no STEVENSON— FORMATION OF COAL BEDS. [April i8, 



geologist happens to be present at the time. Wilkinson^^' states that 

 near Newcastle he saw several trunks of trees, up to i foot thick 

 and with roots attached, starting from a coal seam and embedded in 

 the strata in the original upright position. More commonly the 

 trees found in the shales with attached roots in situ, though of the 

 same general character as those making much of the coal, are not 

 rooted in the coal itself but in the shale. In not a few cases, their 

 relations suggest that they grew on spaces covered with detritus, 

 such as one sees in the large forested swamps, where trees, belonging 

 to species rooting indifferently in peat or in inorganic matter, are 

 growing on sand or clay-covered spaces and with their roots extend- 

 ing beyond to the peat itself. Partings in coal beds unite in them- 

 selves the features of roof and floor ; at times they contain abundance 

 of plant remains and still serve as soil on which a new vegetation 

 arises. Renier has given an illustration. The roof shale of a coal 

 bed is about 4 feet thick. It contains 12 species of plants but, at a 

 little way above the bottom, there appear in addition Stigmaricc, 

 which increase in number toward the top where one reaches another 

 coal bed. In some cases the rootlets of Stigmaria have pierced the 

 leaves of other plants, but in most cases they have avoided that 

 exertion and have moved around them. Robb, Williamson and 

 others have described Stigmaria rooted in parting clays and 

 Williamson has told of a stem rooted in the parting and passing 

 upward into the coal. 



The roof shale varies in color from gray to black, is usually 

 quite fine in grain and argillaceous, though often notably arenaceous. 

 The features are as characteristic in later formations as in the Coal 

 Measures. The dark color is due to organic matter, which is not 

 always derived wholly from land plants, since the deposit at times 

 is not of flood-plain origin. The roof of the Upper Freeport coal 

 bed exhibits the contrast. In extensive areas, it is of the ordinary 

 type, with reasonably well preserved plant remains, but, at some 

 widely separated localities, it contains along with very fragmentary 

 plant remains great abundance of marine fossils, belonging to types 



"' C. S. Wilkinson, "Mines and Minerals Statistics of New South Wales," 

 Sydney, 1875, p. 130. 



