363 
Steam JEngine^ 
med by Messrs. Boulton and Watt, exceeds the deter- 
mination of M. Sauveur, who estimates the mean effort 
of a horse at 175 French, or 189 avoirdupois lbs. with a 
velocity of rather more tlian three feet per second ; and it 
probably exceeds Mr. Smeaton’s statement of 5501bso 
moved 40 feet in a minute ; though, as will soon be seen, 
we are not furnished with proper data to institute a com» 
parison between these various results. It is probable, 
however, as observed by the ingenious contributor of 
the article at page 216, voL IX. of your Journal, tha$> 
the lowest of these performances is more than equal to 
the average power of a horse employed in husbandry 
for eight hours per day.” So far as my own observa- 
tions on this point extend, I am inclined to conclude 
that the average work of a stout London cart horse, for 
eight hours in a day, is little if any more than ISOlbs. mo= 
ved at the rate of three feet in a second, or 2 1-22 miles 
per hour. But this it would be ridiculous to assume po- 
sitively as a universal unit of measure, in a case where 
the causes of variety are so numerous, and my oppor- 
tuaities of experiment comparatively few. The estimate 
just given, it should be observed, is not intended to ex» 
press what a horse can draw upon a wheel carriage, where 
friction alone is to be overcome, after the load is once put 
into motion, and where a horse will often draw much 
more than lOOOlbs. but the weight which a horse would 
raise out of a well, &:c. the animal acting by a hori- 
zontal line of traction turned into the vertical direction 
by a simple pully or roller, whose friction is reduced as 
much as possible.^ 
Before we can institute any comparison between the 
* The late Mr. More, Sec. to the Society of Arts, found by 
the interposition of a graduated spring instrument between the 
horse and his work, that the re-action was between 70 and 80lb. 
when the velocity was three miles in an hour. I think the work 
was ploughing. Scfe Philos. Journal, quarto, vol. Ill, 136, N- 
