110 Fossil Vegetables. 



There can be scarcely a doubt of the vegetable origin of coal, and 

 although the naturalist makes slow advances in disclosing the secrets 

 of this " dark field of existence," yet enough is known to stimulate 

 inquiry, and justify conjecture. 



If it is assumed that coal is of vegetable origin, the varieties of 

 quality, and the appearance of mineralized plants, which are more or 

 less frequent in coal measures, may be easily accounted for. 



Three external forces are in operation to produce these varieties, 

 which are. 



First, the different nature of the superincumbent strata, some of 

 which may insinuate httle of their substance in place of the decom- 

 posing vegetable matter. 



A second is, the effect of great pressure, excluding atmospherical 

 action, and allowing litde or no escape of vegetable matter — and 



A third, the agency of spontaneous heat, which by causing chemi- 

 cal and other changes in the ligneous fibre, and the concrete juices 

 of the plants, results, in the progress of time, in the formation of 

 those combustible masses, which again vary in quality, proportioned 

 to the resinous and other inherent properties of the plants in their 

 original state. 



Some have supposed that anthracite was originally bituminous 

 coal, which time had robbed of its more volatile and more inflammable 

 parts ; that by undergoing continual change, the bitumen became as- 

 similated to the carbon. This is possible, but it seems more proba- 

 ble, that it owes its peculiarities to the properties of the vegetable 

 materials from which it had its origin. 



The absence of either of the forces acting on a coal bed, would 

 leave the vegetable in a fossil state, e. g. if the amount of heat were 

 insufficient to effect the chemical changes essential to the formation 

 of coal ; or if the stratum in which it was imbedded, contained much 

 water holding mineral or metallic substances in solution, which by in- 

 filtration might fill up the cavities made by the decaying portions of 

 the plant, its form would thus be preserved, when all its original 

 constituents had ceased to exist. 



The subject is one of intense interest, and demands the continued 

 attention of the naturalist. The extended discovery of fossil remains, 

 " those records of past ages," in various parts of Europe, and other 

 quarters of the world, within the last twenty years, has much enlarged 

 the sphere of geological investigation, and proves the necessity of 

 further and more minute examinations " among the dark and pathless 

 repositories of an ancient world." 



