J^5 MR« GREGORY ON KORSE POWERS.' 



an advantageous fituation, is able to draw 200lbs. eight hours 



a day, walking at the rate of 2f miles in an hour, or 3| feet 



in afecond. This ftatenient of the power of a horfe, though 



it is not fo great as that which is arbitrarily alTumed by MefTrs. 



—by Sauvear Boulton and Watt, exceeds the determination of M. Sauveur, 



j89lb. avoird. ^^j^^ eftimates the mean efFort of a horfe at 175 French, or 189 



three feet per 



(econd, avoirdupois lbs. with a velocity of rather more than three feet 



per fecond; and it probably exceeds Mr. Smeaton's ftatement 

 of 550!bs. moved 40 feet in a minute ; though, as will foon be 

 feen, we are not furniQied with proper data to inftitute a com- 

 parifon between thefe various refults. It is probable, how- 

 ever, as obferved by the ingenious contributor of the article at 

 page 216, vol. IX. of your Journal, that '' the loweft of thefc 

 '• performances is more than equal lo the average power of a 

 ** horfe employed in hutbandry for eight hours per day." So 

 —by the author f^r as my own obfervationson this point extend, I am inclined 

 J^Xecond, ^^ conclude that the average work of a ftout London cart 



horfe, for eight hours in a day, is little if any more than 130lbs. 

 moved at the rate of three feet in a fecond, or 2— miles per 

 hour. But this it would be ridiculous to affume politively as a 

 univerfal unit of meafure, in a cafe where the caufes of vari- 

 ety are fo numerous, and ray opportunities of experiment com- 

 paratively (ew. The eftiraate juft given, it (hould be obferved, 

 is not intended to exprefs what a horfe can draw upon a wheel 

 carriage, where friction alone is to be overcome, after the load 

 is once put into motion, and where a horfe will often draw 

 much more than lOOOlbs. but the weight which a horfe would 

 raife out of a well, &:c. the animal acting by a horizontal line 

 of tradion turned into the vertical direction by a fimple pully 

 or roller, whofe I'ridlion is reduced as much as poflible,* 

 Miftpplication Before we can inditule any comparifon between the refults 

 of the g'^^^^J* of different experiments, it will always be necelTary to enquire 

 gain in powtr is what machine was interpofed between the weight moved and. 

 -kfs in time. j|jg animal, in each cafe, that we may thence deduce the real 

 Velocity with which the animal moved, from the velocity of 

 the weight or load given by the obfervations. This is too fre- 



* The late Mr. More, Sec. to the Society of Arts, found by the 

 interpofition of a graduated fpring inftrument between the horfe 

 and his work, that the re-a6lion was between 70 and 80lb. when 

 the velocity was three miles in an Iwur. I think the work was 

 ploDghing. Sec Philof. Journal, quarto, Vol. in. 136. N. 



quently 



