The =shape of the grate= is important. The width of the back of the grate should be about one-third that of the front, the sides sloping out towards the front of the recess. The depth of the grate from before backwards should be equal to the width of the back. The sides and back of the fire-place must be made of fire-brick, thus ensuring the heat being retained in the grate. And finally, the chimney throat must be contracted so as to ensure more complete combustion. The =chief objections to an open fire-place= are (1) the great waste of fuel involved, even after the improvements indicated have been carried out. (2) The unequal heating at different distances from the fire. (3) The smoke and dust always produced to some extent, from accidental smoking of the fire, or from the escape of ashes. (4) The trouble involved in frequently replenishing the fire. (5) The cold draughts produced by the currents of air towards the chimney. These travel chiefly along the floor, when, as is commonly the case, the space between the bottom of the door and the floor forms the chief place for the entry of fresh air.
Many patents have been brought out for the =introduction of the fuel at the lowest part= of the fire. The uppermost part of the fuel being first burnt, and the remainder attacked from above, the smoke is consumed in passing through the red part of the fire. Thus a comparatively smokeless fire is produced, and the amount of heat evolved is greatly increased. So far none of these have been altogether satisfactory. The production of _a comparatively smokeless fire_ is a great boon. =Smoke= means so much unburnt fuel, and not only so but the sooty particles float about in the atmosphere, rendering it impure, and changing comparatively harmless mists into town fogs, which are loaded with soot and the products of combustion, and do incalculable mischief to health and property. The prevention of this =smoke nuisance= demands more consideration than it has yet received. The Public Health Acts constitute the emission of black smoke from the chimneys of manufacturing premises a nuisance; and manufacturers can if they use proper boilers, especially those in which mechanical stokers are employed, almost completely obviate this nuisance. The great principle is to prevent the escape of smoke before it is completely burnt. This may be accomplished by careful stoking, by keeping the unburnt coal at the front of the fire, and by ridges exposing the smoke to red-hot fire-clay before it escapes. In domestic fires, gas is gradually replacing coal for cooking, with a corresponding reduction of the smoke-nuisance.