I9II-] STEVENSON— FORMATIOX OF COAL BEDS. 77 



occurred onlv during accumulation of the great beds and that the 

 overflows, bringing about the deposition of sterile rocks, led to 

 transportation of vegetable matter intercalated in the intervals as 

 veinettes, the number of overflows would be greatly reduced. Mal- 

 herbe discusses Fayol's doctrine in detail and at the close expresses 

 much doubt respecting its competence to explain even the phenomena 

 of Commentr}'. 



Renault'*' says that coal beds are intercalated among beds of 

 sandstone and shale and, like those, they have all the features of 

 deposits made in water. In sandstone, the fragments are inorganic 

 and preserve the chemical as well as the mineralogical characters 

 of the rocks whence they came ; in coal, they are derived from plants 

 and conserve the anatomical, at times, also the chemical characters 

 of the plant organs. The fragmentary condition of these organs, 

 the small proportion which they form of the mass, consisting chiefly 

 of a blackish vegetable powder as gangue, show that the plants 

 had been subjected to repeated energetic friction before their burial. 

 So one cannot admit that coal beds were formed solely by accumula- 

 tion, snr place, of debris from an exceptional vegetation, spreading 

 over marshes, lowlands, lagoons, etc., near lakes or the sea; that 

 the surface, subject to elevation and depression, saw, checked and 

 again restored, that great vegetation of which innumerable genera- 

 tions would be represented by successive coal beds. 



The fragments of wood and bark are very small. If the vege- 

 table materials had been changed into coal and buried where their 

 debris is found, it is certain that, in place of these reduced frag- 

 ments, there would be entire trunks, branches and coiuplete leaves 

 as principal constituents of the mass. ]\Iore, taking into considera- 

 tion the diminution of volume, which vegetable tissues experienced 

 in becoming coal, it is evident that numerous forests of high trees 

 growing successively on the same place, would form hardly a few 

 centimeters of compact coal — even though one suppose that, at 

 the foot of the trees, there grew a mass of herbaceous plants. 

 Further, the thick coal beds are separated by great deposits of sand- 

 stone or shale ; as those deposits were fonued slowly after the 

 " B. Renault, " Etudes sur le terrain houiller de Commentry," Livr. 2'"" 

 Flore fossile, Saint-Etienne, 1890, pp. 704-7T2. 



77 



