There is one important circumstance respecting Chimney Fire-places, destined for burning coals, which still remains to be farther examined;--and that is the Grate. Although there are few grates that may not be used in Chimneys constructed or altered upon the principles here recommended, yet they are not, by any means, all equally well adapted for that purpose.--Those whose construction is the most simple, and which of course are the cheapest, are beyond comparison the best, ON ALL ACCOUNTS.--Nothing being wanted in these Chimnies but merely a grate for containing the coals, and in which they will burn with a clear fire;--and all additional apparatus being, not only useless, but very pernicious, all complicated and expensive grates should be laid aside, and such as more simple substituted in the room of them.--And in the choice of a grate, as in every thing else, BEAUTY and ELEGANCE may easily be united with the MOST PERFECT SIMPLICITY.--Indeed they are incompatible with every thing else. In placing the grate, the thing principally to be attended to is, to make the back of it coincide with the back of the Fire-place;-- but as many of the grates now in common use will be found to be too large, when the Fire-places are altered and improved, it will be necessary to diminish their capacities by filling them up at the back and the sides with pieces of fire-stone. When this is done, it is the front of the flat piece of fire-stone which is made to form a new back to the grate, which must be made to coincide with, and make part of the back, of the Fire-place.-- But in diminishing the capacities of grates with pieces of fire-stone, care must be taken not to make them TOO NARROW. The proper width for grates destined for rooms of a middling size will be from six to eight inches, and their length may be diminished more or less, according as the room is heated with more or less difficulty, or as the weather is more or less severe. --But where the width of a grate is not more than five inches, it will be very difficult to prevent the fire from going out. It goes out for the same reason that a live coal from the grate that falls upon the hearth soon ceases to be red hot;--it is cooled by the surrounding cold air of the atmosphere.-- The knowledge of the cause which produces this effect is important, as it indicates the means which may be used for preventing it. --But of this subject I shall treat more fully hereafter.