STEVENSON— INTERRELATIONS OF THE FOSSIL FUELS. 139 



like and of cinnamon color, a Schwelkohle. Some Knorpelkohle is 

 present along with bituminose and petrified wood, the replacement in 

 the latter being with pyrite or silica. The plant remains are chiefly 

 wood, which predominates in some parts. This is wholly coniferous 

 and, excepting a few Abietinae, belongs to cypress. Occasionally 

 one finds great stems passing gradually into either earthy or compact 

 coal, in which Laspeyres thinks he has proof that the varied condi- 

 tions observed in coal must be ascribed to irregular working of the 

 conversion process, though he is convinced that much of the earthy 

 brown coal may be due to destruction of other parts of the plants, 

 which, being tender, offered less resistance to the process and lost 

 all structure. 



Credner,^^^ in discussing the same area, gives as the Oligocene 

 succession : Lower, consisting of light-colored sands, clays with 

 brown coals ; Middle, dark gray to green gray sands and clays with 

 marine forms ; Upper, light-colored sands, gravels, clays with brown 

 coals. 



The Lower Oligocene, about lOO meters thick, is a mass of 

 irregular variable strata. The coal beds are usually 4 to 5 meters 

 thick but in places a maximum of 8 or 9 meters is reached. There 

 seem to be practically two beds, but his general statement exhibits 

 the irregularity of deposit, for he says, (T) That the beds are not 

 continuous, but are interrupted locally, as they thin out; (2) Con- 

 sequently only one bed occurs in places where two were expected ; 

 (3) It is questionable if these apparently local, lens-like individual 

 beds are actually one and the same throughout, for the relations 

 of the beds are extremely variable; (4) Locally, one finds more than 

 two beds. 



The coal is mostly earthy or soft brown coal, mingled with more 

 or less of Knorpelkohle and bitumenose Holz, the latter sometimes 

 though not often replaced with pyrite and silica. The woody ma- 

 terial is in small proportion and all the phenomena indicate swamp 

 origin. In this connection he cites A. Penck's investigation of the 

 Tanndorf brown coal, which showed that the lower shaly portion 

 of the deposit is rich in well-preserved remains of floating plants, 



195 H. Credner, " Das Oligocan des Leipziger Kreises," Zeitsch. d. d. geol. 

 Gcsell, Bd. XXX., 1878, pp. 615. 



