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



mcnts with Arum. The presence of vertical stems is noteworthy 

 because they are so numerous. It is possible for floods to carry 

 away whole trees and to deposit them in vertical position ; that oc- 

 curred in the great debacle near Martigny in Switzerland. This 

 explanation would suffice for an isolated instance ; but the number of 

 such stems in the Coal Measures is too great ; the analogy is in 

 submerged forests of our own day. 



The distribution of plants, both vertically and horizontall}', has 

 an important bearing on the subject. At one locality the flora may 

 consist almost wholly of one species and at another, almost wholly 

 of another species. There is a group-like distribution, so to speak, 

 a social occurrence. In Upper Silesia, the coal may be termed 

 Sigillaria coal, while in Lower Silesia it is Siigmaria coal. He 

 asserts that an observer, in viewing the coal bed, involuntarily thinks 

 of a peat bog. 



Lyell's volumes on his second visit to the United States appeared 

 at this time and had material influence in moulding public opinion. 

 They will be cited in another connection. 



Naumann"*" recognized the distinction between deposits formed 

 on the sea border and those in fresli-water lakes, as had been done 

 by Elie-de-Beaumont and Burat. The former contain, especially in 

 their lower portions, rock layers with organic remains correspond- 

 ing to the marine mode of formation, while the latter, less extensive, 

 have no traces of marine fossils or anvthing else to show co-working 

 of the sea. These types he terms paralisch and limnisch. These 

 terms are equivalent to pelagic and mediterranean of Elie-de-Beau- 

 mont, to terrains houillers dc Iiautr iiicr and terrains houillcrs des 

 lacs of Burat. The coal deposits of Great Britain, Belgium, West- 

 phalia, Russia and America are paralisch or pelagic ; those of central 

 France, Saxony and Bohemia are limnisch or lacustrian. 



The prevailing rocks of the Carl)oniferons are conglomerate, 

 standstone and clay shale, wliicli occur in paralisch and limnisch 

 alike. They are derived most!}' from destruction of other rocks 

 and their materials were transported. The land consisted not of 

 small low-lving islands but mainly of great islands and continents 



^" C. F. Naumanii, "Lclirlnich cUr (Jeognosic," Leipzig, 1854. VdI. II., pp. 

 45 r> 452, 571-580. 



28 



