THE PULLEY. 



85 



Fig. 67 



Pitching hay with horse-power. 



fork, after being thrust into the hay, is lifted by the 

 strength of the horse workmg just without the barn 

 door. It is kept level by means of the rope, b, until the 

 fork is high enough to unload, when this rope is slack- 

 ened, and the hay deposited. The man on the mow 

 can give any direction to the hay he pleases while it 

 remains suspended. The horse is backed, and the op- 

 eration repeated. The arrangement is cheap, and with 

 it six tons have been pitched 20 feet high in an hour. 

 The usefulness of the pulley depends mainly upon 

 its Hghtness and portable form, and the facility with 

 which it may be made to operate in almost any situ- 

 ation. Hence it is much used in building, and is ex- 

 tensively applied in the rigging of ships. In the com- 

 putation of its power there is a large drawback, not 

 taken into account in the preceding calculation, which 

 materially lessens its advantage ; this is the friction of 



