5S AllT OV GLXasMAKlUG. 



producing a red glass with copper, confirm the opmion of 



C[ouet respecting toe dirficulty of rentlerin^? this coIoue, 



Attempt to fixed in the fire. But why. did plate <rlas? alford only re- 



^cccuiM for J 1 1 ., I • , , , • 



the difference. "U*'^« copper, while common wljjte glass produced a vitreous 



oxide ? It seems to me, that it would be difficult to account 

 for it by supposini^, that the latter contained some oxigen- 

 ating substance: but it offers itself naturally when we con- 

 sider, that the composition of the former, beintj much more 

 fusible, occasioned the fusion of the metal, and thus with- 

 drew it from the action of the air, before the temperature 

 was suflicJently hi^h to be effectual. 



it is unnecessary to observe, that this explanation is not 

 inconsistent with the phenomenon before described ; since 

 tbc spoon did not pass to the state of vitreous oxide in the 

 })Iate glass, till it had repeatedly undergone the action of 

 the air and of the heat of the furnace simultaneously. 

 Attempts to Mr. d' Arcet has made several trials for colouring glass 

 cfAmrgSzx^. wjth cements impregnated with colouring metallic oxides. 

 •emsiiur'" ^ ^^^ employed iron, copper, cobalt, and manganese, in 

 various proportions, and in different slates. Iron left but a 

 pa'e colour. Cobalt and manganese coloured only the ce- 

 ments. In that made with copper left -from the distillation 

 of its acetate, the glass w;is completely deviirified, and of a 

 deep green at its surface, the colour growing lighter toward 

 the centre, where it had a reddish tinge. A plate of glass 

 coloured by cobalt having been placed in the common pe- 

 ment with a capsule of white glass, and ejjposed to a beat 

 of 50° of Wedgwood; part of the capsule was found to 

 be tinged blue, without having undergone fusion, the sur- 

 faces being only divested of their polish, and a little rough- 

 ened ; which is readily accounted for by the known pro- 

 perty of this metallic oxide to rise in vapour at a very high 

 tem5)crature. i 



Obs^ IV. O/* the alteration that ghss undergoes by the 

 action of great heat long continued. 



PcTitrifics- The interesting paper of Mr. d' A rtigues on the devitri- 



tica of glass fication of glass* has turned men's opinions toward the 



♦ An. <lc Cliim. fol.L, p. 335 : or Journal;^ vol. X, pp. 58, 89. 



real 



