460 Mr . smeaton on Mechanic Power . 
r a light pulley of about three inches diameter, hung 
upon a Heel axis, and moveable upon two fmall pivots. 
The plane of the pulley, however, is not directed to the 
middle of the upright axis, but a little on one fide, fo as 
to point (at a mean) between the lurfaee of the bigger 
barrel and the lefs. 
s is a light fcale for receiving weights, and hangs by a 
fmall twine, cord, or line, that paffes the pulley, and ter- 
minates either upon the bigger barrel or the lefs, as may 
be required ; the fliding-piece Q^being moved higher or 
lower for each, that the line, in palling from the pulley 
to the barrel, may be nearly horizontal. The end 
of the line, that is furtheft from the fcale, is termi- 
nated by a fmall loop, which hangs on upon the pin 0 , or 
the pin />, according as the bigger or the leffer barrel is to 
be ufed. 
Now, having wound up a certain number of turns of 
the line upon the barrel, and having placed a weight in 
the fcale s, it is obvious, that it will caufe the axis to turn 
round, and give motion to its arms, and to the weights of 
lead placed thereon, which are the heavy bodies to be 
put in motion by the impulfe of the weight in the fcale ; 
and when the line is wound off to the pin, the loop flips 
off, and the fcale then falling down, the weight will ceafe 
to accelerate the motion of the heavy bodies, and leave 
them revolving, equably forward, with the velocity they 
have acquired, except fo far as it muff be gradually lef- 
fened by the fridtion of the machine and refinance of the 
air, which being fmall, the bodies will revolve fometime 
before their velocity is apparently diminifhed. 
MEASURES 
