464 Mr, smeaton on Mechanic Power , 
FURTHER DEFINITIONS. 
I have already denned what I mean by mechanic 
power ; but, before I proceed further, it will be neceffary 
alfo to define the following terms : 
By all which, I under- 
* Hand the uniform en- 
deavour that one body 
Impulfe or Impulfion, 
Impulfive Force or Power, 
Impelling Force or Power, 
exerts upon another, in order to make it move ; and that, 
whether it produces or generates motion by this endea- 
vour or not; and the quantity of this impelling power 
may be mealured either by its being a weight of itfelf, 
or by being counter-balanced by a weight. It may alfo 
adf either immediately upon the body to be moved, lb 
that if motion is the confequence, they move with the 
fame velocity ; and that, either by a fimple contabt, or by 
being drawn as by a cord, or pulhed as by a ftaff : or it 
may abt by the intervention of a lever or other mechanic 
inftrument, in which the velocity of the body to be 
moved may be very different from the velocity of the 
impelling power or mover; but in comparing them, the 
impelling powers mult be reduced according to the pro- 
portional velocities of the mover and moved ; or, in levers 
of different lengths, they may be compared by a ftandard 
length of lever, which is the method taken in the lubfe- 
quent reafoning upon the preceding experiments. An 
impelling power, therefore, confiding of a double 
weight, or requiring a double weight to counter-balance 
it, when acting with equal levers, is a double impelling 
power, or an impelling power of double the intenfity. 
OBSER- 
