J. L. Smith — Carbon Covipounds in Meteorites 389 



wonder at the part it plays, either as an element or in its end- 

 less combinations with other substances, that element is carbon. 



In its elementary condition we see it in crystals of exceeding 

 hardness and brilliancy in the diamond, and also in irregular, 

 nearly opaque masses that are not to be confounded with the 

 diamond. Again, we have carbon in a soft, black, unctuous 

 state, either in lustrous flaky crystals, or in fine-grained masses. 

 It also occurs in the harsh and gritty form of coke, sometimes 

 changed to an unctuous body approaching graphite in aspect, 

 yet different physically as well as in some of its chemical rela- 

 Deposits of anthracite furnish carbon in yet another 

 Besides these, the results of d ' ' ' - - 



known as organic compounds give qu 

 of carbon, made either by the incomplete combustion of hydro- 

 carbons, or by passing through red-hot tubes the vapors of hy- 

 drocarbons, chloride of carbon, sulphide of carbon, etc., or by 

 the decompositions of such substances as carbonic acid, carbides 

 of boron, of iron, of manganese, etc. 



These various forms of carbon have certain chemical differ- 

 ences, more or less marked, which differences have attracted the 

 attention of chemists, although no one has studied them with 

 much care or success except M. Berthelot, their investigation 

 being difficult on account of the want of proper methods. M. 

 Berthelot obtained his results by taking advantage of the sin- 

 gularly slow oxidizing action of a mixture of nitric acid and 

 chlorate of potash on carbon, first pointed out by M. B. C. 

 Brodie, in I860,* in experiments on graphite, by which he pro- 

 duced for the first time what is known as graphitic oxide. He 

 operated by this means on very many specimens of carbon, 

 from the diamond to lamp-black, embracing a large variety of 

 artificially prepared carbons, and discovered certainly six or 

 eight more or less distinct chemical characteristics of these dif- 

 ferent carbons. t The physical differences of some of them are 

 well known ; among these differences none is more remarkable 

 than that of their specific heats. Other bodies known as elements, 

 as silicon and boron, oxygen, etc., take upon themselves different 

 conditions called allotropic conditions,^ — a term applied to the 

 isomeric conditions of simple bodies ; but carbon differs from 

 these, not only in exhibiting a most wonderful variety of allo- 

 tropic conditions, but also in the phenomena coming under the 

 head of isomerism, polymer' 



, April, I 



conditions, < 

 ig and Petit, they still occupy a singular posit 

 . Jour. Sci.-Third Series, Vol. XI, No. 6 



