sewage, water, ground, soil, surface, feet, contaminated, clay and pipes

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Sub-Surface Irrigation.—This method of sewage disposal has been widely advocated by Col. Waring and other sanitary engineers. Under favourable conditions it gives good results ; namely, where there is porous soil or one that is thoroughly under-drained. In a tough clay soil such drainage is absolutely necessary. The sewage is first collected in a small brick cesspool, which serves as a settling-basin, and which is supplied with a tip-over flush-tank or siphon which discharges intermit tently, and spreads the liquid sewage broadcast through a gridiron of open-jointed tile pipes covering half an acre of ground and laid just below the surface, the joints being covered with hay or tarred paper to exclude dirt. The air penetrates through and oxidises the sewage ; the roots of the grass or other vegetation also soak it up. and what remains after filtering through the soil comes out as almost clear water, and is quite harmless. The pipes do not freeze in winter, nor are they seriously affected by frost ; but usually they have to be relaid every few years to preserve a uniform slope. If the ground is nearly level, and there are plumbing fixtures in the basement, as is usually the case, it will be impossible to keep the pipes sufficiently close to the surface of the ground to use this method of disposal, and in this case the old-fashioned cesspool may have to be utilised.

For institutions or small settlements the septic tank and filter-beds may be recommended. The former is simply a tight cesspool in which the sewage is kept in darkness from six to twelve hours, so as to be exposed to the action of anaerobic bacteria which destroy about one-half of the putrescible material. It is then turned on to a series of filter-beds formed of coke, crushed stone, or coarse sand and gravel, and allowed to settle for twenty four hours, each filter-bed being used in turn. Through the action of aerobic bacteria, the effluent will be so purified as hardly to be recognised, and can be discharged into an ordinary stream.

This method of sewage disposal is the most pro mising now in use.

A good plan for disposing of the sewage of a small house has been devised by Dr. H. B.

Bashore. A series of galvanised-iron gutters (old fall-pipes, in short) are arranged four feet apart and perforated with nail-holes, so that when fed from a kitchen or other waste-pipe the sewage is distributed evenly over a garden or field, thus providing an excellent fertiliser at slight expense and without annoyance.

Earth-Closets. Where water-closets cannot be provided, the earth-closet is an admirable substitute for the old-fashioned privy. All that is necessary is to have a cemented vault, and so provide a box full of dry, loamy soil or sifted ashes, with a little chloride of lime to be used sys tematically. this way no odour will be created, and the fluids will be soaked up so as not to furnish a breeding-place for flies or mosquitoes. There

should be an opening at the side of the vault to clean it out at intervals. A better plan is to have a substantial wooden box, coated inside and outside with asphalt paint, and supplied with handles by which it can be drawn out and carted away. For location indoors, a couple of galvanised pails, with a box of sifted earth or ashes (the pails to be used in succession), will give entire satisfaction.

Water Supply.—Most persons consider a spring a safe source of supply for drinking-water, but it should be remembered that spring-water is no better than its source, the ground-water, and that may be seriously contaminated. Mountain streams should be traced to their source to insure that they are not polluted by privies, stables, or rotting vege tation. Eternal vigilance is the price of sanitary safety. In lakes and ponds the deeper parts are purest, and the larger the volume of water the greater the dilution. No large river that receives the drainage of successive towns and villages can be trusted for drinking purposes without filtration. When rain or melted snow sinks into the soil, it passes down until it reaches clay or hard-pan, where it collects in pools or streams which spread for miles and flow like rivers, following the dip of the underlying strata. As surface water passes downward, the soil acts as a filter, and strains out floating dust and other refuse found in settled communities. It is cooled by contact with masses of ice or frozen ground, and this is why spring or well waters are so palatable. If the ground is porous, the process of purification is rapid. In a clay soil it is slow ; and surface water collects in pools, stagnates, gets full of rotting vegetation, and festers malaria.

In most places it is only necessary to sink a well twenty or thirty feet to obtain an ample supply of water. In some districts the underground streams are even nearer the surface, while in other localities tube-wells have been driven a thousand feet without striking water. Dr. Roberts, of the New York Board of Health, states that at Memphis the water in driven wells, under two hundred feet of clay, was contaminated by kerosene-oil spilled on the ground. This shows how easily shallow wells may be polluted if the ground is contaminated by the soakage from barn-yards, cesspools, and privies.

Wells are most likely to be contaminated by surface percolation, and there fore the upper part should be constructed so as to exclude rats, frogs, snakes, decaying leaves, and soakage of rain and melting snow. The well should be lined for some distance down with large tile pipes carefully cemented, provided with a heavy flagstone cover, and the whole roofed over.

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