time are the chief arguments in their favour. In all cases they should be provided with means of ventilation, by a pipe carried into a flue or to the outside. The ordinary fire-place may be adapted for warming by gas by filling the grate with asbestos blocks which are heated by means of a Bunsen burner. In this case there is no necessity for any special flue, as the ordinary chimney answers the purpose, and the ventilation is as perfect as with an ordinary fire. With this particular arrangement the loss of heat is very great, and to remedy this, gas stoves are now frequently fixed in front of the fire-place, with a short pipe leading into the flue to carry off the offensive fumes. It is essential for ventilating purposes that the opening of the fireplace proper should be quite free, and not filled up with sheet iron as is so often done, otherwise the ventilating effect of the chimney will be greatly lessened, particularly when the fire is not actually burning. The air in bedrooms in which gas stoves have been fixed in the objectionable manner just described, is very foul in the morning if the stove has not been burning all night, and in the absence of any special outlet ventilator.

Ventilating gas stoves are a great improvement upon the ordinary kind, from an economical as well as from a health point of view. They are constructed much on the same principle as ordinary ventilating stoves, fresh air being discharged into the room after it has been warmed by passing through a tube which is enclosed in a chamber in which the gas burns; this outer chamber is connected with the chimney by a pipe which carries off the foul products of combustion.

Hot-water and steam pipes are frequently employed for warming the halls and passages of houses, as well as offices and public buildings. This system, if properly applied, is an excellent one, but one usually finds, in cases in which it is in operation, that all principles of ventilation have been completely disregarded. One has only to enter an office, for example, in which a number of clerks are engaged, and in which the ordinary open fire-places have been abolished in favour of hot-water pipes simply run round the walls, to realise the effect that such an arrangement has on the atmosphere of the room. The wholesome influence of the ordinary fire-place in changing the air of the room is lost, with the result that the same foul air, which has been breathed for hours on end, is circulating in warm currents round the room in question.

No system of warming by hot-water or steam pipes is admissible, unless both inlets and outlets are provided for ventilation. The best method of introducing air into a room warmed in this

manner, is by so arranging the openings that the incoming air must first circulate over the hot pipes. By this means its temperature is raised, and thus, as already explained (p. 39), a more frequent change of the air of the room may be effected without causing a sensation of draught. This is now accomplished by radiators (Fig. 25), which are taking the place of the 4-inch pipes and coils formerly used. These radiators are constructed so that as large a surface as possible is exposed for radiation, and the circulation from the boiler is conducted by distributing pipes varying in size, in accordance with the distance they have to travel and the work they have to do, from inch to 2 inches.

The smaller sized pipes, however, owing to the friction which has to be overcome, are not very satisfactory, and it is found in practice that it is unwise to use pipes of a smaller diameter than 1 inch. Two kinds of radiators are made, one which simply warms the air already in the room, and another which, as is shown in the drawing, has hollow columns connected below with an opening in the wall through which air enters and, passing upwards through the radiator, is discharged into the room fresh and warm. Connected with the inlet opening is what is called a hit-and-miss valve, which can be adjusted so that either the outside air or the air of the room may pass through the radiator. The ventilating radiator is much to be preferred to the nonventilating one, but it must be remembered that in this case, as in all cases, ventilation cannot be combined with warming without adding to the first cost and the working expenses, for a larger boiler and larger radiators are required, and the consumption of fuel is in consequence increased. In the low-pressure system of warming just described the temperature of the pipes does not, as a rule, exceed 200° F., and a pipe is conducted from the highest point in the circuit to the outside for the escape of air or steam.

Fig. 25.

In another system (Perkins) no escape pipe is provided and the pipes, which have an internal diameter of inch are not con

nected with a boiler, but are simply coiled within the furnace. Under these circumstances the water circulates under pressure, and, therefore, the temperature of the pipes may reach to from 300° to 350° F.

About 8 feet of such piping will correspond, as regards heating power, to 12 feet of the old 4-inch piping. According to Wynter Blyth, this system is not to be recommended for the purpose of warming houses, owing to the liability to overheat the air, and also because of the sudden variation in temperature that is likely to result unless the fire is constantly kept up.

Steam, as a rule, in this country is only used for heating purposes in the case of factories, where it is necessarily on the spot as a motive power. In America it is largely employed for heating dwelling-houses. A very elaborate system of heating by steam is in operation in the Houses of Parliament. On the whole, perhaps the best system of warming houses is by the lowpressure circulation and ventilating radiators, combined with open fireplaces. The English people have a strong prejudice in favour of the open fireplace, and it must be admitted that its cheerful appearance is worth a good deal, at the same time, it is wasteful, especially as usually constructed, and economy as well as efficiency would be effected by the combined system of open fres and low-pressure hot water ventilating circulation.

Steam, if available, may be used, indirectly, as a heating medium for a low-pressure hot-water circuit. In this case a steam pipe is carried to a water cylinder, within which it is coiled in order to increase the heating surface in contact with the water which circulates in the usual way throughout the building. It thus takes the place of the ordinary furnace and by regulating the steam pressure the heat imparted to the water, which is the distributing medium, may be readily adjusted to any desired temperature.

It is well to be cautious in deciding as to who shall carry out whatever system of warming by hot water or steam may be determined upon, as the successful working of all is dependent upon so many conditions, the non-compliance with one of which will result in failure. It does not follow that all who are willing to undertake the work are capable of satisfactorily completing it, and in this, as in all cases, experienced workmen are worth paying for.

AN intelligent appreciation of the subjects dealt with in this and the following three chapters is perhaps the most essential element in the education of a sanitary inspector. Hardly a day can pass without his knowledge of the subjects being put to the test, and upon its thoroughness, the health and, it may be, the lives of many are dependent. The ignorance that still prevails, even among the educated public, regarding the most elementary facts connected with the drainage of houses, is indeed surprising. To them the whole question appears mysterious and complicated, but in reality it is not so.

Without going minutely into the composition of sewage, it may be said to consist of water containing certain refuse substances in solution and in suspension. These consist of urine and fæces of men and animals; house waste-water, containing grease, soap, and foul matters from the surface of the body and from clothes and general house washing. Sewage may also contain special pollution from manufacturing processes.

Human fæcal matter is sometimes excluded from the drains, and when it is so, it is popularly supposed that the sewage is comparatively innocuous, but this is certainly not the case. An estimate of the difference between the sewage of water-closet towns and of towns where the fæcal refuse is dealt with by the midden or pail systems, may be arrived at by comparing the value as manure of the sewage in each case.

According to the first report of the Rivers Pollution Commissioners, the value for agricultural purposes of 12 tons of sewage from towns without water-closets is equal to 10 tons of sewage from towns with water-closets. This fact is important, as showing how essential it is to provide some means for treating all sewage, irrespective of its nature, before allowing it to enter a stream.

Ordinary sewage, when fresh, is comparatively harmless; but, as all dead organic matter must necessarily undergo change (in the process of which it is split up into its simpler elements) and, as during this process of decomposition (unless it takes place under favourable conditions) nuisance is likely to arise,

it is essential that precautions should be taken to prevent this. By reason of the artificial conditions of our existence, then, art must assist in these natural processes; but we may rest assured of this, that if man does his part of the work, Nature will do hers.

Putrefaction is the result of an attack upon dead organic matter by minute living germs or bacteria, ever present in sewage and air; the process is similar to, in fact it is, fermen tation. Under favourable conditions, these germs multiply with enormous rapidity, until in time complete dissolution of the material is accomplished, and during this time a continual discharge of fœtid organic matter and foul gases takes place, which contaminate the atmosphere, and tax to a great extent the purifying effect of the oxygen it contains. This alone must seriously affect the health of the inhabitants, and if it is not in itself directly responsible for the production of disease, there is no question but that it greatly favours the extension of diseases of the infectious class. Under these circumstances, it is of the utmost importance that all sewage and refuse should be disposed of in a manner that will least contribute to the injurious consequences just described. The great principle then to keep in view is the immediate and thorough removal of all fluid refuse, and the important points to determine, in judging of the efficiency of any system of sewage removal, are as to whether it is immediate and complete.

METHODS OF SEWAGE REMOVAL.

Having considered the broad principles with which all perfect methods of sewage removal must comply, we must now go a little farther and apply these principles to the different methods now recommended.

The present systems of sewage removal may be considered under two heads-viz., the water-carriage system and the conservancy system. In the former, solid fæcal matter is introduced into the sewers, while in the latter it is excluded.

Great difference of opinion has hitherto prevailed as to which ought to have the preference, but the water-carriage system is now pretty generally admitted to be the better one, except, perhaps, in the case of scattered populations dependent for their water-supply upon local wells. The arguments in favour of the water-carriage system seem unanswerable.

If it were possible to get rid of the ordinary slop water by