6C2 GLASS 



thence derives sufficient heat to effect in part, if not wholly, the annealing of the pots, 

 which are always deposited there a long time before they are used. Threo of these 

 arches, exclusively appropriated to this purpose, are called pot-archos. The fourth 

 is called the arch of the materials, because it serves for drying them U-t'oiv they are 

 founded. Each arch h;is, moreover, a principal opening called the throat., another 

 called bonnard, by the French workmen, through which fire may bo kindled in the 

 arch itself, when it was thought to be necessary for the annealing of the pots ; a 

 practice now abandoned. The duration of a furnace is commonly a year, or at most 

 14 months ; that of the arches is 30 years or upwards, as they are not exposed to so 

 strong a heat. 



In the manufacture of plate -glass, two sorts of crucibles are employed, called the 

 pots and the basins (cuvettes). The first serve for containing the materials to be 

 founded, and for keeping them a long time in the melted state. The cuvettes receive the 

 melted glass, after it is refined, and decant it out on the table to be rolled into a plate. 

 Three pots hold liquid glass for six small basins, or for three large ones, the latter being 

 employed for making mirrors of great dimensions, that is, 100 inches long and up- 

 wards. Furnaces have been constructed with 6 pots and 12 cuvettes, 8 of which 

 are small and 4 large ; and cuvettes of three sizes are made, called small, middling, and 

 large. The small are perfect cubes, the middling and the large ones are oblong pa- 

 rallelepipeds. Towards the middle of their height, a notch, or groove, two or three 

 inches broad, and an inch deep, is left, called the girdle of the cuvette, by which part 

 they are grasped with the tongs, or rather are clamped in the iron frame. This framo 

 goes round the four sides of the small cuvettes, and may be placed indifferently upon 

 all their sides ; in the other cuvettes, the girdle extends only over the two large sides, 

 because they cannot be turned up. See m T, fig. 1102. 



The pot is an inverted truncated cone, like a crown-glass pot. It is about 30 inches 

 high, and from 30 to 32 inches wide, including its thickness. There is only a few 

 inches of difference between the diameter of the top and that of the bottom. The 

 bottom is three inches thick, and the body turns gradually thinner till it is an inch at 

 the mouth of the pot. 



The large building or factory, of which the melting furnace occupies the middle 

 space, is called the halle in French. At Ravenhead in Lancashire it is called the 

 foundry, and is of magnificent dimensions ; its length is 339 feet, and its breadth 155. 

 The famous halle of St. Gobain is 174 feet by 120. Along the two side-walls of the 

 halle, which are solidly constructed of hewn stone, there are openings like those of 

 common ovens. These ovens, destined for the annealing of the newly cast plates, 

 bear the name of carquaises. Their soles are raised two feet and a half above the level 

 of the ground, in order to bring them into the same horizontal plane with the casting 

 tables. Their length, amounting sometimes to 30 feet, and their breadth to 20, are 

 required in order to accommodate 6, 8, or even 10 plates of glass alongside of each 

 other. The front aperture is called the throat, and the back door the little throat 

 (gueulette). The carquaise is heated by means of a fire-place of a square form, called a 

 tisar, which extends along its side. 



The founding or melting furnace is a square brick building laid on solid foundations, 

 being from 8 to 10 feet in each of its fronts, and rising inside into a vault or crown 

 about 10 feet high. At each angle of this square, a small oven or arch is constructed, 

 likewise vaulted within, and communicating with the melting furnace by square flues, 

 called lunettes, through which it receives a powerful heat, though much inferior to that 

 round the pots. The arches are so distributed as that two of the exterior sides of the 

 furnace stand wholly free, while the two other sides, on which the arches em-roach. 

 offer a free space of only 3 foot. In this interjacent space, two principal openings of 

 the furnace, of equal size in each side, are left in the building. These are called tun- 

 nels. They are destined for the introduction of the pots and the fuel. 



On looking through the tunnels into the side of the furnace, we perceive to the 

 right hand and the left, along the two free sides, two low platforms or sieges, at least 

 30 inches in height and breadth. See figs. 1093, 109o. 



These sieges (seats) being intended to support the pots and the cuvettes filled with 

 heavy materials, are terminated by a slope, which ensures the solidity of the lire-flay 

 mound. The slopes of the two sieges extend towards the middle of the furnace M. 

 near as to leave a space of only from 6 to 10 inches between them for the hearth. Tim 

 end of this is perforated with a hole sufficiently large to give passage to the liquid ^lass 

 of a broken pot, while the rest is preserved by lading it from the mouth into the ad- 

 joining cuvette. 



In the two large parallel sides of the furnace, other apertures are left, much small. T 

 than the tunnels, which are called ouvreaux, (peep-holes). The lower ones, or tlm 

 ouvreaux en bas, called cuvette-opemngs, because, being allotted to the admission of 

 these vessels, they are exactly on a level with the surface of the sieges, and with the 



