HORSE-POWER 



809 



for raising ore from the mines at Freiberg, the horses being of average size and 

 strength, has concluded that the useful effect of a horso yoked during eight hours, by 

 two relays of four hours each, in a manege or mill-course, may be estimated at 

 40 kilogrammes raised 1 meter 'per second; which is nearly 1 6,440 Ibs. raised one 

 foot per minute ;' being very nearly one half of Mr. Watt's liberal estimates' for the 

 horse-power of his steam-engines. 



Frederick William Simms, M.Inst.C.E., adopted some peculiar conditions of work 

 on which he was engaged to determine the value of horse-power. He had to make 

 a tunnel for the South-Eastern Railway. This tunnel was driven in the middle bed 

 of the Lower G-reensand, between which and the surface of the ground is interposed 

 only the upper bed of the same stratum ; but in sinking the eleven shafts for the 

 work, it was found that at the level of the top of the tunnel, the ground assumed the 

 character of a quicksand, saturated with water, in such quantity that it could not be 

 reduced by manual labour. Under these circumstances horse-gins were erected for 

 drawing the water by barrels, containing 100 gallons each, weighing when full about 

 1,310 Ibs. 



^ The engineer's intention was, to drive simultaneously from these shags, in the 

 direction of the tunnel, an adit or heading to carry off the water ; but *fhe earth, 

 which was sand mixed with fine particles of blue clay, was so filled with water as to 

 become a mass of semifluid mud ; great exertions were therefore necessary to over- 

 come the water, without erecting pumps. At first this was accomplished "by making 

 each horse work for 12 hours and then for 8 hours per day, allowing 1 hour for food 

 and rest : as the water increased it became necessary to work night and day, and the 

 time of each horse's working was reduced generally to 6 hours, and sometimes to 

 3 hours. As all the horses were hired at the rate of seven shillings per day, the 

 engineer, who had charge of the works, ordered a daily register to be kept of the 

 actual work done by each horse, for the double purpose of ascertaining whether they 

 all performed their duty, and also hoping to collect a body of facts relative to horse- 

 power which might be useful hereafter. 



Mr. Simms gives as a proposition, ' That the proper estimate of horse-power would 

 be that which measures the weight that a horse would draw up out of a well ; the 

 animal acting by a horizontal line of traction turned into the vertical direction by a 

 simple pulley, whose friction should be reduced as much as possible.' He states that 

 the manner in which the work was performed, necessarily approached very nearly to 

 these conditions ; and after giving the principal dimensions of the horse-gins, he 

 analyses each set of experiments, and by taking the mean of those against which no 

 objections could be urged, he arrives at the following results : 



The power of a horse for 8 hours = 23,412 Ibs. raised 1 foot high in one minute. 

 Do. 6 =24,360 



Do. 4 =27,056 



Do. 3 =32,943 



Of these results he thinks the experiments for 6 hours and for 3 hours alone 

 should be adopted as practical guides, all the others being in some degree objec- 

 tionable. 



As a means of comparison, the following table of estimates of horse-power is 

 given : 



These are much higher results than the average of his experiments, and would 

 more nearly accord with the extremes obtained by him ; but under such excessive 

 fatigue, the horses were speedily exhausted, and died rapidly. Nearly one hundred 

 horses were employed : they were of good quality; their average height was 15 hands 

 J- inch, and their weight about 10 cwts., and they cost from 20J. to 40*. each. They 

 had as much corn as they could eat, and were well attended to. 



