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 

 accumulated investments of the drusy crystals, just mentioned, 

 formed by the transudation of the clear silicious fluid, into the in- 

 terstices, and round the surface of the saturated bituminous wood. 

 The substance and opacity of the altered wood will, however, ge- 

 nerally prevent that transparency, those linear marks, and those 

 other appearances, which generally characterize the modifications 

 of silex to which the term agate is given. In one specimen, how- 

 ever, 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 consi- 

 derable degree of transparency ; and in the specimen depicted at 

 PL VIII. Fig. 3. and 5. of the starry stone of Chemnitz, the tubuli 

 are filled with agatine matter, conspicuously displaying those .marks 

 which characterize, what is termed, the fortification agate. 



JASPERIZED wood is never of itself transparent, nor has any crys- 

 talline iilinitions, except such as sometimes appear to have been. 



