4&6 Invefligathn of the Poivers of Men and Horfes. 



poflible to be made either by man or bead, and the former is more particularly influenced 

 by his moral habits. From thefe laft it is that the influence of reward, the expe£l:atlon 

 of favour or patronage, and various other fimilar motives, have operated in the temporary 

 exhibition of hydraulic machines, to produce refults contrary to every found deduclion 

 from permanent work, and moft pernlcioufly delufive to the parties concerned in fup- 

 ■porfing or encouraging fuch engines. Defaguliers*, who has taken much pains to afcer- 

 tain the maximum of power in this refpcft, has determined that a man can raife of water, 

 or any other weight, about 550 lbs. or one hogfliead ten feet high in a minute ; and he 

 ■ftates that a horfe will raife five times that quantity ; or, which is the fame thing, that 

 quantity through five limes the height. His dedutStion rcfpefling the man, though he 

 fays it will hold good for fix hours, appears from his own fa£ls to be too high, and cer- 

 tainly fuch as could not be maintained one day after another. Smeaton f confiders this 

 work as the effort of hade or diflrefs. He reports J that fix good Englifh labourers will 

 be required to ra'fe 2 1 141 folid feet of fca water to the height of four feet in four hours. 

 This quantity is of the fame weight as 21669 cubic feet of frefli water, with which, and 

 the above rate, it will be found by an eafy calculation that the men will raife a very little 

 more than fix cubic feet each to the height of ten feet in a minute. Bat the hogfliead con- 

 taining 8^ cubic feet, Smeaton's allowance of work proves lefs than that of Defaguliers in 

 the proportion of 6 to 84^. And as his good Englilh labourers, who can work at this rate, 

 are by him ellimated to be equal to a double fet of common men picked up at random ; it 

 feems very proper to Rate that, with the probabilities of voluntary interruption, and other 

 incidents, a man's work for many days together ought not to be eftimated at more than 

 half a hogfliead raifed ten feet high in a minute. In the fame report laft quoted, Smeaton 

 ftates, that two ordinary horfes will do the work in three hours and twenty minutes, which 

 amounts to a little more than two hogflieads and a half § raifed ten feet high in a minute. 

 One horfe will therefore do the work of five men. 



To apply thefe dedu£lions to our example, it mufl: be recolle£led that the quantity 

 raifed in ten hours to the height of thirty feet was inferred to be 6437 hogflieads, which 

 are equivalent to 32 hogflieads raifed ten feet high per minute. Confequently at the rate 

 of one man for each half hogfliead, the ftream would perform the work of 64 men, or 

 pearly thirteen horfes. ' 



With regard to ftreams which fall by a confiderable declivity, the water may be con- 

 veyed by the well known means of a dam or trough to the buckets of an overfliot wheel, 

 placed in that part of the ftream which is found the moft convenient in point of expencc 

 and local fituation. Suppofe, for example, the fall amounted upon the whole to fifteen 

 feet, upon a length of 200 yards, it might be more convenient to lead the whole ftream in 

 a wooden trough fupported upon pofts, with a flight declivity, to the wheel near the lower 

 end of the current ; or in other circumftances, according to the face of the land, the work 

 might prove cheaper or more durable if the wheel were placed near the upper end of the 

 ftream, and the channel funk fo as ]to convey away the tail water with no more fall than 

 fliould be neceflary for that purpofe. In this cafe It is obvious that the fall muft be afcer- 



'* Courfe of Leftures, ii. 49S, 505, 536.. f Reports,!. 216. J Ibid. i. 323. 



§ He clfewhere (ibid. p. 229.) rates an horfe at 250 hogfheads, ten feet high, in an hour ; but I prefer the 

 ideduflion in the text. 



6 tained 



