Fusion of Plumbago. 343 



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 occupying, 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 degree of beauty. 

 Some of them, 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 colored ; oth- 

 ers still were greyish white, like pearl stones with the trans- 

 lucence 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 I used some of the very pure English plumbago, (saw- 

 ed from a cabinet specimen, and believed to be from Bor- 

 rowdale,) white and transparent globules were formed on 

 the copper side. 



When the points were held vertically, and the plumbago upper- 

 most, no globules were formevi on the latter, and they were unu- 

 sually numerous, and almost all black, on the opposite pole. 

 When the points were exchanged, plumbago being on the 

 zinc, and charcoal on the copper end, very few globules 

 were formed on the plumbago, and not one on the charcoal; 

 this last was rapidly hollowed out into a hemispherical cav- 

 ity, while the plumbago was as rapidly elongated by matter 

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

 microscope, proved to be a concretion in the shape of a cau- 

 liflower — of volatilized and melted charcoal, having, in a 

 high degree, all the characteristics which I formerly describ- 

 ed as belonging to this substance. Indeed, I found by re- 

 petitions of the experiment, that this was the best mode of 

 obtaining fine pieces of melted charcoal. 



In some instances, I used points of plumbago on both 

 poles, and always obtained m.elted globules on both ; the re- 

 sults were however, not so distinctas whenplumoago vvason 

 the copper and charcoal on the zinc pole; but the same elon- 

 gation of the zinc and hollowing of the copper pole took 

 place as before. I detached some of the globules, and part- 



