I9I3-] STEVENSON— FORMATION OF COAL BEDS. 121 



only a conception of greater torrents in greater areas to give basis 

 for hypotheses respecting the origin of rocks. 



The doctrine of flood action was well-outlined at a very early 

 date. Woodward, at the close of the seventeenth century, had 

 announced that materials, swept from the land, sank to the ocean 

 bottom in the order of their specific gravity; this was emphasized by 

 Scheuchzer, Conybeare and several later writers, but it was disputed 

 earnestly by Williams, as not in accord with the actual succession of 

 strata. Applied to coal, modifications were made as acquaintance 

 with the phenomena became more intimate. Sonie authors, Voigt, 

 Parkinson and, much later, Petzholdt, thought that the vegetable 

 material had been reduced to fluidity on the land before removal by 

 floods ; Sternberg and Boue held much the same opinion, for they 

 thought that vegetable materials had been reduced to a pulp before 

 removal and that the change to partial fluidity was produced in the 

 tepid waters of the primaeval globe. Conybeare apparently was the 

 first to conceive that a single flood might give materials for a coal 

 bed of any thickness, and Jukes was the first to suggest that coal 

 beds may have accumulated on the slopes of a submerged delta. 

 But in all, one finds the conception of floods, carrying at one time 

 mingled organic and inorganic debris, at another, mostly plant 

 materials, but at a third, mostly inorganic substances. 



Before undertaking the consideration of allochthony as a doc- 

 trine, it is well to examine several hypotheses, which have been 

 defended by some eminent allochthonists but opposed energetically 

 by others. 



Alohr in 1866 revived suggestions by Parrott and Bischof that 

 some coal beds might be accumulations of seaweed, and made them 

 into a generalization respecting all coal beds. His reasoning is 

 without reference to the conditions in which coal occurs ; the mass of 

 seaweed is incredibly great ; there is enough to account for the coal ; 

 what has become of it? it has been converted into coal. 



But there are some things needing explanation, with which Mohr 

 does not concern himself. The mass of seaweed on the coast of 

 France, Ireland and the Orkneys is enormous and, in all probability, 

 it has always been so since the present climatic conditions began, 



