CHIMNEY (Fr. cheminee, related to Latin caminus, oven), an upright structure of stone, brick, etc., enclosing one or mere flues or pas sages through which smoke and gas from the fire in a stove, furnace or fireplace may escape into the open air. Originally the term chimney included both the fireplace and the shaft. How far the Greek and Roman archi tects were acquainted with the construction of chimneys such as we have is a matter of dis pute. That kitchens and baths were provided with chimneys appears certain, but how far other apartments were so provided is doubtful. An ancient mosaic found in Algeria, and repre senting a Roman country mansion, shows chim ney stacks projecting above the roof. Of course in southern Europe fires are less neces sary than in northern Europe. Chimneys re quire much attention to make them secure and prevent their smoking, so great an annoyance to domestic comfort. It seems at present to be acknowledged that it is much better to exclude the cold, damp air from the flues, by narrow ing the aperture at the top, than to give larger vent to the smoke at the risk of admitting a quantity of air to rush down the flue. For this reason chimney pots are of great use. The longer a chimney the more perfect is its draft, because the tendency of the smoke to draw up wards is in proportion to the difference of weight between the column of air included in a chimney, and an equal column of external air; and the heated air in the chimney being lighter than the external air, the longer the chimney is the greater is this difference. Short chimneys
are liable to smoke, and fireplaces in upper stories are therefore more apt to smoke than those in the lower ones. Two flues in the same chimney should not communicate with each other short of the top. In manufactories tali chimneys are built for the purpose of carrying away the great quantities of smoke, which would otherwise be highly deleterious to the health of those living in the neighborhood. In chemical works, especially, these chimneys are sometimes built to an immense height. Such chimneys are constructed from the inside, by which the expense of the scaffolding is saved.. The shafts of most early chimneys were round and the chimneys contained but one shaft each, from the side of which the smoke generally issued, the top being crowned. In France and Italy chimneys came to form a decorative part of the national architecture.