122 MECHANICS. 



SECTION V. 

 CONSTRUCTION AND USE OF THE DYNAMOMETER. 



The dynamometer, or force-measurer, has been al- 

 ready briefly alluded to, but a more particular descrip- 

 tion will be useful. In the construction and selection 

 of all machines and implements that require much 

 power in their use, the dynamometer is indispensable, 

 although at present but little known. As an example 

 of its utility, the farmer may wish to choose between 

 two plows which, so far as he can perceive, may do 

 their work equally well ; but this instrument, when 

 applied, may show that the team miist draw with a 

 force equal to 400 pounds in moving 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 hundred, which would be worth many times the cost 

 of the trial. The same advantage might be derived 

 in the selection 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 work equally fast and 

 well; but the dynamometer may show that one re- 

 quires a severer exertion fi:om the team, and conse- 

 quently is less valuable for use. 



The operation of this instrument may be readily un- 

 derstood by Figure 97, where b represents the dyna- 

 mometer, made precisely similar to a large and stiff 



