Page:The Strand Magazine (Volume 4).djvu/485

 wards and forwards one above another in the outer air, or lying under water, the object being to keep them cool, so that the gas may be gradually robbed of its heat as it passes along them.

In its passage through the main and the condenser the gas deposits ammoniacal liquor and tar, both of which are drained off, and utilized in various ways. The gas next enters the washer and scrubber. It is brought constantly in contact with water, which assimilates ammonia; and in the scrubber, a tower of considerable height, it is passed through a quantity of coke, shavings, and other materials saturated with water, so that it is really scrubbed as it progresses. From the scrubber it goes to the purifiers, huge square boxes containing layers of grids well covered with lime and oxide of iron. After this, all that has to be done is to measure it and store it. We who have occasion to know only our own domestic meter, do not instantly recognise its big brothers in the two station meters, which have been aptly likened to mausoleums.

Their size affords an idea of the volume of gas which has sometimes to be made and measured. Some of the gas will be sent along miles of mains to London, there to be placed in holders; some will be stored in holders on the spot. We are fortunate in finding a holder in the course of construction at Beckton. To the passer-by it is complete, but a walk over its top discovers a hole a yard square, down which we gaze cautiously. Thirty feet below is a body of water, and we see that the entire structure is supported by scaffold poles. A man on a raft is pulling himself from point to point by means of a hooked stick. Comparatively few people, even among gas-workers, have been inside a gasholder, and it at once strikes us that a novel experience may be had if we choose to risk the consequences of a climb down the swaying rope ladder. The information that a man was recently drowned in such a place only makes us screw our courage more up to the sticking point, and another minute sees us on the ladder. Friendly hands below do what they can to steady it, but only a monkey or an acrobat would make a respectable show on such a contrivance. Landed safely on the raft, the man in charge, whom we immediately dub our gondolier, pulls us round about through a perfect maze of scaffolding which runs from the bottom to the top like a monster umbrella frame. By-and-by the water will be continued right up to the roof, and it will surprise some people to learn that the gas, when it enters the holder, rests on the water and forces the holder up, so that when the holder is full its top is on a level with that of the upright girders which guide its actions, and its bottom only a foot or so beneath the surface of the water, the latter being in a giant stone tank. Water, it should be understood, is an absolute seal for gas, and it is a practical impossibility that a gasholder could, as many imagine, blow up. Such a disaster has certainly never been known.