The arrangement of the windo\v-glass houses is different, and on a much larger scale than in the houses for bottle-glass, and, excepting in gathering and mavcring, all the operations subsequent to the founding are different.
When the founding or melting and the skimming are completed, the workman takes his blow-pipe, which is about 7 ft. in length, heats it at the end, and dipping it into the pot of melted glass or metal through an opening, lie gathers, by a slight turn or two, a quantity of glass, about a pound and a half in weight; this he withdraws, and after turning it about for a minute or two in the air until sufficiently cooled, he then dips it in again, and over the first he makes a second gathering, which increases the weight to about three pounds weight; the same cooling process is repeated, and a third gathering is made, which brings up the weight to about nine pounds, he then holds his blow-pipe perpendicularly with the glass downward, so that it may by its own weight pull down ward from the pipe in the form of a symmetrical pear-shaped bulb; he next takes it to the hollowed block before mentioned, and turns it round in the water placed in the cavity, by which it is made ready for the wavering table. The workman, by skillful management, masers the bulb of glass into the form b. fig. 2, and then forms a little knob at its apex, by turning it on a fixed bar of iron called the bullion bar; lie then com mences blowing, and soon the bulb of nearly solid glass is expanded into a large hollow sphere (e, fig. 2), still, however, with the little nipple made by the bullion liar. A little boy now conies forward with an iron rod, the pointel, upon the end of which has been gathered a small lump of metal, called the panty, about the size of a hen's egg; this he applies to the nipple, to which it firmly adheres, the workman meanwhile rest ing his blow-pipe on a fixed rest called the casher-box, placed for the purpose; by the pressure of the pointel the globe of glass is flattened as in d, fig. 2 The application of a piece of iron, cooled for the purpose by keeping it in water, to the junction of the glass with the blow pipe, detaches it instantly, and the globe of glass is now held with the pointel. The operator carries it next to the nose-hole, and presents the opening formed by the detachment of the blow-pipe to the action of the furnace; this again softens the glass, which is kept eontinuallv revolving by turning the pointel on an iron rest or hook fixed to the masonry of the 'furnace. The revolu tions are at first slow, but are gradually accelerated as the softening of the glass goes on, and the centrifugal force so produced throws the edges of the orifice outwards, as in e, fig. 2. As the glass flattens, it is revolved with greater rapidity, and advanced so near to the month of the nose-hole as to draw the flames outward, by contracting the draught. This completes the softening of the glass, which is done suddenly, with a rushing noise like the unfurling of a flag in the wind, caused by the rapid flying outward of the softened glasS and the rush of the flames outwards. It becomes perfectly fiat, and of equal thickness, except at the bullion or center, formed, as before described, by the bullion-bar and the panty. The flashing is now complete; and the workman removes it from the nose-hole, and still continuing to turn it in his hands, in order to cool and harden it, as lie walks along, carries it to the annealing oven, where another one receives it on a large flattened forklike implement at the moment the flasher, who has hold of the pointel, suddenly detaches it • by a touch of his shears. It is then passed through the
long horizontal slit which forms the opening into the annealing oven, and when fairly in, it is dexterously turned on its edge; here it remains at a temperature somewhat below that required to soften glass, until the oven is filled with these so-called tables of glass, when the heat is suffered to decline, until the whole is cold, when they are removed to the packing-room, to be packed in crates for sale.
Until lately, crown-glass was almost universally employed for windows, but now that which is called German sheet has almost displaced it, besides which British sheet, which is the same glass polished, and piate-glass are much used. The operation of mak ing the sheet-glass is very different from that employed in making crown-glass, inas much as a long and perfect cylinder is sought to be produced by the blower instead of a sphere of glass. This necessitates also a different arrangement of the glass-house, as is seen by the ground-plan shown in fig. 3: as is the furnace, b is the annealing oven, heated by the fine b', which opens into the main furnace; the leer, or annealing oven, is often, however, an independent structure; c, c, c, c, c, c, c, are the eight pots, which is the number usually employed in these works. These, of course, are oppo site to the openings for working them, and in front of each opening is a long opening in the ground, about 8 ft. deep and 3 ft. in width; d, d, d, d, d d, d, d. The workman stands on the edge of this pit, and having made his gathering, as in the crown glass manufacture (a fig. 4), he next meters it, without, however, using the bullion-rod (b, fig. 4). He next proceeds to blow his glass, hold ing it downward whilst doing so, that its weight may widen and elongate the bulb, and from time to time dexterously swings it round, which greatly increases its length (c, d, fig. 4). As it cools rapidly in this operation, he from time to time places his pipe in the rest which if fixed before the furnace-mouth, and gently turning ID round, he brings it again nearly to the melting-point, then he repeats the blowing and swinging, standing over the pit, to enable hint to swing it completely round as it lengthens out. These operations are continued until the cylinder has reached its maxi mum size, that is, until it is of equal thickness throughout, and sufficiently long and broad to admit of sheets of the required size being made from (e, fig. 4). Sometimes these cylinders are made 00 in. in length, allowing sheets of glass 49 in. in length to be made from them, but the Belgians make them much larger. In the Vienna exhibition, they exhibited sheets 10 X 4 feet. The next operation is to place the pipe in the rest, and apply the thumb so as to close the opening at the blowing end, the heat of the furnace soon softens the glass at the closed extremity of the cylinder, and as the inclosed air is prevented escaping as it rarefies, by the thumb placed on the opening of the blow-nine. it bursts at the softened nart (pg. 4,f); the operator then quickly turns the cylinder, still with its end to the fire, and the softened edges of the opening, which at first are curved inwards, are flashed out until they are in a straight line with the sides of the cylinder (g, fig. 4).