J. Reynolds & Son, Philadelphia, Pa., write: "The Engineering RECORD contains an article headed ' Objections to Running a Vent Pipe into a Smoke Flue.'

"We ventilate apartments, etc. into the smoke flue, but not into a plain chimney. Our method is to run a cast-iron pipe from the cellar to a few inches above the chimney coping in the center of said flue. For example, if a flue measures 12x12 inches in the clear, we run an 8 inch cast-iron pipe for smoke immediately up the center of said flue, properly securing each length of 5-inch by iron stays; we then use the brick flue surrounding said pipe for the introduction of all ventilating ducts. It works like a charm and there is no conflict."

[In this case the smoke flue is an iron pipe, and the brick flue, possibly built for a smoke flue, is made to serve the purpose of a ventilating flue. There are doubtless many cases where the conditions were favorable, and satisfactory results were secured, yet it might be well to consider a variety of conditions where satisfactory results would not be secured. We therefore should not advise laying down hard and fast rules in an ordinance to cover all cases.

Vent pipes from the bowls or seats of water-closets can pretty safely be connected with any warm flue in the walls of a building, provided said flue is used for no other purpose and connected with no other flue, unless under conditions mentioned below.

When the waste heat from a furnace or boiler chimney is carried through an iron pipe within a flue, the flue becomes an aspirating shaft, and into it the water-closet rooms may be ventilated; but should there be another vent shaft in the building, then the object of the separate vent shaft for the closets might be vitiated, and the necessity for bringing them together at the top made apparent.

If there is a systematic exhaust ventilation (by fan or aspirating shaft) in the building, this flue should enter the main outlet duct just below the fan, if one is used, and pretty near the top of the heated aspirating shaft - certainly above all other ventilating flues to the shaft which lead from rooms. In such a case, presumably, it is best to vent the water closet room into the same flue as the vent from the bowl or seat, as thereby the possibility of drawing air down one flue and up another is prevented, which might be the case with exhaust ventilation should there be two flues from the same water-closet room, and which in all probability would be the case if they went separately to the coping or outer air.

If the ventilation of the building is plenum ventilation, then the flue, presumably, is best when run to the atmosphere direct, with a separate flue for each purpose, unless indeed there is a combined plenum and exhaust system, when the flues are best arranged as though they were for exhaust ventilation alone.

Houses or buildings warmed by furnace, taking air from outside or by indirect steam radiation with or without a fan may be considered "plenum ventilation," while all warmed by fireplaces or stoves, having the air drawn out of the rooms by waste heat or otherwise, are vacuum or "exhaust ventilation." With a condition of plenum within a house, chimneys and flues "draw," and all flues will show an outward current of air unless they are proportioned too large. With vacuum ventilation, if there is more than one outlet or aspirator (fan or otherwise), the stronger is apt to draw the weaker, and will do so unless there is means of admitting air below or through windows sufficient to supply the outlets which have power to draw.

Small aspirating shafts are made by providing a flue on each side of the kitchen range flues, and boiler and furnace flues, with partitions of one brick between, or by using earthen or iron pipe, or special earthen flues with partitions, within a large brick flue.

The cast-iron pipe within a flue makes the best aspirating shaft, but we know of a case where a building was so tight that the air to supply the boiler furnace was drawn down the aspirating shaft, up which the very same boiler smoke pipe ran. until the boiler was supplied with air directly from the outer air.

In our modern kitchens it now and then happens that the flue running parallel with the range flue for the purpose of drawing the hot air and fumes of cooking from the range under the hood, works the wrong way; in fact, cold air comes down to supply the fire unless a window or door is open, some of the buildings being so air-tight. In such a case it would not be a good thing to have water closets vented into the same flue.]