182 Prof. Silliman on the Fusion of Plumbago, tyc. 
possibility that alkaline and earthy impurities may have contributed 
to the result.” 
The next experiments of Professor Silliman were made upon 
anthracite and the diamond, by means of the oxy-hydrogen 
blowpipe of Dr Hare. 
“ My first trials were made, by placing small diamonds in a cavity 
in charcoal, but the support was, in every instance, so rapidly con- 
sumed, that the diamonds were speedily displaced by the current of 
gas. I next made a chink in a piece of solid quicklime, and crowd- 
ed the diamond into it : This proved a very good support, but the 
effulgence of light was so dazzling, that although, through green 
glasses, I could steadily inspect the focus, it was impossible to dis- 
tinguish the diamond, in the perfect solar brightness. This mode of 
conducting the experiment proved, however, perfectly manageable, 
and a large dish, placed beneath, secured the diamonds from being 
lost (an accident which I had more than once met with) when sud- 
denly displaced by the current of gas. As, however, the support 
was not combustible, it remained permanent, except that it was melt- 
ed in the whole region of the flame, and covered with a perfect white 
enamel of vitreous lime. The experiments were frequently suspend- 
ed, to examine the effect on the diamonds. They were found to be 
rapidly consumed, wasting, so fast, that it was necessary, in order to 
examine them, to remove them from the heat at very short intervals. 
They exhibited, however, marks of incipient fusion. My experiments 
were performed upon small wrought diamonds, on which there were 
numerous polished facets, presenting extremely sharp and well-de- 
fined SQlid edges and angles. These edges and angles were always 
rounded and generally obliterated. The whole surface of the dia- 
mond lost its continuity, and its lustre was much impaired ; it exhi- 
bited innumerable very minute indentations, and intermediate and 
corresponding salient points ; the whole presenting the appearance 
of ha ring been superficially softened, and indented by the current of 
gas, or perhaps of having had its surface unequally removed, by the 
combustion. In various places, ne^r the edges, the diamond was 
consumed, with deep indentations. These results seem to indicate 
that, were the diamond a good conductor, it would be melted by the 
deflagrator ; and, were it incombustible, a globule would be obtained 
by the compound blowpipe.” 
Professor Silliman next subjected the Anthracite of Wilkes- 
barre, Pennsylvania, to similar trials. 
“ It was consumed,” says he, “ with almost as much rapidity as the 
diamond; but exhibited, during the action of the heat, an evident ap- 
pearance of being superficially softened. I could also distinctly see, 
in the midst of the intense glare of light, very minute globules form- 
ing upon the surface. These, when examined by a magnifier, proved 
to be perfectly white and limpid, and the whole surface of the an- 
thracite exhibited, like the diamond, only with more distinctness, ca- 
vities and projections united by flowing lines, and covered with a 
black varnish, exactly like some of the volcanic slags and semi-vitri- 
fications.” 
