OF GLASS. 



boiled together in five pirits of water, for the space 

 of a few minutes. 



MANUFACTURE OF GLASS. 



This beautiful material is hot of modern ihvbn- 

 tion ; it was known to the ancient Romans, but it 

 \tffcs by ho ttieahs common among them, arid they 

 db riot af>|tear to Have had the hifethbd of forming 

 it into vessels of various shapes as is practised at 

 present. 



Glass is made by fusing together sllex Ml 

 potash; or soda, in proper pr^poiiibhs. Seb, saild; 

 which consists alrnost entirely of quartz arid fliiits 

 redhced to powder, is generally tis'e'd for this pur- 

 p'dse'. The alcali is generally procured froni the 

 burning of sea weeds ; these are cut, dried, and 

 burned ih pits dug in tli'e ground ; aifter a sufficient 

 quantity of them have burned in the same jiit, a 1 

 melted or liquid mass is foiiiid in the bottom, 

 which; after being well stirred, is Suffered to cool ; 

 it is then called kelp', and consists of a nrixtiire bT 

 scida; potash, and parts of half burht weeds, toge- 

 ther with shells, sand, and other impurities. 



When the ingredients of which glass is cbihposed 

 ate perfectly fused, and have acquired a certain 

 degree of heat, which is known by the fluidity of 

 the mass, part of the melted matter is taken out at 

 the end of a long hollow tube, which is dipped 

 into it, and turned about, till a sufficient quantity 

 is taken up ; the workmen then rolls it gently 

 upon a piece of iron, to unite it more intimately. 

 He then blows through the tube, till the melted 

 mass at the extremity swells into a bubble, after 



