'The shape of the grate or grid is arrived at in the following way: - Describe a square d - of which the sides shall be 8, 9, or 10 inches, according to the size of the room - within an equilateral triangle E, the two sides of which shall represent the 'covings' of the fireplace, and the base the front line of the fireplace. From each front angle of the square, carry a line from D to c to the 'covings' or sides of the triangle, at an angle of 45° with the front line of the fireplace. These two lines, with the side of the square from which they are drawn, form the front of the grid. The back line of the grid does not correspond with the corresponding side of the square, but is carried 1 ½ inches farther back, so as to give greater depth to the grate, and allow the fire-brick back to overhang the back of the grid to the extent of 1½ inches (see Fig. 460), before it ascends as the ' lean over'."

The Teale grates are now made in a great number of designs; there are, however, only two main types. Fig. 462 illustrates the first type, and clearly shows the economizer, the vertical bars, the solid fixed rim forming the base of the bars, the fire-brick back leaning forward and standing out at the bottom away from the tack of the hearth proper, and the "covings."

Fig 462 -front View of the Teale Fireplace.

Fig. 463. - Front View of the Teale Front hob Urate.

The second type, known as the Front-hob Grate, is illustrated in Fig. 463.

This has no fire-bare whatever; the fire-clay back and sides are as already described, but the grate is only very slightly above the level of the floor of the room, and a special tiled hearth is built up. This becomes hot, and gives off heat to the room, and thus adds to the efficiency of the grate. Access is afforded to the ash-pit by means of the loose door shown in front, but as this door is provided with several air-inlets, the original Teale principle is departed from to some extent This type of grate has been found extremely satisfactory.

The Rational Grate is another good fireplace, not unlike the last, but the ash-pit is sunk below the level of the hearth instead of being raised above it. A section of this fireplace will be found in Fig. 71, p. 131, vol I.

Boyd's Grates, while having the good points of the original Teale design, also possess several other features of interest. Figs. 464 and 465 show a grate with an ash-pit which may be entirely closed for slow combustion, or opened to any extent desired by simply moving forward the economizer. It has the thin vertical bare and the fire-brick back, but the back slants even more forward than in some of our earlier illustrations, and the canopy register is of a good design, easily regulated to enlarge or diminish the mouth of the flue. The makers of these grates differ from Mr. Teale as to the most desirable angle between the sides and back, preferring an angle of 135°. It is extremely important to keep all the ironwork away from the fire, and this firm has even gone so far as to make the grating itself of fire-clay with slits, as shown in Fig. 466. The special stand for the tire-brick bottom is made of iron, and has an adjustable slide for closing the air-slits. The size of the fireplace can be diminished by the use of suitable blocks, which are specially made to fit the various grates.

Fig 464 - Front view of Boyd's register Grate, with Adjustable Canopy and Regulating Ash-pit.

Fig. 465.-Vertical Section of Boyd's Register Grate, with Adjustable Canopy and Regulating Ash-pit.

The power of a given fireplace may be greatly increased by making it of such a form as to allow the air in the room to circulate round it This is done in the case of the fireplace shown in Fig. 467. In the plan, a is the fuel-basket, B the warming-chamber, and C the brick setting at the back; the V-shaped projections are of iron, and afford a large heating-surface to the air, which passes in at the lower holes and out, in a warmed state, at the upper holes. Such a chamber should be occasionally cleaned out, otherwise it will become choked with dust, and will deteriorate the .quality of the air passed through it. The iron just at the back of the fire is protected by fire-brick.

Helm's "Helios" Smoke-consuming Grates are really stoves, the fire being entirely inclosed. They are specially designed to consume their own smoke. The one objection to them, in the minds of many people, is that the fire itself is inclosed, and the flames can only be seen through a mica door. The design, however, is very ingenious, and well worth describing. The National Smoke Abatement Institution has reported as follows respecting these stoves: - "In the course of twenty minutes the smoke entirely ceased, and the chimney was entirely smokeless during the remainder of the trial. The performances of both the grate and the stove stand, in point of economy of fuel and efficiency, in the front rank. The fires burned with perfect continuity and regularity, and they were practically automatic in action."

Fig 466. - Boyd's Grate body and Grating of Fire-brick.

Fig. 467 - Plan and Front View of Boyd's Warm air Grate.