The definition of a flux is according to Morfit, a substance usually saline, mixed with other bodies in order to promote their fusion, and to render them more soluble in water and acids. Mitchell, in his Manual of Assaying, makes two classes of fluxes—metallic and non-metallic. Under the head of non-metallic fluxes, he places silica, lime, magnesia, alumina, silicates of lime and alumina, glass, borax, fluor-spar, carbonate of potash, carbonate of soda, niter, common salt, black flux and its equivalents, argol, salt of sorrel (binoxal-ate Qjf potash), and soap. In the class of metallic Htases he places litharge, ceruse (carbonate of lead), glass of lead (silicate of lead), borate of lead, sulphate of lead, oxide oi copper, and oxides of iron. We have found this classification in no other work and we see no good basis for it. Oxides of metals are found in both classes, and many substances which might properly be considered as fluxes are not enumerated. Matthiessen in his definition of an alloy appears to us, to have given the entire philosophy of the action of fluxes. He defines an alloy as a solidified solution of one metal in another. If this definition be accepted—and we see no reason for rejecting it—a metal which forms alloys with one of more difficult fusibility may be considered as a flux. A flux in this view is a solvent, which acts together with heat to reduce a solid to a liquid state. The limits of this article will not admit of many illustrations of this definition of a flux, but one or two may be mentioned, premising that a flux most generally enters into chemical combination with the substance dissolved. The use of borax in welding iron is one of the most common examples. The object to be attained in this case is the bringing Of the surfaces of two pieces of iron so near together that cohesive attraction may unite them into one piece. This intimate approach can not be attained so long as the oxide which forms in the heating process remains upon the surfaces of the iron. The presence of borax prevents oxidation to a great extent by flowing over the surfaces; at the same time it liquefies whatever oxide is formed, so that the surfaces may be brought closely together and cohesion may take place. Sand is used in welding iron to iron for a similar purpose. Mercury dissolves gold even at ordinary temperatures; the use of heat does not therefore alter the rationale oi the action of fluxes, it only weakens the cohesive power of the substance to be fluxed so that the solvent action may readily take place. It therefore must be concluded that when a flux is used the melting of substances is not a process of simple fusion, but also one of solution. BrlckmaJfliis In Scotland, A writer in the Scotsman, on manufacturing in native clays, says: The number of bricks made in Britain in the year 1802 was 714 millions; in 1840 it was 1, 725 millions; and in 1850, the year in which j;he duty was abolished, it was 1,5631 millions. The numbkr of bricks, made in Scotland annually was 15 J millions in 1802, and 47f millions in 1840. If the great increase in railway and other work% the rapid enlargement of towns, and other recent causes ladling to a more extensive use of bricks be considered, the nuniber now made in Scotland cannot be less than 300 millions a year. There are in Scotland 123 manufactories of bricks, tiles, and articles of a similar nature; and in connection with these from 4,000 to 5,000 persons are employed. The manufactories are widely scattered Over. the country, tho farthest north being at Banff, ard the flattest Wtk at JMbeBttie; bat the great 307 r number are in Lanarkshire and Pifeshire, i n which counties valuable beds of fire-clay exist. The most extensive manufactory is that of the Garnkirk Fire-clay Company, situated. on the Caledonian Eailway line, about six miles east from Glasgow. The company was originally formed to work coal, but, finding that extensive seams of fire-clay existed on their property, they took to manufacturing that material, which now almost exclusively engages their attention. The principal seam of clay is 7ft. in thickness, and lies at the average depth of twenty-eight fathoms. Its quality is considered equal to that of the best Stourbridge clay. The manufactory covers upwards of six acres of ground, and is surmounted by thirty tall brick chimneys, which give it an extraordinary appearance. Eaw material is brought in, and finished goods are sent out, by branch railways, the traffic of which never ceases, from one weeks end to another. Two hundred tuns of clay, and about an equal weight of coal, are used every day. Upwards of 300 men and boys are employed by the company, and these are aided by three steam engines with an aggregate of 150 horse-power. This is exclusive of the power employed to bring the clay and coal out of the pits. The clay is of a dark color, owing to the presence of a small proportion of bituminous matter; but when that is expelled by the action of fire, only silica and alumina remain, and it is the presence of these substances in certian proportions that decide the value of the clay. As it comes from the pits the clay is entirely devoid of cohesion or plasticity; and in order to bring it into working condition it has to be ground very fine, and then mixed with water. Several powerful mills are used for this purpose. They consist of great iron rollers, which travel round a circular trough, and pass over the clay. Several hundredweights of material are operated on at once, the time for which the grinding is continued depending on the quality of -,the articles to be produced.
This article was originally published with the title "What is a Flux?"