346 Fusion of Plumbago. 
melted plumbago were in some instances so thickly arran- 
ged 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 concretions of mammillary chalcedony ; 
among a great number 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 form- 
ed 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 ver- 
tically in an abundant fume like that of the oxid proceeding 
rom the combustion of various metals. I mentioned this 
circumstance in the report of my first experiments (see Vo 
5, p- 112 of this Journal,) but did not then make any 
trial to ascertain the nature of the substance. Although its 
abundance rendered the idea improbable, I thought it pos- 
sible that it might contain alkali derived from the charcoal. 
tis easily condensed by inverting a glass over the fume as 
it rises, when it soon renders the glass opaque with a white 
lining. Although there was a distinct and peculiar odour in 
the fume, I found that the condensed matter was tasteless, and 
that it did not effervesce with acids, or affect the test colours 
for alkalies. Besides, as itis produced apparently in greater 
quantity, when both poles are terminated by plumbago, 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. 
The Deflagrator having been refitted only at the moment 
when a part of this paper had already gone to the press, and 
the remainder is called for, { am precluded by these circum- 
stances from trying the decisive experiment of heating this 
white matter by means of the solar focus in a jar of pure ox- 
ygen gas, to ascertain whether it will produce carbonic acid 
gas. . 
