i6 



THE ANIMAL AS A MACHINE. 



It is evident that power is also measured by the pro- 

 duct of the resistance, or of the effort exerted into the 

 velocity of the motion with which that resistance is 

 overcome or that force exerted. Since s = vt, 



U = Rs= Rvt ; 



and when t becomes unity, the measure of the power, 

 or of the equivalent work done in the unit of time, is 



U = Rv, 



in which the terms are given in units of force and space 

 as above. 



The power of a prime mover is usually ascertained 

 by experimentally determining the work done in a given 

 time, the trial usually extending over some hours, and 

 often several days. It is measured in foot-pounds or 



identical ; but the differences are usually less than per cent. The fol- 

 lowing table, compiled by Mr. Babcock, gives these standards in kilo- 

 grammetres per second, and in foot-pounds per second expressed in 

 the foot and pound standards of each country. 



STANDARD HORSE-POWER FOR DIFFERENT NATIONS. 



Country. 



Kilogram- 

 metres 

 per second. 



Baden 

 ft. -pounds 

 per second. 



Saxon 

 ft. -pounds 

 per second. 



Wurtem- 

 berg 

 ft. -pounds 

 per second. 



Prussian 

 ft. -pounds 

 per second. 



Hanoverian 

 ft.-pounds 

 per second. 



English 

 ft.-pounds 

 per second. 



Austrian 

 ft.-pounds 

 per second. 



France and Baden 



75 



500 



529.68 



521.58 



477-93 



513-53 



542.47 



423.68 





75 -045 



500.30 



530 



523-89 



478.22 



513-84 



542.80 



423.93 



Wurtemberg 



75 • 240 



501-36 



531-12 



525 



479-23 



514-92 



543-95 



424.83 





75-325 



502.17 



531-97 



525-85 



480 



515-75 



544.82 



425-51 





75-361 



502.41 



532.23 



526. 10 



480.23 



516 



545.08 



425.72 





76.041 



506.94 



537-03 



530.84 



484-56 



520.65 



550 



429.56 





76.119 



507.46 



537-58 



531-39 



485.06 



521 . 19 



550.57 



430 



