STATIONARY ENGINES.
209
Fig. 132.—Plan of Pumps.
inch on the surface of the steam piston. These engines areworked at a fair duty, performing about 27,000,000 Ibs. lifted
1 foot high per minute, with a consumption of 1 cwt. of thesmall slack in the neighbourhood; with Newcastle or Welsh smallcoal they would perform a duty of 36,000,000 lbs. The pumpvalves are of the ring de-
scription, rising on a centralspindle; they are made of castiron galvanized, beating onwooden faces. Originally theybeat upon a mixture of leadand tin, but this soon becameloose in the seating, causingleakage; oak was then tried,but the acid peculiar to thiswood corroded the cast iron,and it had to be discontinued;lancewood, box, and beechhave also been tried, but no wood answers so well as holly, whichis now used for this dass of valve. The area of the suction valve is325 square inches, being about two and a half times the area of theplunger; and that of the delivery valve is 163 square inches, or aboutone and a third times the areaof the plunger. The enlarge-ment of the suction valve tothis extent is found to be veryserviceable where the velocityof the plunger is likely to begreat in the ascending stroke.
The water was originally deli-vered over a stand pipe 180feet high, whence it flowed bygravitation to the town; butnow a reservoir is substituted,and the stand pipe dispensedwith.
The engine at Goldthorn Hill is a low-pressure condensing beamengine. The cylinder is 48 inches in diameter, with an 8-feet stroke.The boilers are 30 feet long and 7 feet in diameter, with two tubes,
2 feet in diameter beyond the furnace, and 2 feet by 2 feet 4 inches