GRAPHITE 735 



transformed by the action of heat ? The presence of graphite is explicable by neither 

 hypothesis. For, at a certain temperature, which need not be very high, carbon 

 decomposes carbonate of lime. This salt may, no doubt, under strong pressure, be 

 heated to the melting-point without losing its carbonic acid ; this is a laboratory 

 experiment often cited by the Plutonists. But it is quite a different thing with a 

 mixture of carbon and carbonate of lime at a high temperature. If we reject the 

 Neptunian origin of granulated limestone, we must then, as with crystalline rocks, 

 suppose that graphite has been introduced by the wet way at a more recent period. 

 The same remark applies to magnetic pyrites (sulphide of iron), often yery rich in 

 plumbago kerns. 



Does graphite, like all carbon, belong to the organic kingdom ? It is certain that 

 anthracite, lignite, and coal are the result of a slow decomposition of an enormous 

 quantity of vegetables, the impressions found on them often indicate the kind of 

 vegetables, most of them extinct, which have contributed to these carbonaceous for- 

 mations. Graphite, if not formed in precisely the same way as coal and anthracite, 

 nevertheless bears signs of an organic origin. The formation of nuclei and veins of 

 graphite in crystalline rocks is sufficiently explained by the decomposition of car- 

 buretted hydrogen ga"s at a high temperature ; this gas, disengaged from organic 

 matters, and penetrating the fissures of the burning rock, would undergo decomposition 

 into hydrogen and carbon. 



It is this deposited carbon which forms graphite. If in our laboratories we do not 

 obtain exactly the same product, it must be remembered that Nature has means at her 

 command which escape our researches. We find it impossible to make coal from 

 wood. The wood may be carbonised by the dry or by the wet way. In the first 

 case the carbonisation is very rapid ; in the latter it is extremely slow, as is shown 

 by the blackened points of piling sunk in water. 



Finally, graphite has been found in meteorites and aerolites. Attempts have been 

 made to explain its presence here by the continuance of these stones in soil more or 

 less rich in carbonised principles. But with regard to newly-fallen stones, this ex- 

 planation is inadmissible. If it be maintained that graphite is an organic product, 

 it must be admitted that in the case of newly-fallen meteorites it can proceed only 

 from organic matters belonging to another world than our own. 



In his report on Alibert graphite, M. Dumas presents some considerations on the 

 probable origin of graphite and of the diamond. M. Despretz and others ascribe to 

 fire the change of carbon into diamond. Newton ascribed it to the coagulation of a 

 fatty or oily body ; Liebig says the diamond is slowly formed by processes which 

 determine the prolonged putrefaction of a liquid body rich in carbon and in water ; 

 then, contrary to M. Despretz's method, a high temperature would be unfavourable 

 to a successful attempt. Adopting Newton's hypothesis, M. Goppert states, in a 

 ' Memoir on the solid bodies entering into the composition of the diamond, and con- 

 sidered with regard to their organic or inorganic origin,' that he is disposed to class 

 the diamond among the produce of the decomposition of organic matters. All these 

 hypotheses M. Dumas rejects ; according to him the diamond is crystallised carbon, 

 at the moment of its production, and in the midst of a mass which has been exposed 

 merely to the heat necessary to soften it, provided this condition is sufficiently pro- 

 longed. 



Finally, M. Dumas frankly admits that nothing positive is known as to the true 

 origin of the diamond, though the substance most allied to it, silicium, is perfectly 

 known, and very beautiful crystals of it are obtained. 



However, it is positively ascertained that the diamond and graphite have not the 

 same origin, and that the residue of every carboniferous substance, treated at a high 

 temperature, proves to be but a variety of graphite. The graphite found by 

 M. Alibert in the mines of Marinski. situated at the summit of Batougol, on the 

 Siberian frontiers, is, then, a graphitoid carbon of the most "beautiful kind, formed 

 by volcanic phenomena. M. Jaquelain, after carefully comparing the external charac- 

 teristics of Alibert graphite with that obtained by his process, concludes that the 

 conditions under which they are produced must be analogous. 



In fact, on comparing the texture of the two carbons, they will be found sometimes 

 of a metallic, mirror-like lustre ; at another time the surface will be of shining steel- 

 grey, mammillated as if it had been half fused, and had passed through a pasty stage. 

 This appearance is similar to that of oxide of iron, nodular, brilliant, with mammil- 

 lated surface, known by the name of brown hematite. 



M. Jaquelain is inclined to admit that tarry and pyrogenated products, transformed 

 in immense proportions into carbon and hydrogen under the influence of igneous rocks, 

 become accumulated in rents and excavations, causing an aggregation of carbon and 

 inducing a fusion analogous to that of carbon in retorts for lighting gas, and of 

 graphitoid carbon destined to form the pencils used for the electric light. 



