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THE POPULAR SCIENCE MONTHLY. 



an aventurine effect, and add greatly to its brilliancy. In the 

 cathedral glass the surface is rendered wavy and uneven, so that 

 the transmission of light shall be correspondingly irregular. In 

 the flash glass ordinary sheets are covered with a thin plating of 

 colored glass, a process which permits a very delicate color tone, 

 and materially decreases the expense, where a costly glass, such 

 as ruby, is needed to give the color. But in mosaic work it is 

 now generally preferred that the glass shall not be at all trans- 

 parent, since the effect is much richer. The most of the glass is 

 therefore cast, the process being a repetition in miniature of the 



In the Painting-Room. The Artist lating in the Heads. 



casting of rough plate. The pots containing the molten colored 

 glass always remain, however, in the furnace, and the " metal " is 

 dipped out in small iron ladles. It is poured at once on a little 

 casting table, and is smoothed out by means of an iron roller. 

 The small sheets thus obtained are readily handled, and permit 

 the use of the convenient rod leer. In this, the annealing process 

 requires from three to six hours, and at the end of that time the 

 sheets are ready for use. 



In case more than one color is to appear in the same sheet, the 

 effect is obtained by mixing together several masses of differently 

 colored and still plastic glass on the casting table, by means of a 

 copper instrument not unlike a plasterer's trowel. In this way 

 three or even four colors are combined in the same piece of glass, 

 and, though the results are always more or less experimental, 



