444 STEVENSON— INTERRELATIONS OF FOSSIL FUELS. 



ite ; evidently the old surface was irregular and the overlap is nota- 

 ble, for only the highest part of the Schlaner beds is present. 



The Pilsen Basin, not more than 30 miles south from Rakonitz 

 and at extreme western extremity of the larger area has a total 

 extent of not far from 150 square miles; the succession is practically 

 the same as in the basin at the north, but the strata have endured 

 much greater disturbance. Dips on the border reach 55°, though 

 in the interior they sometimes become insignificant. The lower or 

 Radnitz group shows 3 coal seams, known locally as the Fiirstenflotz, 

 Oberflotz and Unterflotz, the second and third being equivalent to the 

 Hauptflotz and Grundflotz of the Kladno-Rakonitz region, while the 

 highest seam is the same with that at Lubna near Rakonitz. 



The variations in interval-thicknesses within this petty area are 

 as remarkable as those proved by actual mining within the Anthra- 

 cite fields on Pennsylvania. Dannenberg gives these measurements 

 for opposite sides of the basin, separated by not more than 10 or 

 12 miles : 



Eastern Side. Western Side. 



1. Upper coal group. 



2. Interval 200 



3. Fiirstenflotz 0.32 to worthless 0.5 to 1.15 



4. Interval 15 to 132 17 



5. Oberflotz i.i to 2.1 i.o to 2.0 



6. Interval 45 to 70 18 



7. Unterflotz 1.8 to 4.4 0.5 to i.o 



The surface of the underlying rock is uneven, so that the Unter- 

 flotz is often wanting. The important seam is the Hauptflotz, which 

 is usually i to 2 meters thick, but toward the north, occasionally 

 swells to 3 or even 5 meters. The highest or Fiirstenflotz is avail- 

 able midways in the basin, where it is known as the Niirschan can- 

 nel. Katzer*" placed this in his " Middle Zone " and believed it to 

 be lower Permian. He has given a detailed section of the bed as 

 seen at Niirschan: (i) cubical black coal, 0.30; (2) black clay, 0.03 

 to 0.30; (3) cubical black coal, 0.30; (4) cannel, rich in Stigmaria, 

 a few ferns, some bones; (5) Brandschiefer, thinly laminated, re- 

 mains of ferns, some saurians and fishes, 0.25 ; (6) Platterkohle, in 

 thick slabs, the chief source of saurian remains, with streaks of clay, 



^0 F. Katzer, " Geologie von Bohmen," p. 1148. 



