Ptimping Stations. 145 



pressure of from 40 lb. to 45 lb. beneath the interior piston, which 

 is then raised, carrying with it the annular piston, crosshead, and a 

 weight of about 30 tons of iron, with which it is loaded, the total 

 dead-weight lifted being about 100 tons. Steam is cut off at tV^'^s 

 of the stroke, at the end of which an equilibrium valve is opened 

 and the steam admitted to both sides of the piston, which is 

 held in its place for a short interval by two hydraulic rams, one 

 on each side of the cylinder, in order to enable the pump valves 

 to adjust themselves ; the equilibrium valve is then closed, the 

 eduction valve opened, and the steam passes through the large 

 cylinder to the condenser, the piston descending by gravity, draw- 

 ing down the balance-beam of the pumps, and lifting the water 

 on to the upper floor of the well. The various valves for the 

 admission of steam to the cylinder, the equilibrium valve, and 

 to the condenser, and for the cataract, are opened and closed 

 by tappets on rods, which strike levers actuating the valves. 



The pumps at this station are eleven in number, and each of them 

 62, inches in diameter ; at the t^^o other stations there are only eight 

 pumps, each 73 inches in diameter. The pumps are attached to 

 cast-iron balance-beams turning upon a centre in the wall of the 

 engine-house, the other end of the beam being connected with the 

 crosshead of the engine. Each pump-rod is of wrought iron, 3 inches 

 in diameter and 16 feet long. The steam and pump pistons have a 

 stroke of 10 feet. The eleven pumps make ten strokes a minute, 

 and raise each 6 tons per stroke — equal to 660 tons per minute. 

 The weight of the several parts is as follows: — ^beams, 9* 82 tons 

 each; the cylinder, 24*2 tons; crossheads, 18 '8 tons; pump cylin- 

 ders, 6*82 tons each; and buckets, 3 tons. 



The first trial of the Leeghwater was made in September 1845, and 

 was in full working order in the following November. The engine 

 was found at the trial to do a duty equal to raising 75,000,000 lb. 

 one foot high by the consumption of 94 lb. of good Welsh coal, 

 and exerting a net effective force of 350 horse-power with a lift of 

 13 feet. There are fiVQ boilers, each 30 feet long by 6 feet in 

 diameter, with a single flue 4 feet in diameter. The Cruquis has 

 eight pumps 6 feet in diameter with 10 feet stroke, lifts 8 tons per 

 stroke, making ten strokes a minute, or a total for all the pumps of 

 640 tons per minute, the average lift being 15 • 58 feet. The Lynden 

 machinery is similar to the Cruquis — it works generally during the 

 winter, using only seven pumps, making seven strokes a minute ; 



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