STEVENSON— INTERRELATIONS OF FOSSIL FUELS. 427 



beds are termed the Rand group because they are on the border of 

 the field. The Rand or Ostrau beds form the Schlesische Stufe. 



Dennenberg has given a careful synopsis of his observations and 

 of those by other students in this region, which may be utilized here. 

 The thickness of the Saarbriick and Sudetic stages is, at most, not 

 far from 7,000 meters ; but the coal is distributed unequally. The 

 Sattelflotz, at most barely one-twenty-eighth of the whole mass, 

 contains about one fifth of the workable coal. The deposits de- 

 crease toward the north and east, the Sudetic mountains being the 

 source whence the sediments were derived. The Sattelflotz beds 

 near Zabrze measure 240 to 250 meters but at the east, on the Gali- 

 cian border, they are only 14 to 15 meters. According to Gaebler, 

 the Ostrau or sub-Sattelflotz beds are 4,000 meters thick near Os- 

 trau at the southwest, but only 500 meters near Golonog on the 

 extreme northeastern border of the field. The total of Upper Car- 

 boniferous diminishes from about 7,000 meters at the west to barely 

 1,220 at the east. This thinning of sediments leads to frequent dis- 

 appearance of intervals with resulting union of coal seams and rela- 

 tive enriching in coal-content. 



The Upper Carboniferous rocks in this field are remarkably uni- 

 form in general character ; sandstones, mostly white, prevail ; while 

 shales are subordinate and become important only in the highest 

 division. Clay ironstone is present in nodules or in workable beds. 

 Conglomerates are insignificant and red beds are practically want- 

 ing. The maximum thickness of the several divisions is Saarbriick 

 (Karwin or Orzesch), 2,700 meters; Satterflotz beds, 240 meters; 

 Ostrau beds, 4,070 meters. The total of coal is 299 meters, of which 

 only 169 are in workable seams. 



But emphasis must be laid on the fact that this statement of coal 

 resources is merely general and is the maximum. The number and 

 thickness of coal seams vary from place to place ; the Ostrau beds 

 are usually barren in the northern parts of the field, but there are 

 a few seams which occasionally become workable. The Satterflotz 

 beds, "the glory of the field," show extreme variation. They are 

 exposed by anticlines in the neighborhood of Zabrze, Konigshiitte 

 and Myslowitz, but elsewhere in the greater part of the Prussian 

 area they are buried deeply. The chief expansion is at Zabrze on 



