&c.
FUNG′I. In botany, a natural order of cellular plants, producing their fructification in the air; growing in or upon decaying or living organic substances, and nourished through their vegetative structure called the spawn or mycelium. Fungi have very variable properties. Some are medical, others edible, others are deadly poisons. The various diseases of plants known as blight, mildew, rust, smut, vine-mildew, potato-disease, ergot, &c., are either caused by or accelerated by the agency of fungi. See Agaric, Mushroom, &c.
FUR′NACE. An enclosed fireplace for obtaining a high degree of heat. Furnaces vary much in construction and size, according to the particular manufacture in which they are employed. They may be broadly divided into two classes—WIND-FURNACES and BLAST FURNACES. In the former a high temperature is produced without the aid of bellows by means of a powerful draught. In the latter heated air is blown in through a pipe or pipes at the bottom. For many metallurgic and large chemical operations REVERBERATORY FURNACES are employed. A furnace of this kind is usually long, with a low roof to keep down the flame and hot air upon the ‘hearth’ or space between the fireplace and the flue.[322] For the smaller operations in chemistry, a variety of furnaces have been invented, and the introduction of coal-gas as a fuel by Develle, Griffin, Gore, Fletcher, and others, has wrought a complete change in the arrangements of the laboratory. The GAS-FURNACES of Mr J. J. Griffin are adapted for almost every operation performed by the aid of heat. Those more recently introduced by Mr W. Gore are very compact and portable, and will rapidly produce a ‘white heat,’ without the help of bellows or high chimney, by means of ordinary coal-gas and atmospheric air. The first and smallest size consumes 33 cubic feet of gas (value seven farthings) per hour, and is suitable for assayers, jewellers, analytical chemists, experimentalists, dentists, and others. It is capable of fusing eight ounces of copper or six ounces of cast iron, copper begins to melt in it in about twelve minutes from the time of lighting. The second-sized one consumes about twice that quantity of gas, is suitable for manufacturing jewellers generally, and for a great variety of practical persons who require to melt small quantities of gold, silver, copper, german silver, brass, cast iron, glass, and other substances, or require a small crucible heated to high temperatures. It is capable of melting 45 ounces of copper, or 40 ounces of cast iron, and with its heat up it melts one pound of copper in eight minutes; copper begins to melt in about twenty minutes from the time of lighting.
[322] For an illustration of this kind of furnace, see Sodium, Carbonate of.
Fletcher’s[323] Universal Furnaces for high temperatures, which are said to require neither blast nor attention, are intended for laboratory purposes, enamel burning, heating soldering irons, and for jewellers’ and dentists’ work. These furnaces are made in two distinct types; one with a perforated cover to the crucibles and muffles to attain the maximum heat; the other with a slide chimney and a double lid over the crucible.
[323] Manufactured by Thos. Fletcher, Museum Street, Warrington.
The power and rapidity of working depend in each case on the length of the chimney used. A furnace with a four-feet chimney will melt a crucible of cast-iron in thirty-five minutes; a furnace with an eight-feet chimney will melt the same quantity of iron in about twenty minutes, starting with the furnace cold. The stove with the side chimney, although more convenient in use, is slower in working, taking about twice as long to obtain the same temperature.
The following are varieties of Fletcher’s Universal Furnace:—
1. Small Laboratory Furnace for crucibles, with nickel-plated burner tubes. This takes crucibles up to 21⁄2 by 21⁄4 inches outside, and with a three-feet chimney, as supplied with the furnace, will, it is stated, melt copper, gold, silver, &c., in about ten minutes, or cast-iron in thirty-five minutes from the time the gas is lighted. Small muffle fittings, with muffles 21⁄4 by 3 by 21⁄2 inches inside, can be supplied with this furnace.
2. Small Crucible Furnace, with fixed chimney. This furnace is more especially designed for gold, silver, copper, &c., and, as sent out with a four-feet chimney and a single lid, is amply powerful, and practically of a very convenient form.