76 ^ MECHANICS. 



strokes an hour, should not wield a needless ounce. If 

 any part is heavier than necessary, even to the amount of 

 half an ounce only, he must repeatedly and continually 

 lift this half ounce, so that the whole strength thus spent 

 would be equal, in a day, to twelve hundred and fifty 

 pounds, which ought to be exerted in stirring the soil and 

 destroying weeds. Or, take another instance: A farm 

 wagon usually weighs nearly half a' ton; many might be 



Fiff. 8G. 

 Oy .=:=*=^ 



Badly-fortneO.fork handle. 



reduced fifty pounds in weight by proportioning every 

 part exactly to the strength required. How much, then, 

 should we gain here ? Every farmer who drives a wagon 

 with its 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 dis- 

 tance of forty miles. 



Now a knowledge of mechanical science will often ena- 

 ble the farmer, when he selects and buys his implements, 

 to judge correctly whether every part is properly adapted 

 to the required strength. We shall suppose, for instance, 

 that he intends to purchase a common pitchfork. He 

 finds them differently formed, although all are made of the 



Fig. 87. 

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Badly -formed fork handle. 



best materials. The handles of some are of equal size 

 throughout. Some are smaller near the fork, as in fig. 86, 

 and others are larger at the same place, as in fig. 87. 

 Now, if he 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 thei'efore the one represented by 

 fig. 88 is both stronger and lighter than the others. 



