76 



MECHANICS. 



Fig. 56. wheel be attached, so that 



this cord too may wind upon 

 the larger wheel. These two 

 wheels (fastened together so 

 as to form one), as they are 

 made to revolve on their axis, 

 will now constitute, in a man- 

 ner, a succession of levers, act- 

 ing through an indefinite dis- 

 tance according to the length 

 of the cords. The levers here 

 successively acting are of the 

 "fhst kind," and the axis of 

 the wheel is the fulcrum. This arrangement consti 

 tutes in substance the wheel and axle ; and its power. 

 Hke that of the simple lever, depends on the compara 

 tive velocity of the weight and the movmg force. If, 

 for example, the larger wheel is four times the circum 

 ference of the smaller, a force of one hundred applied 

 to the outer cord will raise a weight of four hundred 

 pounds. 



The annexed figure exhibits at one view the pow- 



Fig. 57. 



Wheel and axle, showing the heavier weight foi 

 less motion. 



er exerted through 

 the wheel and axle, 

 where a small weight 

 of 6 pounds will wind 

 up (or balance) oth- 

 er weights separate- 

 ly, weighing 8, 12, 

 or 24 pounds, as the 

 difference increases 

 between the size of 



