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



Potonie's description of secondary-allochthonous formations, due 

 to erosion and transport of materials from beds already existing, 

 will find place in another connection, as will also his arguments 

 drawn from the testimony of the fossil plants, respecting which his 

 authority is unquestioned. 



Ochsenius"-' published man}- noteworthy papers but that of 1896 

 is especially important in this connection. The author recognizes the 

 force of the objection to allochthony — that, as running water carries 

 organic and inorganic materials together, the deposit should be an 

 indiscriminate mass of both kinds but his recent study of coal beds 

 in the Lahn country has convinced him that phenomena observed in 

 the Frische Haff present a true explanation and destroy the force of 

 the objection. The history of the Frische Flaff is complete since 

 1510.-" 



The A'istula, a stream laden with everything that can be drawn 

 from a rich lowland province, gives off an arm at Peickel, the Nogat, 

 which flows northeast to the long narrow Frische Haff, separated 

 from the Gulf of Dantzig by the Frisch Xehrung or lowland, and 

 communicating with the gulf by the Pillauer Tiefs at its northern 

 end. For convenience of discussion, he confines his attention to the 

 Nogat, ignoring the old \'istula and the rivers which enter from the 

 east. 



Under the supposed conditions, the sea having control and the 

 Hafif being filled with salt water, a marine bed is deposited on the 

 floor. Such beds occur locally at the bottom and higher up in the 

 series of coal deposits. Phase i of coal formation is brought about 

 through sanding up of Pillauer Tiefs by wave action, and the conse- 

 quent conversion of the Haft" into a fresh-water basin by influx from 

 the Nogat. The debris brought down by that river, an indiscriminate 

 mass of organic and inorganic material, will be deposited on the 

 bottom. H now the sea cut a shallow i)assage through the lowland, 

 floating stems and twigs would form a " rake " at the head of the 



'■" C. Ocliscnius, "Die Bildung dcv Kohleiiflotzc," Verhandlungcn, II., 

 Erste Ilalftc, pp. 224-230. 



'""The Frische Haff is a great souiul on tlie border of the Gulf of Dantzig, 

 about 60 miles long by 5 to 7 miles witle. It may be compared as to super- 

 ficial area and position to Lake Ponchartrain on the Mississippi delta. 



100 



