THERE are modes of purifying the sewers; the consists in removing the foul air, the other in removing the solid deposits. I shall deal with that mode of purification which consists in the mechanical removal or chemical decomposition of the noxious gases engendered within the sewers.

This is what is termed the Ventilation of the Sewers, and forms a very important branch of the inquiry into the character and working of the underground refuse-channels, for it relates to the risk of explosions and the consequent risk of destruction to men's lives; while, if the sewer be illventilated, the surrounding atmosphere is often prejudicially affected by the escape of impure air from the subterranean channels.

A survey as to the ventilation, &c., of the sewers was made by Mr. Hawkins, AssistantSur- veyor, and Mr. Jenkins, Clerk of the Works. examinations took place of sewers; of those in Bloomsbury; those from Tottenham-court-road to , Strand; from the Guard-room in Buckingham Palace to the Horseferry-road, ; and in and the streets adjacent. There were difficulties attending the experiment. From to there was a drop of feet in the levels, so that the examiners had to advance on their hands and knees, and it was difficult to make observations. In some places in also the water and silt were knee deep, and the lamps ( were used) splashed all over. In Bloomsbury the sewers gave no token of the presence of any gas, but in the other places its presence was very perceptible, especially in a sewer on the west side of Grosvenorsquare, a very low , in which the gas was ignited within the wire shade of of the lamps, but without producing any effect beyond that of immediately extinguishing the light. There was also during the route, in the neighbourhood of Sir Henry Meux's brewery and of an adjoining distillery in , a considerable quantity of steam in the sewer, but it had no material effect upon the light.

The examiners came to the conclusion that where there was any liability to an explosion from the presence of carburetted hydrogen, or other causes, the Improved Davy Lamp afforded an almost certain protection.

The attention of the Commissioners seems to have been chiefly given of late, as regards ventilation and indeed general improvement, to the sewers on the Surrey side of the metropolis. Among these a new sewer along , running from the Blackfriars to the Southwarkbridge- road, is of the most noticeable.

is of the smaller off thoroughfares, the character of which is, perhaps, little suspected by those who pass along the open Blackfriars-road. As you turn out of that road to the left hand, advancing from the bridge, almost opposite the , is . On its left hand, as you proceed along it, are gas-works, and the factories, or work places, of tradesmen in the soap-boiling, tallow-melting, cat and other gut manufacturing, bone-boiling, and other noisome callings. On the right hand are a series of short and often neatly-built streets, but the majority of them have the look of unmistakable squalor or poverty, though of the poverty of the industrious. Across , , and other ways, few of them horse thoroughfares, hang, on a fair day, lines of washed clothes to dry. Yellowlooking chemises and petticoats are affixed alongside men's trowsers and waistcoats; coarse-featured and brazen-looking women, with necks and faces reddened, as if with brick-dust, from exposure to the weather, stand at their doors and beckon to the passers by. Perhaps in no part of the metropolis is there a more marked manifestation of moral obsceneness on the hand, and physical obsceneness on the other. With the low prostitution of this locality is mixed the low and the bold crime of the metropolis. Some of the off-shoots from communicate with places of as nefarious a character. Hackett, whom his newspaper admirers seem to wish to elevate into the fame of a Jack Sheppard, resided in this quarter. The gang who were last winter repulsed in their burglarious attack on Mr. Holford's villa in the Regent's-park favoured the same locality, and were arrested in their old haunts. Public-houses may

A Report of the , shows that a new sewer, feet in length, had been "put in along , with a fall of inches from the level of the sewer in Blackfriars-road to . The sewer," states the Report, "with which it communicates at its upper end in the Blackfriars-road contains nearly feet in depth of soil; it in consequence has silted up to that level with semi-fluid black filth, principally from the factories, of the most poisonous and sickening description, forming an feet in length, the filth at its lower end being upwards of feet in depth. Since the building of this sewer, the foul matter so discharged into it has been in a state of decomposition, constantly giving off pestilential and poisonous gases, which have spread into and filled the adjoining sewers; thence they are being drawn into the houses by the house-drains, and into the streets by the street-drains, to such a fearful extent as to infect the whole atmosphere of the neighbourhood, and so to cause the very offensive odour so generally complained of there. Sulphuretted hydrogen is present in these sewers in large quantities, as metals, silver and copper, are attacked and blackened by it; and the smell from it is so sickening as to be almost unbearable."

On the question of how best to deal with sewers such as the , Messrs. John Roe and John Phillips (surveyors) and Mr. Henry Austin (consulting engineer) have agreed in the following opinion:—

The most simple and convenient method would be by placing large strong fires in shafts directly over the crown of the sewers. The expense of each furnace, with the inclosure around it, will be about 20l. The fires would be fed almost constantly, by which little smoke would be generated. The heat to be produced from these fires would rarefy the air so much as to create rapidly ascending currents in the shafts, and strong draughts through the sewers, the foul air in which would then be drawn to the fires and there consumed; and as it was being destroyed fresh air would be drawn in at all the existing inlets of house and street drains, pushing forward and supplying the place of the foul air.

Concerning the explosions of, or deaths in, the sewers from the impure gases, there is, I believe, no statistical account. The most remarkable catastrophe of this kind was the death of persons in a sewer in , in ; of these, were regular sewer-men, and the others were a policeman and Mr. Wells, a surgeon, who went into the sewer in the hopes of giving assistance. Mr. Phillips, the then chief surveyor of the Commission of Sewers, stated that the cause of these deaths in the sewers was entirely an exceptional case, and the gas which had caused the accident inquired into was not a sewer gas. "There is often," he said, "a great escape of gas from the mains, which found its way into the sewers. The gas, however, which has done the mischief in the present instance would not explode."

Dr. Ure's opinion was, that the deceased men died from asphixia, caused by inhaling sulphuretted hydrogen and carbonic acid gas in mixture with prussic vapour, and that these noxious emanations were derived from the refuse lime of gas-works thrown in with other rubbish to make up the road above the sewer. Other scientific gentlemen attributed the deaths to the action of sulphuretted hydrogen gas, or, according to Dr. Lyon Playfair, to be chemically correct, hydro-sulphate of ammonia. The coroner (Mr. Bedford), in summing up, said that Mr. Phillips wished it to be supposed that gas lime was the cause of the foul gas; and Dr. Ure said that gas lime had to do with the calamity. But Dr. Miller, Mr. Richard Phillips, Mr. Campbell, and Dr. Playfair, more especially the latter, were perfectly sure that lime had nothing to do with it. The verdict was the following: —"We find that Daniel Pert, Thomas Gee, and John Attwood died from the inhalation of noxious gas generated in a neglected and unventilated sewer in Kenilworth-street. And we find that Henry Wells and John Walsh met their deaths from the same cause, in their laudable endeavours to save the lives of the sufferers. The jury unanimously consider the commissioners and officers of the Metropolitan Sewers are much to blame for having neglected to avail themselves of the unusual advantages offered, from the local situation of the Grosvenor-canal, for the purpose of flushing the sewers in this district."