409 
each one pursues its allotted path and operations : and, like the 
locusts, as mentioned by the prophet Joel (chap. ii. v. *] , 8,) so 
aptly quoted by Sellius, “they march every one on his ways, and 
they break not their ranks ; neither does one thrust another, they 
walk every one in his path.” This curious circumstance will appear 
evidently on a view of Plate VIII. Fig. 9. 
As in the ordinary fossil wood we have perceived that its la- 
pideous impregnation may be either effected by the introduction of 
lime, silex, or alumine, so also, in this variety of fossil wood, similar 
impregnations are met with. In Plate VIII. Fig. 8, is represented 
a most beautiful specimen of silicized bituminous wood, in which 
the ravages of the teredo are very manifest. In this specimen, the 
filtrated silicious matter, having acquired a strong brown or yel- 
lowish tinge, perhaps from the admixture of fluid bitumen, fills up 
one of the cavities left by the worm, with a transparent topazine 
calcedony, giving an appearance exactly resembling that of the 
larva of some insect. Its other cavities are filled with a substance 
so strictly agatine, as to possess not only the colours, but even the 
lines, which characterize that species of agate called the fortification 
agate. Fig. 10 of the same Plate represents a piece of silicized 
wood, which has the appearance of having suffered but little change 
from bituminization ; having rather the appearance of a dry withered 
wood. In this specimen the cavities formed by the teredo are uni- 
formly filled by a white pellucid calcedony, apparently free from 
any foreign intermixture. Fig. 9 of the same Plate is from a spe- 
cimen which is impregnated with carbonate of lime, which, in a 
spathose state, has filled several of the tubes formed by the teredo, 
and invested the internal surface of others. Frequently particles of 
pyrites may be seen intermingled with the calcareous spar ; and 
frequently also will the wood be so permeated by clay, as to allow 
it to be termed aluminous wood ; employing the term in that loose 
3 G 
VOL. I- 
