2D6 On the Jjfin'ttlts of 



tained, which of itself may nearly account for the disap-? 

 pearance of the various proportions of carbon. The various 

 proportions which each contain will account, in a great 

 measure, for any dissimilarity of result which the glasses 

 indicated. The fusion of the refracting spar, Experiment 

 No. I, is productive of a glass similar to No. VI, in which 

 chalk per sa was reduced;' but the fusion of the marble 

 yielded a glass materially difierent from both (F2xp. XIV), 

 and more akin to the fusion per se of the pure lime. Expe- 

 riment XIX. The two latter yielded less iron than the 

 former ; from which it was presumable that their high co- 

 lours resulted from the extra quantity of iron united to the 

 carbonates. 



When the carbonates are fused with l-20th part their 

 weight of carbon, the results are thus recapitulated. Double 

 refracting spar yields a deep fiery amber-coloured glass. Chalk 

 a glass snnilar, but a shade or two less brilliant, both with- 

 out any signs of revived iron ; but with the sanie propor- 

 tion of carbon the Kilkenny carbonate yielded a clouded lead- 

 coloured glass, presented a portion of its carbon still vin- 

 consumed, and gave out four globules of iron. Experi- 

 ments No. II, Vni, and XVI, the direct inference 1 would 

 draw from this circumstance would be, that as the Kilkenny 

 carbonate coittained less iron than either of the other two 

 substances, a smaller portion of carbon was sufficient to 

 discharge the iron ; and seeing that a variety of aniber co- 

 lours mixed with greens existed no longer than the iron 

 remained in a state of oxide, I would also infer that these 

 colours depended upon the state of oxygenation of the iron 

 altered by the different doses o,f carbon, and not on any pe- 

 culiar combination of carbon with the matter of lime. This 

 is further deducible from the fact of the glasses always at- 

 ' taining to the same colour, and nearly to the same trans- 

 parency, as soon as the whole of the iron is revived : be- 

 yond this the addition of carbon even prevents the fusion of 

 the lime, as in Experiment No. IX, and by no means unites 

 to it by cementation, which shall be proved hereafter. 

 The proportions of iron revived in all the carbonates are in 

 the ratio of the r[i:antity of carbon necessarily added to dis- 

 charge the same. Upon a fair mean of ail the experi- 

 ments made with the carbonates respectively, it appeared 

 to me that the chalk contamed nearly 3^ per cent., the 

 refracting spar from 2^ to 3, and the Kilkenriy marble 

 about 1 \ or per cent, of iron. Hence v/e findj, tiiat in the 

 formpr there disappeared 3i grains of carbon, or 7 per cent.; 



in 



