116 MECHANICS. 



Farm implements and machines for working the soil 

 should be, as far as possible, simple and not complex, be- 

 cause they mostly meet with an irregular resistance, con- 

 sisting of hard and soft soil and stones variously mixed 

 together. A locomotive is made up of many parts ; but 

 having a smooth surface to traverse, the machinery works 

 uniformly and uninjured ; but if in its progress it met 

 with formidable obstructions and uneven resistance, it 

 would be soon racked and beaten to pieces. Hence the 

 long-continued and uniform success of the simple plow ; 

 as well as the failure of complex digging machines, unless 

 worked exclusively in soils free from stone. A complex 

 machine, that meets with an occasional severe obstruction, 

 receives a blow like that of a sledge ; and when this is 

 repeated frequently, the probability is that some part will 

 be bent, twisted, knocked out of place, or broken. If the 

 machine be light, the chances are in its favor; but if 

 heavy, its momentum is sucli that it can scarcely escape 

 severe injury. If composed of many distinct; parts, the 

 derangement or breakage of one of these is sufficient to 

 retard or put a stop to its working, and men and teams 

 must stand idle till the mischief is repaired. 



Hence, after the trial of the multitude of imi^lements 

 and machines, we fall back on those of the most simple 

 form, other things being equal. The crow-bar has been 

 employed from time immemorial, and it will not be likely 

 to go out of use in our day. For simplicity nothing ex- 

 ceeds it. Spades, lioes, forks, etc., are of a similar char- 

 acter. The plow, although made up of parts, becomes a 

 single tiling when all are bolted and screw^ed together. 

 For this reason, with its moderate weight, it moves 

 through the soil with little difficulty turning aside from 

 obstructions, on acc(5unt of its wedge form, when it can- 

 not remove them. The harrow, although composed of 

 many pieces, becomes a fixed solid frame, moving on 

 through the soil as a single piece. So w^ith the simpler 



