AUT OF* GLiSSMAKlNG, 57 



made at the laboratory of the Polyteclinic school, tends to 

 ^confirm this conjectiire. 



It is the ])vact"K'e in plate p;Iass manufactories, when the part of a ladfie 

 glass is refined, to ladle it out of the pot into a cistern, which ^^'"fL!^'^ |^,, 

 is afterward taken out of the furnace, that the glass may be 

 run on a table. The ladles are made of copper, with an 

 iron handle, and are dipped into water, as soon as they begin 

 to get hot. A workman, having neglected this precaution^ 

 brought out only a part of his ladle. It was supposed, that 

 the melted portion would sink to the bottom of the pot, and 

 be preserved there as under a vitreous flux. Accordingly the 

 casting and annealing were proceeded with as usual ; but to 

 the surprise of the workmen, the glass exhibited, not only 

 a few metallic grains embedded in it, but bands pretty uni* 

 formly coloured of a very bright red. I lay before tht 

 (Class a piece of this glass, polished on one side, 1 7 cent. 

 £6'7 in.] long, 12 cent. [4*7 ui.] wide, and 7 niil. [2*73 lines] 

 thick. 



There can be no doubt, that this colour was produced by Theory.. 



the copper carried suddenly to that degree of oxidation, 



which gives it this property ; and fixed in this state by its 



ditluslon through the vitreous mass. But can we be cer- Can we pre. 



taiu of reproducing the same circumstances? and bv what, "^^ ^'^'i ^^* 

 \ . . . ■' lect at plea« 



means? This I was desirous of ascertaining by experi-.suic? 



raent. 



I took some powdered plate glass, mixed it with three per Experimfnl 

 cent of copper tilings, and brought the mixture to complete ^^ P'**^^ 

 fusion. The glass was without colour, and the copper in 

 metallic globules. 



1 repeated the experiment with common white glass -and with commaa. 

 six per cent of copper filings; and obtained a vitreous S^*^*^* 

 mass, well fused, and of a very uniform red colour, but so 

 deep, that it appeared in the state of enamel rather than of 

 glass. On the surface was observable a crust less compact, 

 approaching to the nature of scoriae, of a brown inclining to 

 black. 



Mixtures of glass and copper in the state of oxide, even „. ,. , 

 in the lowest degree, afllbrded only a greenish tinge, and part of copper, 

 of the copper was reduced. 



These results, while tiiey announce the possibility of 



producing 



