333 
existed, may be presumed to have been in a more fluid state, than 
the bituminous wood which had helped to constitute the two before - 
mentioned specimens. Specimens of this kind of fossil wood are, I 
believe, rather rare ; but the separation of silicious matter, with 
which solid bituminous wood has been saturated, may be very fre- 
quently seen in specimens, in which the whole silicized bituminous 
substance is covered with resplendent drusy quartz crystals. In- 
stances of this kind are so numerous, as to render an illustration of 
this appearance, by a Figure, unnecessary. 
Agatine fossil wood. This term may be appropriated to such 
fossil wood as possesses a glassy lustre, breaks with rather a con- 
choidal fracture, gives sparks freely with steel, and is either marked 
by spots and illinitions of a bright crystalline matter, with which its 
vacuities have been filled, or has its several surfaces and cavities 
lined with quartz crystals. The blending of the characters of agate, 
and of fossil wood, seems to have been generally effected, by the ac- 
cumulated investments of the drusy crystals, just mentioned, formed 
by the transudation of the clear silicious fluid, into the interstices, 
and round the surface of the saturated bituminous wood. The sub- 
stance and opacity of the altered wood will, however, generally 
prevent that transparency, those linear marks, and those other ap- 
pearances, which generally characterize the modifications of silex to 
which the term agate is given. In one specimen, however, now 
before me, such appears to have been the tenuity and the smallness 
of quantity of the bituminous wood, as to have allowed the silicious 
matter, with which it is involved, to possess a considerable degree of 
transparency ; and in the specimen depicted at PI. VIII. Fig. 3. 
and 5. of the starry stone of Chemnitz, the tubuli are filled wdth 
agatine matter, conspicuously displaying those marks which charac- 
terize, what is termed, the fortification agate. 
Jasperized wood is never of itself transparent, nor has any 
crystalline illinitions, except such as sometimes appear to have been 
