191 1.] STEVEXSOX— FORMATIOX OF COAL BEDS. 115 



down, seeing there the conditions of deha formation as long recog- 

 nized by geologists in American coal fields ; but he could discover no 

 reason for supposing that the coal beds were formed of plant ma- 

 terials washed in from the drainage area. That hypothesis, as pre- 

 sented for this region, seems to be self-contradictory. The supposed 

 surface conditions at the beginning of the history were such that 

 dense vegetable cover seems in the last degree improbable ; but the 

 vegetation required by the hypothesis was so dense, that it would 

 have been its own protection against any but a long-continued series 

 of the most terrific cloud-bursts ; in case of such a debacle, only a 

 small part of the vegetable matter could be deposited as a coal bed, 

 for the trees, supposed to have composed one half of the whole 

 vegetation, would be loaded by material around their roots, would 

 be snags in the mass of detritus and would be buried in the sands ; 

 even the twigs and underbrush would be entangled in the mass, for 

 there could be no sorting action in the short course of the little tor- 

 rent and all would be dropped when the flood's velocity was checked 

 on the comparative]}' broad delta surface, supposed to exist when 

 formation of the Grande Couche began. Only the finest material, 

 mineral, or vegetable, could find its way to the bottom of the basin — 

 yet it is certain that trees make up a very considerable part of the 

 Grande Couche. The objections presented by this writer will be con- 

 sidered in another connection. He thinks that the structure of the 

 Grande Couche shows that its vegetation accumulated /// situ and 

 that there is no evidence to favor the suggestion that Lake Com- 

 mentry was a deep water basin at the time when coal accunuilation 

 began. 



Study of the Decazeville basin led him to similar conclusions 

 respecting that area. The conditions there are very different from 

 those in the Commentry basin, so dift'erent that any doctrine of 

 transport formulated to account for the conditions at Commentry 

 could not be applicable at Decazeville. 



Studv of investigations by v. Giimbel and Potonie led Gothan"^ 

 to studv the coal area near Fiinfkirchen. The economic importance 

 of the Liassic coals within that area had been known for more than 



"' \V. Gothan, " Untersiichungen iiber die Entstehung der Lias-Stein- 

 kohlenflotze bei Fiinfkirchen (Pecs. Ungarn),"' Sifcungsbcr. d. k. prcus. 

 Akad., VIIL, 1910, pp. 129-143. 



115 



