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Show MEANING OF "HORSE POWER" Simple Manner by Which the Now Familiar Fa-miliar Term Was First Brought -Into Use. The use of the "horse-power" as a measure of an engine's work came naturally from the fact that the first engines were built to do work which had formerly been performed by horses. John Smeaton, who built atmospheric at-mospheric engines before Bolton and Watt placed their more complete machine ma-chine on the market, had valued the work done by a strong horse as equal to lifting a weight of 22.000 pounds one foot high a minute. When Bolton and Watt began to bid for public favor, fa-vor, they agreed to place their engines en-gines for "the value of one-third part of the coals which are saved in its use." They also increased the value of the horse-power to 33,000 footpounds, foot-pounds, so that their engines were half again as powerful for their rated power as those of their competitors. In this way they established the value of the horse-power. The following are the various values of a horse-power: Thirty-three thousand foot-pounds a minute. 550 foot-pounds a second, 2,-565 2,-565 thermal units an hour, 42.75 thermal ther-mal units a minute. The horse-power of a boiler depends on its capacity for evaporation. The evaporation of 30 pounds of water from 100 degrees Fahrenheit into steam at seven pounds' gauge pressure equals 34 pounds, and at 212 degrees Fahrenheit Is equivalent equiv-alent to a horse-power. |