Fig. 769 shows the details of the space between two pillars or flues of an old-fashioned circular furnace: F are the pillars containing flues leading into the cone; D, iron doors for cleaning and mending the flues ;'B, iron buck-staves, carrying the iron ring R, and supporting the weight of the cone. There are usually 20 of these staves. The mouth A of the crucible, is partially closed by a fire-clay collar ; H is the bed of the furnace, upon which the crucible rests ; C, the arch in the side of the common dome ; E, a door of ironwork and bricks, to protect the workman from the heat of the furnace ; X, an iron-grooved rest, which supports the working-irons of the glass blower; S, a fire-clay box or "shoe," in which the ends of the irons are heated ; P, a small round opening, closed with a movable fire-clay plug, and through which the interior of the furnace can be viewed.
Where small crucibles are used, it is customary to continue work throughout the week, alter nately melting and working out the glass, By this means, great economy is effected, but it is impossible to produce glass of first-rate quality. As soon as the glass is completely fused and purified, and the workmen have returned to work, the mouths of the crucibles are opened, and the surface of the molten glass is skimmed, in order to remove any infusible impurities, which may have fallen into the crucible, or may have been introduced together with the raw materials. The glass may now he considered ready for work ; but before describing the processes of manipulation, the workmen themselves and the tools employed, demand notice. Work is continued night and day, and the workmen are divided into two sets, or "turns," relieving each other at the end of every 6 hours. Each turn is made up of groups, or "chairs," of workmen, the number varying with the number of crucibles in the furnace. The usual complement is one "chair" in each turn to every two crucibles; but it varies with the size of the crucibles, and the style of work. If the crucibles hold sufficient glass to supply a larger number of " chairs," a larger number may be accommodated by providing additional auxiliary working-furnaces. It must be remembered that, for manipulation, every workman requites a supply of heat, which is usually provided by the month of the cruciblo from which the glass is gathered. Each chair is made up of a " workman," a first assistant or "servitor," a second assistant or " footmaker," and one or more boys.
The tools used in the manipulation of blown-glass are represented in Fig. 770 :--a, hollow iron
blow-pipo, usually 5 ft. long, and used for gathering glass from the cruoible, as represented in Fig. 771, and for the first or blowing process ; b, solid iron working-rod, lighter and slighter than the blow-pipe, tapering from the handle to the point, and used for holding vessels by means of a seal of glass during the later manipulatory processes ; c, sugar-tong spring tool with knife-blades ; d, a similar tool with wooden legs, valuable for opening wine-glass bowls, &c., and for fashioning other objects in which it is important that the glass shall not bo scratched or marked ; e, shears, for removing any surplus ; f, a flat plate of iron, with handle, for flatten ing the bottoms of tumb lers ; g, pincers, for taking hold of and fixing the ends of handles, and other purposes. At H, Fig. 772, is shown a flat slab of polished iron, called a " marver," resting upon a firmly constructed stool, on which the glass is rolled, immediately after gathering, with a view to its consolidation. Very important is the seat in which the glass-blower works. Fig. 773 repre sents a glass-blower at work in his chair. The arms A B project 18 in. in front of the seat, are exactly parallel, and slope gently downwards from B to A. The innumerable forms of blown-glass are mainly due to the power possessed by the workman of imparting to the viscid glass a continuous rotatory motion, whilst he simultaneously fashions it. The blow-pipe, with the glass attached, is rolled backwards and forwards upon the arms A B with the left hand, whilst the right hand remains free to shapo the glass.
Moulds are used (1) for giving the exact form to dishes which are required to fit into metal work, or are of an oval or irregular form. In Fig. 774, a b represent two methods of blowing dishes into moulds : in a, after a bulb has been blown, and has been forced by the breath to take the form of the mould, the surplus glees is blown out so thin as to be easily broken away ; in b, the surplus remains thick, and has to be removed by the glass-cutter. Moulds, especially wooden ones, are used (2) for shaping the bowls of wine-glasses and the bodies of decanters, though not often for this purpose in England ; and (3) for imparting patterns to the sur face of blown-glass ; c shows a mould ; and the remaining figures, the section of a mould, and the glass before and after it has been moulded.