I9II.] STEVENSON— FORMATION OF COAL BEDS. 59 



objection. In the little basins of Saint-Etienne, beds can be followed 

 5 to lo kilometers in one direction and 2 to 4 in another with little 

 change. He thinks that a current capable of uprooting trees would 

 tear away the soil and pebbles also, so as to give a mingling of trees 

 and detrital matter. 



As large streams carry much mineral material there should be 

 an alternation of vegetable elements and mud — and this is found 

 in coal beds where shale appears in thin layers between benches 

 of coal. These shales or the nerfs of fine sandstone could be pro- 

 duced only by water-currents, by inundations of brief duration cov- 

 ering the debris on the surface or invading shallow basins in which 

 leaves, etc., were deposited slowly. The two modes of accumulation 

 went on simultaneously in the coal period as they do now in peat 

 bogs. He does not assert that coal was the peat of palaeozoic times; 

 the flora and the climate were difl^erent ; but the mode of formation 

 was the same. The plants of the coal epoch grew where their 

 remains are found. He cannot accept Grand' Eury's theory, which 

 opposes the doctrine of in situ accumulation because stumps and 

 trees are wanting in the coal beds themselves. Grand' Eury main- 

 tains that the vegetable matter was transferred from the place of 

 growth to the basin where the coal is found, but the distance was 

 small. 



Gruner maintains that the current would have brought more than 

 leaves and stems and that it would have distributed its load unecjually ; 

 he thinks it preferable to conceive of a marshland extensive enough 

 to admit of a thick cover of vegetable debris over an area of several 

 thousands of square kilometers — as one finds in the Nord basin. 

 Grand' Eury emphasizes the absence of stumps and roots passing 

 from coal beds to the mur. But at Saint-Etienne itself, Lyell and 

 Gruner saw rootlets passing from the coal into the underclay and 

 Gruner saw the same condition in the Batardes coal bed, where 

 Stigmaria abounds in the mur. The absence of stumps in the coal 

 is to be expected, because the soft tissues would be crushed quickly 

 under pressure and all traces would be effaced ; moreover, in the 

 nature of the case, stumps would be only a small portion of the 

 mass. A negative result of study does not prove that the plants 



59 



