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elevation of about 100 feet above New Swindon, and this latter portion of the town is built on Kimmeridge clay, and was formerly much subject to floods.

Dr. Blaxall shows that measles, whooping cough, and pneumonia, diseases especially affecting the respiratory organs, were far more fatal in New Swindon than in Old Swindon. During six years preceding his investigation the death-rate from measles in New Swindon was as much as twenty times that in Old Swindon, from whooping cough more than double, and from pnuemonia and bronchitis one-third as much again. He is led to the conclusion that this increased severity of these diseases in New Swindon is chiefly attributable to the dampness of the subsoil upon which the houses in the new town are built, together with a complete absence of precaution to prevent the exhalations from the ground rising up into the houses. (“Our Homes,” Cassell and Co., p. 35.) I have now probably said sufficient to prove to you the importance of the subject, and, above all, the necessity of good drainage, and of some' means of preventing ground air from penetrating into houses.


By J. CORBETT, Engineer to the House Inspection Department of the Manchester and Salford

Sanitary Association.

'HE terms draining and sewering are used somewhat uncertheir proper definitions to be that draining is the carrying away of comparatively clean surface water and surplus water from wet ground, and sewering is the carrying away of liquid refuse, or sewage.

Many districts have ample natural drainage by porous subsoil, such as gravel, sand, or loose shale, through which the surplus water escapes to some lower place, such as a stream or river. Sometimes a porous and naturally well-drained subsoil has a bed of clay over it, and by merely piercing holes through this clay bed the surface soil may be effectually drained.

Most land is so comparatively impervious that it can only be rendered fairly dry and healthy by drains placed not more than ten or twenty yards apart under its whole surface. These drains should not be not less than four feet deep, and may with advantage be six or eight feet deep. Heavy land improves for many years after first being drained, owing to the continued action of the earth worms, which gradually pierce and thereby drain and aërate the soil down to nearly the depth of the drains; and thus in place of a shallow depth of surface soil resting on a hard sodden bed of undrained subsoil, the worms, when aided by deep drainage, transform the subsoil into a moist, well-aired sponge, through which the surplus water escapes freely to the drains, and from which the surface soil will draw moisture during dry weather. Thus, by good deep drainage, a heavy sodden soil may be made fairly dry during wet weather, and yet made more permanently moist during dry


weather, and it will therefore be much more fruitful ; its average temperature will be raised five or ten degrees, and it will become much more healthy both for men and cattle. As a land drain has usually to convey only a very small stream of water, running almost continuously, and being almost free from sand or sediment, it follows that a rough and uneven channel is quite efficient while it lasts, and so in poor moss land it is usual to form a channel of sods of turf, set like tiles over a channel cut at the bottom of an excavated trench ; loose stones are sometimes filled into the trench bottom for the same purpose. The usual plan for draining ordinary fields is to lay tile pipes made of brick clay, each a foot long, from two inches to six inches diameter, and with butt ends, that is, without sockets. The best plan is to use two lines of pipes, one within the other, with overlapping joints, so as to keep out sand, &c., and prevent the pipes getting out of line.

For land draining about a dwelling, or in connection with main sewering, glazed socketed pipes are most suitable, though they are too costly for field work. As to the degree of slope, or fall, as it is called, requisite in land drains, if they are of good quality, a slope of 1 in 220 or 8 feet per mile is ample, and even turf or loose stone drains will do well at 1 in 110 or 16 feet per mile. In the flat fen districts, the open dikes or drains have only from an inch to a foot fall per mile. The quantity of water flowing from land drains in very wet weather is about three cubic feet per acre

per minute.

Turning now to sewering, with which we dwellers in towns are more interested, the whole requirements are different. Drains have to take in drops of water at every joint along their course, and convey it in an even stream to the outfall, while sewers have to receive their supplies through definite inlets, at irregular times, in large or small quantities at a time; and they should convey their contents rapidly to their outfall without losing any by the way. The sewage which sewers are required to convey often contains much hot, greasy waste from kitchens, which is liable to set in the pipes when cooled, and thus gradually stop them up. Then some peculiar people try to make their sewers carry away old wigs or bunches of hair, brushes and combs, sponges, flannels, towels, and many other things which will not dissolve in water, and are therefore very liable to accumulate at bends or junctions, and so cause obstructions. If the sewer joints are not watertight, they permit the liquids to escape, and retain all solids whenever

the slightest obstruction occurs, and thus the evil is aggravated until a positive stoppage ensues, the surrounding soil being meantime soaked with foul liquid.

Sanitary engineers have a complicated task in so arranging the sewers of houses that all these difficulties may be overcome, and so that the sewers may be kept as comparatively sweet and harmless as possible. One of the greatest difficulties in this district is to persuade workmen that sewers ought to be positively watertight, and able to stand some pressure of water within them without leaking. The common practice is to joint the socketed pipes with clay, so that they can be easily taken up when out of order. When I meet with such a principle as this one, I like to apply it more widely ; thus, I would also have clay jointing to plumbers' work, instead of soldering, and clay jointing to our walls instead of mortar or cement ; the principle is as soundly applicable to these uses as to sewering. But the right way is so to construct the sewers that they never will want repairing, and this can best be done by jointing them perfectly watertight with cement of some kind. Great care is required to prevent scraps of cement remaining within the pipes and causing obstructions. The plan I prefer is to use cement formed of one part of good Portland cement to one of sharp, clean sand. A mop or cloth plug, fitted to the size of the pipes, with a handle about three feet long, should be provided. As soon as one pipe is set in place the plug should be thrust into it with its handle projecting; the pipe socket should then be cemented all round inside, the next pipe put over the plug handle into the cemented socket, and firmly bedded in its true position; the cement pointed smoothly round the outside of the joint, and finally the plug drawn out through the new joint, drawing with it any loose cement from within the joint. The plug must then be cleaned and replaced, ready for the next joint, and meantime, it serves to keep any loose material from entering the pipes.

Another plan is to put a collar or gasket of rope yarn round the pipe end before pushing it into the socket, then ramming this collar to the end of the socket, so as to prevent any cement getting inside the pipes, and finally pointing the socket all round with cement.

To make really watertight joints in either of these ways, under the surrounding difficulties of a narrow trench, loose wet soil, propping timber and other obstructions, requires considerable skill and constant care, so that a much better class of workman is

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