass,—in projecting a cannon ball, for 
example.—The application and measurement 
of mechanical force producing changes of 
figure are indeed the chief occupations of 
practical men, in the construction and ma- 
nagement of machinery. 
The force spent in producing change of 
figure in the collision of bodies, was noticed 
by John Bernoulli in his dissertation De vera 
es 
notiope virlim vivarum, as follows. “ Si 
