As soon as it arrives in a current of heated air, it will ascend, passing along with the current, and descending or rising as the current is either warm or cold.  The effect of the cold fresh air from windows or doors, as well as the effect of the radiant heat from the fire, can be thus thoroughly studied.  Some of our pet theories may receive a cruel shock from this experiment; but, in the end, the ventilation of the room will doubtless be benefited, if we apply the information obtained.  It will be discovered that the wide-throated chimney is the cause of the little black arrows turning their backs on the right path and our theoretical outlets for vitiated air becoming inlets.  The chimney flue must have an enormous supply of air, and it simply draws it from the most easily accessible places.  From 1,000 to 2,000 cubic feet of air per hour is a large “order” for a small room.  Therefore, until we have made ample provision for the air supply to the fire, it is quite useless to attempt to ventilate the upper part of the room, either by ventilating gas lights or one of the cheap ventilators with little talc flappers, opening into the chimney when there is an up draught, and shutting themselves up when there is any tendency to down draught.  The success of these and all other ventilators depends upon there being a good supply of air from under the door or through the spaces round the window frames.  These fresh air supplies are, of course, unendurable; but if one of the spaces between the joists of the floor is utilized to serve as an air conduit, and made to discharge itself under the fender (raised about two inches for the purpose), quite another state of things will be set up.  Then the supply of air thus arranged for will satisfy the fire, without drawing from the doors and windows, and at the same time supply a small quantity of fresh air into the room.  But the important fact that the radiant heat from the fire will pass through the cold air without warming it all must not be lost sight of.  In reality, radiant heat only warms the furniture and walls of the room or whatever intercepts its rays.  The air of the room is warmed by passing over these more or less heated surfaces; and as it is warmed, it rises away to the ceiling.  Therefore, if we desire to warm any of this fresh air supplied to the fire, it must be made to pass over a heated surface.  The fender may be used for this purpose by filling up the two inch space along the front, as shown in the drawing, with coarse perforated metal.  This will also prevent cinders from getting under it.  It will be found that for the greater part of the year the chimney ventilator and the supply to the fire will materially prevent “stuffiness,” and keep those disagreeable draughts under control, even although the room be lighted with a 3 light chandelier burning a large quantity of gas.

[Illustration]

With improvements in gas burners, we may expect to light rooms perfectly with a less expenditure of gas than we now do.  But we cannot light a room without in some measure creating heat; and I think I have shown that we want this heat at the ceiling line for the greater part of the year.