350 Experiments upon Diamond, Anthracite and Plumbago, 



ling, that, although, through green glasses, I could steadily 

 inspect the focus, it was impossible to distinguish the dia- 

 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 1 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 «n- 

 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. These 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 1 used a support of plumba- 

 go, there were some interesting varieties in the phenomena. 

 The 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, 

 hovered over it; the surface appeared as if softened, numer- 



