Want of sufficient height in the flue. The outlet of the chimney being placed in an exposed and cold situation, while the air with which the fire is supplied is drawn from a warmer and more sheltered region. Excessive width in the fine, by which a large volume of cold air is drawn in and allowed to lower the temperature of the ascending column. Low temperature of the interior of the flue, in comparison with that of the external air. Humidity of the air. Too accurate fitting of the windows and doors, and joints in the flooring. The draft of one fire injuring that of others in the same house. A current caused by the heat of the fire circulating in the room. A flue of insufficient size. A foul fine. Displace ment of masonry, or accumulation of mortar within the flue. The sudden obstruction of the draft, by gusts of wind entering the chimney-top. Increase of density of the air at the chimney -top, due to the effect of wind in chimneys rising from the eaves of roofs. Drafts within the room which throw the smoke out of the influence of the ascending chimney current.