STRENGTH OF MEN AND HORSES. 239 



we find the relative force p = 205lbs. which agrees very well 

 with what we have just found above. 



If instead of this first formula, the second be taken, it gives 

 p = 153lbs. which is far too little. 



By this it is evident, that the first of Euler's two formulae is Enter* first 

 to be preferred in all respects. I have also made a great num- ^J.™^ pre " 

 ber of combinations, and I almost always found the same 

 effect. 



Dividin^the 205lbs. which we have just found, by seven, 

 the number of workmen, we get 29lbs. for the relative force, 

 with 2'45 feet relative velocity for each man, which is rather 

 more than the values commonly adopted in the computation 

 of machinery. A number of other observations on different A man's 

 machines, which I intend to relate another time, have given Jf 6 !^^ || |£ 

 me the same result j that is to say, we must value the mean veloc. per 

 human strength at 29 or 30lbs. with a velocity of l\ feet per secoud * 

 second. 



To obtain the ratio of the strength of a horse to that of a 

 man, I had the same machine moved by a horse, without alter- 

 ing any thing ; and I found by ten different horses which I * 

 used successively, that a horse makes 6*03 turns in two hours 

 instead of 281 j therefore, by supposing the static motion of 

 a horse seven times greater than that of a man, we find that 

 the former has 5 3 feet per second of velocity. 



By this it is evident, that the effect of a horse is fourteen Horses exceed 



times greater than that of a man, or, which amounts to the ™ e ? 1 * tim * s 



/- 1 1 . 1 r 1 in drawing, 



same thing, fourteen men must be used instead of one horse. 



Hence it appears, that it is much more advantageous to employ 

 horses than men in moving machines, if other reasons did not 

 require us to prefer men. 



I have also made a number of other interesting observations 

 on horses and oxen, which are likewise used in moving ma- 

 chines ; but as I am now waiting for observations of this kind, . 

 which other persons are making according to my plan, I shall 

 reserve them for another memoir. 



II. 



