144 ^^^ Drainage of Fens and Low Lands^ 



The average annual consumption of coal was, during the same 

 period, 2690 tons. The rainfall for the ten years — 1877-86 — 

 averaged 32 inches, the maximum being 39*13 inches in 1877; 

 and the minimum, 26*69 inches in 1884. The average number 

 of hours the pumps were working, during the same period, was 

 6823 hours ; equal to ninety-four days of twenty-four hours for each 

 station, the average quantity of water pumped being 96,091,600 tons. 

 The water is kept at an average level of at least 3 feet below the 

 surface of the arable land, and about 2 feet for the grass land. 



The Leeghwater was the first machine erected ; the three sets of 

 machinery are almost similar in design and dimensions. The engines 

 are beam engines of the Cornish type, single-acting, condensing, and 

 working expansively, giving motion to a series of pumps, working at 

 a single lift arranged concentrically round the engine. The water is 

 delivered by the buckets of the pumps on to a spilling-floor A, Plate 

 8, Fig. 13, at either side of which are self-acting doors B, which 

 open out to a short channel leading to the main canal. These doors 

 open as soon as the water on the floor rises above the level of that in 

 the canal, and close as soon as the pumps cease. There are valves 

 which, when opened, leave the spilHng-floor dry, so that the buckets 

 and other parts of the pumps can be drawn out and laid on the floor 

 for repair. The general arrangement of these engines will be seen 

 from the drawing, Fig. 14. The foundation for the machinery and 

 buildings consists of 1400 piles driven to a depth of 40 feet into a 

 stratum of hard sand. On these a platform was laid 21 feet below 

 the surface of the lake, and upon this a brick well was built in which 

 the pumps were fixed. The engine was placed in the centre, with 

 the pumps C, eleven in number, ranging round three sides in the 

 segment of a circle, the boilers being placed at the back. The 

 engine is of peculiar construction, having two cylinders, D, E, one 

 within the other, united at the bottom, and having a clear space of 

 I J inches between them at the top under the cover, which is common 

 to both. The outer or annular cylmder, E, is 12 feet in diameter, 

 and the inner, D, 7 feet. The pistons are connected to the rocking- 

 beams by one main piston-rod attached to the smaller piston, 

 12 inches in diameter, and four small rods attached to the annular 

 piston, each 4^ inches in diameter, and having a large crosshead 

 with a circular body 9 feet 6 inches in diameter, and formed to 

 receive the ends of the balance-beams of the pumps. When the 

 pistons are at the bottom of the cylmder, steam is admitted at a 



