APPLICATION OF LABOR. 167 



placing the platform in too steep a position for a horse 

 to work comfortably. He is therefore attached to a 

 whipple-tree placed on the frame of the machine, so 

 that in drawing he pushes the platform backward with 

 his feet. In this case, the power can be only ascer- 

 tained by the use of the dynamometer, already de- 

 scribed. 



SECTION V. 



APPLICATION OF LABOR. 



Most of the moving powers applied by the farmer to 

 accomplish labor are the exertions of animal strength. 

 A principal object of the preceding pages is to point out 

 how this strength can be applied in the most econom- 

 ical 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 

 differently apphed. 



The amount of work which any machine is capable 

 of performing is denoted by comparing this amount 

 with the power of a single horse ; hence the common 

 expressions of twenty, or fifty, or a hundred horse- 

 power engines. The strength of different horses varies 

 greatly, but the expression, as commonly understood, 

 indicates a force equivalent to raising or pressing with 

 a force equal to 150 pounds 20 miles a day, at the rate 

 of two and a half miles an hour. This is the same as 

 33,000 pounds raised one foot in one minute. The re- 

 sults of numerous experiments in different places give 

 the actual power of the average of horses at somewhat 



