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, 
Furst, the different nature of the superincumbent strata, some of 
which may insinuate little of their substance in place of the decom- 
posing vegetable matter. 
A second is, the effect of great pressure, excluding sicioapberal 
action, and allowing little or no escape of vegetable matter—an 
Al 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 bins 
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 Bagetable 
materials from which it had its origin. 
The absence of cither of the forces acting ona on bed, A 
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 bobdine 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.” 
