WORKS OF CREATION FREE FROM MISTAKES. 115 



from its own weight. The larger spiders rarely have legs 

 so slender in form as the smaller ones ; the form of the 

 Shetland pony is quite different from that of the large 

 cart-horse ; and the cart-horse has a slenderer form than 

 the elephant. 



The common flea will leap two hundred times the length 

 of its own body, and the remark has been sometimes made 

 that a man equally agile, with his present size, would 

 vault over the highest city-steeple, or across a river as 

 wide as the Hudson at Albany. Now, if the flea were 

 increased in size to that of a man, it would become a 

 hundred thousand times stronger, but thirty million times 

 heavier; that is, its weight would become three hundred 

 times greater than its corresponding strength. Hence we 

 may infer that the enlarged flea would be no more agile 

 than a man ; or that, if a man were proportionately 

 reduced to the size of a flea, he could leap to as great a 

 distance. 



All this serves to illustrate in a striking manner the 

 great difference in the working of models and of machines. 



CHAPTER X. 



CONSTRUCTION AND USE OP FARM IMPLEMENTS AND MA- 

 CHINES IMPLEMENTS FOR TILLAGE. 



The application of mechanical principles in the struc- 

 ture of the simpler parts of implements and machines has 

 been already treated of. It remains to examine more 

 particularly those machines chiefly important to the farmer, 

 and to show the application of these principles in their 

 use and operation. 



