STEVENSON-INTERRELATIONS OF FOSSIL FUELS. 461 



There is every reason to believe that the Ruhr basin is contin- 

 uous under cover with the Aachen basins at the west ; it may be 

 continuous also with the Limbourg area of Holland and the Campine 

 area of Belgium, in both of which the coal is deeply buried and its 

 existence has been proved by borings. 



The Aachen Basins. — These, often referred to as the Westpha- 

 lian basin, embrace, according to Dannenberg,^^ two areas, the 

 Wiirm- (or Worm-) Revier, north from Aachen, separated by a 

 strip of Upper Devonian from the Stollberg-Eschweiler Revier, 

 southward from that city. The latter is known also as the Inde- 

 Becken. 



The Wiirmrevier, locality of oldest coal mining operations on the 

 Continent, has not less than 45 coal seams in the western portion, of 

 which II have been exhausted. Of the others, 14 are workable with 

 12.5 meters of coal, the lowest being the Steinknipp, about one meter 

 thick. The disturbance in this portion was extreme and the coal is 

 in great part anthracitic. Dannenberg notes that these coals are at 

 horizons, which, in the Inde basin, have coals much richer in vola- 

 tile. He suggests that the change was not due to disturbance alone 

 but possibly in part to lack of thick cover. In the eastern portion, 

 where disturbance, though severe, is less than in the western, one 

 finds coking coal with 16 to 24 per cent, of volatile, and non-coking 

 coal with 15 to 17 per cent. The remarkable horizon is the marine 

 roof of Bed 6 at the Marie mine. The Flotzleeren Sandstein has 

 not been recognized in this area. 



The Inde-becken or Eschweiler revier has the succession com- 

 plete from Lower Carboniferous to and including the Saarbrijck. 

 The boundary between Lower Corboniferous and Coal Measures is 

 sharp, there being no passage beds between the limestone below and 

 the sedimentary rocks above ; yet there appears to be complete con- 

 formity. A mass, almost wholly sandstone and 8cx) to 1,000 meters 

 thick, rests on the limestone. This, practically barren, as it contains 

 only two or three unworkable seams of coal at 150 to 200 meters 

 above the base, seems to be equivalent to the Millstone Grit. The 

 Productive Coal Measures, somewhat thicker than the barren meas- 

 ures below, have two groups of coal seams, the Aussenwerke and 



51 A Dannenberg, " Geologie der Steinkohlenlager," pp. 83-101. 



