86 THE PULLEY. 



lever of the second Und. When the power is applied 

 between the fulcrum and the resistance, as in the treadle 

 or footboard used by a knife-grinder, we use a lever of 

 the third kind. A pair of scissors, nutcrackers, a pair 

 of tongs, are respectively instances of double levers of 

 the first, second, and third kind. 



200 



i l c 



FIG. 60 



The pulley consists of a wheel moveable sound an 

 axis which passes through a frame called the block. 

 A groove is cut round the edge of the wheel for the 

 reception of a cord. 



