342 Fusion of Plumbago. 



ed, through the remaining coils. As my hopes of success, 

 in the actual state of the instrument, were not very san- 

 guine, I was the more gratified to find a decided result in 

 the very first trial. To avoid repetitions 1 will generalise 

 the results. The best were obtained, when the plumbago 

 was connected with the copper, and prepared charcoal with 

 the zinc pole. The spark was vivid, and globules of melted 

 plumbago could be discerned, even in the midst of the igni- 

 tion, forming and formed upon the edges of the focus of 

 heat. In this region also, there was a bright scintillation, 

 evidently owing to combustion, which went on where air 

 had free access, but was prevented by the vapor of carbon, 

 which occupied the highly luminious region of the focus, 

 between the poles, and of the direct route between them. 

 Just on and beyond the confines of the ignited portion of the 

 plumbago, there was formed a belt of a reddish brown 

 color, a quarter of an inch or more in diameter, which ap- 

 peared to be owing to the iron, remaining from the com- 

 bustion of the carbon of that part of the piece, and which, 

 being now oxidized to a maximum, assumed the usual co- 

 lor of the peroxide of that metal. 



In various trials, the globules were formed very abundant- 

 ly on the edge of the focus, and, in several instances, were 

 studded around so thickly, as to resemble a string of beads, 

 of which the largest were of 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 were very peculiar results. This pole was, in every 

 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 vapor, from the plumbago of the other pole, and 

 had been formed by the carbon taken from the hemispher- 

 ical cavity. It was so different from the melted charcoal, 

 described in my former communications, that its origin 



