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similarly ventilated. The main drain shall be disconnected from the sewer or cesspit by means of a syphon trap of approved construction, provided with means for cleaning the trap, and the portion of the drain between the trap and the sewer or cesspit, and it shall be ventilated by an inlet air-pipe or ventilated disconnecting man-hole; and if there be more than one outlet ventilating pipe connected with the house drain, then each such portion of drain and outlet ventilating pipe shall be provided with a suitable syphon trap and an inlet airpipe or disconnecting man-hole, as already described; and the area of the inlet air-pipe shall in all cases be at least double that of the outlet ventilating pipe in the clear.

It is contended by some writers that the inlet for fresh air should be at the head of the drain, and the outlet at or near the disconnecting man-hole. The objection to this arrangement is that the soil-pipe will either remain unventilated or a separate system of ventilation will have to be provided for it, thus introducing unnecessary complications. The argument in its favour, that it follows the flow of the drain, does not seem to be at all conclusive, for as no house drain ever runs more than one-third full, unless under most exceptional circumstances, there is not much reason to fear that the air passing up the drain, which is more volatile than the water flowing down it, would have its current arrested by the traversing current of water; on the contrary, it is probable that the effect would be that the current of air would be temporarily accelerated, and especially would this be the case when, as frequently happens, the drain has a diameter of 6 in., while that of the ventilator is 4 in.; also, if the water in the drain were giving off vapour this would rise in the drain and travel in a direction contrary to that of the water; this, therefore, seems to be the natural direction of the current.

Writers have repeatedly stated that the number of ventilating shafts should, if possible, be increased indefinitely, and from some of the statements to this effect it may be inferred that the relative elevation of the several shafts is a matter of no importance, and that rain-water pipes may be used for this purpose. It cannot be too often or too urgently repeated that this is altogether a mistake (see Hood on "Warming and Ventilation of Buildings," p. 360), that under no circumstances should rainwater pipes be used as drain ventilators; they cannot go above the eaves of the roof, and therefore the foul air from them is liable to enter the house; also if more than one upcast shaft be used it will not, unless each shaft be of exactly the same height and heated to exactly the same extent, and affected by the wind in just the same manner, increase the ventilating

efficiency, but will rather diminish it. The writer has frequently come across systems of ventilation which were faulty on this account; but when the system of ventilation is simple, that is to say where there is one upcast shaft for each inlet, where the inlet opening is of ample dimensions, and leads as directly into the drain as possible, with few or no angles or bends, he has found no difficulty, and he is of opinion that cowls of any kind should be avoided, and that a Mica return flap on the inlet opening is unnecessary. Where the work can afford it, a ventilating disconnecting man-hole should be built, as it affords easy access to the drain; but a perfectly satisfactory arrangement can be made without it so long as the drain remains in good order.

The disconnecting trap should be self-cleansing; therefore, it must be of large radius with easy curves in all directions, and there must be no projections or corners in it which will either arrest the flow through it or tend to collect deposit. These requirements condemn all forms of dip trap, and in fact the only trap which will satisfy them is the ordinary syphon trap, if the radii of the curves be sufficiently great, and it be of good form throughout and well glazed. No inspection pipe in the middle of the length of the trap is possible; this would seriously retard the flow and cause deposit. A cascade action is recommended by some, but consideration will, it is thought, show that this action, while it may by the greater head obtained with a small supply of water force an obstructed trap, does not really offer any advantage which does not exist to a greater degree in the ordinary syphon described above. If with the cascade action a greater local head be obtained with a reduced amount of water, it is at the sacrifice of the general gradient of the drain, and therefore of the rate of flow in it. With the cascade action the distance travelled is greater than with the other system for the same fall, and the very fact of the head being obtained proves conclusively that this trap has a retarding effect on the flow, and the conclusion arrived at by the writer is that it is far better to make the best of the gradient procurable, to have a length of drain next to the trap from 1 ft. 6 in. to 2 ft. long, falling at the rate of 1 in 6, than to have a local vertical fall, whether small or great, and that in this manner a far better scouring action and a cleaner trap would be secured than with a cascade action trap.

(3.) No pipe which passes through any part of a house not being a soil-pipe or soil-drain shall be connected directly with the main drain.

(4.) No water-closet shall be situated next to a larder or place where food is stored. No pan-closet or D trap shall be

used, and every water-closet shall be trapped, and shall be arranged so as to prevent syphonage.

(5.) The overflows from safes of closets and of baths, and from cisterns, shall be discharged into the open air in an exposed position, and shall not be connected with the soil-drain or rain-water pipes, either directly or indirectly, but shall act as detectors.

(6.) All sinks, baths, lavatories, and urinals shall be trapped with suitable traps, and the discharges from them shall be carried outside the walls of the house, and shall not be connected directly with any soil-drain, nor shall they be introduced under the grating of any trap, but they shall terminate in the open air, and not near any window or other opening.

The writer is aware that many sanitarians prefer to introduce the pipes leading from sinks, &c., under the gratings of the yard gullies, but he thinks that this is a mistake, and that it is far preferable that the discharge should be made fully in the open air, so that there may be as little chance as possible of the collection of any matter in the pipes, than that it should be hidden out of sight and, possibly, choked. If the gratings become foul from this cause, it is better that this should be apparent than that it should be hidden; it is the object of scientific drainage to bring any collections of foul matter to light, not to hide them.

(7.) All water-closets, urinals, and slop sinks shall be provided with suitable flushing cisterns, and the flushing-pipe for any closet shall not have a less internal diameter than 14 in., and the height of the flushing cistern above any closet, urinal, or slop sink, shall not be less than 4 ft. It shall be impossible to draw water from any cistern used for flushing purposes for any other purpose than that of flushing.

(8.) The cisterns used for general purposes shall be easily accessible, and shall be provided with covers ventilated into the open air outside the house by a rising pipe other than the overflow pipe, and no pipe from them shall be connected in any way with any soil-pipe drain, or with any pipe receiving the discharge from any bath, lavatory, urinal, sink, or flushing cistern.

(9.) No rain-water pipe used to receive the waste from any bath, lavatory, sink, or urinal, shall be placed near a window or other opening, and no rain-water drain shall connect directly with a soil-drain, and no rain-water pipe shall be used as, or connected with, the soil-pipe nor as a ventilating pipe.

Though there are many bad sanitary appliances in the market, the selection of good ones is a simple matter, requiring little more than common sense knowledge, it being obvious that sharp bends and angles and straight vertical sides are undesirable,

that all utensils should retain matter liable to decomposition for as short a time as possible, but should pass it quickly to the drain, which in its turn should pass it quickly to the sewer. Complications both in apparatus and in the drains and ventilating and inspection chambers are most undesirable, and economy without loss of efficiency should be studied. Finally, whatever sanitary work is done it is of the first importance that it should be done well, that the construction should be thoroughly accurate and carried out in a trustworthy manner.

[For discussion on this paper see page 286.]

On "The size of House Drains, and the use and misuse of Traps," by JOHN HONEYMAN, F.R.I.B.A.

RECENT investigations seem to prove that certain elements of ordinary atmospheric air-chiefly oxygen-acting upon aerobian microbes, destroy or attenuate their virulence, so that in either case the microbe, as a vehicle of specific disease, is annihilated.* The significance of this fact, in relation to the proper ventilation of sewers and house drains, has, I think, not been generally realized. The earlier advocates of such ventilation-among whom I venture to claim a place-aimed rather at the dilution and rapid removal of sewage emanations than at the destruction of associated microscopic organisms; but they were not without some apprehension of the truth, since demonstrated, that such organisms are practically destroyed by the action of atmospheric oxygen. It is exactly thirty years since I myself published a paper on sewer ventilation, in which I endeavoured to arouse the better class of my fellow citizens by pointing out the fact that while they in the most elevated and least crowded parts of the city had to submit to the frequent recurrence of epidemic disease, the people on the banks of the river (which seemed to them so pestiferous) were almost exempt from anything of the kind. And my explanation was this: I said that "the agents at work in both localities were identical, but they were differently developed." In the one case tainted air, undiluted and confined for miles in unventilated sewers, remained pestilential, whereas in the other, "mingling freely with the

I venture parenthetically to ask, if the protective effect of attenuated virus can only be obtained by inoculation? There seem to be grounds for inferring that it may also be obtained by inspiration or absorption.

atmosphere, it became harmless-as a homoeopathic globule in a glass of water." I would be inclined to use very much the same language now-and I regret to say there is almost as much need to use it- but we have made an immense stride when we are able to plant our feet upon ascertained fact instead of reasonable but somewhat vague deduction.

We may indeed say that we have now a new and potent argument in favour of drain ventilation. We advise it not merely for the dilution of noxious gases, and their rapid removal, or for the relief of hydrostatic pressure, or the aeration of sewage, but also for the destruction of disease germs, or at least the attenuation of suspended virus; and it is evident that if we succeed in this we render our aerial drainage, if I may so call it, innocuous, so that even if it accidentally gained admission to our houses it would do no harm. To secure this, however, even partially, it is obvious that we must allow a much larger volume of fresh air to pass through our drains than has hitherto been customary-in short the more nearly we can make them approach in airiness to the condition of open drains the better. These remarks apply to drains of every size, but in this short paper I shall refer to house drains only.

One reason why I do so is that it seems almost a hopeless task to convince those who have control of the common sewers that anything in the shape of ventilation is called for. After nearly forty years of sanitarian effort, argument, entreaty, and painful and costly experiences, it is now almost as necessary as ever that those who connect their drains with common sewers should carefully protect themselves against the risks they run in doing so. In this and many other things, sanitarians have been very much like the "importunate widow," but after so many years' ineffectual reiteration of the same tale, they may almost be pardoned if they begin to despond. In the case of house drains, however, they are able to appeal to individuals, and individuals are more amenable to reason. Now, our house drains are under our own control, we can cut them off entirely from the common sewer and ventilate them as much as we like; and in view of the facts already referred to, this important question presents itself: do we in practice ventilate our house drains sufficiently to secure the best results? I think it is perfectly manifest that we do not, and that it is simply impossible to do so with drains of the size generally used.

Pipes of small diameter are recommended to facilitate rapid flow and scour; but we want rapid flow and scour of aerial as well as of liquid sewage, and we are met by this difficulty, that whereas small pipes are best for the one purpose, large pipes are absolutely necessary for the other. Now while we admit

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