SEWER VENTILATION.
The question of ventilation is a very difficult one, whether it is in connection with sewers or buildings.
The ventilation of buildings has received more attention than that of sewers, excepting within the last three years.
In the ventilation of buildings we have the work and experience of Mr. Haden, Captain Galton, Dr. Parkes, Messrs. Howarth, Tobin, Boyle, Banner, and others, who have not only made the ventilation of buildings their principal study, but have also spent large sums of money in carrying out experiments with a view of getting a system of ventilation applicable to any building. I have no doubt that each of the above authorities in house ventilation would candidly admit that some of the most favourable experiments they had made, and from which at the time they expected the greatest results, had, when they had been practically applied in different localities and under different circumstances, proved their worst failures in providing a regular supply of fresh air to and the extraction of foul air from any building.
If in the ventilation of buildings so many failures to get a perfect and universal system can be recorded, it is quite natural that the same will be the case in the ventilation of sewers.
The most eminent engineers of the present day will admit that vast improvements must be made in sewer ventilation before they can say of a district where a quantity of drains are laid and a large bulk of sewage matter is carried through them, that the atmosphere of that district is as pure as that of one where no drains are laid or where no sewage matter can be found.
It was not until 1840 that the question of sewer ventilation received very much attention, and it is in the reports to the City Commissioners of Sewers and to the Metropolitan Board of Works that the earliest results are recorded.
The report of Colonel Hayward to the City Commissioners of Sewers, dated 18th March, 1858, contains some of the earliest and most valuable information as to sewer ventilation.
In that report it is stated that, previous to 1830, “the sewers were ventilated by the gulleys, which were large open shafts or shoots connected with the sewers without traps of any description: they were connected with gratings of large size, the bars of which were farther apart than those at present in use; there were no ventilating shafts rising to the centre of carriageways, nor were there any side entrances by which access to the sewers could be had. Whatever ventilation took place therefore was effected by the gulleys, and if a sewer required to be cleansed or examined the mode adopted was to open holes in the centre of carriageways down to what are technically called manholes, or working shafts, and perform these operations from these apertures, the shafts being left open a sufficient length of time to ensure ventilation before the men descended, and if there was fear of an accumulation of gas or mephitic vapour, which sometimes was the case near the heads of sewers, but at few other points in them.”
Complaints of the effluvium from these gulleys were made before the year 1830, and are stated to have grown louder and stronger after that date.