Figure 3 represents the ground plan of the fire-place in figure 1; but instead of square, it is to have sloping sides, and is to be filled up as in figure 4. To do this according to rule, a line A, B, is to be drawn straight from one jamb to the other; and from the centre of this, a cross line e is to be drawn from front to back. The mason is then to hold a plumb-line against the inside of the chimney breast, where it begins to run straight upwards, as, for example, at a, figure 1, and the spot where the plumb-line rests on the cross line e is to be carefully marked. Four inches behind this mark is the position for the back of the fire-place, as shown by the brickwork in figure 2, which, by being so placed, gives four inches as the dimensions from back to front of the throat of the chimney seen at d.
This brickwork, and the sides, are to be carried up from six to nine inches above the lowest part of the chimney breast, so as to give a sufficient length and form to the throat d; and instead of being finished irregularly, or with a slope at the top, it must be perfectly flat and level; because when the wind sets down the chimney, if it strikes against a slope it drives the smoke into the room, but not if it strikes upon a flat Too much pains cannot be taken to make a good finish of the inside of the breast; it should be quite smooth and perpendicular, so as to offer no impediment to the ascent of the smoke. The lower part is to be carefully rounded off with plaster, as at i, figure 2, instead of being left square or rough and badly finished, as it nearly always is.
The way to fix the sides or coverings of the fire-place is at aslope or angle, as shown at figure 4. It has been found that an angle of 45 degrees is that which throws the most heat into the room. These angles and the back should be made of fire-brick, and if each of one piece the better, as it will then be easy to place them in the position represented in the diagram. The hollow spaces behind may be filled up with regular layers of brickwork, all brought to the same fiat level at the top. It is a mistake to suppose that iron is the best material for the back and sides of a grate ; fire-brick is much better. Iron absorbs the heat - fire-brick throws it out, and besides it can be white-washed which is a great economy, for white throws out both light and heat, which black does not. All parts of a fire-place not liable to be blackened by smoke, should be kept white, it is a common practice to do so in the United States.
Any workman may get the angle of the sides by an easy way, shown at figure 5. On a board, bench, or table, or on the floor, draw three equal squares, from twelve to fifteen inches each way, as A, B, C; and from the back corner e of the central square B, draw a diagonal line across the square A, to the outer corner f. This gives the angle at which the sides are to be fixed; and it a wooden bevel or mould-board be made exactly to this plan, a bricklayer will always be able to use it in setting out his work, and with something like certainty that he is doing right. If the chimney should be an uncommonly smoky one, or if the grate should not be exactly of the required width, either of the other two angles shown by the dotted lines may be chosen. To leave room for sweeping the chimney, the upper Earl of the back is to be a single slab, as at o, figure 2, which is to be fitted so as to shift in or out. This can easily be done by standing: the slab in its place, and finishing the other work up to it, being careful to leave all level at the top. By taking out this slab when the chimney requires sweeping, room is left for the passage of the brush, and when it is replaced it leaves the chimney throat as perfect as before.
The true proportions of a grate are, to hare the width of the front three times the width of the beck. Nine inches should be the width of the back, and the depth of the grate from back to front the same, which multiplied by three, gives twenty-seven inches as the width of the front. These dimensions are not to be departed from, unless under strong necessity ; by keeping to them, the sides or copings of the fire-place will always be at an angle of 45 degrees, as above-mentioned. As a rule, the height of the fire-place should be the same as the width.
If these directions are carefully followed, it will be found that the fire-place will be complete all but the bars, a matter worth consideration, because the less iron there is about a grate the better. The bars and bottom may be made of iron all in one, and the bottom II not to be more than five inches above the hearth; for a grate when fixed low sends more heat into the room than when fixed high. Figure 6 represents a fire-place complete. It does not look so elegant or showy as those which modern taste has produced, but it will be found far more serviceable and economical.
In cases where the breast of the chimney is nine inches thick, the four inches which have to be allowed for the throat behind this, will make the fire-place thirteen inches deep. The back most then be thirteen inches wide, and the front three times thirteen, or thirty-nine inches, and the angles will be in their true position. A fire-place of this size will warm a large room, while a grate nine inches deep will serve for all ordinary sitting-rooms.
A cheerful and steady fire is so great a comfort as to make it worth while to take a little pains to insure it. The plan here described, if properly carried out, cannot fail of success, and will leave little need for chimney-pots or cowls.