horse-power

(hérs’pou’ér), n. 1, The power ofa horse orits equivalent; the rate at which a horse works in drawing. Hence—2, A unit for the measurement of the rate at which a prime motor works. Several values have been a igned to this uni but the one which prevails at the present time in Englan and America is Watt's horse-power, which is defined as 550 foot-pounds per second. ‘This is 7,460 megaergs per second. ‘The real power of a horse is about three quarters of a horse-power. Abbreviated A. eh 3. A machine for converting the weight or direct pull of a horse into power useful in moying machinery. Such machines are either treadmills or circular sweeps. The latter consist e entially of a long sweep to the end of which the horse is harne ed, a simple form of gearing for transmitting the motion of the sweep to a pulley, with generally an increase of velocity, and a belt or shafting for conveying the power of the machine to the work, as a mill, threshing-machine, pre , pump, elevator, fire-engine, or other machine, to be driyen.—Indicated horse-power, the work, expre ed in horse-power, performed per minute by steam, air, or other gas upon the piston of an engine, in the computation of which the mean effective pre ure per square inch of piston is taken from an indicator diagram. See indicator. Also called true, actual, real, or dynamic horse-power.— Nominal, calculated, or commercial horse-power, horse-power calculated from the area of the piston, sometimes not more than one tenth of the real horse-power. Though the commercial horse-power is arbitrarily called calculated horse-power, it is easy to calculate the true horsepower by the principles of thermodynamics when the volume or weight and pre ure of the steam, air, or gas used for each piston-stroke and the number of strokes per minute are given. horsepox (hors’poks),. A pustular disease of horses, which, communicated to cows, produces cowpox. M, Blachez related the particulars of an outbreak of casual horse-pow among the she-a es used for giving suck to the inmates of a nursery. N.Y. Med. Jour., XL. 548.