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By Dr. Manson.
383.-You give it us your definite opinion that the present system of ventilation, supposing it is perfect in every respect, that the traps of the houses and the gullies are perfect, these shafts are quite inefficient?
A.-No, I will not go so far as that. I say suppose all the house drains and the street gullies are trapped efficiently, these ventilators would relieve the pressure of gas in the sewers, but I would not call that sufficient ventilation. In a steep city, I should say you want ventilators on the line of the sewers themselves.
384.-In what way would it show its inefficiency?
A.-By having a sudden rush of foul gas from the ventilator.
385.--But that is intended?
A.-But where is the gas to go in case of a severe rainstorm and a sudden rush of
water?
386.Where would it go in your opinion?
A. Supposing the sewer were perfectly tight, there would be an accumulation and a great pressure of sewer gas somewhere.
387.—Yes, but you assume the sewers are quite full?
A. They are nearly full. The volume of water in the sewers is considerably increased at such a rapid rate during a heavy rainstorm that the gas cannot get out quick enough.
388.-I can understand that, if you assume the sewers are quite full and in that case the pressure of water would be so great, that the sewers would burst without the gas?
A. Yes, but gas ascends and water descends.
By Dr. Jordan.
389. In time of heavy rainstorms have you known the sewers quite full?
A. Yes, I have seen the water coming out. They have burst several times.
390.-On the lower levels?
A. Yes.
By Dr. Canthie.
391.—It is a common thing for sewers to burst in storms?
A.-I don't say they burst from gas. Gas is far more elastic than water.
392. They do burst?
A. Yes, they have done so generally on the lower levels.
By the Chairman.
393.-But from the pressure of water?
A. Yes, they have burst so many times that the Public Works Department has, I think, now found out all the weak points.
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