MECHANIC POWERS. 47 



working in the teeth of the wheel D, which sup- 

 pose to be 48 in number. It is plain, that for every 

 time the wheel C and the screw are turned round 

 by the winch A, the wheel D will be moved one 

 tooth by the screw; and therefore, in 48 revolutions 

 of the winch, the wheel D will be turned once 

 round. Then, if the circumference of a circle, de- 

 scribed by the handle of the winch A, be equal to 

 the circumference of a groove round the wheel D, 

 the velocity of the handle will be 48 times as great 

 as the velocity of any given point in the groove. 

 Consequently, if a line G goes round the groove, 

 and has a weight of 48 pounds hung to it, a power 

 equal to one pound at the handle will balance and 

 support the weight. To prove this by experiment, 

 let the circumferences of the grooves of the wheels 

 C and D be equal to one another; and then if a 

 weight H, of one pound, be suspended by a line 

 going round the groove of the wheel C, it will 

 balance a weight of 48 pounds hanging by the line 

 G; and a small addition to the weight H will 

 cause it to descend, and so raise up the other 

 weight. 



If a line G, instead of going round the groove 

 of the wheel D, goes round its axle I, the power of 

 the machine will be as much increased as the cir- 

 cumference of the groove exceeds the circumference 

 of the axis: supposing it to be six times, then one 

 pound at H will balance six times 48, or 288 

 pounds, hung to the line on the axis: and hence 

 the power or advantage of this machine will be as 

 288 to 1. That is to say, a man, who by his 

 natural strength could lift a hundred weight, will 

 be able to raise 288 cwts. by this engine. If a 

 system of pulleys were applied to the cord H, the 

 power would be increased to an amazing degree. 



