19I3-] STEVENSON— FORMATION OF COAL BEDS. 131 



blocks encased in coarse to fine granitic sand, are merely disin- 

 tegrated granite, the same as that which one sees at many localities 

 between Alontlngon and Decazeville. This is much like the great 

 deposit underlying the Alesozoic coal area in Virginia, described 

 by Shaler and Woodworth.'^*^ The writer could discover no evi- 

 dence that a deep body of water occupied the Decazeville basin at 

 any time, but there is abundant evidence that the water area was 

 never extensive, except possibly toward the close of deposition. ^^^ 



The doctrine of allochthony is not bound to the hypotheses which 

 have been considered, for some of its defenders have no patience 

 with either the Delta or the Barricade theory. The essential feature 

 of the doctrine is, that vegetable matter growing on the land was 

 removed by running water and deposited in water-basins, there to 

 become coal ; but there are individual differences in detail. Wood- 

 ward, Scheuchzer, Conybeare, Buckland, Murchison, Fayol, de 

 Lapparent, Renault, Ochsenius, Lemiere and Stainier believe that 

 the work was done by energetic floods ; Grand 'Eury and Sterzel see 

 no proof of devastating floods, but appear to regard great rains and 

 mild floods as sufficient ; while de Jussieu, Buffon, Hutton, Faujas- 

 St.-Fond, Naumann and Jukes do not concern themselves with the 

 work of transference, but deal only with distribution after materials 

 have reached the water-area. But for all, the principle of distribu- 

 tion by gravity holds an important place. One author puts the 

 matter compactly. Coal plants grew on continents bordering great 

 depressions, into which the meteoric agencies carried vegetable 

 debris along with materials torn from the land by erosion. As 

 calm was restored, the materials went to the bottom in well-defined 

 order, determined by density ; sandstone first, then the mur, then 

 the coal and, finally, impalpable clays reached the bottom to form 

 the roof. 



Many authors appear to be convinced that all portions of a 



"^ N. S. Shaler and J. B. Woodworth, " Geology of the Richmond Basin, 

 Virginia," 19th Ann. Rep. U. S. Geol. Surv., 1899, Part II., PI. XXI. 



"' J. J. Stevenson, " The Coal Basin of Commentry in Central France," 

 Ann. N. Y. Acad. Sci., Vol. XIX., 1910, pp. 161-204; "The Coal Basin of 

 Decazeville, France," ibid., Vol. XX., 1910, pp. 243-294. 



