^911.] STEVEXSOX— FORMATION OF COAL BEDS. 101 



passage. If the water-surface of inflowing stream be lowered, a 

 "barricade" of wood would accumulate in curves and narrows of 

 the Nogat. to become compacted in time — a familiar phenomenon in 

 this day. This " barricade " would prevent passage of large wood 

 and only fine material. " Spulgut '' would go over to be deposited as 

 a layer in the coal basin, /. c, the Haff. Brushwood would be caught 

 by the " rake " beyond. Thus a bituminous shale with plant impres- 

 sions and paper-like laminae of bright coal would accumulate. 



Phase 2 comes with moderate height of the water. Now there 

 goes with the " Spulgut " also the " Sperrgut," stems, rooted stumps, 

 branches and the rest, which the Mstula pushes over into the Nogat ; 

 but the " rake " does not permit its escape to the sea, it circles round 

 in the basin, finally sinks and forms pure coal. So much of the mud 

 as does not pass through the " rake " will accumulate on the borders 

 or be mingled with the coal magma, as clay is in the globigerina ooze ; 

 or it may form bands in coal beds. Repeated sinkings of waterlevel 

 in the feeding stream, the Xogat in this case, would give a clay shale 

 like the floor as roof, the roof of the coal. Xo sand or gravel could 

 pass the " barricade "" but it would be heaped up there. Phase 3 

 comes with a high flood, which overthrows the " barricade " and 

 pushes all into the coal basin. The sand and gravel form sandstones 

 and conglomerates as roof of coal beds and formation of coal ceases. 

 The woody portions become at most only isolated stems buried in the 

 " Rollgut " ; by repeated pressure they may perhaps be pushed into 

 an oblique position. If the " rake " be torn away, the sea water again 

 enters the basin and lays down a marine bed. 



This is the characteristic succession in coal bed formation. All 

 depends on the condition of the water-level. Changes in that cause 

 alternation of clay, shale, coal and psammite. and effect the sharp 

 mechanical separation of those substances by the easily explained 

 formation of " Rakes " and '" Barricades." The elevation of import- 

 ant mountain ranges in Carboniferous and Tertiary times afforded 

 abundant material for widespread lowlands, approximating sea-level. 

 These advanced seaward and their luxuriant forest growth yielded 

 material for the stone-and brown coals. Networks of rivers must 

 have cut through the lowlands and must have deposited their loads 



101 



