Fig. 32 illustrates a few typical specimens of modern improved open grates devised to increase the radiation of heat and perfect the combustion of the fuel: A is a combination of Parson’s grate and economiser with a Milner back; B is Nelson and Sons’ “rifle” back; C is a Galton back; D, Jaffrey’s grate. “The Manchester Warming and Ventilating Grate” (E. H. Shorland, St. Gabriel’s Works, Manchester) is somewhat similar in principle to Captain Galton’s grate, i.e. the warm fresh-air inlet is at the ceiling, and the vitiated air is carried off by the chimney, or in some instances ventilation at a lower part of the room is provided. Fig. 33 will acquaint the reader with the details: _a_, fireplace; _b_, outer wall; _c_, inner wall; _d_, smoke flue; _e_, _f_, cold-air inlets; _g_, _h_, warm-air passages; _i_, inlet for cold or warm air into room. [Illustration: 33. Shorland’s Manchester Warm-air Grate Back.] The shape of the back brick advocated by Dr. Teale (first invented by the celebrated Count Romford, to whom much is owing for the various means undertaken by him to promote the consideration of the question of improving our fire-grates and to abate the smoke nuisance) has since its discovery met with universal favour, and is coming into general use by all makers, as the expense of the stove is scarcely increased and its result in use is a most decided improvement. The actual shape or section of this brick varies with the different stove makers, but the result is the same; the brick is made to slope forward from the bottom up to about 15 or 16 in. high; at that height the top of the brick overhangs the bottom by about 5 to 6 in.; its section is appropriately defined by a maker, who likens it to a “dog’s hind leg.” Some makers shape the brick like a curved scallop-shell, inclining forward at the top; the effect is that as the heat ascends from the fire, it strikes or comes in contact with the projecting part, and rebounds or is deflected into the room; it is a similar action to that which takes place if an object, say a ball, is thrown upon a wall and comes in contact with a similar projection--it would bound off or be deflected. It would be impossible to describe all the existing improvements upon the ordinary or old form of open-fire stove (commonly known as a “register grate”), but the following are some that are tolerably well known and have a good share of favour.