THE CHEMISTRY OF GLASS. 465 



THE CHEMISTRY OF GLASS. 



Ghass is so familiar a substance that we are likely to overlook its wonderful 

 character. If we imagine ourselves suddenly deprived of it, and ask where we 

 should find a substiiute in many of its uses, we shall better appreciate its 

 unique value. There is absolutely nothing known to us in nature or in art 

 that could take its place in some of its most important applications. In our 

 windows, for example, what could we use instead of it that would not be a 

 mere barbarian makeshift ? What dreary prisons our dwellings would be in 

 a New England winter with no light except what could be got through oiled 

 paper or canvas, and no opportunity^ of seeing anything outside without 

 opening the window ! 



To the man of science the loss would be infinitely greater if not irrepar- 

 able. We will not attempt to picture the dismay, the despair, of the astron- 

 omer and the chemist if deprived of the instruments and apparatus in which 

 glass forms an essential part. It may, indeed, be asserted that the sciences 

 could not have attained their present development without the aid of glass. 

 The partial and imperfect substitutes that are available are so costly as to 

 be within the means of comparatively few, and the progress of investigation 

 would be proportionately slow and difficult. 



But we must leave our readers to follow out these reflections for them- 

 selves, our present purpose being rather to give facts than to indulge in 

 fancy pictures of the "might have been." 



The manufacture of glass dates back to a pre-historic antiquity. We do 

 not even know to what race or nation its invention is to be credited. Arch- 

 ceologists are disposed to assign it to the Egyptians, but apparently on no 

 other ground than the convenient one of assuming that any art whose origin 

 cannot be .traced may safely be ascribed to a people among whom so many 

 other arts had their rise and development. The story of Pliny that glass 

 was the accidental discovery of some Phoenician merchants was of course a 

 mere tradition, and it is, moreover, improbable on the lace of it.° He tells 

 us that those merchants, landing on the banks of the river Belus, made use 

 of blocks of soda to support the caldron in which they cooked their food, 

 and that the alkali melted and united with the sand to form glass ; but it is 

 difficult to believe that an open fire on the sand would be hot enough to 

 elfect the vitrification. If the process was discovered by chance, as it may 

 have been, it is more likely that it was connected with the early art of j)Ot- 

 tery or some of the primitive operations in the extraction of metals from 

 their ores. 



Although the art of making glass is so ancient, it is little more than half 

 a century since the scientific principles on which it depends were explained 

 by the Swedish chemist, Berzelius. He was the first to discover that silica 

 is an acid, and that glass is a true chemical compound, or a salt formed by 

 the union of this acid with alkaline bases. From that time the manufacture 

 of glass, which had been carried on empiratically for ages, was put upon a 



