312 Scientific Intelligence. [Oct. 



the size of the smallest shot ; others were merely visible to the naked 

 eye, and others still were microscopic. No globule ever appeared on 

 the point of the plumbago, which had been in the focus of heat, but 

 this point presented a hemispherical excavation, and the plumbago 

 there had the appearance of black scoriae or volcanic cinders. These 

 were the general appearances at the copper pole occupied by the 

 plumbago. 



" On the zinc pole, occupied by the prepared charcoal, there v/ere 

 very peculiar results. This pole was, in everj^ instance, elongated 

 towards the copper pole, and the black matter accumulated there, 

 presented every appearance of fusion, not into globules, but into a 

 fibrous and striated form, like the half flowing slag, found on the 

 upper currents of lava. It was evidently transferred, in the state of 

 vapour, from the plumbago of the other pole, and had been formed 

 by the carbon taken from the hemispherical cavity. It was so different 

 from the melted charcoal, described in my former communications, 

 that its origin from the plumbago could admit of no reasonable doubt, 

 I am now to state other appearances which have excited in my mind a 

 very deep interest. On the end of the prepared charcoal, and occu- 

 pying frequently, an area of a quarter of an inch or more in diameter, 

 were found numerous globules of perfectly melted matter, entirely 

 spherical in their form, having a high vitreous lustre, and a great de- 

 gree of beauty. Some of tlumi, and generally they were those most 

 remote from the focus, were of a jet black, like the most perfect ob- 

 sidian ; others were brown, yellow, and topaz coloured ; others still 

 were greyish white, like pearl stones with the translucence and lustre 

 of porcelain ; and others still, limpid like flint glass, or, in some 

 cases, like hyalite or precious opal, but without the iridescense of the 

 latter. Few of the globules upon the zinc pole were perfectly black, 

 while very few of those on the copper pole were otherwise. In one 

 instance, when 1 used some of the very pure English plumbago, (saw- 

 ed from a cabinet specimen, and believed to be from Borrowdale,) 

 white and transparent globules were formed on the copper side. 



*' When the points were hddveriicaili/, ajid the plumbago uppermost^ 

 no globules were formed on the latter, and they were unusually nu- 

 merous, and almost all black on the opposite pole. When the points 

 were exchanged, })lumbago being on the zinc, and charcoal on the 

 copper end, very few globules were formed on the plumbago, and not 

 Qnfe on the charcoal ; this last was rapidly hollowed out into a hemi- 

 spherical cavity, while the plumbago was as rapidly elongated by mat- 

 ter accumulating at its point, and which, when examined by the 

 microscope, proved to be a concretion in the shape of a cauliflower, 

 of volatilized and melted charcoal, having, in a high degree, all the 

 characteristics which I formerly described as belonging to this sub- 

 stance. Indeed, I found by repetitions of the experiment, that this 

 was the best mode of obtaining fine pieces of melted charcoal. 



** In some instances, I used points oi" plumbago on both poles, and 

 always obtained melted globules on both ; the results were, however, 

 not so distinct as when plumbago was on the copper and charcoal on 

 the z>nc pole ; but the same elongation of the zinc and liollowing of 

 the copper pole took place as before. I detached some of the glo- 

 bulus, and partly bedding them in a handle of wood, tried their hard- 

 ness «pd firmnees ; they bore strong pressure without breaking, aud 



