Fluor spar occurs subordinate to metallic veins; as to those of lead, in Derbyshire; of tin, in Saxony and Bohemia; but it is found also in masses or veins, either in crystalline rocks, associated with quartz, heavy spar, &c., as in Auvergne, Forez, Vosges, Norberg in Sweden; Norway; Petersburg; near Hall; Gourock, in Scotland, &c.; or among secondary limestones, slates, and sandstones, in Derbyshire, Cumberland, Cornwall, and New Jersey. It exists also in the amygdaloids of Scotland, and in the volcanic products of Monte Somma at Vesuvius. The variously coloured specimens, called Derbyshire spar, are worked upon the turning lathe into vases and other ornamental objects.
FLUX, (Eng. and Fr.; Fluss, Germ.) signifies any substance capable of promoting the fusion of earths or metallic ores by heat. White flux is the residuum of the deflagration in a red hot crucible, of a mixture of two parts of nitre, and one of cream of tartar. It is in fact merely a carbonate of potash. Black flux is obtained when equal parts of nitre and tartar are deflagrated. It owes its colour to the carbonaceous matter of the tartaric acid, which remains unconsumed; the quantity of nitre being too small for that purpose. The presence of the charcoal renders this preparation a convenient flux for reducing calcined or oxidized ores to the metallic state. Limestone, fluor-spar, borax, and several earthy or metallic oxides are employed as fluxes in metallurgy.
FLY POWDER; the black coloured powder obtained by the spontaneous oxidizement of metallic arsenic in the air.
FODDER; is the name of a weight by which lead and some other metals are sold in this country. It varies in its amount in different parts of the kingdom; being in Northumberland estimated at 21 cwts., and in other counties 22, 23 or even more cwts.
FONDUS; is the name given by the French to a particular style of calico printing resembling the rainbow, in which the colours are graduated or melted (fondus) into one another, as in the prismatic spectrum. See [Paper hangings], for a description of the process.
FORGE; (Eng. and Fr.; Feuer, Germ.) is the name either of the furnace, where wrought iron is hammered and fashioned with the aid of heat, or the great workshop where iron is made malleable. The former is called a smith’s forge, the latter a shingling mill. See [Iron].
[Fig. 466.] represents a portable truck forge of a very commodious construction. A is the cylindric leather bellows, pressed down by a helical spring, and worked by means of the handle at B, which moves the horizontal shaft C, with its two attached semicircular levers and chains. D, is the pipe which conducts the blast to the nozzle at E. The hearth may be covered with a thin fire-tile or with cinders. F is a vice fixed to the strong rectangular frame. This apparatus answers all the ordinary purposes of a smith’s forge; and is peculiarly adapted to ships, and to the execution of engineering jobs upon railways, or in the country. The height is 2 feet 6 inches; the length is 2 feet 9 inches; the width 2 feet. Weight about 2 cwt.
FORMIATES; are compounds of [formic acid], with the salifiable bases. Many of them are susceptible of crystallization.