This section is from the book "A Treatise On Architecture And Building Construction Vol2: Masonry. Carpentry. Joinery", by The Colliery Engineer Co. Also available from Amazon: A Treatise On Architecture And Building Construction.
234. Fig. 95 shows a section through a fireplace with an ash flue leading down to the cellar. The back of the fireplace is often constructed of firebrick and brought forward as shown at a, and an iron damper arranged as shown at b, to slide back and forth, to regulate the draft. At c is shown the chimney flue, in this case made 8 in. X 12 in.; d is the facing of the fireplace, which should project 4 inches beyond the outside brickwork of the chimney breast, so as to bring the grate forward into the room, the height of this opening or facing above the hearth being usually 30 inches; e shows the tile border to the fireplace opening, and /, the mantelpiece. The bottom of the fireplace has an opening in it, covered with an iron cover g, to let the ashes down through the ash shaft h, into the ash-pit in the cellar, shown at j. This ash-pit has an iron door k for the removal of the ashes. The stone foundation wall of the cellar shows at /, and m is the concrete bottom. The hearth is generally supported by a trimmer arch n, springing from the chimney, and resting against a header framed in the floor. The space above the arch o is filled with concrete, and leveled off to receive the tile or brick hearth p.