bad connections, as they will not contain water. The possibility that cisterns may be found under floors must not be overlooked.

Having completed the examination inside the house, the outside drains or cesspools, closets, or privies, and the provision for refuse storage, must be inspected.

The true state of the drains cannot be ascertained except by the tests which are described later, but all traps that are accessible, and none ought to exist that are not, should be examined to see that they are structurally in accordance with sanitary principles, and are kept properly cleansed. The provision for drain-ventilation in the shape of air-inlets and outlet-shafts, and the position of the latter with regard to windows, their size, the soundness of their joints, &c., must be noticed. It may be found that the rain-pipes are made use of as soil-pipe or drain-ventilators, or that they are not properly disconnected over gullytraps. If underground rain-water tanks exist, their condition as regards cleanliness should be noticed, and their overflows ought invariably to be traced.

As regards receptacles for filth, privy-middens, ashpits, and cesspools, it should be ascertained whether they are so constructed as to be impervious, and, in the absence of a public water-supply, their position with regard to the well must be considered.

Drain Testing.-It is not possible to assert positively that the drainage of a house is satisfactory from a mere surface inspection, particularly if the drains and their connections are within the house. The aim of all sanitary experts is to avoid laying drains under houses, and to carry each connection by as direct a route as possible through an external wall, all joints being placed where they can easily be inspected. Under such circumstances, it is easy to detect defective work in the case of new houses, but however thoroughly old houses may have been overhauled and their defects corrected, one never can tell that some disused drain may not have been allowed to remain concealed from view, although none the less dangerous on that account. The only means of ascertaining with certainty whether all is right, is by applying one or other of the approved tests, and as this involves but little time or trouble, it is advisable to make it an invariable practice, however perfectly the work may seem to have been carried out.

The smoke-test is handy and fairly reliable. It consists in filling the drains with smoke, so that it may find its way through any faulty joint or defective trap, and thus demonstrate by its presence, near to or within the house, the exact site of each of

the various faults. It must be remembered that where smoke can penetrate, sewer gas may, and the ocular demonstration of the danger to which the inmates of the house are exposed, will often be the means of convincing them of the necessity for certain alterations, which might otherwise meet with opposition, on account of the expense or temporary discomfort they involve. There is nothing like smoke to convince a sceptic that the suggestions of an expert have a solid foundation in fact, and are not, what they are too often supposed to be, the outcome of a theorist's imagination.

In applying the smoke-test, one of the various apparatus that are made for the purpose must be used, and the best opening at which to blow in the smoke is the air-inlet to the drain on the house side of the trap which disconnects it from the sewer or cesspool, or, failing this, it may be introduced at any con

Fig. 88.

venient trap, by removing its water-seal. As soon as the smoke is seen to issue from the various soil-pipe or drain-ventilators, they must be plugged, as all are then charged with smoke, and afterwards a little pressure applied by the apparatus, not sufficient, however, to force the various traps, will send the smoke through all imperfections, if it has not already found its way through, which is more than likely.

For small systems of drains, handy little machines are made which answer the purpose, but it is well to use one of the larger apparatus, such as Burn & Baillie's (Fig. 88), in the case of large premises. This apparatus consists of a double-action bellows, which communicates with a cylinder in which the smoke is generated by burning oily cotton-waste, and from which it is carried by a pipe into the drain. At the end of this pipe a flange surrounded by an india-rubber ring is fixed, which acts as a plug when introduced into the drain; these are

made of various sizes, to suit different sized pipes. By means of an ingenious contrivance connected with the cylinder this apparatus can determine whether any leakages exist previous to their exact position being demonstrated by the smoke. This is managed as follows:-Round the cylinder is an outer casing containing water and supporting a float, which is raised with a few strokes of the bellows; provided there is no leakage at any point, the float will remain in its raised position; on the other hand, it will fall if the slight pressure of air that maintains it is lost through leakage. There is not much advantage gained by this, as, if leakage is demonstrated, it is afterwards necessary to make use of the smoke, in order to establish where the faults

are.

Smoke rockets are sometimes used for testing drains, and they have often been instrumental in exposing faults, but they can in no way compare with an apparatus such as has been described. Having ignited the rocket, it is introduced at the terminal end of the drain, which, of course, must afterwards be plugged.

Oil of peppermint is also used as a drain-tester, although it cannot be compared with smoke in efficiency. It may either be discharged down the soil-pipe (from 1 to 2 ounces, followed by a few cans of boiling water), or introduced at a trap on the soilpipe drain. The same precautions with regard to sealing up all ventilators is necessary in this case also, and if the trap is the place selected, it must afterwards be thoroughly covered with wet cloths to prevent the odour of the peppermint from escaping at that point. The person who introduces the oil ought not to be the one to search for the smell of it about the house, as the slightest particle of it on his hands or clothes will suffice to distribute its scent wherever he goes, and so blunt his power of detecting any escape. Also, if the peppermint should be introduced from a water-closet, the operator must remain in the closet until such time as others can satisfy themselves with regard to the soundness of the various connections.

Water Test.-The integrity of drains may be thoroughly tested by filling them full of water, until it reaches the level of one of the traps, having carefully plugged the outlet into the sewer or cesspool. If the water remains at the same level for about an hour, the drain may be pronounced sound; on the other hand, should it subside, leakage must be taking place, either from imperfect joints or fractured pipes. In order to discover which section of the drains is at fault, each must be tested separately. To apply this test to soil-pipes, even if

practicable, would not be reasonable; the smoke test in that case fulfills all requirements, as it at once reveals any leakages arising from imperfect joints or other faults. All new drains before they are covered in should be tested with water as described.

CHAPTER VII.

SEWAGE AND REFUSE DISPOSAL.

THE practice of discharging sewage in its crude state into streams, although contrary to law, is by no means an uncommon one, and, at the present moment, the question of sewage disposal is occupying the attention of sanitary authorities throughout the country. The Local Government Act of 1888 imposes the duty on County Councils of enforcing the provisions of the Rivers Pollution Acts, and this duty is being exercised in some counties with excellent results, although in others little attention appears to have been given to the question.

In those counties where active measures have been taken by the County Councils, authorities who, hitherto, have failed to realise their responsibility as guardians of streams, are seriously considering what is to be done. That the question is no easy one to settle has been demonstrated over and over again by failures on the part of many authorities in obtaining good results notwithstanding large outlays of money.

It must be understood at the outset that treatment to be effective must accomplish more than simple clarification. It is possible by several methods so to treat sewage as to remove practically all the solid or suspended matters, leaving a clear fluid which, in appearance, may differ only slightly from potable water, but this treatment alone will not render the sewage fit to be discharged into a stream, for it still contains in solution an immense amount of organic matter, which, as decomposition proceeds, will become turbid, and give rise to nuisance from deposit on the bed of the stream of putrefying solid matter. The process, to be complete, must go further than this; the soluble organic matter must undergo a change which so alters its nature as to convert noxious organic into harmless inorganic substances. Until lately it was believed that the only really efficient means of accomplishing this was by submitting the sewage, after chemical precipitation in tanks, to land treatment,

but recent experience has shown that equally good results may be obtained by artificial filtration, and still more lately it has been demonstrated that in the case of ordinary domestic sewage, at any rate, the preliminary precipitation process is needless, and that the solid organic matter may be liquefied and so prepared for further treatment (either by land or artificial filters) by much simpler and less expensive methods to be presently described.

In order to appreciate the importance of certain conditions indispensable to successful sewage treatment, it is necessary to understand the operation of the process.

Sewage when brought in contact with suitable land, or properly constructed artificial filters, is immediately attacked by living organisms (bacteria) universally present in the upper strata of the soil and in sewage, and which in time develop in the interstices of filters; by these its organic matter is split up into simple constituents, which, with the assistance of the oxygen and carbonic acid gas present in the ground air or the air in the filter, unite with certain mineral bases in the soil and in the sewage itself, and thus are transformed from organic, unstable compounds, liable to putrefactive changes, into more fixed inorganic salts of an innocent nature.

The chief requirements, therefore, essential to success, are land or artificial filtering media which are permeated throughout by microscopic life, and of such a consistency as will allow of the free penetration of air.

Before describing the methods more in detail, let me here emphasize the fact that a profit must not be looked for from any system of sewage treatment. If, in the case of land treatment, the returns cover the working expenses, that is as much as can reasonably be expected. It must be remembered that the first consideration is the effectual treatment of the sewage; if this can be accomplished at a profit, well and good, but no profit will justify any sacrifice of efficiency in this respect. Failure, in many instances, arises from too much thought being given to what is best for the crop, little consideration being paid to efficient sewage treatment. For this reason, it is important that sewage farms should be under the direct management of the Sanitary Authorities, in place of being let to farmers, whose interests are not, or may not be, in conformity with the prin ciples of sewage treatment.

The methods of sewage disposal have now to be considered, and these have to be viewed in the light of the principles just laid down, always remembering that, although the details must