. III. DIST. CHAR. Mode. 49 



vata. Carbon, as a fixed principle,, exists in recent 

 vegetables,, and forms the chief part of their ligneous 

 substance. When buried in mineral matter., the 

 dissipation of the principles,, with which it was com- 

 bined in the living plant, is followed by oxidation, 

 and an oxide of- carbon, f still retaining the ar- 

 rangement of the original substance,, is the result. 



Bituminated vegetable substances,, or vegetable 

 matter under a certain degree of bituminization^f f 

 are also common as conservata. 



f- Vegetable matter, in a state similar to that of charcoal or 

 burnt wood, is frequent in the mineral kingdom. It not only oc- 

 curs in recent strata, but also in the modern and less ancient, 

 when productive of coal. Some species of coal, indeed, appear 

 to consist almost entirely of this substance. It is only, however, 

 when it retains its vegetable texture or form, that it is to be rank- 

 ed as an extraneous fossil. 



f f We do not conceive it possible, that in perfect bitumens, 

 the product of this process when complete, the texture of the ori- 

 ginal can be preserved, though the form sometimes may, (v. Bitu- 

 minous Petrifactions.) 



Vegetable matter, in the progress of a mineral change, is first 

 deprived of its mucilage, tannin, and other principles soluble in 

 water, extract excepted. In this state, the fossil is to be referred 

 to those which have undergone a partial decomposition and loss 

 (III. 2. privation}, but not an absolute con version (IIL3.) or chemi- 

 cal change, of principles in the remaining matter. The vegetable, 

 however, may now be distinguished from that, which has been sub- 

 jected to a still less degree of change, by its ashes affording no potash 

 after combustion. The next stage of the process appears to be 

 the loss of the extractive principle ; to which succeed the pro- 

 duction of ihe l^s indurated bitumens, from the rttinous part of 



H 



