STRENGTH. The power exerted by an animal or machine in overcoming re sistance. That of the horse is used as a standard ; it certainly is the most useful, and that whose labor is susceptible of the most numerous and varied applications. It is therefore very important to ascertain his average force ; and accordingly a great number of estimates have been published,• both of the amount of labor he is capable ofperforming, and of his absolute mus cular power. For the purpose of deter . mining the latter, the dynamometer may be conveniently used; but as the action of the animal is very quickly reduced by continued exertion, it is more usual to estimate it according to the amount of daily labor performed. Desaguliers and Stneaton estimate the strength of a horse as equivalent to that of five men ; the French authors have commonly stated it as equal to that of seven men ; and Schulze makes it equal to that of fourteen men in drawing horizontally. According to Des aguliers, a horse's power is equivalent to 44,000 lbs. raised 1 foot high in one min ute • Smeaton makes this number 22,916; Hachette 22,000 ; and Watt 83,000. This -last estimate is what is commonly under= stood by the term horse power as applied to steam engines.
The quantity of action which a horse can exert diminishes as the duration of - • 1 the labor is prolonged. Tredgold gives the following table, showing the average maximum velocity with which a horse unloaded can travel, according to the number of hours per day : The useful effect a horse is capable of producing, depends much on the manner in which his strength is applied. One of the best modes is to make him draw a loaded carriage. The carriers in Scot land usually transport in a single-horse cart, weighing about 7 cwt., the load of a ton, and travel at the rate of 22 miles per day. Neglecting the weight of the ani mal and of the cart, and supposing the journey to be accomplished in 10 hours, the useful effect reduced to dynamic units (1000 lbs. one foot in one minute) is 260,198 dynamic units.
Napier gives the following results : A horse, drawing in a cart a load of 1540 lbs., (700 kilogrammes,) travels at the
rate of 2161 feet per minute, during 10 hours per day. Here the useful effect is 200,048.
A horse harnessed in a coach, and drawing a load of 770 lbs. avoirdupois, goes at a trot at the rate of 433 feet The minute, during 44 hours per day. The useful effect is consequently 90,020.
A horse carrying on his back a load of 264 lbs. can travel at the rate of 2161 feet per minute, 10 hours a day. The useful effect is 84,294 dynamic units. Going at a trot with double the velocity, during 7 hours a day, and carrying a load of 176 lbs., the useful effect is 82,007.
A horse harnessed in a mill, going at a pace of 195 feet per minute, and exercis ing a force equal to a pressure of 99 lbs., during 8 hours a day, produces a useful effect represented by 9266 dynamic units.
On the strength of mules, oxen, and the other animals employed in industry, there are few correct observations. The following are the principal results : Tak ing the useful effect of the daily labor of a man according to Coulomb's estimate as unity, then the comparative effects of the labor of some of the other animals applied in the same manner are thus estimated : For carrying loads in a horizontal plane— Strength of a man l (Coulomb.) of a horse 4.8 (BrunaccL) " of a horse 6.1 " of a horse 7.6 (BrunaccL) For transporting burdens with a wheel carriage— Man with a barrow 1 Coulomb.) Horse in a four wheel wagon 17 5 (Weserm.) Horse with a cart 29 3 (Brunacct) Mule with a cart 23.3 (Brunacci ) Ox with a cart.. .......... 12.2 (BrunaccL ) The above comparisons are probably nearer the truth than the following, which are us_ually quoted from Hassenfratz (Eneydopaie ifethodique): In carrying loads on a horizontal plane— Strength of a man 1 " of a horse 8 " of a mule 8 " of an ass 4 " of a camel. ....... 31 " of a dromedary 25 " of an elephant 197 " of a dog............
" of a reindeer ....
In drawing a weight along a horizontal plane— Strength of a man 1 " of a horse " of a mule 7 " of an ass 2 " of an ox 4 to 7 " of a dog " of a reindeer 01