Engineering Wonders of the World
Volume III

THE DRAINAGE SYSTEM OF LONDON. 217 lowering weirs into a culvert leading to the river. When all the top water is gone, the “wet sludge” left is pushed, by The Sludge. .° r . means of large squeeges, along the channel to the sump of the sludge pumps. On its way to the sump the sludge traverses a screen, which arrests all rags, wood, and down the river to a point called the Barrow Deep, about 57 miles below Barking, but now deposit the sludge in the Black Deep, about 5 miles further out to sea, over a length of from 8 to 10 miles. The sludge vessels are loaded through, hatch- ways in two cases, in others through a cen- DISCHARGING SLUDGE INTO STEAMER AT BARKING. (Photo, Pictorial Agency.) other things which might damage the pumps. These last deliver the sludge into setting chan- nels, where a further deposition of the solid matter takes place. The supernatant “ liquor ” is drawn off by telescopic weirs, given a stiff dose of lime and iron, and returned to the sewer to pass through the precipitation channel again with other sewage. The sludge is then pumped into overhead tanks, from which, it runs by gravity, or is pumped from the sludge channels direct through pipes, into specially constructed tank vessels, holding about 1,000 tons each, which formerly steamed tral hopper. At the bottom of a hopper are four rectangular valves, each governing the inlet to one of the four compart- ments into which the vessel’s Vessels. tank is divided by a longi- tudinal and a cross bulkhead. The two triple- expansion 500-horse-power engines are aft of the tank. Between the forecastle and the tank is a large water-ballast tank of 170 tons capacity. The Burns, the latest addition to the fleet, is fitted with electric light through- out, and contains a saloon, two staterooms, bathrooms, and other luxuries which one would