338 
not in the least, in its appearance, from the knot in a piece of 
recent wood, but is perfectly impregnated with silicious matter. 
Is it possible, that the change, which this knot has suffered, could 
have been effected, by an abstraction of the greater part, or of the 
whole, of its original constituent parts, and a substitution of par- 
ticles of a totally different nature ? Its hardness, and its closeness of 
texture, must oppose an insuperable bar to the supposition ; whilst 
the mysteriousness of the change is entirely dispelled, by admitting 
the softening operation of bituminization, and the consequent ad- 
mission of silicious matter. 
But another circumstance, peculiar to this species of fossil wood, 
requires a particular inquiry ; the result of which cannot but affect 
the opinion just noticed. This circumstance is the peculiar lustre 
which this species of wood displays : its fracture, in general, exactly 
resembles that of newly-broken resin ; and, generally, the lustre of 
its external surface approaches, as near as possible, to that which 
would have been produced by pouring over it a thin coat of melted 
resin, or of fine varnish. 
In the specimen of a petrified root, represented in PI. II. Fig. 2. 
this kind of coating, thinly spread, covers and softens down ail the 
asperities of its surface : and in Fig. 3. of the same Plate, the larger 
pores seem to have been diminished, and some of them obliterated, 
by the diffusion of this matter. The rough edge of the specimen, 
Fig. 4. of the same Plate, also derives a bright gloss from this seeming 
resinous varnish. 
Struck by this appearance, the celebrated Hauy terms it, as we 
have seen, quartz resinile ocyloidc*; and Mr. Walch’s attention was 
particularly excited by this peculiar resinous or waxy gloss, which he 
endeavoured to account for, by supposing that this petrified wood 
had been impregnated by a peculiar spathose matter ; which had 
* Trait 6 de Mineralogie, tom. ii. p. 139. 
