78 STEVENSON— FORMATION OF COAL BEDS. [Apiil2i. 



manner of sediments, one must assign, if he admit this succession, 

 an extraordinary duration to the coal epoch. 



Renault accepts the explanation offered by Fayol and commends 

 especially the shortness of the time which it requires. During the 

 Carboniferous time, the air held more moisture than now, as no 

 ice cap covered the polar regions ; the rains were frequent and 

 abundant; depressions occupied by lakes were filled rapidly. If one 

 consider the strength of the torrents, greater than now, and the 

 vigorous growth of vegetation, surpassing that of the present tropical 

 regions, he will recognize that the formation in the Basin of Com- 

 mentary could have been deposited in even less time than is re- 

 quired by the Fayol hypothesis. The selection, so distinct in deposi- 

 tion in inorganic materials, would take place with equal readiness 

 in the plant materials. Coarse fragments, such as trunks, branches, 

 would be dropped with the sand and clays, while the lighter, finer 

 materials would be carried beyond into deeper parts of the basin. 



Erect stems have little bearing upon the question at issue. 

 Many of them are merely in-floated fragments, while those, which 

 are in situ, do not penetrate the coal beds and have no relation to 

 them. 



Spring*" undertook investigation along a new line. His study, 

 though bearing largely on the question of transformation, finds 

 place here because the results have an important bearing on the 

 manner of accumulation. The homogeneity, the structure and com- 

 position of coal beds all seem to favor the doctrine of transport ; but 

 the stratification within coal beds does not exclude the doctrine 

 of in situ origin, for with rare exceptions modern peat bogs show a 

 structure resembling that of coal. It is clear that a definite conclu- 

 sion respecting mode of formation cannot be reached by study of 

 the coal bed alone : he determined to investigate the shales of mur 

 and toit. 



The mur of a bed formed by transpcM't would be impregnated with 

 vegetable matter to some distance below the coal while the toit 

 should contain little. In the Belgian terrane, the shales of the toit, 



*** W. Spring, "Determination du carl)onc ct de I'hydrogene dans Ics 

 scliistes houillers," Ann. Soc. Geo!, dr Brhilqnc, XIV., 1888, " Memoire.s," pp. 

 131-154. 



78 



