342 Dr George Wilson on the Possible Derivation of 
tance to the mere preponderance of the latter in the mineral, 
for if abundance of carbon were the criterion of the con- 
vertibility of a chemical compound into diamond, then gra- 
phite should have a decided preference to anthracite. as the 
source of the gem; and there are many reasons for thinking 
that graphite may change its crystalline form, and become 
the transparent octahedral diamond. But anthracite has 
the great advantage over graphite, that, whilst it consists 
in greatest part of carbon, it contains other ingredients 
which can be volatilised out of it by the action of the air on 
it, and the escape of those bodies (carbon, oxygen, nitrogen, 
hydrogen, and sulphur) must disturb the molecular equili- 
brium of the anthracite, and leave gaps between its particles 
of carbon. We may suppose these, accordingly, to fall in, 
or move towards each other, and that in the act of so mov- 
ing, they arrange themselves in the crystalline form of the 
diamond. 
We have evidence so ample at the present day, that the 
most solid bodies can crystallise, though persistent during 
their crystallisation as solids, that it certainly is not neces- 
sary to assume any such interstitial motion in the anthracite 
as has been referred to. But it is not less certain, on the 
other hand, that crystallisation is much more easily induced 
among moving particles returning to rest, than among mole- 
cules locked together so as to have little freedom of mo- 
tion among themselves. The elimination of the hydrogen, 
oxygen, nitrogen, and sulphur, along with a certain amount 
of carbon, would give the opportunity for this molecular mo- 
tion which is so desirable, and yet give it to but a small ex- 
tent at any one time, so that the particles of carbon would 
approximate with great slowness, and assume a position of 
very stable equilibrium. All, I think, will acknowledge that 
the diamond must have been formed by a very slow process. 
Its physical characters, but especially its general chemical 
purity, its solidity, and its regular symmetrical form, forbid 
the notion that it can have been the product of a hasty crys- 
tallisation. 
Sir David Brewster has suggested that a body like amber 
may have been the origin of the diamond, as Sir Isaac New- 
ae ee et ds ee 
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