THE TECHNOLOGIST. [Sept. 1, 1864. 



fob MACHINERY FOR THE MANUFACTURE OF PLATE GLASS. 



particles of dust deposited, and found them very uniform in size at any- 

 one part of the long chamber. In this process also the ground coal dust 

 was removed immediately from the grinding apparatus by the air blast, 

 instead of remaining there to clog the grinding. The same method 

 would, he thought, be applicable for separating emery into its different 

 degrees of fineness for polishing glass, if it were preferred to separate it 

 dry instead of employing water for the purpose. 



The Chairman thought it was matter of regret that no means had 

 yet been arrived at for making the best plate glass from home sand, 

 instead of foreign sand : and he suggested that some mechanical mode 

 of bleaching the sand might be discovered, to render the English sand 

 as good for the purpose as the foreign sand : the application of heat 

 might perhaps be tried, as that was known to produce a great difference 

 in the colour of many materials, such as clays and other earths. 



With regard to the origin of the waviness on the surface of the glass 

 plates after leaving the annealing oven, it had been stated that this 

 unevenness did not exist when the roller left the surface of the glass on 

 the casting table, but that it became developed during the gradual 

 cooling of the plate in the annealing oven ; and it occurred to him that 

 possibly the glass at the time of casting might be in a viscid or plastic 

 state, like gutta-percha, instead of being completely and uniformly 

 liquified throughout the entire mass, the result of which would be that 

 it would yield under the roller, but the rolled plate would be irregular 

 in density and would thus become uneven during annealing by swelling 

 up again at various parts. If, however, the unevenness could be pre- 

 vented by packing the plates of glass between iron plates in the 

 annealing oven, as had been suggested, he thought the saving effected by 

 the smoother surface in the subsequent grinding process might make up 

 for the additional expense of the iron plates in the first instance : and 

 the number of iron plates required would be only one more than the 

 number of glass plates to be laid between them, if they were laid in a 

 continuous pile. 



The particulars given in the paper regarding the increase in the 

 manufacture of plate glass during the last few years afford another 

 and a very clear illustration of the effect of cheapening any article in 

 causing a great extension of its use. 



