72 MECHANICS. 



cattle, wagons loaded with hay, and other heavy arti- 

 cles. The wagon rests on the platform A {Fig. 52, 

 p. 71), and this platform rests on two levers at W, W, 

 which presses their other ends both on a central point, 

 and this again hears on the lever D, the other end of 

 which is connected by means of an upright rod with 

 the steelyard at F. 



There are two important points gained in this com- 

 bination. In the first place, the levers multiply the 

 power so much that a few pounds' weight will balance 

 a heavy load of hay weighing a ton or more ; and, in 

 the next, the load resting on both the levers, commu- 

 nicates the same force of weight to the central point, 

 from whatever part of the platform it happens to stand 

 on ; for if it presses hardest on one lever, it bears light- 

 er, at a corresponding rate, on the other. In practice, 

 there are always two pairs, or four levers, which pro- 

 ceed from each corner of the platform, and rest on one 

 point at the centre. We have taken the two only, to 

 simplify the explanation. 



. STUMP MACHINES. 



A simple contrivance for allowing a succession of 

 efforts in the use of the lever is represented in the ac- 

 companying figure {Fig. 53), and is used for tearing 

 out the roots of partly decayed stumps. It may be 

 also applied to lifting heavy weights, and to various 

 other purposes. Two pieces of strong, three-inch white- 

 oak plank, eight inches wide and seven feet long, are 

 connected at the ends, and are furnished with the 

 movable leg, d. Two rows of holes are bored through 

 them, to receive iron pins, which are to serve as ful- 



