I20 The Drainage of Fens and Low Lands. 



stations are about 8 and 15 miles respectively above Denver Sluice, 

 where are self-acting doors, which shut against the tide at the time of 

 high water. The lift at the north station is rather the highest, the 

 average of the two stations being about 10 feet 6 inches, rising in 

 heavy floods to 1 6 feet. The north station consists of a scoop wheel 

 34 feet 6 inches in diameter, with scoops 4 feet 9 inches long by 



2 feet wide, motion being given by one engine of 40 nominal horse- 

 power. The wheel is driven by a condensing engine of the old marine 

 side-lever type, having the beam below the cylinder. The piston has 



3 feet 6 inches stroke, and makes 28 revolutions of the engine to 5^ 

 of the wheel. The working pressure of the steam is 15 lb. on the 

 inch. The station at the Fish and Duck was provided, until recently, 

 with a scoop-wheel ; but as, owing to the subsidence of the peat, the 

 surface has settled in this district 4 feet 6 inches since the beginning 

 of the present cen*-ury, it was necessary to provide more efficient 

 machinery ; and under the advice of Mr. Carmichael, the superin- 

 tendent of the works in the South Level, the scoop wheel and engine 

 were replaced by a centrifugal pump. The new engine is of the 

 horizontal tandem type, high-pressure compound condensing, fitted 

 with expansion gear, 60 nominal horse-power, the cylinders being 

 t8 inches and 30 inches in diameter, with 3 feet stroke, provided 

 with variable expansion valve working on the back of the high- 

 pressure valve. Steam is provided by three Lancashire boilers, 

 25 feet long by 7 feet diameter; the working pressure being (>^ lb. 

 Only two of the boilers are in use at the same time. The engine 

 makes 70 revolutions with steam at 65 lb. in the boiler, and cut off in 

 the small cylinder at half of the stroke, the pump making at the same 

 time 105 revolutions with a lift of 14 feet per minute, and delivering 

 120 tons. The case of the pump is 9 feet 6 inches diameter, situated 

 in a well immediately outside the wall of the engine-house. This well 

 is 9 feet 10 inches in diameter; the diameter diminishing below the 

 pump to 6 feet. The outlet for the discharge is 9 feet 6 inches above 

 the centre of the pump, and is 5 feet 6 inches high by 3 feet 6 inches 

 wide. The pump is driven by a bevel wheel geared into a bevel 

 pinion on the crank shaft, which is 1 1 feet long. The fan is single, 

 made of gun-metal, 6 feet diameter by 12^ inches deep at the peri- 

 phery, with a short suction-pipe attached to the case below the disc. 

 The spmdle is suspended by an onion-bearing, supported by a girder 

 across the top of the cylinder of the pump-well. When the pump is 

 working it is found that little weight is carried by the onion-bearing, 



