324 Dr Petzholdt 07i the Formation of the Diamond. 



oxplanation of the origin of the diamond, which cannot be 

 k'ft unnoticed, as they are well calculated to place the truth 

 of our assertions in a clearer point of view. As I have already 

 stated elsewhere, diamonds not unfrequently exhibit at their 

 surface blackish spots, which disappear on the application 

 of heat ;* and, moreover, they very frequently present in 

 their interior perfectly black, amorphous bodies, which cannot 

 be considered as any thing else but uncrystallized carbon, — 

 a fiict observed in the course of Parrot's investigations, as well 

 as my own. This phenomenon can only be explained by as- 

 suming a somewhat accelerated decay of the matter containing 

 carbon and hydrogen ; in the course of which the carbon has 

 been produced in the form of a black powder, instead of being- 

 separated in a crystalline state. On the other hand, I have on 

 several occasions had an opportunity of convincing myself of 

 the tendency of carbon to crystallize, when the combustion 

 (the accelerated decay t) of a substance rich in carbon and 

 hydrogen is retarded. Thus, on the wicks of badly burning 

 tallow candles, I have seen the well-known accumulations of 

 carbonaceous matter (soot), which have generally globular or 

 semi-globular forms, assume distinctly an octahedral shape ; 

 and I believe that this appearance has long been observed by 

 others, for it is only by the resemblance of an octahedron 

 to the envelope of a letter that I can explain the popular say- 

 ing, of there being a letter in the wick of a candle. I have 

 even preserved, for some time, one of these tolerably well- 

 defined octahedrons, and exhibited it to my class ; but it was 

 at last broken, and it then appeared that the fragments were 

 harder than the ordinary soot, although they could still be 

 easily bruised between the fingers. 



Lastly, let me add a few words regarding the experiments 

 made in recent times on the production of artificial diamonds, 

 for I believe that I may say, without exaggeration, that, since 

 it was discovered that the diamond consists of pure carbon, 



* See Parrot, Notice suv les Diamans, p. 30 and 31. 



t That combustion is only a rapid decay, and decay only a slow combus- 

 tion, is known to .ill cliemists. Above all, see Liebig's remarks on this 

 subject in the second part of bis Organic Chemistry. 



