BRASS 



467 



coals ; into this crucible the contents of four of the melting pots are poured ; the dross 

 is raked out with an iron scraper. As soon as the melting pot is emptied, it is im- 

 mediately re-charged in the manner above described, and placed in the furnace. The 

 surface of the melted brass is swept \vith the stump of a broom, and then stirred about 

 with the iron rake, to bring up any light foreign matter to the surface, which is then 

 skimmed with a little scraper ; the crucible is now seized with the casting tongs, and 

 emptied in the following way : 



The mould or form for casting sheet brass consists of two slabs of granite, a a, fgs. 

 212, 213. These are 6J feet long, 3 feet broad, 1 foot thick, and, for greater security, 



girt with iron bands, b b, 2 inches broad, 1 thick, and joined at the four corners with 

 bolts and nuts. The mould rests upon an oaken block, c, 3 feet long, 2|th broad, and 

 l thick, which is suspended at each end upon gudgeons, in bearing blocks, placed 

 under the foundry floor, d d, in the casting pit, e e. This is lined with bricks ; and 

 is 6| feet long, 5 broad, and 2 deep ; upon the two long side walls of the pit are 

 laid the bearing blocks which support the gudgeons. The swing blocks are 10 inches 

 long, 18 inches broad, 15 inches thick, and somewhat rounded upon their back edge, 

 so that the casting frame may slope a little to the horizon. To these blocks two cross 

 wooden arms, //, are mortised, upon which the under slab rests freely, but so as to 

 project about 5 inches over the block backwards, to secure an equipoise in the act of 

 casting, g g are bars, placed at both of the long sides, and one of the ends, between 

 the slabs, to determine the thickness of the brass plate. Upon the other slab the gate 

 h is fastened, a sheet of iron 6 inches broad, which has nearly the shape of a parallel 

 trapezium (lozenge), and slopes a little towards the horizon. This serves for setting 

 the casting pot upon in the act of pouring, and renders it more convenient to empty. 

 The gate is coated with a mixture of loam and hair. The upper slab is secured to 

 the under one in its slanting position by an armour or binding. This consists of 

 tension bars of wood, i, k, I, m, of the iron bars n, (3 to 3J inches broad, 1-J inch thick, 

 see the top view, fig. 213) of a rod with holes and pins at its upper end, and of the 

 iron screw spindle o. The mode in which these act may be understood from inspec- 

 tion of the figure. In order to lift the upper slab from the' under one, which is 

 effected by turning it round its edge, a chain is employed, suspending two others, 

 connected with the slab. The former passes over a pulley, and maybe pulled up and 

 down by means of a wheel and axle, or the aid of a counterweight. Upon each of 

 the two long sides of the slab are two iron rings, to which the ends of the chains 

 may bo hooked. The casting faces of the slab must bo coated with a layer of finely 

 ground loam ; the thinner this is the better. 



When calamino is employed, % cwt. of copper, J cwt. of calamine, and |rd the volume 

 of both of charcoal mixed, are put into seven crucibles, and exposed to heat during 

 11 or 12 hours ; the product being from 70 to 72 Ibs. of brass. 



Brass-Plate Boiling. At Hegermiihl there are two re-heating or annealing furnaces, 

 one larger, 18 feet long, and another smaller, 8 ; the hot chamber is separated from 

 the fireplace by iron beams, in such a way that the brass castings are played upon by 

 the flames on both their sides. After each passage through the laminating rolls, they 

 are heated anew, then cooled and laminated, until they have reached the proper length. 

 The plates are smeared with grease before rolling. 



Fig. 214 shows the ground plan of the furnace and its railway; fig. 215, the cross 

 section ; and fig. 216 the section lengthwise; a a, the iron way bars or rails upon 

 the floor of the foundry for enabling the wheels of the waggon to move rapidly back- 

 wards and forwards ; b b, the two grates ; c c, the ash-pits ; d d, the fire beams ; 



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