112 STEVENSON— FORMATION OF COAL BEDS. [April 21. 



geologically, have succeeded in solving the problem for the basins 

 of central France. He hopes by following their methods to solve 

 the problem in the great basins of northwestern Europe. 



If one study not the coal beds alone but also the whole series 

 of deposits in those coal basins, he finds that their strata differ in 

 no wise from those of terranes, whose marine origin is recognized 

 by all. No feature of coal. beds suggests a different origin for them. 

 On the contrary, when one endeavors to explain the formation of 

 coal beds by the in situ doctrine, he find himself, at each step, con- 

 tradicting the best established laws of geology. These contradic- 

 tions, naturally not apparent to the botanists, ought long ago to have 

 spurred geologists to make investigations for themselves. They 

 have led Stainier to believe that coal beds, like the encasing rocks, 

 are of purely sedimentary origin. 



For him, the coal plants grew on continents, bordering great 

 depressions, into which meteoric agencies carried the vegetable 

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

 materials, vegetable and inorganic, were mingled intimately while 

 the water was in agitation ; but in proportion as the condition of 

 calm was re-established, they were thrown down to the bottom in a 

 well defined order, determined by density of the materials. In cases 

 where the succession is complete, there was formed, first, a bed of 

 sand, ultimately becoming a bed of sandstone; then a peculiar, 

 irregular rock, which constitutes the mur and contains the denser 

 parts of the vegetables, /. c, the sub-surface organs ; then the remain- 

 ing portion of the vegetable debris was deposited to form a coal bed ; 

 and finally, the impalpable elements, fine clays, reached the bottom, 

 giving tender fine shales, the roof of the coal bed. 



The reasoning on which the conclusions are based is to be given 

 in a memoir not yet published. 



Ashley'"^ has offered suggestions which are not without interest 

 here. Adopting the doctrine of autochthony, he ignores in his cal- 

 culations the cannels as well as other merely local deposits, which 

 are allochthonous and therefore outside of the discussion. He finds 



'"*' (j. H. Ashley, " .Maxiniuin Deposition of Coal in the Appalachian Coal 

 Field," Ecdii. (Jcology, I., i()o6, pp. 788-793: II.. pp. 34-47: " Signiticai.t Time 

 Breaks in Coal Deposition," Science, N. S., XXX., 1909, p. 129. 



112 



