335*33 
called Sydneia or Terra Australis. 125 
plumbago ; especially as some experiments which I purposely 
made, on that from Keswick in Cumberland, were attended 
with similar results. 
It is also evident, that these particles could not be eisen- 
glimmer or micaceous iron, as nitre has little or no effect on 
that substance, when projected into a heated crucible. 
In a subsequent experiment on the same, the crucible was 
removed immediately after the last projection, and I then ob- 
served that an effervescence, with a disengagement of carbonic 
acid, took place, upon the addition of the muriatic acid, as is 
usual when pure plumbago is decomposed by nitre, and that 
less of the gelatinous matter was formed by evaporation. 
The cause of this difference was evidently the duration of 
the red heat ; for, in the first instance, the alkali developed by 
the decomposition of the nitre had time to unite with the sili- 
ceous earth, so as, when dissolved, to form liquor silicum ; but, 
in the second experiment, a portion of alkali remained com- 
bined with the carbonic acid, produced by the carbon of the 
decomposed plumbago. 
The produce of 100 grains by this analysis was, 
grains. 
Silica - - - \ 
[ D. 0.30 
I tt 
hk a 
' ** *’•’ ■ •• *** 
1 
[H. 75.25 
!* t y 1. i 
Alumine - 
F. 7.20 
r 
> D/C J ^ X 
Oxide of iron 
E. q. 20 
-a' 
Graphite or plumbago 
I. 10.25 
10-2342 X 
Water r 
A. 2.20 
-Mojalz .. 
98.40 
12-S-4QJ J 
Mr. Wedgwood says, that sulphuric 
acid cannot dissolve 
■ 
the precipitated earth, and has but little effect on the mixed 
