Page:Willich, A. F. M. - The Domestic Encyclopædia (Vol. 3, 1802).djvu/47

"fiaces, heated with coke, char- Coal, peat, or turfj near the bot- tom of which, by means of a tap- hole, the liquid metal is discharged into furrows made in a bed of sand. The larger mass, which set-, ties in the main furrow, is called by the workmen, a sow ; and ihe smaller ones, pigs of iron. Stoves, grates, &c. are formed bf casting ladles full of the rough metal into proper moulds made of sifted sand. In this state it is called casL-iron j but, if cooled too hastily, it be- comes brittle, and is apt to crack Kke unannealed glass : it is not malleable, and is so hard as to resist the file. With a view to improve it, the raw iron is now" melted down a second time In another furnace, where a strong blast of air is im- pelled on the surface of the metal ; in consequence of which its fu- sion is considerably facilitated, and the iron concretes into a mass call- ed a loop, that is conveyed beneath a large hammer raised by the mo- tion of a water-wheel. The metal is there beaten into a thick square form, again heated so as nearly to melt it, and then forged. By re- peating this process, the iron is rendered perfectly malleable^, and at length formed into bars for sale. Lately, however, cast-iron has been reduced to a state of mallea- bility, by passing it through rollers, instead of forging it. For this va- luable improvement w'e are in- debted to Mr. Henry Cort, of Gosport, who in the year 1783, obtained a patent for preparing, welding, and w^orking various sorts of iron, by means of machinery, &c. — As, however, this specifica- tion would be intelligible only to iron manufacturers, the inquisitive reader will consult the 3d vol. of tiie Repertory of Arts, ^c. Yet iko [2^ justice requires us to observe, that the raw, or cast-iron is, by Mr. Cort's process, perfeftly freed from those impurities which are not discharged by the common me- thods of remicring this metal mai- lable } and that it has been proved by experience to be equal, and, ia some cases, superior, to the best Swedish iron. As Mr. C.'s patent is now expired, we trust it will be generally adopted at Birmingham> Carron, Colebrook-Dale, and the other iron manut'a6tories of Britain ; becau.se the metal thus treated, may not only be procured at a cheaper rate than it is sold at pre- sent, but a saving will be made of one mil /ion sterling per annum, w^hich is now paid to Sv/eden and Russia for bars, while we possess a sufficient quantity of the raw materials, which may be v/orked at home to that amount. Beside the cast ciud J'orged iron, there is an intermediate state, in w hich that metal is soft and tough. This is called steel, and is usually made from the best forged iron, by cementation with certain inflam- mable matters : some account of the process will be inserted in its alphabetical series. Iron being of such essential ser- vice for a great variety of purposes, several persc«:s have obtained ex- clusive privileges for different in- ventions to which it may be ap- plied. — Among these, the patent granted to Mr. Jonathan- Tay- lor (now expired) for casting oval- bellied pots, and nealing, turning, and finishing the same, &c. ; then Mr.RowLANDBuRDON's, in 17<)5, for a method of making, uniting, and applying cast-iron blocks, to be substituted for key-stones, ia the construftion of arches ; and Mr, John Wilkinson's^ in 1794, for