GLASS-MA KING, 6 1 3 



In the selection of the crude materials great care is taken to 

 secure purity. Tlie melting is carried out in large, open pots, the 

 furnaces differing in their construction from those already de- 

 scribed only in their greater size, and in the substitution of iron 

 doors lined with tiles for the customary gathering-holes. When 

 the melting is completed, the door nearest the pot to be emptied is 

 opened, and a two-pronged fork, mounted on wheels, is inserted 

 into the furnace. The prongs fit into depressions in the sides of 

 the melting-pot, and thus secure it in a firm grasp. The pot 

 of molten metal is then removed from the furnace and carried 

 on a low truck to the casting table. At Creighton, the casting 

 house, containing furnaces, tables, and annealing ovens, is 650 by 

 160 feet, about four times as large as the famous halle of Saint- 

 Gobain in France, and nearly double the size of the British casting 

 house at Ravenshead. The capacity of the American works has re- 

 cently been greatly increased, and several new plants established in 

 different sections of the natural-gas territory. The casting tables, 

 the most important pieces of apparatus in a plate-glass works, are 

 nineteen feet long, fourteen feet wide, and seven inches thick. 

 Each is provided with an iron roller, thirty inches in diameter and 

 fifteen feet long. Strips of iron on each side of the table afford a 

 bearing for the rollers and determine the thickness of the plate of 

 glass to be cast. The rough plate is commonly nine sixteenths of 

 an inch in thickness ; after polishing, it is reduced to six or seven 

 sixteenths. The casting tables are mounted on wheels and run on 

 a track that reaches every furnace and annealing oven in the 

 building. The table having been wheeled as near as possible to 

 the melting furnace, the pot of molten glass is lifted by means of 

 a crane, and its contents quickly poured on the table. The heavy 

 iron roller is then passed from end to end, spreading the glass into 

 a layer of uniform thickness. The whole operation of casting 

 scarcely occupies more time than it takes to describe it. Each 

 movement is made with almost nervous rapidity. Few industries 

 offer such fine scenic display as the pouring of the molten glass. 

 One feels like crying Encore ! it is so very brilliant. 



In contact with the cold metal of the table, the glass cools rap- 

 idly. As soon as possible, the door of the annealing oven is 

 opened, and the plate of glass introduced. The floor of the oven 

 is on the same level as the casting table, so that the transfer can 

 be conveniently and quickly made. When, after several days, the 

 glass is taken out of the oven, its surface is found to be decidedly 

 rough and uneven. A small quantity is used in this condition for 

 sky-lights and other purposes where strength is required without 

 transparency. It is known in the market as rough plate. The 

 greater part of the glass, however, is ground, smoothed, and pol- 

 ished before it leaves the establishment. The work of the " hall 



