MOS'INO FORCE. 
59 
It true they hnve not been usually stated in the same On«~^tion. 
terms: but I believe the same inferences striciiy follow „f ,i,p 
from the rea-iooing of many other good writers on this sub 
ject. If forces be mathematical quantities, we may reason- In- il ifinilt to 
ably Miquire, how is it that they are so indeterminate in rela- 
five magnitude ? 
If two given lines, angles, surfaces, or solids, be equal, they 
are equal in whatever manner they may be applied, or how- 
ever they may be measured. But if we have two given bodies, 
moving with velocities inversely as their masses, their forces, 
it would appear, are either equal or unequal, according as they 
may be classed under one or other of the above subdivisions of 
rnechanical pbenomena. 
If the forces of two given bodies in motion are either equal Clagsifiration 
1 1- 1 I • I 1 . ®f •bf p'i«-na- 
or unequal, according to the purpose to which they may be nipua desir- 
applied, it would be very desirable to have a complete and ?c- 
curate classification of all tlic phenomena of force, exhibiting 
the variations to which they may be subject ; and we are so 
far inelebted to Mr. Atwood, that he is, I believe, the only au- 
thor who has attempted to make such an arrangement. But 
his arrangement is not complete, for he has omitted to include 
in it msnv important practical applications of force ; such, 
for example, as the raising of a hrxly 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 hammering and rol- 
Jing of metals; and various other applications of force of a 
similar kind. 
Mr. Atwood appears, however, to have been aware that the The doctrinn 
doctrines of force, as they are usually treated, could not he of us Jally^tr^-at 
much service in practice; for a little farther on he observes, are »f litile 
"It is not probable, that the theory of motion, however 
inconiestible its principles m-y 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 Whence it is 
been propagated concerning the effects of forces considered in s"PP®»cd that 
, , . errors in 
a theoretical view, have at all impeded the due construction of thcorv have 
useful machines, such as are impelled by the force of wind or 
^ ' noxious. 
vater. 
