IRON. 



finery, except in tke hearth being more like the fmith's 

 forge. 



Fig. 5. exhibits tongs for taking the balls from the fur- 

 nace to the hammer ; and /f^. 7. an iron ladle, employed to 

 throw water into the puddling furnace, to oxydate the 

 iron. 



Fig. 8. the face of th? (lamping hammer, which is made 

 to be taken out occafionally. 



Fig. 9. the face of the hammer employed for drawing out 

 the bars : b is the part ufed to extend the bars in length 

 with more expedition ; the part a being employed for 

 fmoothening or finilhing the bar. 



Figs. 10. and 11. are different views of the balling fur- 

 nace : a is the fire-grate ; b, the hole where the fuel is ad- 

 mitted ; d d, the roof made of fire-brick ; c, the door 

 through which the balls are admitted; sxiAbb, the hearth 

 on which the balls are laid to be heated, by the flame which 

 13 carried by the draught of the chimney G. This furnace 

 is bound on all fides by bars of iron, fecured by bolts. 



The puddling furnace is fo nearly Cmilar to this, as not 

 to require a feparate diawing. The hearth is more concave 

 oppofite the door, for the purpofe of containing the metal 

 which is liquid, previous to its alTuming its malleable (late. 

 The door of this furnace, for heating the balls, confifts of a 

 frame of wrought iron, containuig fire-bricks, to prevent 

 the efcape of heat. It (luits and opens upon the hole, by 

 being attached to the end of a lever ; its weight being coun- 

 terpoifed at tke other end. Seejf^. i. Plate IV. where 

 R is the lever ; b, the door ; and f, the part by which it is 

 raifed. 



The door of the puddling furnace confids of a folid piece 

 of cad-iron, about 3 inches thick, having a fmall hole 

 through it, for the purpofe of infpecling the procefs, and 

 introducing the puddling inftruments. 



Plate III. fgs. I. and 7. are views of the reverberatory 

 furnace, ufed by the call-iron founders, for melting large 

 quantities of metal at once. This furnace, like the lall, is 

 heated with flame from its fire place a, the fuel bemg in- 

 troduced at B ; c d K 3. doping hearth, on which the pigs 

 or other pieces of metal are laid ; b, the door where it is in- 

 troduced ; and g, the chimney. The melted metal runs 

 down to the part 0, where it is accumulated, and is let out 

 at f; or a door may be opened at e above, and the melted 

 metal carried out in ladles, to be poured into the moulds. 



Fig. 2. is a feclion of a cupola, in which a is the interior 

 of the furnace containing the metal and cokes ; e, the tap 

 hole;, b, the nofe-pipe ; d, a leathern pipe connefting the 

 air-pipe, which comes from the blowing cylinder, with the 

 fame ; e, a (Inp-cock to regulate or turn off the blafl. 



It generally confifts of four plates of caft-iron, firmly 

 bolted together ; the interior being lined with fire-brick. 

 Tliis furnace is generally employed for the bed kind of 

 work, and will melt many charges in a day, according to 

 the nature of the metal expofed in it. 



Plate YV.Jigi. I. and 2. are two views of forge-hammer 

 machinery, ercfted by the celebrated Smeaton. A is the 

 water-wheel; H, a fly-wheel ; D, wheel-work to open the 

 ftiuttle by a little at once, for the purpofe of adjulling the 

 quantity of water; F, a cog-v/heel to give motion to the 

 wheel G ; at the other end, I, are a number of cogs, which 

 lift the hammer K, _fig. 2, by paffing under its fliaft, or 

 helve, as it is fomctimes termed ; L, a large beam of wood 

 inferted into the pod M, and paifing horizontally over the 

 hammer. Into the pods, M and N, is inferted a piece of 

 a(h-timbcr 0, againd which the hammer K drikes in its 

 afcent, and by its elafticity re-afts upon the hammer, and 



gives it a greater defcending Telocity than would be pro- 

 duced by gravity alone. Q is a number of heavy pieces of 

 metal laid upon the beam L, to increafe its vij inertia, and 

 will, in confequence, receive lefs motion from the hammer. 

 (See Mill-Work and Water-Wheel.) The hammer 

 here defcribed has been much improved, fo far as regards 

 the fpring at 0. 



That already mentioned in the plate is much preferred. 

 The whole of it is made of cad-iron, and its weight is about 

 3J cwt. It ads fimply by its gravity ; its extra force, 

 therefore, over the common one, confifts in its greater 

 quantity of matter. It is made exceedingly malTive near 

 the centre of motion, by which means its centre of ofcilla- 

 tion is thrown nearer to that point, and it confequently de- 

 fcends with greater velocity. Although this is an advan- 

 tage with refpeft to the number of drokes in a given time, 

 it is a difadvantage in another way ; fince the centre of ofcil- 

 lation is alfo the centre of percuflion, or the point where 

 the greateft ftroke is made. Could the velocity be obtained 

 without this evil, the advantage would be material. See 



TiLTIXG-MlLL. 



Iron, in the Materia Medico, is faid to have greater virtues 

 than any of the other metals, which is not to be wondered at, 

 as being the only one that is in a manner foluble in the human 

 body. All the other metals, whether hard or loft, poifonous 

 or falutary, nay even fluid mercury itfelf, fwallowed in their 

 crude date, pafs out of the body again unaltered ; but this 

 is not the cafe with iron, its crude fihngs are often taken as 

 a medicine, and are always fo much ailed upon by their 

 juices, as to produce confiderable effetts. It is fo eafily 

 wrought upon out of the body alfo by fire, and by different 

 mendruums, that it becomes an aperient or aftrmgent, as it 

 is differently treated ; and is, under proper management, 

 greatly fuperior to all other medicines in chronic cafes. 



Iron or ileel, that is, the ftrrum or chalyhs, may be em- 

 ployed indifferently, as CuUen fuggefts, in the preparation 

 of the rubigo ; but he thinks that, upon the whole, the 

 preference is due to the iron in ite foft malleable ftate, or in 

 that which is called " forged iron." As iron, fays this me- 

 dical writer, like all other metals, in its fohd and entire ftate, 

 is not aftive with regard to our bodies, without being cor- 

 roded or diffolved by faline matters, he is of opinion, that 

 it is rendered adlive only by being combined with acids. It 

 has indeed been common to give the entire metal, brought by 

 filing into a fine powder, and with very good effefts, as a 

 medicine. But this he does not confider as an exception to 

 his general rule ; becaufe he is perfuaded that there is con- 

 dantly prefent in the human llomach a quantity of acid ca- 

 pable of diffolving iron ; and as a proof of it he alleges 

 that he never knew iron given in its metaUic or flightly cor- 

 roded ftate, without producing a blacknefs in the dools, 

 which affords a prefumption of a previous folution of the 

 iron in acids. As this combination with acids is ncceffary, 

 phyficians and chemifts have diverfified this combination in 

 a variety of ways ; Dr. Cullen obferves, that he has not 

 known a preparation of iron for the purpofe of medicine, 

 that has not been prepared by a combination with acids, or 

 by bringing the iron into a (late that rendered it readily fo- 

 luble by the acid of the llomach, and Dr. Lewis very pro- 

 perly remarks, that Pruffian blue, though truly containing a 

 quantity of iron, as it is not foluble in any acid, is the lead 

 promifing of all the medicinal preparations. 



Its virtues internally were not unknown to the ancients ; 

 Diofcorides attributes both an aftringency and aperiency to 

 it, and prefcribes it in hxmorrhages. He alfo recommends 

 its ruft, or crocus marlis, in fuppreflions of the mtnfes; 



though 



