350 Experiments upon Diamond, Anthrante and Plumbago. 
ling, that, although, through green glasses, I could steadily 
inspect the focus, it was impossible to distinguish the di 
mond, in the perfect solar brightness. This mode of con- 
ducting the experiment, proved, however, perfectly manage- 
able, and a large dish, placed beneath, secured the diamonds 
from being lost, (an accident which | had more than once 
met with) when suddenly displaced by the current of gas ; 
as however, the support was not combustible, it remained 
permanent, except that it was melted in the whole region of 
the flame, and covered with a perfect white enamel of vit- 
reous lime. The experiments were frequently suspended, 
to examine the effect on the diamonds. ‘They were found 
to be rapidly consumed, wasting so fast, that it was necessa- 
ry in order to examine them, to remove them from the heat, 
at very short intervals. They exhibited however, marks of in- 
cipient fusion. My experiments were performed upon small 
wrought diamonds, on which there were numerous polished 
facets, presenting extremely sharp, and well defined solid 
edges and angles. nese edges and angles were always 
rounded and generally obliterated. The whole surface of 
the diamond lost its continuity, and its lustre was much im- 
paired; it exhibited innumerable very minute indentations, 
and intermediate and corresponding salient points; the whole 
presenting the appearance of having been superficially soften- 
~ed, and indented by the current of gas, or perhaps of having 
had its surface unequally removed, by the combustion. In 
various places, near the edges, the diamond was consumed, 
with deep indentations, and occasionally where a fragment 
had snapped off, by decrepitation, it disclosed a conchoidal 
fracture and a vitreous lustre. These results were nearly 
uniform, in various trials, and every thing seems to indicate 
that were the diamond a good conductor, it would be melt- 
ed by the deflagrator, and were it incombustible, a globule 
would be obtained by the compound blow pipe. 
In one experiment, in which | used a support of plumba- 
Are there were some interesting varieties in the phenomena. 
he plumbago being a conductor, the light did not accumu- 
late as it did when the support was lime, but permitted me 
distinctly to see the diamond through the whole experiment. 
It was consumed with great rapidity ; a delicate halo of blu- 
ish light, clearly distinguishable from the blow pipe flame, 
overed over it; the surface appeared as if softened, numer- 
