56 STEVENSON— INTERRELATIOxXS OF FOSSIL FUELS. 



found in the same section with other coals, some of them belonging 

 to the " black coal " type. This Blatterkohle consists chiefly of 

 Abies linki and Pterophyllum lycllianum, whose densely packed 

 leaves and twigs, mostly brown and transparent, become flexible, 

 when soaked in water ; coalification is extremely imperfect. Dunker 

 thinks that lycopods and ferns are the chief constituents of the black 

 ■coals, as no remains of other plants have been discovered. It may 

 be noted in passing that the Blatterkohle bears great resemblance 

 to the conifer peat of the Fichtelgebirge,*^ as described by Reinsch, 

 and to the " coarse " coal of the Carboniferous ; in the latter the 

 conversion is complete. It must not be forgotten that David dis- 

 covered equally flexible remains of plants in the Permo-carbonif- 

 erous of New South Wales. 



The coals vary in quality ; partings thicken and at times the 

 whole scam becomes carbonaceous shale ; occasionally masses of 

 silicious matter, limestone or pyrite become so abundant as to render 

 the deposit worthless. In some mines, a waxy substance, clear or 

 dark yellow, occurs, which Dunker thinks may be hatchettin. 



Near Biickeburg and Schaumburg, the Wealden sandstone is 

 I20 to 150 feet thick and contains 4 coal seams, of which two are 

 workable. On the Osterwalde, the thickness is not far from 450 

 feet and 18 seams were seen, mostly thin or too poor in quality to 

 justify mining, the greatest total thickness of coal being 9 feet. 

 Well-marked coal seams, in nearly every case, have a black clay 

 roof and floor, the latter occasionally passing into Brandschiefer or 

 cannel shale. The roof clay, at times, contains abundance of plant 

 impressions and even becomes coaly — a true faux-toit. In the upper 

 part of the section there are two seams consisting mostly of the 

 black coal, but this, in part, is continuous with brown coal, contain- 

 ing pieces of wood-like anthracite. 



The plants enumerated by Dunker include 2 species of Equi- 

 setum, 26 of ferns, 10 of cycads, 5 of conifers and one palm, Endo- 

 gamites, now taken to be Sedgzcickia. One species of Equisetum 

 occurs abundantly in a sandstone, where the stems are more or less 

 nearly vertical. Stems of trees were observed at many localities ; 



^ See " Interrelations of the Fossil Fuels, I.," Proc. Amcr. Phil. Soc, Vol. 

 LV., 1916, p. 54. 



