Fusion of Plumbago: 345 



fectly visible to the naked eye; they exhibited all the col- 

 ours before described, from perfect black, to pure white, 

 including brown, amber, and topaz colours; among the 

 white globules, some were perfectly limpid, and could not 

 be distinguished by the eye Irom portions of diamond. In 

 different repetitions of the experiment with the plumbago 

 points, there were some varieties in the results. In one in- 

 stance only, was there a globule formed on the point; it 

 would seem as if the melted spheres of plumbago as soon as 

 formed, rolled out of the current of flame, and congealed on 

 the contiguous parts. In every instance, the plumbago on the 

 copper side, was hollowed out, into a spherical cavity, and 

 the corresponding peice on the zinc side, received an accu- 

 mulation more or less considerable. In most instances and 

 in all when the Deflagrator was very active, besides the glo- 

 bules of melted matter, a distinct tuft or projection was form- 

 ed on the zinc pole, considerably resembling the melted 

 charcoal, described in my former communications, but ap- 

 parently denser and more compact; although resembling 

 the melted charcoal, as one variety of volcanic slag resem- 

 bles another, it could be easily distinguished by an eye fa- 

 miliarized to the appearances. In one experiment the cav- 

 ity, and all the parts of the plumbago at the copper pole 

 were completely melted on the surface, and covered with a 

 black enamel. The appearances were somewhat varied 

 when specimens of plumbago from different localities were 

 used. In some instances it burnt, and even deflagrated, 

 being completely dissipated in brilliant scintillations ; the 

 substance was rapidly consumed and no fusion was obtained. 

 This kind of effect occurred most distinctly when there was 

 a plumbago piece on the copper side, and a piece of char- 

 coal on the zinc side. I have already mentioned the cu- 

 rious result which is obtained when this arrangement is re- 

 versed, the charcoal on the copper, and the plumbago on 

 the zinc side ; this effect was now particularly distinct and 

 remarkable, the charcoal on the copper side was rapidly vol- 

 atilized, a deep cavity was formed, and the charcoal taken 

 from it, was instantly accumulated upon the plumbago point, 

 forming a most beautiful protuberance, completely distin- 

 guishable from the plumbago, and presenting when viewed 

 by the microscope, a congeries of aggregated spheres, with 

 every mark of perfect fusion and with a perfect metallic lus- 

 VoL. VL— *No. 2. 44 



