Mechanic Powers. 247 



his natural strength, could lift a hundred weight, 

 will be able to raise two hundred and eighty- 

 eight hundred weight, or 1 4 tons 8 hundred, by 

 this engine. 



But the following engine is still more power- 

 ful, on account of its having the addition of 

 four pulleys ; and in it we may look upon all the 

 mechanical powers as combined together, even 

 if we take in the balance. For as the axle D of 

 the bar AB (fig. 104) enters its middle at C, it 

 is plain that if equal weights are suspended upon 

 any two pins equi-distant from the axis C, they 

 will counterpoise each other. It becomes a lever 

 by hanging a small weight P upon the pin n 9 and 

 a weight as much heavier upon either of the pins 

 b 9 d y or e, as is in proportion to the pins being 

 so much nearer the axis. The wheel and axle 

 FG is evident ; so is the screw E which takes in 

 the inclined plane, and with it the half wedge. 

 Part of a cord goes round the axle, the rest 

 under the lower pulley K, over the upper pulley 

 L, under AT, over /, and then it is tied to a hook 

 at M in the lower or moveable block, on which 

 the weight W hangs. 



In this machine, if the wheel F have thirty 

 teeth, it will be turned once round in thirty re- 

 volutions of the bar AB, which is fixed on the 

 axis D of the screw E : if the length of the bar 

 be equal to twice the diameter of the wheel, the 

 pins e and n at the ends of the bar will move 

 sixty times as fast as the teeth of the wheel do ; 



