146 The Drainage of Fens and Low Lands. 



delivery, 7 tons each stroke, with an average lift of 15 feet; the 



steam pressure in the boiler being 40 lb., and ciit-off in the cylinder 



at half the stroke. 



The coefficient of useful effect of these pumps is stated by Sig. 



Cuppari to be higher than any other machines in Holland, the 



ratio of effective to calculated discharge for the Cruquis being 89 per 



cent., and for the Leeghwater rather less. The ratio of horse-power in 



^40 W H P 



water lifted to that indicated of the Cruquis is—: ^^ ^^ ' = 60*60 



560 I.H.P. 



per cent. The average consumption of coal over a long period is 



6 • 82 lb. per W.H.P. per hour. At trials made by Mr. Elink Sterk, the 



engineer of the Haarlem ermeer, it was found that with the engine 



making three strokes a minute the consumption of coal was 5 *44 lb. 



per I.H.P., and 7-80 lb. per W.H.P. ; the ratio of efficiency of the 



machinery being '698. With seven strokes a minute 4*94 lb. of 



coal were used per I.H.P., and 6-74 lb. per W.H.P. The ratio 



^ W.H.P. 361 ^ . 



"^ ijlp: ^ ^^^^^ '^^^- 



To compensate the district of Rijnland for the loss of the large 

 area of polders taken from it by the drainage of Lake Haarlem, and 

 to effect the maintenance of the water in the Ringvart or surrounding 

 canal at a uniform level, pumping stations were erected at Halfweg, 

 half-way between Haarlem and Amsterdam, to lift the water into the 

 Y, when it rose above the height at which it would flow away by gravi- 

 tation ; at Spaamdam, near Amsterdam, to lift it into the Spaarn ; 

 and at Katwijk, to lift it into the North Sea. A pumping station was 

 also erected at Gouda, to regulate the water in the Gouda Canal, 

 and to discharge the flood water into the Yssel. The table on p. 147 

 gives the principal dimensions and particulars of the engines and 

 wheels. 



Halfweg. — The six scoop wheels * at this station are ranged in two 

 sets of three €ach on either side of the engine-house. The wheels 

 have a combined width of 39*36 feet Each set of these wheels is 

 fixed on a c^st^ron axle, but is so arranged that the couplings can be 

 disconnected and only part of the wheels worked when the lift is 

 high. The fmmiiig for each of the wheels consists of three heavy 



* Illustrations of the scoop wheels at Katwijk and Halfweg, and also of other 

 drainage machinery, will be found in the atlas of plates of * Stoomhemaling van 

 Polders en Boezems,' hy A. Huet, C.E., published 2^1 The Hague. 



