362 
Steam Engine^ 
Power in horses 
according to 
Boulton and 
! Watt. 
Do. ac- j 
cording 
to Desa- 
guliers. * 
Do ac- 
cording 
to Smea- 
ton. 
34 hours work 
according to ,. 
Smeaton ia 
horses. 
71b. pressure 
per round 
inch. 
17^ or 18 
very nearly 
21 
25 
75 
iOlb, pressure 
35J 
per round 
inch. 
25 
30 
107 
9 NwK Journ, 214, 
Memarks on the estimation of the Strength of Horses, 
In a letter from Mr, O. Gregory, of the Royal 
Milytary Academy^ Woolwich, 
To Mr. NICHOLSON. 
SlEj 
The remarks of your ingenious correspondent, Mr. 
Hornblower, on the various estimates of the Power of 
a HorsCy and the absurdity of adopting a quantity so 
fluctuating and so difiicult to ascertain, as a common 
measure by whicli the powers and effects of steam en- 
gines and other machines are to be estimated and compa- 
red, have induced me to throw together a few observa- 
tions on the same subjects ; the theoretic part of which^ 
though familiar to most men of science, seems not to 
be always known, or at least recollected, by some per- 
sons who are employed in the practice ; and which are 
altogether much at your service for insertion in the Jour- 
nal, if you think them likely to be of any utility. 
Dr. Desaguliers has given another estimate of the 
labour of a horse, beside that mentioned by Mr. Horn- 
blower, and which indeed does not seem very consist- 
ent with it ; for in vol. II. p. 251. of his Experimental 
Philosophy, he affirms that a horse in an advantageous 
situation, is able to draw 2001bs. eight hours a day, 
walking at the rate of 2 1-2 miles in an hour, or 3 2-3 feet 
in a second. This statement of the power of a horse, 
rhoxigh it is not so great as that which is arbitrarily assin 
