APPLICATION OF MECHANICAL PRINCIPLES, ETC. 97 



needless fifty pounds, on an average of only five miles 

 a day, draws an unnecessary weight every year equal 

 to the conveyance of a heavy wagon-load to a distance 

 of forty miles. 



Now a knowledge of mechanical science will often 

 enable the farmer, when he selects and buys his im- 

 plements, to judge correctly whether every part is prop- 

 erly adapted to the required strength. "We shall sup- 

 pose, for instance, that he intends to purchase a com- 

 mon pitchfork. He finds them differently formed, al- 

 though aU are made of the best materials. The han- 

 dles of some are of equal size throughout. Some are 

 smaller near the fork, as in Fig. 78, and others are 



Fi-. 78. 



, w 



Badly-formed fork handle. 



larger at the same place, as in Fig. 79. Now, if he 



S^^ 



Badly -formed fork handle. 



understands the principle of the lever, he knows that 

 both of these are wrongly made, for the right hand 

 placed at a is the fulcrum, where the greatest strength 

 is needed, and therefore the one represented by Fig. 80 



Fig. 80. 

 r- a, „^^ ^ 



Well-formed fork handle. 



is both stronger and Ughter than the others. Again, 

 hoe handles, not needing much strength,, chiefly re- 

 quire hghtness and convenience for grasping. Hence, 

 in selecting from two such as are represented in the 

 E 



