342 VEGETABLE ORIGIN OF COAL. 



tion takes place of the simpler forms which predominated 

 through the two preceding periods. Smaller Equisetacea; 

 also succeed to the gigantic Calamites ; Ferns are reduced 

 in size and number to the scanty proportions they bear on 

 the southern verge of our temperate climates; the presence 

 of Palms attests the absence of any severe degree of cold, 

 and the general character marks a Climate nearly approach- 

 ing to that of the Mediterranean. 



We owe to the labours of Schlotheim, Sternberg and Ad. 

 Brongniart the foundation of such a systematic arrangement 

 of fossil plants, as enables us to enter, by means of the analo- 

 gies of recent plants, into the difficult question of the Ancient 

 Vegetation of the Earth, during those periods when the 

 strata were under the process of formation. 



Few persons are aware of the nature of the evidence, 

 upon which we have at length arrived at a certain and 

 satisfactory conclusion, respecting the long disputed ques- 

 tion as to the vegetable origin of Coal. It is not unfrequent 

 to find among the cinders beneath our grates, traces of 

 fossil plants, whose cavities having been filled with silt, at 

 the time of their deposition in the vegetable mass, that gave 

 origin to the Coal, have left the impression of their forms 

 upon clay and sand enclosed within them, sharp as those 

 received by a cast from the interior of a mould. 



A still more decisive proof of the vegetable origin, even 

 of the most perfect bituminous Coal has recently been dis- 

 covered by Mr. Hutton ; he has ascertained that if any of 

 the three varieties of Coal found near Newcastle be cut 

 into very thin slices and submitted to the microscope, more 

 or less of vegetable structure can be recognised.* 



concentric layers from without; these form the rinsjs^ wliich mark tlie 

 amount of annual growtli in the Oak and other forest trees in our climate. 



* "In these varieties of coal," says Mr. Hutton, ''even in samples 

 taken indiscriminately,, more or less of Vegetable Te.\ture could alway.-i 



