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



nally soluble, but became insoluble, so tliat tbe whole is amorphous 

 and apparently structureless." The taking up of this material is the 

 Inkohlungsprozess. 



Adjacent rocks, containing plant remains, may have contributed 

 to this coalification by means of circulating waters. It is self- 

 evident that this soluble material might be deposited by itself apart 

 from any remains of plants, not merely as layers of a coal bed but 

 also in cracks and fissures : but such layers of structureless coal 

 could have contributed in only subordinate manner to the formation 

 of coal beds. 



The several types of coal, Glanz-. ATatt-, Faser-, Cannelkohle 

 and the rest cannot have originated under similar conditions. In 

 considering these he takes the most complicated condition — where 

 several varieties occur in the same bed. Three modes of explana- 

 tion are suggested by the investigations : ( 1 ) Original diiTerences in 

 kinds and parts of plants; (2) differing conditions, chemical and 

 mechanical, in which the plants came to contribute toward making 

 the coal; (3) heterogeneous external conditions under which the 

 transformation was completed. 



Difference in material in the several types of coal appeared con- 

 stantly during the study ; bark, and woody parts along with leaves 

 in Glanzkohle ; abundance of leaf organs, especially of the epidermis 

 layers and less abundance of hard parts in Mattkohle; constant 

 recurrence of little balls, membranes, the spores of authors, in aston- 

 ishing abundance with algae-like clumps in cannel-like layers; all 

 proving a certain dej)endence of constitution on the character of 

 the plant remains. It is clear that the condition under which the 

 {)lant material was accumulated was of great importance. This is 

 evident from the great amount of b'aserkohle | fusain, mineral char- 

 coal]. If this material result from decay in free air, as would occur 

 in the occasional (lr\ing of the surface in peat l)ogs, one must con- 

 cede that this process was of vast extent during the coal-making 

 time. It is unnecessary to sup]:)ose that the great supply was swept 

 in ; it could have been produced as readily on the bog surface. Simi- 

 larly the dismembered parts of plants, clods or flocks, and the rest 

 belong to a stadium anterior to formation of the coal. The pres- 



62 



