108 MECHANICS. 



the force is applied to it, so that the weight at m shall rep- 

 resent the force truly. The weight m is, of course, to be 

 multiplied by the power it exerts on the lever ^, which 

 should be graduated like the bar of a steelyard. 



There are a few other parts of this dynamometer not 

 yet described. One is the cylinder o, filled with oil, in 

 which a perforated piston works, preventing the rapid 

 vibration of the lever i^ as the force varies, precisely 

 similar to the cylinder of oil described in fig. 110, p. 100. 

 Another part is the pendulum p, with the wheel r, which 

 measures the time. 



The use of this instrument has been already attended 

 with some important results in detecting the great amount 

 of friction existing in some thrashing-machines of high 

 reputation, which has been found to amount, in certain 

 cases, to more than one-half of the whole power applied. 

 It is only by detecting so great a waste that we are ena- 

 bled to take measures for its prevention. 



CHAPTER VIII. 



APPLICATIOX OF LABOR. 



Most of the moving powers applied by the farmer to 

 accomplish labor are tlie exertions of animal strength. A 

 principal object of the preceding pages is to point out how 

 this strength can be applied in the most economical 

 manner, and to aid in the substitution of cheap horse- 

 power for more costly human labor. It will doubtless 

 contribute to the end to exhibit the relative efficiency of 

 each, as well as the results of strength difierently applied. 



The amount of work which any machine is capable of 

 perfonning is denoted by comparing this amount with 



