GLASS-MAKING. 



21 



added immensely to the brilliancy of modern designs, and have 

 been particularly effective when introduced as a setting or frame- 

 work to a picture-window. They are imported for the most part 

 from Germany. The greater part of the flat glass used, however, 

 is made in the immediate neighborhood of New York, under the 

 direct supervision of the art- workers who are to utilize it. I had 

 recently the pleasure of going through such a factory in Brooklyn, 

 probably the largest of the kind in this country, and it was a veri- 

 table chromatic treat to visit the store-rooms, for some five hun- 

 dred different color combinations were recognized in stock. The 

 mosaic ateliers of the Vatican contain, it is true, not less than 

 twenty-six thousand different tints ; but these, it must be remem- 

 bered, are simply opaque enamels, while the glass mentioned is 

 all easily translucent, and much of it is clearly transparent. 



In the manufacture of this glass the materials employed are 

 much the same as in ordinary sheet and plate glass. It is a double 

 silicate of lime and soda, the coloring being due to the addition of 

 metallic oxides which are soluble in the fused glass. The mate- 



In the Glass-Shop. Selecting the Glass from the Sheets. 



rials needed for the basis are, as before, sand, limestone, and 

 alkali. They are mixed in the proper proportions — that is to say, 

 about thirty parts of lime and forty of soda to every hundred 

 parts of sand — and are fused in fire-clay crucibles in the customary 

 glass-furnace. The coloring matter is added at different stages of 

 the process, according to the nature of the material. 



The mineral world has been pretty thoroughly ransacked to 



