HORSE-POWER 



811 



Stakes were fixed near the margin of the canal, so as to ascertain tho rise and fall 

 of the wave caused by the boat in passing ; and it was observed that when a boat 

 passed with a velocity of from 4 to 6 miles per hour, the rise of the wave was 5 inches 

 and the fall 5 inches, making a wave of 10 inches in depth ; and when the velocity 

 was 11 J miles, tho rise was reduced to 2 inches and the fall to 2^ inches. 



Great difference existed in the power of horses, their weights and structure; and 

 the large dray-horses used by Messrs. Barclay, Perkins, and Co. did a full average 

 duty as assumed by Boulton and Watt ; but considering the average power of strong 

 and weak animals, ho had adopted 22,000 Ibs. raised 1 foot high as the standard : 

 much, however, depended on the nature of tho work performed. 



Mr. Davidson has given the following statement of the work performed by a London 

 brewer's horse per day ; the cost of feed and of wear and tear per horse per annum 

 being derived from actual experience among a large number of horses at Messrs. 

 Truman, Hanbury, and Co.'s brewery. The feed, &c,, is supposed to have cost the 

 tjamo per quarter, per truss, &c., each year : 



Mr. Beardmore mentions a case which occurred in a work near Plymouth, which he 

 believed would give the fair value of the work actually performed daily by a horse for 

 a considerable period. 



A quarry -waggon, weighing 2| tons, carrying an average load of stone of 5f tons, 

 was drawn by one horse along a railway 960 feet in length, 260 of it being level, and 

 the remaining 700 feet having an inclination of 1 in 138. During 48 working days 

 the number of trips was 1,302, or an average of 27*1 trips each day ; the time of per- 

 forming each trip was 4 minutes, or at a speed of 2*72 miles per hour; and the 

 total weight drawn, including that of the waggons, was 23,959,600 Ibs. 



Eepeated experiments proved, that upon the incline of 1 in 138 the waggons in 

 their ordinary working state would just remain stationary ; the friction was therefore 

 assumed to be 16'2 Ibs. per ton; by calculation it was, found that the horse raised 

 39,320 Ibs. 1 foot high per minute during the 8 working hours each day: the useful 

 effect, or net amount of stone carried, being 21,738 Ibs. raised 1 foot high per minute. 

 This difference between the work done and the useful effect arose from the necessary 

 strength and weight of the waggons. 



The animal employed was a common Devonshire cart-horse, 8 years old, 15 hands 

 high, and weighed lOf cwts. ; he continued doing the same work throughout a whole 

 summer, remaining in good condition ; but a lighter horse was found unequal to it. 



Prof. Rankine defined horse-power in a somewhat different form. ' The power of 

 a machine is the energy exerted, and the effect the useful work performed in some 

 interval of time of definite length, such as a second, a minute, an hour, or a day.' 

 There is a peculiar unit of power appropriated to its expression, called a HOESE- 

 POWEB, which is in Britain 



550 foot-pounds per second, 

 or 33,000 foot-pounds per minute, 

 or 1,980,000 foot-pounds per hour. 



In France the terms Force de Cheval or Cheval- Vapeur is applied to the following 

 rate of work : 



