Mr. smeaton on Mechanic Power. 469 
the neceffary allowances before mentioned are made, to- 
gether with fome fmall inequality arifing from the me- 
chanical power loft by the difference of the motion given 
by gravity to the weight in the lcale : I fay, from thefe 
agreements, under the very different mechanical powers 
applied, which were varied in the proportion of 1 to 1 6, 
we may fafely conclude, that this is the univerfal law of 
nature, relpecfting the capacities of bodies in motion to 
produce mechanical effedts, and the quantity of mechanic 
power neceffary to be employed to produce or generate 
different velocities (the bodies being fuppofed equal in 
their quantity of matter); that the mechanic powers to 
be expended are as the fquares of the velocities to be ge- 
nerated, and vice verfd\ and that the fimple velocities 
generated are as the impelling power compounded with, 
or multiplied by, the time of its action, and vice verfa. 
We ffiall, perhaps, form a ftill clearer conception of 
the relation between velocities produced, and the quan- 
tities of mechanic power required to produce them ; to- 
gether with the collateral circumftances attending, by 
which thefe propofttions, feemingly two, are reconciled 
and united, by ftating the following popular elucidation, 
which, indeed, was the original idea that occurred to me 
on conff dering this fubjedt; to put which to an experi- 
mental proof gave birth to the foregoing apparatus and 
experiments. 
Suppofe then a large iron ball of 10 feet diameter, 
turned truly fpherical, and fet upon an extended plane of 
the fame metal, and truly level. Now, if a man begins to 
Q q q 2 pufh 
