Moving Force. 1i1 
body to a given height, where it is to be left 
at rest ;—the driving of piles ;—the overcoming 
of friction ;—the grinding of corn ;—the ham- 
mering and rolling of metals; and various 
other applications of force of a similar kind. 
Mr. Atwood appears, however, to have been 
aware that the doctrines of force, as they are 
usually treated, could not be of much service 
in practice; for, a little farther on he observes, 
“It is not probable, that the theory of motion, 
however incontestible its principles may be, 
can afford much assistance to the practical 
mechanic; and there appears as little room to 
imagine, that any errors or misconceptions 
which may have been propagated concerning 
the effects of forces considered in a theoretical 
view, have at all impeded the due construction 
of useful machines, such as are impelled by 
the force of wind or water, by springs or any | 
other kind of motive power. Machines of 
this sort, owe their origin and improvement to 
other sources: it is from long experience of 
repeated trials, errors, deliberations, correc- 
tions, continued through the lives of individu- 
als, and by successive generations of them, 
that sciences, strictly called practical, derive 
their gradual advancement from feeble and 
aukward beginnings, to their most perfect 
state of excellence.”* 
* Treatise on Rectil, and Rotat. Motion, p. 381 
