344 | Fusion of Plumbago. 
ly bedding them in a handle of wood, tried their hardness 
and firmness; they bore strong pressure without breaking, 
and easily scratched, not only flint glass, but window glass, 
and even the hard green variety, which forms the aqua for- 
tis bottles. The globules which had acquired this extraor- 
dinary hardness, were formed from plumbago which was so 
soft, that it was perfectly free from resistance when crush- 
ed between the thumb and finger, and covered their surfa- 
ces with a shining metallic looking coat. These globules 
sunk very rapidly in strong sulphuric acid—much more so 
than the melted charcoal, but not with much more rapidity 
than the plumbago itself, from which they had been formed. 
The zinc of the deflagrator is now too far gone to enable 
me to prosecute this research any farther at present; as soon 
as the zinc coils can be renewed, | shall hope to resume 
them, and I entertain strong hopes, especially from the new 
improved and much enlarged deflagrator, which you are so 
kind as to lead me soon to expect. from Philadelphia. 
April 12.—Having refitted the Deflagrator with new 
zine coils, | have repeated the experiments related above, 
and have the satisfaction of stating that the results are fully 
confirmed and even in some respects extended. The De- 
flagrator now acts with great energy, and in consequence I 
have been enabled to obtain good results when using Plum- 
bago upon both poles. Parallelopipeds of that substance, 4 
of an inch in diameter and one inch or two inches long, being 
screwed into the vices connecting the poles, on being 
brought into contact, transmitted the fluid, with intense 
splendor, and became fully ignited for an inch on each side; 
on being withdrawn a little, the usual arch of flame was | 
formed for half an inch or more. Indeed when the instru- 
ment is in an active state, the light emitted from the plum- 
bago points, appears to be even more intense and rich than 
from charcoal; so that they may be used with advantage, in 
class experiments, where the principal object is to exhibit 
the brilliancy of the light. 
On examining the peices in this, and in numerous other 
cases, I found them beautifully studded with numerous glo- 
bules of melted plumbago. They extended from within a 
quarter of an inch of the point, to the distance of } or 4 of an 
inch all around. They were larger than before and per- 
