Prof. Silliman on the Fusion of Plumbago, <$fc. 181 
knitted the fluid with a splendour even more intense than when 
charcoal was used. 
On examining the pieces, I found them beautifully studded with 
numerous globules of melted plumbago. They extended from within 
a quarter of an inch of the point, to the distance of one-fourth or one- 
third of an inch all around. They were larger than before, and per- 
fectly visible to the naked eye : They exhibited all the colours before 
described, from perfect black to pure white, including brown, am- 
ber, and topaz colours : Among the white globules, some were per- 
fectly limpid, and could not be distinguished by the eye from portions of 
diamond 
While again repeating the experiments, Professor Silliman 
obtained still finer results. 
“ The spheres of melted plumbago were in some instances sd 
thickly arranged as to resemble shot lying side by side ; in one case 
they completely Covered the plumbago, in the part contiguous to the 
point on the zinc side, and were, without exception, white, like minute, 
delicate co?icretions of mammillary chalcedony. Among a great num- 
ber there was not one of a dark colour, except that, when detached 
by the knife, they exhibited slight shades of brown at the place 
where they Were united with the general mass of plumbago. They 
appeared to me to be formed by the condensation of a white vapour, 
which, in all the experiments where an active power was employed, 
I had observed to be exhaled between the poles, and partly to pass 
from the copper to the zinc pole, and partly to rise vertically in an 
abundant fume like that of the oxide proceeding from the combus- 
' tion of various metals. It seems possible that it is white volatilized 
carbon, giving origin, by its condensation, in a state of greater or less 
purity, to the grey, white, and perhaps to the limpid globules *. 
u I have already stated, that the white fume mentioned above, ap- 
pears when points of charcoal are used. I have found that this mat- 
ter collects in considerable quantities a little out of the focus of heat 
around the zinc pole, and occasionally exhibits the appearance of a 
frit of white enamel, or looks a little like pumice stone, only it has 
the whiteness of porcelain, graduating, however, into light grey, and 
other shades, as it recedes from the intense heat. In a few instances, 
I obtained upon the charcoal, when this substance terminated both 
poles, distinct, limpid spheres, and at other times they adhered to the 
frit like beads on a string. Had we not been encouraged by the re- 
markable facts already stated, it would appear very extravagant to 
ask whether this white frit and these limpid spheres could arise from 
earbon, volatilized in a white state even from charcoal itself, and con- 
densed in a form analogous to the diamond. The rigorous and ob- 
vious experiments necessary to determine this question, it is not now 
practicable for me to make ; and I must, in the mean time, admit the 
* Upon exposing these globules to the solar focus, in a small jar of pure oxy- 
gen, Professor Silliman found, that they gave out part of their substance, viz. car- 
bonic acid, to the oxygen. 
