64 STEVENSON— FORMATION OF COAL BEDS. [April 21. 



them, proceeded from occasional overflows. Coming down a step 

 farther to the coal making of our own time and ignoring for the 

 present the various local modifications of peat, one can recognize 

 two distinct modifications ; Autochthonous, that forming or originat- 

 ing in place, and Allochthonous, the sedimentary, due to deposit of 

 plant detritus in pent up waters. The latter shows, of course, evi- 

 dence of sedimentary origin, is more or less dense and homogeneous, 

 contains much earthy matter and the plant remains are notably 

 advanced in change. Often it shows lamination only on drying. 



All kinds of peat have the lamination. In Moortorf there are 

 often alternating layers, dififering in color, density and composition ; 

 in Specktorf the structure is especially distinct. Peat then is not 

 an unstratified mass and one cannot say that the lamination of coal 

 places it out of comparison with peat. Close investigation shows 

 so many similarities between the peat layers and those of some coals, 

 that this kind of structure favors rather than opposes comparison 

 of coal-making with peat-making. This lamination appears in the 

 autochthonous peat, in the diluvial brown coal originating in peat 

 and in the whole range of the brown coal formation. But one must 

 remember that the coals were not all formed on the same model ; 

 that comparison with peat is only tentative, as modern peat is made 

 from moss and swamp grasses, while in the coal time the deposits 

 came from a wholly difi^erent moor and swamp vegetation. 



The stone coal formation for the most part is to be regarded 

 as an inland formation, originating in widespread leveling and sub- 

 siding of the land, in many cases on swampy lowland along the sea- 

 coast, over which floods distributed materials, such as shale and 

 sandstone. On the extensive but not high land of the Carboniferous 

 time, waters were penned in great areas and became converted into 

 morasses, where a luxuriant vegetation flourished. It is very prob- 

 able that in occasional drying of the swamp followed by renewal of 

 the flooding, one may find explanation of the alternating bright and 

 dull coal. This does not exclude influ.x of broken and shattered 

 plant stuff from the higher surrounding region ; that might even 

 have predominated in some localities and have been the basis for 

 cannel and boghead. Even from llic swamp vegetation itself, decay- 



64 



