1^067^ " of ihe nem Varieties of Carbon^ ^c. 195 



compressed, modified, and intermingled. That such is the 

 structure of mamillary concretions, the examination of a specimen 

 of botryoidal iron-stone, or of malachite, will convince every 

 observer. And the tendency to unite around centres, which all 

 bodies manifest, when at liberty to exert their inherent qualities, 

 unaffected by surrounding or contiguous substances, would 

 produce this mamillary structure, as in the instances just men- 

 tioned, from the filaments already formed by the attractioti 

 before described. 



I cannot but think it probable, that if this carbon could be 

 kept in fusion, and be slowly instead of rapidly cooled, the 

 atoms would arrange themselves in several directions at once, 

 or in a crystalline arrangement, and that thus the diamond 

 would be the result. We know crystallization to be in all 

 cases a gradual process, and to arise from liquidity continued 

 for a sensible portion of time. On the other hand, the 

 instantaneous transition from the liquid to the solid statfe 

 appears to be the cause of the pulverulent or irregular form 

 of the varieties of carbon, obtained by passing alcohol and cer- 

 tain oils through ignited porcelain tubes. And it may be 

 remarked, that the carbon produced by the decomposition of 

 the gas, in Mr. Macintosh's process for making steel, must 

 necessarily be in a state to exert its inherent properties, much 

 more freely and independently, than in the cases last referred 

 to ; and hence the greater approximation of the carbon, sepa- 

 rated in that process, to what we may suppose to be, pre- 

 eminently, the proper form of that substance. As so many 

 other substances, when in their nascent state, exhibit their 

 properties in a much more decided manner than at other times, 

 this may also be one of the reasons why this carbon is in a 

 denser state of aggregation, &c. than in its more common forms, 

 obtained under circumstances less favourable to the free deve- 

 lopment of its inherent properties. 



But it may, perhaps, be objected to the hypothesis I have 

 advanced on the formation of the mamillary and filamentous 

 varieties of carbon, that we have no proof that the liquid 

 state necessarily intervenes between the aeriform and the solid 

 states, and that, for aught we know, a body may pass di- 

 rectly from the former to the latter. It appears to me, how- 

 ever, that the great bulk of facts in Chemistry, in which the 

 passage of bodies from one state to another is concerned, 

 together with all that we know of the production of vapours from 

 liquids, and the condensation of vapours into liquids reci- 

 procally, points to the conclusion, that the liquid is a necessary 

 and an invariable intermediate state to the sohd and the gaseous. 

 1 shall not, however, content myself with this general statement. 

 I shall first urge some reasons for thinking that the above is the 

 case in all instances, derived from some recent discoveries in 



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