Tetramorphism of Carbon. 



153 



Whence the mean specific gravity of anthracite may be taken to 

 be about 1-760. In the case of charcoal and lamp-black, the latter 

 experiment in both was with the substance not first heated to dull 

 redness, but the first in each case was most carefully conducted, and 

 I think it is more correct than a mean of the two observations would 

 be. I therefore conclude that the specific gravity of charcoal is very 

 near 1'784, and lamp-black 1*774, which it will be seen to agree very 

 closely with one another, and with that of anthracite, but differ very 

 considerably from that of coke. The mean of the three is 1-773. 



The present may perhaps be as proper a place as any for me to 

 state my reasons for thinking that anthracite, charcoal, and lamp- 

 black are one species. I certainly will admit that in some cases 

 what is not genuine anthracite is so called ; but that which I have 

 experimented on not only has the same specific gravity, as I have 

 shewn above, but in all other properties agrees most closely with 

 charcoal and lamp-black, whilst they all differ very considerably 

 from coke, as I shall subsequently shew. Moreover, as I remarked, 

 the angles found in very minute particles of charcoal appear to be the 

 same as those in anthracite, though they are so very minute that I 

 will not insist on their correct measurement. Taking these facts 

 into consideration, I think it is very highly probable that the square 

 prismatic crystallization found in anthracite is really that which 

 belongs to these three varieties. 



I have not examined the specific gravity of diamond, but the 

 mean of many statements which I find recorded is 3-521. 



By comparing the above specific gravities with the crystalline 

 forms of the various species, I have come to the conclusion that they 

 all result from atoms having the relative volumes of ^, J, and ^, 

 arranged in the manner indicated by their respective forms and 

 cleavages. 



A 



