Tttramorplmm of Carbon. 155 



All these calculated results, and the mean specific gravities found 

 by experiment, will be more readily compared by inspecting the 

 table given farther on, and it will be seen that they agree so very 

 closely, that I think there can be no doubt of the relative volumes 

 and arrangement of the atoms being as above described. Whence, 

 I think, I am safe in concluding that the four species of carbon are 

 brought about by its existing in atoms of the relative volumes of i, 

 ^, and I, of the shape f and arranged in the manner indicated by 

 their respective crystalline forms. I would remark, that the extreme 

 simplicity of these relations, and the close agreement of observation 

 and theory, prove most satisfactorily the truth of the usual supposi- 

 tion, that the atom^ of bodies crystallized in the regular system^ are 

 spheres^ and in the square prismatic, spheroids ; for unless they be 

 assumed so to be, their relationships would not be as above described. 

 Moreover, it is easily shewn mathematically, that the spheroids of 

 the square prismatic system must be generated by the revolution of 

 an ellipse, for no other simple form would answer the conditions of 

 the problem. 



It must also be borne in mind, that in these calculations I have 

 assumed, that the spherical or ellipsoidical atoms really touch one 

 another. This is of course a point about which there may be differ- 

 ence of opinion, but whether we consider them to do so or no, it will 

 be seen that this assumption agrees remarkably well with experi- 

 ment. At all events, if the atoms be supposed to have variable at- 

 mospheres of heat and electricity, these atmospheres would appear to 

 possess the same properties as rigid spheres or ellipsoids. Whether 

 the difference of volume be attributable to the variation in magnitude 

 of these atmospheres, or to that of the elementary atoms themselves, 

 can only be a matter of conjecture. I have therefore in the present 

 paper used the term atom for those ultimate spherical or ellipsoidical 

 particles, the difference in volume, form, and arrangement of which, 

 in my opinion, produce the different properties of the four species 

 of carbon. 



I would also call attention to the necessity of making a most 

 marked distinction between the arrangement of the spherical atoms 

 as an octahedron and a cube, for, though both coke and diamond are 

 crystallized in the regular system, their difference is such that we 

 cannot say that they exist in the same form, the former being a cube 

 and the latter a regular octahedron. 



It has been usual to consider graphite to be crystallized in the 

 rhombohedi-ic system. I however think that its structure agrees 

 much better with the supposition of its atoms being arranged as a 

 regular six-sided prism, and the close agreement of the calculated 

 and found specific gravity proves to my mind that I am correct in 

 so thinking. I would therefore call attention to the necessity of 

 making a wide distinction between its primary form and a rhomb, 

 although undoubtedly the regular six-sided prism is, in many cases, 

 a secondary form of the rhombohedric system. 



