il46 JFiision of Plumbago. 



tre. I would again recommend this arrangement when the 

 object is to attain fine pieces of melted charcoal. 



April 14. — In repeating the experiments to day, I have 

 obtained even finer results than before. The spheres of 

 melted plumbago were in some instances so thickly arranr 

 ged as to resemble shot lying side by side j 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 

 from the combustion of various metals. I mentioned this 

 circumstance in the report of my first experiments (see Vol. 

 S, 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. 

 It is 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 it is 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. 



