Q. During the recent cold snap I was called up-town to investigate the cause of escape of sewer-gas into the house of a well-known gentleman of this city. I knew the house-drains were thoroughly ventilated, and was at a loss to locate the cause. Upon examining the work we found it apparently all right,, but in spite of that fact, when we lifted the plunger of the water-closet, the traps immediately syphoned out, and on going to the roof, thinking something was wrong there, imagine our astonishment at finding the ventilating-cap frozen solid. Other houses in the same row were found to be in the same condition; the damp vapor rising through the sewer had struck the upper or dome-like portion of the cap and gradually frozen its way down like an icicle, and finally closed it tight. In our climate this is liable to happen at any time during the winter, and, in my opinion, calls for an air-cap of a different pattern. Upon examining the present air-cap you will wonder how the sewer-gas escapes from it, as the dome falls down over the lower or straight part at least one-fourth of an inch, while it really ought to stand clear above it at least 1 1/2 or 2 inches. This would also prevent its freezing, as the space would not be so confined, and would be more difficult to fill up with ice, as there would be no support.

Either remodel the hood or dispense with it entirely, and leave the end of the pipe open to the air. This, I know, would be open to objections, as malicious persons would probably drop obstructions down the pipe.

A. We think this letter of great importance. We have hitherto preferred the open pipe or a properly constructed hood to a return-bend or cowl, as we consider the latter liable to be closed by ice during very cold weather. From our correspondent's experience it appears that the hoods were so constructed that ice readily formed and closed them, while return-bends were found open. After this experience we should advise that open pipes be used, and, if it is necessary to prevent articles from being thrown down the pipe, our preference would be an open-mouthed pipe sufficiently high to be beyond the reach of children, and properly supported.

A similar experience to that of our correspondent was brought to our attention also about that time, and on frequent occasions since we have expressed our objection to the return-bends or hoods of this description for this climate, and even the wire-basket, in localities north of this, we should apprehend, would close up and become a ball of ice, unless the mesh were large.