1146. _To improve Chimney Fire-places, and increase the Heat, by a proper attention to the Setting of Stoves, Grates, &c._--The best materials for setting stoves or grates are fire-stone and common bricks and mortar. Both materials are fortunately very cheap. When bricks are used, they should be covered with a thin coating of plaster, which, when it is dry, should be white-washed. The fire-stone should likewise be white-washed when that is used; and every part of the fire-place, which is not exposed to being soiled and made black by the smoke, should be kept as white and clear as possible. As _white_ reflects more heat, as well as more light, than any other color, it ought always to be preferred for the inside of a chimney fire-place; and _black_, which reflects neither light nor heat, should be more avoided. 1147. _To cure Smoky Chimneys._--Put on the top of the chimney a box, in each of whose sides is a door hanging on hinges, and kept open by a thin iron rod running from one to the other, and fastened by a ring in each end to a staple. When there is no wind, these doors are at rest, and each forms an angle of 45 degrees, which is decreased on the windward side in proportion to the force of the wind, and increased in the same ratio on the leeward side. If the wind be very strong, the door opposed to the wind becomes close, while the opposite one is opened as wide as it can be. If the wind strikes the corner of the box, it shuts two doors and opens their opposites. This scheme has been tried with success in a chimney which always filled the room with smoke, but which, since adopted, has never smoked the room at all. The expense is trifling, and the apparatus simple. 1148. _A Preparation to preserve Wood from catching Fire, and to preserve it from Decay._--A member of the Royal Academy at Stockholm says, in the memoirs of that academy, "Having been within these few years to visit the alum mines of Loswers, in the province of Calmar, I took notice of some attempts made to burn the old staves of tubs and pails that had been used for the alum works. For this purpose they were thrown into the furnace, but those pieces of wood which had been penetrated by the alum did not burn, though they remained for a long time in the fire, where they only became red; however, at last they were consumed by the intenseness of the heat, but they emitted no flame." He concludes, from this experiment, that wood, or timber, for the purpose of building, may be secured against the action of fire, by letting it remain for some time in water, wherein vitriol, alum, or any other salt has been dissolved, which contains no inflammable parts.