68 MECHANICS. 



fulcrum, and power. In a lever of the first kind, if 

 the weight and power he equally distant from the ful- 

 crum, they will move through equal distances, and 

 nothing will be gained ; that is, a power of 100 pounds 

 will lift a weight of 100 pounds only. If the power be 

 Fig. 47. twice as far as the 



'[^'-"-"-T-... weight, its force 



' ;' ""'■:.- . will be doubled; 



' I I '^ ~c^^-i^^^.._ if three times, it 

 ^ )K^ will be tripled; 



Lever of the second kind. and SO forth. In 



a lever of the second kind, if the weight be equidistant 

 between the fulcrum and power, the power will move 

 through twice the distance of the weight, and the pow- 

 er of the instrument will therefore be doubled ; if twice 

 as far, it wiU be tripled, and so on, as shown in the an- 

 nexed figures. The same mode of reasoning wiU ex- 

 plain precisely to what extent the force is diminished 

 in levers of the third kind. 



These rules will show in what manner a load borne 

 on a pole is to be placed between two persons carrying 

 it. If equidistant between them, each will sustain a 

 like portion. If the load be twice as near to one as to 

 the other, the shorter end wiU receive double the weight 

 of the longer. For the same reason, when three horses 

 are worked abreast, the two horses placed together 

 should have only half the length of arm of the main 

 whipple-tree as the single horse. Fig. 48. The farmer 

 who has a team of two horses unlike in strength, may 

 thus easily know how to adjust ithe arms of the whip- 

 ple-tree so as to correspond with the strength of each. 

 If, for instance, one of the horses possesses a strength 



