148 STEVENSON— INTERRELATIONS OF THE FOSSIL FUELS. 



nite or bituminous wood is present in this coal and the species are 

 like those as on the Hardt and at Friesdorf ; stems are especially 

 well preserved in mine Friedrich Wilhelm JMaximilian, near Turnich 

 on the Erft, but many of the Hardt species are not represented. 

 Deposits between the Rhine and the Erft are quite regular, with clay 

 floor, containing more or less brown coal, and often have a clay roof, 

 but very frequently the cover is a diluvial deposit of varying thick- 

 ness, through which water passes into the porous brown coal and 

 downward to the clay floor; this surface water injures the coal. 

 There is no distinction here into earthy brown coal and Schwelkohle 

 as in Sachsen ; the only difference is in state of preservation — earthy 

 and lignite-like brown coal. The former is from the soft parts of 

 plants and is utilized in manufacture of briquets ; the latter yields the 

 lump coal. It is not known whether or not any Schwelkohle like that 

 of Sachsen exists in this region. The Schmierkohle, found in the 

 Hangenden near Bruhl^ is said to yield a greater proportion of distil- 

 lation products than does the underlying earthy coal ; but it is much 

 mixed with clay and has a great percentage of water ; both water and 

 ash decrease downward in the mass of the bed. The thickness in the 

 area of earthy brown coal varies greatly and abruptly ; in the Bruhl- 

 Liplar region it is from 5 to 104 meters. 



The Rhenish brown coal contains in many places what is known 

 as oolite wood, the woody matter being largely or wholly replaced 

 with spherules of carbonate of iron. In searching the survey coal 

 collections at Berlin, Gothan-''^ found a piece of the brown coal from 

 the Donatus mine near Cologne, which contained similar spherules 

 of carbonate of iron. Deposition had not been confined to the wood, 

 but had reached into the actual peat. Specimens were obtained from 

 Fliigel, who had mapped the area, and they proved to be a part of the 

 bed replaced with material like that of the plant-balls described by 

 Stur. Gothan suggested the name of Torfdolomite. IMicroscopic 

 examination by Horich showed that the plant remains as a rule are 

 not well preserved ; they are so disintegrated that in many cases they 

 cannot be identified. Roots are best preserved, probably because they 



205 W. Gothan und O. Horich, " Ueber Analoga der Torfdolomite (Coal 

 Balls) des Carbons in der rheinische Braunkohle," Jahrb. k. preuss. Lande- 

 sanst., Bd. XXXI., Teil II., 1910, pp. 38-44. 



