92 On the Decomposition of the Earths. (Jan. 
2. Carbonaceous Substance which floats on Pig Iron during its 
first Fusion.—This substance, owing to its property of soiling the 
fingers, and to its general appearance, has been supposed to be 
plumbago. It was transmitted to me by Mr. Herschell, as a subject 
for trial before the ignited gas; in consequence of the request of a 
lady, Mrs. Lowry, from whom he received it. Dr. Wollaston, 
according to Mr. Herschel’s information, had “ considered it as 
being the most intractable substance by fire he had ever met with.” 
By a letter which I have since received from Dr. Wollaston, I find 
that he has proved this substance to be a carbwret of manganese}; 
and he states that it is called Aish by the iron masters. Mr. Lowry 
had, however, found some specimens of it containing 3222, of 
carbon. When brought, per se, into contact with the ignited gas, 
a scintillation ensues resembling the sparks thrown out by the sort of 
firework which is called a flower-pot, but upon a smaller scale. When 
placed upon charcoal the same appearance takes place, until fusion 
begins, when a bead of metal is formed upon the charcoal; and as 
soon as this begins to boil, sucha rapid combustion takes place that 
the whole of the metad seems to be sent forth in a volume of sparks. 
The bead of this metal exhibits to the file a bright me/allic lustre 
like cron; both before and after fusion it is magnetic. 
3. Carburet of Iron, or Plumbago, from America.—Having 
by me a specimen of this substance, remarkable for its purity, 
which was presented to me by the late Professor Tennant, I 
selected a small fragment, and brought it into contact with the 
iguited gas. Its fusion immediately ensued ; being accompanied, at 
the same time, with that vivid scintillation which was remarked in 
the preceding experiment, and which denotes the combustion of 
metallic bodies ; especially of iron and of platinum. No change of 
colour was, however, to be observed in the flame; the light, as 
usual, was intense. Upon examining the appearance of the plam- 
bago, after fusion, its surface was covered with innumerable minute 
globules, some of which were a limpid and transparent glass; others 
a glass of a brownish hue ; and the larger globules are jet black, and 
opake ; and seem to exhibit a dark metallic lustre; but being so 
exceedingly minute, it is difficult to ascertain their real nature. 
They sink in zaftha, disengaging bubbles of gas. Water produces 
no change in their appearance; they fall rapidly to the bottom, and 
remain there without alteration. 
4. Substance commonly called Gadolinite—Nothing is more 
usual among mineralogists than to see a substance exhibited under 
the name of gadolinite, which is supposed to be distinguished in its 
external characters from dantalite. But these minerals are often 
confounded. It is therefore necessary to premise that the substance 
now alluded to, which came to me from Sweden under the name of 
gadolinite, is utterly infusible by the commen blow-pipe: conse- 
quently, according to the observations of Hausmann,* it ought 
rather to be considered as éanfalite. Before the ignited gas its 
fusion is instantaneous ; it leaves a black shining bead, which is not 
magnetic ; and this upon the action of the file discloses a brilliant 
* See Jameson's Mineralogy, iii. 567. Edinburgh, 1816, 
