654 



GLASS 



Sometimes tho cylinders are spread in a large mnfilc-furnaco, in order to protect them 

 from being tarnished by sulphureous and carbonaceous fumes. 



Fig. 1087 represents a ground plan of both tho spreading and annealing furnace; fig. 

 1088 is an oblong section in the direction of the dottcd-lino x x,fig. 1087. 



a is tho fire-place ; b b, tho canals or flues through which the flame rises into I.-ith 

 furnaces; c, the spreading furnace, upon whoso sole is tho spreading slab, d, is the 

 cooling and annealing oven ; c c, iron bars which extend obliquely across tho anneal- 

 ing arch, and servo for resting tho glass tables against during tho cooling ; / /, tho 

 channel along which the previously-cracked cylinders are slid, so as to bo gradually 

 warmed ; g, the opening in tho spreading furnace, for enabling tho workmen to regu- 

 late the process ; h, a door in the annealing arch, for introducing the tools requisite for 

 raising up and removing the tables. 



The series of transformations in sheet-glass, already described, is 

 represented in fig. 1089, at A, B, c, D, E, F, G, H. 



6 Figs. 1090 and 1091 represent a Bohemian furnace in which ex- 



jf| cellent white window-glass is founded. Fig. 1090 is a longitudinal 

 7A section of tho glass and annealing furnace. Fig. 1091 is the ground 

 plan, a is the ash pit vaulted under tho sole of tho furnace ; the 

 fire-place itself is divided into three compartments, with a middle 

 1 jr slab at d, which is hollowed in tho centre, for collecting any split 



A TV glass, and two hearth tiles or slabs b b. c c arc tho draught or air- 



holes ; c e are arches upon which the bearing slabs // partly rest. 

 In the middle between these arches, the flame strikes upwards upon 



1090 



1091 



the pots g g, placed as closely together as possible for economy of room, h is the breast- 

 wall of the furnace ; i, fig. 1091, the opening through which the pots arc introduced; 

 it is bricked up as soon as they arc set. Jc k is the base of the cone or dome of the 

 furnace ; 1 1 1, the working orifices, which are made larger or smaller according to the 

 size of the glass articles to be made, m is the flue which leads to the annealing stove 

 n, with an arched door. Exterior to this there is usually a drying kiln, not shown in 

 the figure ; and there are adjoining stoves, called arches, for drying and annealing the 

 new pots before they are set. 



The cooling or annealing arch, or leer, is often built independent of the glass-house 



1092 



furuaco ; it is then heated by a separ.it n 

 fire-place, and constructed like a very 

 long reverberatory furnace. 



The leer pans, or trays of sheet iron, 

 are laid upon its bottom in an oblong 

 scries, and hooked to each other. 



3. Crown - glass. The crown - gl ; i ss 

 house with its furnace is represented in 

 fig. 1092, where the Mowing operation is 

 shown on the one side of the figure, and 

 the flashing on the other. The furnace 

 is usually constructed to receive 4 or 

 6 pots, of such dimensions as to mako 

 about a ton of glass each at a time. 

 There- are, however, several subsidiary 

 furnaces to a crown-house : 1, a rever- 

 beratory furnace or calcar, for calcining 

 or fritting tho materials ; 2, a blowing 

 furnace for blowing tho poar-shaju <l 

 balls made at tho pot-holes, into largo 

 globes ; 3, a flashing furnace, and bot- 

 toming bole for communicating a - 

 ing heat, in expanding tho globo into a circular plate ; 1, tho annealing arcli for tho 



