339 
been deposited, whilst in a fluid state, and afterwards congealed. 
There appears, he says, commonly, in this wood, something which 
resembles amber, or resin ; and which has, by some, been actually 
supposed to be so, and to have assumed a stony hardness. This 
he, however, concludes is not the case ; but believes that this sub- 
stance, as he had already asserted, must actually be a particular 
species of spar*. 
Nothing certainly, as far as the evidence of the eye can be ad- 
mitted, can more strongly favour the opinion, that the formation 
of this species of fossil wood has depended on a combination of 
silicious and bituminous matter, than the peculiar lustre which 
it possesses; which is pi-ecisely such as might be expected from 
the mixture of these two substances. Different specimens, indeed, 
seem to display the bituminous wood in all its several degrees of 
change ; from its first assumption of a bituminous nature, to the ac- 
quiring of the state of pure translucid bitumen ; and evince its having 
obtained, in these several states, its present degree of hardness, 
from the introduction of the silicious matter. In such varieties of 
this fossil wood, as manifest evident and strong traces of the original 
fibres, there seems to be reason for supposing, that the wood had 
not undei-gone the bituminizating operation, to such a degree as to 
have been thereby rendered a fluid bitumen. But that the wood, 
previous to its impregnation with silicious matter, had been so far 
affected by its bituminization, as to have been rendered soft and 
yielding, is evident from the appearances which specimens of this 
kind of fossil wood generally yield. Their fibres will generally be 
seen disturbed, and thrown out of their natural direction ; not as if 
broken, but as if displaced whilst in a yielding state, and thrown 
into gentle contortions and undulations. An idea of what is here 
meant may be furnished by a view of PI. II. Fig. 7- 
* Recueil des Monuraens des Catastrophes, &c. tom. iii. p. 32 and 39, 
