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841. You are reasoning from analogy?
A.-Reasoning from analogy I should say it would exist.
By Dr. Cantlie.
842.—Would you say the shafts at the top of the sewers are sufficient ventilation?
A. No.
843.-Why not?
A. You see the shaft is at the top of the one main sewer. may ventilate to a certain extent downwards.
That main sewer it
844.-What is your opinion of the passage of sewer gas-up, or down, or irregular?
A.—I think it is irregular. In a sewer about two-thirds full the current would carry the sewer gas down, but if the sewer were practically empty it would rise.
845.-Suppose you get a lot of ventilators, would it always rise? Would not the air come in at one and go out at another?
A.-It might do so.
846.—We understand there are a large number of ventilators in the sewer, but do think there are sufficient to cause a regular passage of the gas, or if not sufficient to cause that, do you think they are sufficient to cause it to ascend?
you
A.--I think with the present outlets in most cases the tendency is an outward current, because they are so few.
847.-You think they are too few then?
A. Certainly. You see there are only about ten of these main drains from the military ground to West Point, that is ten openings. Some of these have shafts, some have not. I may say I think the shaft makes very little difference. The open end of the sewer would be the same. The only slight difference it makes is the difference in the density of the gas in the additional height of the shaft. The shaft may ventilate the one sewer down to a certain distance, but you must not forget that the sewer has innumerable offshoots running into the side streets and splitting up into others. All of these run down to the main sewer; to ventilate them with the present system, the gas must go down these and up the other. Sewer gas will not do that for
anyone.
848. So none of the collateral drains are ventilated at all?
A.--I don't think the shaft ventilates them.
849. So there are a large number absolutely unventilated?
A. Yes.
By Dr. Yarr.
850.—What about the gully holes and traps?
A.--I know whole streets where every gully is trapped or flapped.
851.In the Western District?
By Dr. Cantlie.