92 STEVENSON— INTERRELATIONS OF THE FOSSIL FUELS. 



position, to be exposed as irregular strings of peat when laid bare by 

 a drainage canal. If, however, the filling be abrupt and violent, 

 masses of the peat are rubbed off to be embedded in the sand, while 

 the adjacent portion of the bog is very apt to show crushing or 

 folding. 



Filled channels occur frequently in rocks associated or con- 

 temporaneous with the peat deposits. The Missouri and Mississippi 

 Rivers have shifted the channels at many places and the abandoned 

 " ox-bows " in numerous instances have been filled with material dif- 

 ferent from that of the banks. The rivers of the Gran Chaco of 

 Paraguay and Argentina flow in constantly shifting channels, the 

 older ways becoming filled to be exposed by a new change in direc- 

 tion of flow. A. Geikie^^'' has described several cases of channels in 

 the drift beds of Scotland, eroded and refilled during the Glacial 

 period. Others have been noted by J. Geikie and by J. Croll. 



Some Chemical Features of Peat. — It is well known that mature 

 peat, when first taken out, is plastic ; but when thoroughly dried it 

 is no longer plastic. The same effect is said to be produced by 

 freezing. It is evident, as said by v. Giimbel more than thirty years 

 ago, that peat contains some substance, which is soluble in the fresh 

 condition but is insoluble when dried. Microscopical study of ma- 

 ture peat shows that the minutely divided vegetable matter is accom- 

 panied by an amorphous substance, sometimes so abundant that 

 the fragments appear to be cemented by it or even to be embedded in 

 it. The earliest reference to this substance, known to the writer, 

 is that by Reinsch,^"^ who stated that in the Fichtelgebirge there are 

 two kinds of peat, Rasen- and Pechtorf. Rasentorf occurs in thick 

 deposits, 2 to 12 feet, but Pechtorf is in thin layers, as shown in 

 his material from near Rautengriin on the left bank of the Eger river. 

 The latter feels damp, almost greasy, is about twice as heavy as 

 Rasentorf, has lustrous, brown-black surface and consists of roots 

 embedded in an almost black substance. 



Definite information respecting this material seems to be due 



^30 A. Geikie, " On the Glacial Drift of Scotland," Trans. Geol. Soc. 

 Glasgow, Vol. L, Pt. II., i868, pp. 65 ff. 



131 H. Reinsch, " Ueber den Torf des Fichtelgebirge," Jonrn. f. pr. 

 Chcmie, Vol. XVI., 1839, PP- 489-495- 



