167 
think that the ultimate atoms are converted into the coke 
form, though they retain their former crystalline structure, 
and are therefore pseudomorphous. It is, however, remark- 
able that the specific gravity of anthracite is not increased 
by this treatment, when it is determined from fine powder. 
One point of geological interest in this inquiry is, the fact 
that anthracite is found in the same condition as wood takes 
when exposed to a red heat, and not that produced by the 
action of heat on coal; for in the latter case we, I believe, 
invariably obtain the coke form. Why this should be so I 
will not venture to say, farther than that perhaps it may be 
owing to the manner of heating, joined to the great pressure 
which must usually have been in operation in the case of coal 
converted into anthracite. Moreover, it should appear that 
anthracite cannot have been exposed to a white heat, or else 
it would, in all probability, have been converted into pseudo- 
morphous coke. 
As to the manner in which anthracite has been converted 
into graphite, the fact of the piece of coke which is attached 
to the anode being converted into it, and not that to the 
cathode, would point not so much to the mere efiJ'ect of heat, 
as to the combined action of a positively electric condition. 
I should therefore conclude, from various circumstances, 
that diamond has been formed at a low temperature; the 
square prismatic or charcoal form at about a red heat ; the 
coke form at a still higher temperature ; and graphite at an 
intense heat, combined with the action of highly-developed 
positive electricity ; and it is worthy of remark that the re- 
lation of their specific gravities, as calculated and as found 
by experiment, coincides with this view of the subject. I 
have compared them by calculation, (see table), supposing the 
charcoal form to be normal, and it will be observed that the 
specific gravity of diamond is lower, and those of coke and 
graphite higher, than indicated by theory; which agrees 
