In closing the chimney, it will be necessary to leave a square opening for a trap-door, by which a chimney-sweeper may ascend; and which may be made of slate or tin, and be placed in such a direction, that, by being turned up against the back of the chimney when open, it may close the vacancy behind the false back, and discharge the soot which falls in sweeping upon the hearth. It will also be convenient to have a small hole, about five or six inches square, cut through near the ceiling into the funnel, and provided with a shutter which, being occasionally opened, may carry off the heated air of the room, as well as the smoke of tobacco, &c.
For a farther account of the manner of using this fire-place, the advantages attending it, answers to cavils and objections, together with instructions for bricklayers in fixing it, we refer the reader to Dr. Franklin's "Experiments and Observations on Electricity," &c. 4to. 10s. 6d. 1769.
FIRE-PROOF, a term which expresses the effect of certain applications to combustible substances, especially in buildings, with a view to prevent them from being reduced to ashes. This important object may also be attained by means of erecting whole houses with a mixture of earth and clay, well beaten together, as devised by M. Cointereau, in his "School of Architecture," (8vo. Hildburghausen, 1793, in German); an ingenious work that, we believe, was originally published in the French language. Although we are persuaded that such a method of raising edifices is not only durable and economical, but the buildings also are thus effectually secured from fire, yet it will be of great importance to afford security to combustible dwellings already erected. For this useful purpose, M. Boulard, architect, at Lyons, has lately discovered a very simple remedy, attended with little expence or trouble, and admirably calculated to defend wooden materials from being consumed by flames, though exposed to their influence for two hours. After many tedious experiments, he found that a solution of pot-ash is the most efficacious liquid for resisting the action of fire, longer than any other fluid. This observation induced him to apply that substance in a kind of paint or coating on wood, which was completely rendered fire-proof, in the following easy manner: Dissolve such a quantity of pot-ash in cold water as that fluid is capable of holding in solution, wash or daub with it all the boards, wainscoting, shingles, &c. which are intended to be prepared. Then dilute the same liquor with a little water; add to it such a portion of fine yellow clay as will make the mixture of the consistence of the common paint employed on wood; and lastly, stir ihto it a small quantity of flour-paste, in order to combine both substances intimately. With this mixture all wooden materials ought to be coated three or four times, similar to painted work. Thus, wood will be secured from the action of fire, though exposed to it for a time exceeding two hours; but the greatest advantage of this excellent preparation consists in the circumstance, that it prevents the wood from ever bursting into flames.—M. Boulard remarks, that 20lbs. of sifted yellow clay, 112lb. of flour for making the paste,
