MANUFACTURE OF GLASS. 153 



whole properly inclosed in a crucible, was exposed to the heat of 

 a blast furnace, by which the diamond disappeared, and the metal 

 was fused, and converted into a small mass or bottom of cast steel. 



[Editor. 



CHAP. XII. 



MANUFACTURE OF GLASS. 



VJLASS is a strictly chemical substance, and well entitled to our 

 attention as to its history, properties, and manufacture. 



SECTION I. 



History of the discovery. 



THE word glass is formed of the Latin glastum^ a plant, called 

 by the Greeks, isatis ; by the Romans, vttrum ; by the ancient 

 Briton?, guadum ; by the English, wood. We find frequent men- 

 tion of this plant in ancient writers, particularly Caesar, Vitruvius, 

 Pliny, Sic. who relate, that the ancient Britons painted or dyed 

 their bodies with glastum, guadum, vitrum, &c. i. e. with the blue 

 colour procured from this plant. And hence the factitious matter 

 we are speaking of came to be called glass, as having always 

 somewhat of this blueishness in it. 



At what time the art of glass-making was first invented is 

 altogether uncertain. Some imagine it to have been invented be- 

 fore the flood : but of this we have no direct proof, though there 

 is no improbability in the supposition ; for we know, that it is al- 

 most impossible to excite a very violent fin-, such as is necessary 

 in metallurgic operations, without vitrifying part of the bricks or 

 stones wherewith the furnace is built. This, indeed, might furnish 

 the first hints of glass. making ; though it is also very probable, 

 that such imperfect vitrifications would be observed a long time 

 before people thought of making any use of them. 



The Egyptians boast, that this art was taught them by then 

 great Hermes. Aristophanes, Aristotle, Alexander, Aphrodiseus, 

 Lucretius, and St. John the divine, put it out of all doubt that 



