1 5 2 The Drainage of Fens and Low Lands, 



upper. The working pressure of steam is 75 lb. The lift varies from 

 5 feet to 13 feet These machines give off in water lifted from 40 to 

 50 per cent of the indicated power, the average being 40. The con- 

 sumption of coal is at the rate of 7*67 lb. per water horse-power 

 per hour. The four centrifugal pumps, with the engines and boilers, 

 cost 11,833/. Taking the power in water lifted for such as 62-64, 

 this is at the rate of 47 '22/. per water horse-power. The pumps work 

 under some disadvantage as compared with the wheels, the work of 

 the latter being more regular and constant, while that of the pumps 

 frequently varies both with regard to the lift and time of working. 

 At a trial of one of these pumps made in 1877, the consumption of 

 coal was found to be at the rate of 5 '95 lb. — 2*7 kilogs. — per horse- 

 power of water lifted. The average lift was 12' 73 feet; the number 

 of revolutions, 105; discharge, 87*17 tons per minute. 



Beemster Tolder, North Holland. — A pair of direct-acting 

 engines and centrifugal pumps were fixed for the drainage of 

 this polder by Messrs. Gwynne and Co. in 1878. Each of these 

 engines is stated to be capable of raising 100 tons of water a minute 

 to a height of 17 feet. The cylinders of the engines are steam 

 jacketed, 27 inches in diameter, with 20 inches stroke. The engines 

 work at the rate of 100 revolutions a minute. The steam in the 

 boiler is supplied at a pressure of 75 lb. per square inch, and is cut 

 oif at one-eighth of the stroke by adjustable expansion valves. Four 

 smaller sets of similar pumps were erected by Messrs. Gwynne in 

 the previous year. At the trials of these pumps they each discharged 

 %'^ tons of water per minute while going at xoo revolutions ; the coal 

 consumption being at the rate of 5 • 94 lb. per hour per horse-power 

 of water lifted. Pumps erected by the same firm at Dordrecht, 

 lifting 54 tons of water a minute 6-56 feet high, running at 120 

 revolutions a minute, took 24*3 horse-power, and consumed at the 

 trial, made in 1876 and lasting over if hours, 6 •691b. of coal per 

 hour per horse-power of water lifted. Two smaller pumps, dis- 

 charging together 65I tons a minute to the height of 6-56 feet, with 

 125 revolutions per minute, required 29*4 horse-power, and consumed 

 at the rate of 7 J lb. of coal per hour per horse-power of water lifted. 



Waterland, Holland. — This polder is situated near Amsterdam, 

 and contains 25,000 acres. There are three pumping stations pro- 

 vided with engines driving scoop wheels. The Buiksluit station has 

 two curved scoop wheels, with the concave side of the curve towards 

 the internal water. The curve is struck to a large radius, and, although 



