134 STEVENSON— FORMATION OF COAL BEDS. [April i8, 



In applying the doctrine to larger areas, defenders of allochthony 

 find many illustrations which they regard as more than important. 

 Much is said of timber rafts on great rivers, the masses of floating 

 vegetation on the Amazon, Congo, Orinoco and other great streams, 

 the rake at the outlet of lake Tanganika, the dredgings by A. Agassiz, 

 the accumulation of drift wood on many coasts and the distributing 

 power of currents. But it is not easy to discover what bearing any 

 or all of these can have upon the formation of a coal bed with its 

 orderly succession of floor coal and roof. 



The timber composing the Atchafalaya raft was gathered from 

 caving banks along more than 20,000 miles of river courses ; very 

 little of it was contributed by floods. Neither the Atchafalaya nor 

 the Red river raft was a solid mass ; each was in patches, separated 

 by considerable spaces of open water. If they had sunk to the 

 bottom, no coal bed would have been formed, there would have been 

 only a mass of sediment enclosing logs. And this was the actual con- 

 dition discovered, when the floating portion of the Red river raft was 

 removed. But, in any event, the statements respecting the extent 

 and character of those rafts, found in many publications, have been 

 proved to be fabulous. If those statements had been true, if trees 

 60 feet high had grown on the Atchafalaya raft, those very state- 

 ments should have restrained allochthonists from utilizing the rafts 

 in their defense, since they go to show the immensely long time re- 

 quired to convert timber to the sinking condition and to show also 

 the great amount of inorganic matter entangled in the rafts. Refer- 

 ence to descriptions^"*' by competent observers will be sufficient for 

 the reader. The same remarks apply to all accumulations of drift- 

 wood. As has been shown on earlier pages, the observations by un- 

 critical voyagers were inexact; photographs prove that driftwood on 

 coasts occurs in scattered fragments, occasionally collected into loose 

 piles. On the shores of lakes or bays, the wind often drives consider- 

 able quantities into masses, upon which waves toss sand or silt. 

 McConnell's detailed examination of driftwood deposits on Lake 

 Athabasca made the conditions clear and showed how erroneous 

 were the conclusions drawn from Richardson's description. Con- 



'^'"' Formation of Coal Beds," II., these Proceedings, Vol. L., pp. 548-551. 



