Q. Will you be kind enough to inform me through the columns of your paper on two points which I have no means of deciding - viz.:

First - What proportion should the area of a pipe, ventilating a trap, bear to the area of the pipe on which the trap is located?

Second - Is the placing of a gully with trap, at level of yard, the best way of breaking connection between a rain-water leader and the main house-drain? Would frost injure its efficiency?

Being somewhat of a novice in sanitary engineering, an answer with-the weight of authority your paper carries with it will greatly oblige.

A. The size of a pipe used to ventilate a trap, should be as near the size of the trap as practicable and depends largely on the distance such a pipe has to go to reach air. Moreover, if the climate is a frosty one, say above a latitude of 40 degrees in the United States, the part of the pipe extending through the roof should not be less than four inches in diameter in any case, to prevent its being filled up with ice from condensation.

Second - The gully with strainer on a level with surface of yard with a trap below is a good method of breaking the connection of rain-water leaders with drains, provided the trap is supplied with water by some more reliable source than the rain; otherwise it might dry up and leave the trap inoperative; also, provided the water in the trap is protected from freezing, which is purely a local question, depending on climate and exposure.