191 1.] STEVENSON— FORMATION OF COAL BEDS. 75 



with a certain inclination, there is no need of calHng in, for lake 

 basins, dislocations to explain phenomena which may very well be 

 primordial. The time required for the deposits is vastly shortened. 

 Not only a complete coal bed, whatever its thickness, but also a por- 

 tion of the underlying clay and sandstone, becomes before our eyes 

 the product of a single flood. Fayol has shown also the rapidity with 

 which vegetable matter is transformed into coal. The coal of pebbles 

 in the rocks is coal, so that when a portion of the delta was exposed 

 by a change in equilibrium of the surface, its coal sufi^ered erosion as 

 did the other rocks. De Lapparent finds in the study of Commentry 

 some important matters bearing on the origin of the coal itself, which 

 will be considered in another connection. 



The coal of the maritime basins of France is a vegetable allu- 

 vium deposited in a delta ; but the material has been brought from 

 a greater distance and by the action of the waves it has been 

 spread out over a greater area. In the central plateau the vegetable 

 paquets descended violently from the neighboring steep slopes to 

 be deposited en bloc with pebbles of the torrent, thus producing some 

 thick but very localized masses of coal. In the Nord area, there 

 must have been, far above the mouth, wide river sheets in time 

 of flood, many kilometers broad, like the Amazon and Orinoco, on 

 whose surface the vegetable matter was spread. In subsiding, the 

 ulmic materials, which formed the chief mass, separated themselves 

 from the fine clays. This explains the constancy of the floor, while 

 the roof may consist of any materral. As the uniuacerated vegetable 

 matters, fronds and barks, had to float on the surface of the ulmic 

 materials, one can understand why they are so abundant in the 

 roof. The mouth of rivers changed their position, which explains 

 the invasion of brackish waters. Thus is understood easily the 

 filling of the old arm of the sea. 



Why is it that a theory, so luiuinous, has not gained the adhesion 

 of any but Frenchmen? De Lapparent thinks the hesitation due 

 to lack of confidence in anything novel which comes from outside, 

 and tends to overthrow notions so long accepted that thev seem 

 to be part of a national patrimony. Foreign doctrines are subjected 

 to quarantine as foreign goods at a custom house. It is possible that 



75 



