UNCLE IN ENGLAND. 45 



of the glass parallel. The iron rulers being 

 moveable, serve also to determine the width of 

 the glass plate, and to prevent the matter from 

 running over the sides; the waste metal falls 

 into a trough of water at the end of the table, 

 and is reserved for the next melting. 



As soon as the glass has cooled to a proper 

 consistence it is examined ; and if any bubbles or 

 flaws are found, it is broken up and returned to 

 the melting pot : but if it has a sound appear- 

 ance, the table is rolled to the mouth of the 

 annealing furnace, and the plate is carefully de- 

 posited there. The heat of this furnace is at 

 first very great, but it is diminished every day 

 for a fortnight, by which time the glass is suffi- 

 ciently annealed. This process renders the glass 

 less brittle ; for, if suddenly cooled, my uncle 

 says, it would fly into pieces when touched. 



Ydth. Much as we were all interested by the 

 manufacture of plate glass, my uncle steadily 

 refused to carry us any further yesterday than the 

 annealing furnace : this evening, therefore, as soon 

 as we were comfortably collected round the fire, 

 after dinner, we reminded him that he was to 

 describe both the grinding and polishing opera- 

 tions ; and the following is the substance of what 

 he said. 



The annealing furnace generally contains six 

 plates of glass; when they are withdrawn, they 



