IS'o '^'ckntijic IiiteU'gence — Mineralu(/// and CheinUtrif. 



bustion of the diamond, Messrs Erdmann and Marchand liavc ob- 

 tained, like these chemists, a residuum of very small volume, scarcely 

 perceptible in the case of small diamonds, and which consisted of a 

 reddish substance, the parts of which sometimes presented a brilliant 

 surface, and seemed as if they had been already formed and enclosed 

 in the fissures of the burnt mineral. M. Petzholdt found that this 

 residuum (which was not more than 0.0072 gram, in a diamond of 

 5.6344), consisted principally of a great number of small plates or 

 scales, among which were found mingled, but very rarely, softer 

 and more rounded parts. Under the microscope these bodies ap- 

 peared some of them black and not transparent, others like- 

 wise black, but passing into brown, and a little transparent ; 

 Others also were transparent, lig-ht brown, passing into yellow, 

 and, finally, some were yellow or white. With regard to their 

 internal structure, as far at least as it was disclosed by the micro- 

 scope, it appeared to ditt'er in an equal degree, particularly in 

 such as were transparent and semi-transparent; generally it ap- 

 peared granular in those that were transparent and white, radi- 

 ated or plicate in the yellow. Sometimes black masses, similar 

 to grains, might be observed here and there in the substance of the 

 transparent splinters, as well as in the leaflets, whicli gave these 

 portions a brownish aspect when they were looked at with the 

 naked eye. The most interesting circumstance of all is, tliat in 

 a great nuniber of these bodies, we distinctly perceive a delicate 

 net-work, black or deep brown, with hexigonal meshes, many of 

 which often run into each other, and bear an absolute resemblance 

 to those which the researches of the microscope discover in the 

 parenchyma of plants. Sometimes this net-work appears to dis- 

 solve, or rather to have been affected in sucli a way that its con- 

 tours appear to become confounded and disappear, while in the 

 other parts of the same body it v.'as perfectly entire. 



These observations give rise to the conjecture, that this net- 

 work, and the black siilistances which accompany it, are nothing 

 more than the debris of vegetable carbon, the combustion of which 

 could not take place simultaneously with that of tlie diamond, 

 because they were surrounded by bodies incapable of burning". 



The analysis of this residuum by means of the blowpipe lor 

 sale, shews that it consists of silica, with traces of iron. 



On examining the diamonds of commerce at Dresden, and 

 those of the niineralogical collection at the Royal Museum, M. 

 Petzhold has again found among- many of them the same plates 

 or scales, and, in tlie middle of one of them, a small brown, 

 transparent, triangular leaflet, in which he remarked one of these 



