GAS-MAKING AND OTHER COALS 379
The Duquesne Lighting Company of Pittsburgh have recently constructed a huge concrete basin, capable of containing 100,000 tons of coal below the water-line. It is 791 feet long, 153 feet wide, and 25 feet 6 inches deep, built of concrete slabs 40 feet X 50 feet, arranged to permit expansion and contraction. The expansion joints are made watertight by means of pitch and tar paper, and are supported on ] 2-inch. concrete blocks. The internal walls have a 1 : 1 slope, and the outer embank-ment a batter of 2 : 1. A stone wall is erected on. the top of the embankment, as
Frø. 260.— Coal Stobe Tunnel showing Convkyoi: and Pouches.
a protection against erosion at high water, and cranes are provided for handling the coal. The water discharge system comprises four 18-inch pipes fitted with check v alves, which permit the water to rise inside the basin when the river rises during flood season, thus guarding against risk of lifting the bottom when the external water e\ el is considerably higher tlian the internal. Water is pumped in as required, through a 14-inch pipe leading from the power-house to four 12-inch outlets, 160 feet apart and 6 feet below the top level of the reservoir.
As an instance of the immense Stocks of coal held in reserve on gasworks it may be mentioned that the bunkers at the Tegel works at Berlin are over half a mile m length. and are capable of containing nearly a million tons of coal.