IRON 



low 



out. In order to tin the plates, they are immersed in a bath of melted tin. the sur- 

 face of which is covered with tallow or palm-oil; when sufficiently covered, they 

 are transferred to the brusher on the left-hand side of the tinner ; he passes a rough 

 brush rapidly over each side of the plate, whereby the superfluous tin is removed ; he 

 then plunges the plate again into the tin-bath, and passes it on to his left hand neigh- 

 bour, who gives it a washing. The plate passes through several hands before it is 

 dried. Great skill is required in the tinning process ; nevertheless, in a well-conducted 

 work the wasters do not amount to more than 10 per cent. ; a small percentage of 

 which are so bad as to require to be re-worked. Great care is taken to avoid waste, 

 tin being worth about 150/. per ton. A box of 225 sheets of tin plates, 10 inches 

 by 14, consumes about 8 Ibs. of tin. See TIN PLATE. 



On the Continent, iron is frequently refined from the cast metal of the blast-fur- 

 naces by three operations, in three different ways.^ In one, the pig being melted, 

 with aspersion of water, a cake is obtained, which is again melted in order to form 

 a. second cake. This being treated in the refinery fire, is then worked into a bloom. 

 In another system, the pig-iron is melted and cast into plates : these are melted anew 

 in order to obtain crude balls, which are finally worked into blooms. In a third mode 

 of manufacture, the pig-iron is melted and cast into plates, which are roasted, and 

 then strongly heated, to form a bloom. 



The French fusible ores, such as the silicates of iron, are very apt to smelt into 

 white cast iron. An excess of fluxes, light charcoals, or too strong a blast, produce the 

 same results. A surcharge of ores which deranges the furnace and affords impure 

 slags mixed with much iron, too rapid a slope in the boshes, too low a degree of heat, 

 and too great condensation of the materials in the upper part of the furnace ; all tend 

 also to produce a white cast iron. In its state of perfection, white cast iron has a 

 silver colour, and a bright metallic lustre. It is employed frequently in Germany for 

 the manufacture of steel, and is then called steel floss, or lamellar floss, a title which 

 it still retains, though it be hardly silver- white, and has ceased to be foliated. When 

 its colour takes a bluish grey tinge, and its fracture appears striated or splintery, or 

 when it exhibits grey spots, it is then styled flower floss. In a third species of white 

 cast iron we observe still much lustre, but its colour verges upon grey, and its texture 

 is variable. Its fracture has been sometimes compared to that of a broken cheese. 

 This variety occurs very frequently. It is a white cast iron, made by a surcharge of 

 ore in the furnace. If the white colour becomes less clear and turns bluish, if its 

 fracture be contorted, and contains a great many empty spaces or air-cells, the metal 

 takes the name of cavernous floss or tender floss. The whitest metal cannot be em- 

 ployed for casting. When the white is mixed with the grey cast iron, it becomes 

 riband or trout cast iron. 



TheGerman Refining Forge. Figs. 1283, 1284, represent one of the numerous refinery 

 furnaces once common in the Hartz. The example is taken from the Mandelholz works, 

 in the neighbourhood of Elbingerode. Fig. 1284 is an elevation of this forge. B is the 



1283 



1284 



refinery hearth, provided with two pair of bellows. Fig. 1283 is a vertical section, 

 showing particularly the construction of the crucible or hearth in the refinery forge D. 

 c is an overshot water-wheel, which gives an alternate impulsion to the two bellows a b 

 by means of the revolving shaft c, and the cams or tappets dfeg. 



D, the hearth, is lined with cast-iron plates. Through the pipe I, cold water may be 

 introduced, under the bottom plate m, in order to keep down, when necessary, the tern- 



