Rensselaer Semi-Weekly Republican, Volume 37, Number 18, Rensselaer, Jasper County, 7 March 1905 — HORSEPOWER. [ARTICLE]

HORSEPOWER.

•The Unit as It Was Originated and Defined by Watt. When steam engines were employed to drive mills, pumps and other machinery Which bad been previously driven by horses, it was natural to attempt to express the work done by them in terms of the working power of the horse. James Watt was the first to define the unit of horsepower, which by experiment he found to be 33,000 foot pounds a minute. In other words, a one horsepower engine would raise 33,000 pounds one foot every minute, and so on proportionally to the number of “horsepowers” indicated by the engine. He arrived at this conclusion by observing the work done by heavy dray horses in breweries working eight hours daily and found that a horse going at the rate of two miles and a half an hour could raise a weight of 150 pounds by a rope led over a pulley, which is equal to 33,000 pounds raised one foot in one minute. Watt, for the credit of his engines, selected horses of more than average power.