44 BERTHA'S VISIT TO HER 



the materials are melted, are made of a sort of 

 tough clay that is found at Stourbridge, in Wor- 

 cestershire, as it has the property of standing the 

 most intense heat ; and they contain about twenty 

 hundred weighf of melted glass, or metal, as it is 

 called by the workmen. The cuvettes, or cis- 

 terns, which convey the liquid glass to the casting 

 table, are made of the same clay. 



When the metal is sufficiently fluid, refined, 

 and settled, which happens in about thirty-six 

 hours, it is put, by means of ladles, into the cis- 

 terns, which are left in the furnace about six 

 hours longer, till the little bubbles formed by 

 this disturbance of the glass have all disap- 

 peared, The door of the furnace is now opened, 

 and by a chain the cistern is drawn out upon an 

 iron carriage, and conducted to the casting table. 

 Here it is raised, by means of a crane, against 

 two iron bars, which are so contrived as to in- 

 cline the cistern, and empty the fiery torrent on 

 the table. 



This table is covered with a thick copper plate 

 made very smooth on the surface ; and it is sup- 

 ported on wheels, so that it can be moved from 

 one annealing furnace to another. To regulate 

 the thickness of the glass, two iron rulers are 

 placed along the table, and on these rest the 

 extremes of a very heavy roller, or cylinder of 

 copper, which, as it moves along, drives the super- 

 fluous matter before it, and renders the two faces 



