62 The Drainage of Fens and Low Lands. 



water actually raised. Allowing an efficiency of * S 5 for the 

 machinery, this is equal to 3*63 lb. per I.H.P. Some of the 

 best pumping engines for land drainage purposes in this 

 country consume from 4 lb. to 4^ lb. of coal per indicated 

 horse-power per hour, which is above the Dutch standard, 

 being at the rate of 7^ to 8J lb. per W.H.P. At the trials of 

 the engines and pumps put up at Fos, Bouches de Rhone, the 

 consumption of coal was at the rate of 4-45 lb. per W.H.P. 

 or 2 '47 lb. per I.H.P ; and in those erected for the drainage of 

 the Ferrara marshes 4 lb. per W.H.P., and 2| lb. per I.H.P. 



Neither with pumps nor scoop wheels is the consumption of 

 coal proportional to the lift, the relative quantity increasing 

 as the lift decreases. This is what would naturally be ex- 

 pected, as the dead weight of the machinery bears a larger 

 proportion to the total quantity of work the smaller the lift. 

 At trials at the Halfweg station in Holland the consumption 

 of coal varied from 14 '20 lb. per actual horse-power per hour 

 when the lift was under i foot to 5 ' 5 lb. when it was doubled. 

 With a lift of only 6 inches the consumption of coal was at 

 the rate of 50 lb. per horse-power per hour, the difference 

 being accounted for by the large amount of power required 

 simply to drive the wheels. Mr. Barker, one of the com- 

 missioners, gives the consumption of coal for engines working 

 centrifugal pumps, as varying with the lift, as follows — not 

 counting coal for getting up steam : — 



Feet of lift I 2*40 3*30 to 7*20 



Lbs. of coal per horse-power of 5*30 



water lifted .. • 9*37 8*22 7-71 6*6o 



(Trans. Inst. C. E., vol. Ixxv. p. 274.) 



In recent contracts made for centrifugal pumps in Holland, 

 this matter has been taken into consideration, and three con- 

 ditions of lift are specified. 



The conditions in some of the competitions for pumping 

 machinery in Holland, are that on the completion of the con- 

 tract for the erection of the machinery there should be two 



