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



Andrews thought that cannel was originally vegetable mud. He 

 emphasizes the abundance of Stigniaria, saying that they fairly 

 reveled in this ooze. They, with their rootlets, abound throughout ; 

 their existence in these beds for hundreds of miles almost necessitates 

 the conclusion that they are /// situ. If they are roots of Sigillaria, 

 those trees must have grown in the wettest portions of the marsh, 

 wdiich, in that case, could not have been lagoons. The Stigniaria are 

 evenly distributed. If they had been drifted in, he thinks they ought 

 to have gone to nmck with the rest. 



Newberry,""' in the following year, discussed the origin of the 

 various deposits composing the Coal Measures. The coarse rock 

 underlving the series contains rounded pebbles of quartz, igneous 

 and metamorphic rocks, with rounded and angular sand of the same 

 material as well as cherty pebbles from the Lower Carboniferous. 

 The pebbles for the most part must have come from Archean areas 

 at the east and north : but he finds difficulty in explaining how ma- 

 terial from those areas could be distributed in sheets at hundreds of 

 miles from the only possible sources of supply. It is difficult to con- 

 ceive of rivers as the transporting agency and he is inclined to find 

 the explanation in the drift deposits of the Mississippi valley, ice 

 being the transporting agent. Where the rock is coarse, fragments 

 of the tree trunks, of Calauiifcs and of roots are present, all broken, 

 and sometimes heaped in masses covering several rods. Fruits, like 

 Trigonocarpitiii, occur in hollow calamites and the mass is like 

 driftwood, everything broken and battered. 



The fireclays sometimes contain stumps of Sigillaria and Lcpido- 

 dcndron in unbroken connection with Stigniaria roots. Coal is 

 seldom wanting above fireclay, though at times it has been removed 

 bv erosion. Coal beds were formed in situ. Fine sediment accumu- 

 lated in pools and these were invaded by vegetable growth, to be 

 filled up finall\- by bitumenized remains of generations of plants. 

 Aquatic plants remove alkalies, phosphorus, sulphur and silica from 

 the soils, as is seen in peat bogs, where the imderclays are often 

 fireclavs. The varxing deposits are explained l\v alternate eleva- 

 tions and depressions of the surface. Limestones were formed in 

 arms of the sea and their presence is proof of imequal subsidence. 



■''^J. S. XevvlKTi-y, Geo). Survc\- of Ohio, Vol. II., part I., Columbus. 1874, 

 pp. 1 04- 1 1 5. 118. 



46 



