expansion of the gas is then sufficient to carry it out of the ventilators without the aid of the watery vapour as a vehicle, and therefore it is discharged under our noses in its most offensive and undiluted form. But even when mixed with watery vapour the latter expands so rapidly upon reaching the outer air that the heavier gas is left to fall to the ground if there is not sufficient wind to disperse both before the separation takes place.

In winter, when decomposition is at its minimum, and consequently little or no gas is generated, the watery vapour predominates, and if the outer air is colder than the sewage the vapour is sufficiently condensed to become visible, rising like smoke from the ventilators on a frosty morning: it is then, however, quite harmless, from the absence of decomposition.

The above is the action of a system of sewers having the outfall below low-water mark, and ventilated as at Gloucester by open grids 36 square inches in area at every 60 yards along the public streets; this is so because the difference of level between two ventilators at that distance apart is not sufficient to convert the lower one into a downcast shaft and the upper one into an upcast shaft, but the action is simply a slow respiratory one, due to the expansion and contraction of gases and watery vapour, overflowing or not from the ventilators in response to the atmospheric changes above mentioned. But no system of ventilation can be efficient that does not establish a constant current of air through the sewers and house-drains of sufficient strength to prevent a reversal of direction under all ordinary variations of the atmosphere; nevertheless we do not want to produce, or even stimulate, a general tendency or rush of gas to the higher branches of a system of sewers, or to any one point in a town, but on the contrary, the object of ventilation is, or should be, to prevent the accumulation of gas by passing a free current of air through both the sewers and house-drains.

To prevent this accumulation of gas, ventilation alone must not be relied upon if the sewers are in any way defective, or a nuisance will be the result; and although it is better to have the gas discharged into the open air than into private houses, it is difficult to convince the general public of the utility of any system of ventilation that emits a stink into the streets; for defective sewers there is an obvious remedy, therefore ventilation to be successful should be applied to well-constructed sewers with gradients sufficient to keep them free from deposit.

In such a system of sewers, the sewage passes off before decomposition sets in, and it is only the vapour from fresh sewage we have to deal with by ventilation; this vapour should not be discharged in its crude state at the street grids, but the latter should be converted into inlets for air, the outlets for the oxidized vapour being above the roofs of the houses, some 30 feet or more above the street level.

In order to establish this current of air entering downwards at every street grid, it is necessary that the ventilating shafts fixed against gable ends or other convenient walls of the house, should be so numerous, that the sum of their sectional areas should exceed that of the two street vents between which they are placed, sufficiently to overcome the friction of the air through the pipes; these should be not less than 4 inches in diameter, and may be either independent connections with the sewer, or simply the continuation of the house-drains.

In a distance of 60 yards we may have, say twelve houses in close order on each side of the street, or we may have say eight semidetached houses on each side in the same distance, so that at the lowest estimate we shall have sixteen soil-pipes 4 inches diameter, or about 12 square inches sectional area each, that can be converted into ventilation outlets, or a total of 200 square inches of outlets sucking away at 72 square inches of inlets.

But the property owner asks at once, Why should I help to ventilate the public sewers? The answer to this is, that the sewers are laid down for the benefit of the houses draining into them, and therefore those who use the sewers should also help to ventilate them and thus complete their efficiency, by simply ventilating their own house-drains; that is to say, the sewers and house-drains should be treated as parts of the same system, as mutually dependent upon each other as a man's hand and fingers. In detached or semidetached houses, where the drains can be kept outside, there is no reason why the soil-pipes should not be continued 4 inches diameter up above the roof as a ventilator, but with houses in close rank there may be some risk, although there should not necessarily be a great deal, if the sewers and house-drains are properly constructed; in passing the drains under the houses, in this case, therefore, it is safer to ventilate the house-drains independently, and have special ventilators for the sewer in addition, although such a proceeding doubles the expense.

If these conditions could be obtained, and there ought to be very

little difficulty about it, there would be no necessity for any complicated closet apparatus from 50s. to 100s. prime cost; but a simple pan and siphon trap, such as the "Artizan," now made by several makers, is all that is necessary, provided always that they have a good flushing rim discharging the water from all sides straight into the siphon. The flushing-box should never be less than 6 feet above the seat and have not less than 1 inch flush-pipe.

In conclusion, notwithstanding the almost universal condemnation of the pan and container closet, about which Mr. Pridgen Teale quotes from 'Scribner's Magazine' of New York that "it probably is not, but it certainly might be, the invention of the devil," they are still to be found in the majority of indoor closets and are even now fixed daily by builders and plumbers who must or ought to know their defects.

DISCUSSION.

Mr. FOWLER: We have had several papers on the ventilation of sewers from time to time, and it is not well to make comparisons I know, but I do not think that for scientific treatment of the question, we have had a paper dealing so carefully and so ably, perhaps, as the present one. The other papers have generally dealt with the passing off the sewage by means of channels, conduits, or something of that class; but this one goes deeply into the scientific researches of the question, and I think we ought to be deeply indebted to Mr. Read for the very able manner in which he has brought it forward. In regard to the connection of sewage with the wells in towns, I can bear testimony to that serious fact, inasmuch as at Cardiff, some twenty-seven years ago, when I was there, the wells of the town were formed in gravel. All the town of Cardiff is gravel formation. The sewers, I may say, were along the centres of the streets, and cesspools in many of the gardens, and a plague prevailed throughout the district-small-pox. The surveyor at that time, Mr. Wareing, who held the appointment just previous to my engagement with him, was fearfully disfigured—I apprehend in the discharge of his duty—with the malady, and it was traced, principally, I believe, to the connection of the wells with the sewers. It is easily understood that the sewage or liquid filth percolates through the gravel into the wells. The wells being a little deeper, perhaps, than the sewers, had the effect of drawing it from

the sewers into the wells.

I do not mean to deviate or to

turn from the question of the ventilation of sewers, but I would remark that in 1832 a similar thing occurred in London. Then, by a public enactment, the whole of the privies were swept away from the metropolis, and water closets were introduced. We know that London has now a less death-rate; a steady rate of about 20 per 1000 throughout the year. That supported what Mr. Read had said. Whilst practising on the ventilation of sewers in Leeds, with my colleague (Dr. Robinson), we proved this to be the case beyond doubt. Therefore it is with pleasure that I support Mr. Read's views.

Mr. HEWSON: I am sorry, Sir, to rise, to say that I do not feel that the author has presented us with a true description of the action of sewers as they really operate in towns. Of course I would much rather have added an opinion of approval than what I am going to say. However, we are here, as I take it, as a mutual improvement society as much as in any other capacity. I would like to put my remarks in the form of a question. The author claims to ventilate sewers by a motive power, which he gains by the difference in the height between two inlets of a sewer; that is, the difference in height between the grid in a street, and the top of pipe, say if you like 30 feet higher. He claims that if such an arrangement were made, circulation, so to say, would take place; exhaust the foul air and substitute purer air from the street. The difference in these two levels is what is going to do this. Now, how can that be, when perhaps 200 yards higher up the same street, the grids there might be 50 feet higher than the first grid? How can you expect that this isolated, and local, and special circulation will take place against the general set or current of gases in the sewer making their way to the higher levels of the town? In my opinion, what would take place if such a system as that suggested by the author was carried out, would simply be this—all low inlets in the lower parts of the town would supply air for the general circulation taking place, and it would be again discharged at the higher levels of the town. From my experience I have come to the conclusion that you cannot get this local circulation.

Mr. GODFREY: This is the first time I have had the pleasure of attending a meeting of the Association. I am glad to hear the remarks on the ventilation of sewers. My attention has been directed to the subject for some time past, as I have been connected

with one town in which the plan recommended is very fully carried out. I refer to the town of Kendal. They have a large system of sewers there, and the Corporation has done very much to induce owners to ventilate every branch drain. They have also erected a great many 6-inch ventilators where they could get permission. The physical geography of Kendal is such that the old portion of the town lies in a valley, and the new portion is upon a hill, varying in height from 50 feet to 200 feet, and there is very little cause for complaint from the sewers in the town. In the district I represent now there is only one upright or shaft ventilator. That was put up just before I took charge of the district, because there was a fearful stench from the manhole. From my investigations in this district, as well as in Kendal, I have found that very frequently the stench from a manhole is caused by some local circumstance (hear, hear), and that it does not follow, because one manhole stinks, that you must condemn the whole system. If there is that preponderance of sewer gas, as so many of the opponents of the sewerage system of the country are so fond of asserting, when one manhole smells the whole of them should smell, if the thing was to be consistent. I have had one or two striking instances lately of the reasons why one or two manholes have smelt, and it puzzled me very severely for eight months to discover the cause. One was in such a state that several tenants in the district gave notice that they would remove unless a remedy was effected. The Corporation of Birmingham, who supply the gas, were charged with being the cause of it, and took up the whole of the gas main for 300 yards, and it was found that the gas leaked into the sewer. That was often the cause of far more nuisance than all the good flowing sewage put together. If sewage was allowed to become stagnant, and accumulate-and I am sorry say that in some instances there are five or six inches of fæcal matter in the sewer-you will have a stink, and I do not think upright shaft ventilators, or any others, will do away with it. The only thing is to keep the stuff clean out of the place. With regard to the ventilation of private drains, under the model bye-laws of the Local Government Board, the owner of every new house is called upon to ventilate his own drains. I think we should each, in our own districts, put it strongly to every owner of property to contribute towards the ventilation of his portion of the sewers. Until we have our general system of sewers perfectly ventilated by increasing the number of inlets very largely, we shall never be free from these

to