94 
MOVING fOnCK. 
Cases of (ilffi- rev Ive ahoiU a centre or axis. In tlie first case, tlie molinn 
cully in the 
aoetriiifs or lost is always equal to the motion corrimunicalecl in an oppo- 
inoviiig toree. j.jjg direction ; in the second, the motion lost is to he increased i 
or diminished in the ratio of the levers before it will be equal 
to the motion communicated*.” 
We do not find, however, that the absolute forces or their 
efl'ects, can be increased or diminished by any alteration in the 
le'nglhs of the levers. For if the arm HG, for example, be , \ 
extended to any assumed lenglb, the same velocity will still be |d 
jiroduced in m by tlie motion of P ihrougb the .same space. It L 
is true the velocity will not be produced in the same time ; but jU 
tlie result will be the same, in wbaiever time, or by whatever | 
• coiiiplicalion of levers or wheels, it may be produced. ' 
"I'he converse ol ibis case is stilled by Dr. Wollaston as fol- [1 
lows: “ It mav be of i:se also to consider another application [(! 
of the .same energy, and to shew more generally, that the same Ih 
quantity of total effect would be the consequence nut only of || 
diicct anion of bodies upon cacli oilier, but also of their in- i| 
direct action through the medium of any mechanical advan- I 
tage^or disadvantage ; although ilie time of action might, by [jf 
that me.ans, be increased or decreased in any desired proponion. I 
For instance, if the body supposed to be in motion w'cre to act It 
by means of a lever upon a spring placed at a certain distance if 
from the reiilre of motion, the retarding force opposed to it u 
be inversely, as the distance of the body from the centre ; and' ^ 
since the space through which the body would move to lose its I 
w’hole velocity would be reciprocally as the retarding force, the I 
angular motion of the lever and space through whish the l 
spring must bend, would be the same, at whatever point of !• 
the lever the body actedf .” Practical men are much beholden ' 
to Dr. Wollaston. He is, I believe, the only author, profes- *■ 
sedly on the theoretical principles of mechanics, who has writ- 
ten decidedly in support of Mr. Smeatoii’s conclusions; and (I 
we have only to legiet, thatj,e has not pursued the subject 
farther, ! 
• r>r. Miliirr. P!ul. Trans. 17 76, j>. 37 1. 
1 I'iiii. Trans. ItiOo, p. VI. I 
It' I 
I 
I 
