defects which admitted either drain or sewer air to the house, and to these defects the medical attendant has attributed the disease.

In other cases, particularly in boarding-schools, where there has been no specific form of disease that could be diagnosed by the medical attendant, but a general low condition of health has been prevalent among the inmates, he has found the sanitary arrangements most defective.

In his opinion, it would be necessary, in the event of the intercepting trap being abolished,

(a) To insist on a very high standard of workmanship and material in connection with the construction of house drains and sanitary arrangements generally. (b) To arrange for a much better system of supervising the carrying out of such work. (c) To arrange for periodical tests and examinations at much more frequent intervals than is usual at present, to make sure of the pipes and fittings being maintained tight and sound, and proof against allowing drain or sewer air to pass into the house. (d) To discontinue the practice of providing low-level inlet ventilators to drains, as now provided under most local authorities' by-laws, and to arrange for all ventilating openings to be carried to a point well above the roof and away from all windows. (This plan, it was pointed out, is desirable even where there is an intercepting trap, but it would be much more so were the interceptor abolished.)

The speaker's observations, extending over a period of many years, makes it clear to him that the low condition of health shown by the inmates of houses where drain or sewer air has access to the house is often to be attributable to the imbibing of such air.

Ventilation of Sewers and Drains.—The ventilation of sewers and drains (said Mr Moss-Flower) is absolutely necessary, and in the case of house drains-(a) To prevent the air in any part of the drains or pipes from being compressed to such extent (by the discharge into the drains or pipes of such as a bucket of water) as would endanger loss by momentum of the water seal of traps. (b) To prevent stagnation of the air in the drain, so that if there were defects in the drains or fittings, the air passing into the house because of them would not be so harmful or obnoxious as would be the case where there is no ventilation. In the case of drains there should be not less than two ventilating openings, as far apart as possible; and low-level inlet opening, now often fixed in basement areas and such places, should not be permitted, a low-level inlet only being allowed where it can be fixed a long way from the house, and where the discharges from it cannot be a danger to the occupants of the house or anyone else.

Since one of the objects aimed at by those who advocate the abolition of the intercepting trap is the ventilation of the sewer by means of the soil-pipe continuation to the roof, the point of outlet for the ventilating pipe would have to be selected with great care, and that in many instances it would be most difficult to find a point which would be sufficiently far from windows and other openings into the house to avoid a nuisance and danger to the health of the inmates.

The ventilating pipes from the drains of one house should not be so arranged that, although the outlets may be clear of all the openings into the house they serve, they may be a danger to the inmates of an adjoining house, as is very often found to be the case.

*The author does not agree with this statement, because with outlet shafts only how can through ventilation be maintained?

As regards sewers, Mr Moss-Flower's experience teaches him that ventilating openings at the ground-level are the most undesirable, and give rise at least to serious nuisances. Generally speaking, tall ventilating shafts and columns fixed in carefully selected positions are the most desirable; and in places where columns must be erected in exposed positions and close to frequented places or houses, then one of the forms of lamps for cremating the emanations is desirable.

If the size and form of sewers are properly apportioned to the work they have to do, and they be constructed of non-absorbent and otherwise proper materials, be laid with self-cleansing velocities, be regularly flushed, and have ventilating shafts fixed at proper and convenient places so as to prevent undue pressure from rise of temperature and rapid increase in volume of flow; moreover, if manufacturers' refuse, which should be properly treated before being discharged into sewers, and steam and hot liquids above a certain temperature be excluded from the sewer, much will have been done to reduce the nuisance caused by the emanation from sewers.

CHAPTER XXXI.

REFUSE DISPOSAL.

MOST towns have some system of disposing of house refuse in connection with the sanitary department. There are various methods in use. In small towns such refuse is spread on waste ground, used for filling up depressions and reclaiming low-lying flood lands, and land from the sea, or taken away out to sea in boats and there disposed off. Another method is the destruction of refuse in suitable destructors, and it is this method with which we are chiefly concerned here. The destruction of refuse by fire seems to date back to the Jewish era, while with the Romans the practice seems to have been discontinued. But one of the most important things in connection with the modern disposal of refuse is the heat energy which can be successfully abstracted therefrom, a practice which also seems to have been in vogue centuries ago for providing heat for Turkish baths in Cairo. The chief reason for the invention of the modern destructor was the difficulties local bodies had in obtaining an adequate area of land on which to dispose of their ever-increasing amount of refuse without nuisance, a necessity which began to be felt about the year 1860. Before going any further it will be well to ascertain what constitutes domestic refuse.

Domestic refuse is naturally principally composed of ashes, to which must be added tins, pots, broken pottery and glasses, paper, rags, bottles and straw. Towns-people should be provided with proper ash-bins. These are usually supplied by the local authorities at cost price. They are then periodically emptied according to arrangement, but some places have large ash-pits which are only occasionally emptied, a practice which is not to be recommended. Such ash-pits would only be cleansed about once a month. The practice is only admissible for hotels, hospitals, and other large buildings.

The best ash-bins are made of galvanised iron, and the carts for removal require particular attention regarding their design, to avoid blowing about of dust and loose paper and bad smells, special sliding covers being the most satisfactory for the purpose. The sorting of the refuse demands attention also. Tin cans are of value for making copperas. Mineral-water bottles, which are frequently found, command sale in themselves, while broken glass and crockery fetch as much as £2 per ton. Again, cast iron is often found and can be made a source of revenue, while people will even pay to be allowed the privilege of picking large heaps of refuse.

But it is the moisture, decaying animal and vegetable matter which make the refuse so offensive and difficult to deal with.

The original furnaces used were of crude construction, and failed principally, it is stated, by the deficiency of flue area, which was less than 3 per cent.

of the grate area. The original practical form of destructor was patented by Mr Alfred Fryer, a Nottingham gentleman, now of the firm of destructor manufacturers of Manlove & Alliot, who are one of the principal builders in the country at the present day. The original Fryer furnace seems to have existed for about ten years, and was put up in Birmingham, Manchester, Bradford, and other large towns. The failure of the early plants was the slow and imperfect combustion, it being found necessary to have independent coke fires to aid the process by re-igniting the gases by aid of forced draught. Then the Horsfall destructor was introduced, which employed a steam jet to effect the same purpose. Of all the destructors at present employed, perhaps the best known is the "Heenan," of Messrs Heenan & Froude, Manchester, fig. 739, known as the twin-cell destructor, the idea, which was patented in 1898, being to have two cells, each charged alternately, and so to alternate the flow of the products of combustion, so that the outlet is always over the incandescent fire, the effect being obtained by a deflecting arch and a single opening in the reverberatory arch.

Meldrum's furnace, of the simplex type, is shown in figs. 740 and 741, and another favourite type is Beaman & Dea's destructor, while it is only fair to mention the Sterling destructor.

was

Refuse destructors resolve themselves into two main groups, that is, those having isolated cells, having a number of grates in each chamber, communicating with a secondary combustion chamber by small passages, and those having a primary combustion chamber common to a number of grates having a single outlet into a secondary combustion chamber. Each grate has a separate closed ash-pit. The early forms had only natural draught, which totally inadequate for the purpose, and the rate of burning has gone up by the use of forced draught to 60 lbs. per sq. ft. of grate area per hour (85 lbs. is said to have been obtained under exceptional circumstances), while the temperature obtained is well over 2000° Fahr. Again, the old furnaces had no steam-raising power, while to-day that item easily reaches 2 lbs. per lb. of refuse at and from 212° Fahr.

The essentials of a successful refuse destructor are

1. It must consume or reduce all putrescible and organic matter.

2. The resulting gases must be inodorous, innocuous, and completely sterilised.

3. No dust must escape from the chimney; it must be easily removable and recoverable.

4. A maximum temperature of at least 1300° Fahr. must be attained.

5. The furnace must be kept at the proper heat without the addition of any fuel other than the refuse.

6. The resulting clinker must be incombustible, hard, vitreous, inodorous, and sterile.

As before stated, refuse will contain a large amount of moisture, which will be naturally to its detriment, and may reach anything up to 40 per cent., the other matter being about 30 per cent. combustible and 35 to 40 per cent.

FIG. 741.

incombustible, depending chiefly on the amount of ashes in the refuse, but combustible material is not usually present in sufficient quantity to warrant the use of natural draught. Regarding the actual combustion, the necessary temperature would be about 1600° Fahr.; and although this is above the oxidising temperature of most of the issuing gases, it is necessary to replenish the waste of heat absorbed by the moisture. The issuing gases are generallyMarsh gas (CH4).

Hydrogen.

Olefines.

Carbonic oxide (CO).)