144 STEVENSON— INTERRELATIONS OF THE FOSSIL FUELS. 



and roots, 2.50. The measurements are in meters. Fiebelkorn 

 makes no reference to the Rnsskohle, which Stohr found associated 

 with the Schwelkohle. The distribution of the latter is quite different 

 from that seen by Stohr, for here the two types of coal alternate. 

 The Schwelkohle changes into pyropissite toward the border of the 

 trough. 



The Oligocene coal of the Cologne-Bonn region on both sides of 

 the Lower Rhine has been mined during a long period. Davis-°- has 

 given a brief description of the deposit near Horrem, which shows 

 the general conditions. The brown coal contains about 60 per cent, 

 of moisture and is soft, at most, slightly consolidated in the bed. 

 Fresh from the mine, it resembles rather woody, half dry peat or 

 muck from a swamp forest. The included wood, mostly lignite, 

 appears, even when dry, to be no more changed or carbonized than 

 the wood found in many peat beds. When dry, it is still soft enough 

 to be whittled easily, the chips being scarcely more brittle than those 

 from kiln-dried wood of similar types. The deposits range from 32 

 to 328 feet in thickness, the average being about 72 feet. The coal 

 is covered with relatively thin gravel and clay ; this overburden is 

 removed by stripping, and the coal is mined in open cuts. The 

 moist brown coal, as it lies in the bed, is nearly black, unconsolidated 

 and contains a large percentage of fine material, which is friable even 

 when wet. 



The brown coals near Bonn were studied long ago by Horner,-"^ 

 who saw four types at the mines : ( i ) A dark brown or black earthy 

 substance, friable to pulverulent, rarely showing lamination and 

 found usually as the upper portion of the beds ; (2) a cemented mass, 

 in which leaves and fragments of wood are mingled with the earthy 

 coal; (3) wood in different stages of bitumenization, with all shades 

 of color from light brown to black, the last approaching jet; (4) 

 Papierkohle, highly bituminous, burning with bright flame, separating 

 into laminse as thin as writing paper and leaving a white ash ; it is a 

 mixture of earth and comminuted vegetable matter. It should be 



202 C. A. Davis, " Production and Uses of Brown Coal in the Vicinity of 

 Cologne, Germanj'," U. S. Bureau of Mines, Techn. Paper 55, 1913, pp. 5, 6. 



-02 L. Horner, " On the Geology of the Environs of Bonn," Trans. GcoL 

 Soc, II., Vol. II., 1836, pp. 449, 450, 459. 



