different Earths for Carlon. 203 



A very handsome spherule of iron, slightly marked with 

 carburet, was obtained, which weighed l^ grain, equal to 

 3 per cent, from roasted chalk, or i3 per cent, from the 

 chalk in a raw state. This fxperiment, compared with 

 No. XI, shows that 5-6ths of a grain of additional carbon 

 was requisite to precipitate the iron in a metallic state from 

 its dose of oxvgen and hmej but compared with No. XII 

 proves, that although part of the carbon remained untakeu 

 up, yet there ^tiU remained in the glass a portion of iron in 

 the state of oxide ; to disengage which a greater aggregate 

 of affinity was necessary. 



Experiment XIV — Kilkenny Marble. 



Fifty grains of this carbonate was fused into a glass of a 

 mixed greenish blue cloudy colour. The upper surface 

 porous, or raiher cellular, of a lighter greenish colour and 

 more transparent than the mass. The want of uniformity 

 in the colour of this glass induced me to repeat the experi- 

 ment four times ; three of which yielded similar glasses. 



Experiment XV. 



Kilkenny marble, raw - - 50 grs. 

 Lamp carbon 1 -50th - - 1 



The fusion of this mixture alforded a perfect glass, wherein 

 the charcoal had totally disappeared. The colour of the glass 

 was a darkish green amber, v. hleh in some particular lights 

 exhibited some fiery tints of a ruby colour. It resembled 

 No. VI n considerably, but did not possess the same depth 

 of lustre and transparency. The surface exhibited no ap- 

 pearance of metal in a revived state, although it was pre- 

 sumable that a portion of iron existed in the glnss, and 

 w hich had been affected, in poiiit of colour^^ by the com- 

 bination of the present dose of carbon. 



Experiment XVI, 

 Kilkenny marble, raw - - 50 grs. 

 Lamp carbon 1 -20th, or - 2^ 



A glass resulted from the fusion of this mixture exactly 

 Mmilar to Experiments No. lil, V, IX, XI, XII, and XIII. 

 There" were found upon its surface four globules of iron, 

 which weighed a minute fraction more than a grain, or 

 2 percent. Haifa grain of charcoal ren)ained untakeu up, 

 £o that only two grains, or 4 per cent., were here absorbed; 

 whereas raw chalk, Experiment No. IX, took up 3^ grains, 

 or 3i^ per cent, more than the Kilkenny carbonate, probably 

 Irom its conta'uiin^ a larger quantity of oxide of iron. 



T 3 i^'^-po- 



