150 The Drainage of Fens and Lozv Lands. 



of tlie Haarlemermeer drainage. This pump has very long suction 

 and delivery pipes, doubtless reducing its efficiency to a small extent. 



BijLMEHMEER, HOLLAND. — The first compouud centrifugal pump- 

 ing engine put down in Holland was supplied by Messrs. J. and 

 H. Gwynne for this drainage in 1883. When tested, the pumps 

 raised 70 tons per minute 14 feet high ; the ratio of water to indi- 

 cated horse-power was '613; and the coal used, German, was 

 4-67 lb. — 2*12 metres — per W.H.P. per hour. Although German 

 coal is inferior to good English steam coal, the consumption would 

 not have been so high as stated had the boilers been more per- 

 fectly proportioned to the requirements of the engines. Two are 

 provided, one is rather too small to give steam enough, while both 

 are quite too large. 



ZuiDPLAS Polder, near Mobericht, Holland. — This is a very- 

 low polder, the peat having been used largely for fuel. The lift 

 from the surface of the water to the mean level of the river Yssel, into 

 which the water is discharged, is about 22 feet. The area of the 

 polder is 11,050 acres, of which 682 acres are occupied by the 

 Ringdyke, leaving 10,368 acres. At the beginning of the present 

 century windmills driving scoop wheels were erected to keep down 

 the level of the water. In 1825 the Dutch Government determined 

 to thoroughly drain the lake. For this purpose it was divided into 

 two parts, the lower level being separated from the upper by a 

 surrounding canal or Ringvart, into which the water from the lowest 

 part was lifted, and from which it was raised with the drainage of 

 the rest of the polder into a collecting basin, which discharged into 

 the river Yssel by sluices. The lower level was drained by fifteer|^ 

 windmills, eight driving Archimedean screws, and seven scoop wheels. 

 For the lift from the upper level there were fifteen windmills, ten of 

 which drove screws and five wheels. There were also erected in 

 1838 two steam engines driving screws. The windmills were in 

 operation until 1873, the annual cost of maintaining them being at 

 the rate of 60/. each. The Archimedean screws, erected in 1838, 

 were 5-83 feet in diameter, the axle being 1*70 feet, and the blades 

 o'i2 foot thick. The axle was laid at an inclination of 30°. The 

 screws made 47 revolutions a minute, and the engines 19*86. The 

 engines were direct double action, with cylinders 1*66 feet diameter, 

 and having 7 feet stroke. The spur wheel fixed on the crank shaft, 

 geared into a bevel wheel on the axle of the screws. With a lift of 

 6*16 feet, the discharge was 1*17 tons per revolution, equal to 



