MECHANICS. 118 



SCHULZE considers the quantity P, in the case of a 

 horse, as seven times greater than in the case of a 

 man, and the velocity, at the common rate of work- 

 ing, as twice as great ; so that the work done by a 

 horse is fourteen times that done by a man. Mem. 

 de TAcad. de Merlin, ibid. This exceeds DESAGIT- 

 LIER'S estimate. Course of Etrp. Phil. Sect. 4. 

 Notes, 6. 



When a horse's work is estimated by the load he 

 draws in a cart or waggon, a great reduction must 

 be made, in order to compare the force he exerts 

 with that which is necessary for raising a weight, 

 by drawing it over a pulley. Though accurate ex- 

 periments on the friction of wheel-carriages are want- 

 ing, we probably shall not err much in supposing 

 the friction, on a road, and with a carriage of the or- 

 dinary construction, to amount to a twelfth part of 

 the load. If, then, a horse draws a ton in a cart, 

 which a strong horse will continue to do for several 

 hours together, we must suppose his action the same 

 as if he raised up the twelfth part of a ton, (2240 

 lb.), or 186 Ib. perpendicularly against the force of 

 gravity. To raise a weight of 186 lb. therefore, at 

 the rate of two miles, or two miles and a half an 

 hour, (that is 2.9, or 3.6 feet per second), may be 

 taken as the average work of a strong draught horse 

 in good condition. 



A different manner of estimating animal force has been 

 followed by COULOMB, Mem. de TInst. Nat. torn. n. 

 p. 380, &e. 



VOL. I. Tl 183. It 



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