158 Henry Clifton Sorby, Esq., on the 



By comparing the facts tabulated above, it will readily be seen 

 that these four species differ in properties in a very decided man- 

 ner ; and the comparison of these differences with the crystalline 

 form and volume of the atoms, appears to lead to some interesting 

 results. In the first place, it is obvious that the properties of the 

 different species must depend either on the different forms and vo- 

 lumes of the atoms, on thuir manner of arrangement, or on both. I 

 have shewn that the specific gravity is a function of both, and the 

 omission of the correction required for the difference of arrangement 

 appears to me to be one of the chief reasons for the difficulty hither- 

 to experienced in attempting to arrive at a correct theory of the 

 relative volumes of solid bodies, as I hope on another occasion to 

 shew. This will more readily be seen by inspecting the upper row 

 of figures in the table, representing the relative specific gravities, in 

 which the figure on the left hand of the x is the inverse volume of the 

 atoms, and that on the right the variation produced by their differ- 

 ence of arrangement ; and if it were omitted, we should obviously 

 have no simple relation between the volumes, and the connection of 

 it with the specific heat would not be at all simple. It will, however, 

 readily be seen that the specific heat is a simple function of the vo- 

 lume of the atoms, and in no way related to the space between them, 

 which depends upon the crystalline form. Such would also appear 

 to be the case with the power of conducting electricity, or transmit- 

 ting and reflecting light, for these properties are the same when the 

 volume of the atoms is so, though the crystalline forms differ, and 

 differ when it differs. The hardness, however, seems to be a com- 

 pound function both of their volume and arrangement. 



It has long been known that diamond, when subjected to intense 

 heat, increases in volume, becomes black, and a conductor of elec- 

 tricity. I do not know whether it then takes the form of anthracite 

 or coke, but conjecture that it may become pseudomorphous coke, 

 such as the square prismatic species is converted into by a high 

 temperature. 



When anthracite, charcoal, or lamp-black have been heated only 

 to dull redness, though they conduct electricity, they do so very in- 

 differently compared with coke or graphite ; and their hardness is 

 then very much less than that of coke. If, however, they are heated 

 to a bright red or white heat, they conduct electricity vastly better 

 than before, and anthracite then cuts glass in the same manner as 

 coke was shewn to do by my esteemed relative Mr James Nasmyth. 

 In the case of charcoal, De la Rive and Marcet have shewn that 

 this treatment causes the specific heat to decrease from *2964 to 

 •2009, which is from that of the square prismatic form to that of 

 coke, or nearly so. When examined by the microscope, anthracite 

 nevertheless still presents the same crystalline structure as before, 

 and its specific gravity, as determined from fine powder, is also the 

 same. I therefore think that a high temperature converts the ulti- 



