THE DYNAMOMETER. 



99 



must draw with a force equal to 400 pounds in mov- 

 ing one of them through the soil, while 300 pounds would be 

 sufficient for the other. He would, therefore, select the one 

 of easiest draught, and by doing so would save the labor of 

 one day in four to his team, or twenty-five days in a hund- 

 red, which would be worth many times the cost of the 

 trial. The same advantage might be derived in the selec- 

 tion of harrows, cultivators, horse-rakes, straw-cutters, and 

 all other implements drawn by horses or worked by men. 

 Again, the farmer may be in doubt in choosing between 

 two thrashing-machines, which in other respects may Avork 

 equally fast and well ; but the dynamometer may show 

 that one requires a severer exertion from the team, and 

 consequently is less valuable for use. 



The operation of this instrument may be readily under- 



Fig. 108. 



a 



Dynamometer, or Force-measurer. 



Stood by fig. 108, where b represents the dynamometer, 



Fi<?. 109. 



Elliptic Dynamometer. 



made precisely similar to a large and stiff spring balance, 



