inc eetintt t— 
Experiments upon Diamond, Anthracite and Plumbago. 351 
ous distinct but very minute scintillations were darted from 
itin every direction, and I could see the minute cavities and 
projections which I have mentioned, forming every instant. 
In this experiment I gave the peat. but one heat.of about 
a minute, but on examining it with a magnifier, I was sur- 
prised to find, that only a very thin layer of the gem, not 
much thicker than writing paper remained, the rest having 
been burnt.* 
I subjected the anthracite of Wilkesbarre, Penn. to 
similar trials, and by heating it very gradually, its de- 
crepitation was obviated. It was consumed, with almost 
as much rapidity, as the diamond; but exhibited, during 
the action of the heat, an evident appearance of being 
superficially softened; I could also distinctly see, in the 
midst of the intense ‘glare of light, — minute globules 
forming upon. the surface. These when examined b: 
a magnifier, proved to be perfectly white and limpid, and 
the whole surface of the bia Bog exhibited, like the dia~ 
mond, only with more distinctness, cavities and projections 
united by flowing lines, and covered with a black varnish, 
exactly like some of the volcanic slags and semi-vitrifications. 
The remark already made, respecting the diamond, appears 
to be equally applicable to the anthracite, i. e. that its want 
of conducting power, is the reason why it is not melted by 
the deflagrator, and its combustibility is si sole obstacle to 
its complete fusion by the compound blow-pipe. 
I next subjected a eee of plumbago to the com- 
pound flame. It w nsumed_ with considerable ra i pe 
but presented at es me time, numerous globules o melt- 
ed matter, clearly ee by the naked eye, and 
when the piece was afterwards examined, with a good glass, 
it was found richly adorned, with numerous perfectly white 
and transparent spheres, connected also by white lines of the 
same matter, covering the greater part of the surface, for thie 
*In Tilloch’s Phil. Mag. for November 182, Vol. 58, page 386, I observe 
the following notice by Mr. John Murray. “By repe por. axporing | a 
diamond to the action of the oxy-hy yatogen i blo W-pipe ina s of magne 
it became as ned as charcoal, and split into fragments which, Malayad the 
It will be found, that this gem affixed in magnesia “area ff in minut 
ragments, exhibiting t the impress of the conchoidal 
In lately exposing the diamond fixed on a support of pibe-clay, oe the igni- 
ted gas, I succeeded in completely indenting it :—examin r the ex- 
periments, it exhibited proofs of having undergone fusion.”’ 
