194 STEVENSON— INTERRELATIONS OF THE FOSSIL FUELS. 



as a rule. At times, prostrate stems as well as rooted stumps are 

 abundant especially in the lower portions, but at others they occur 

 within definite horizons in the higher portions ; the smaller fragments 

 are frequently converted into mineral charcoal. These conditions, 

 observed in widely separated American localities, are similar to those 

 observed in many European places, though, there, mases of logs are 

 not so common as in the American lignitic coals ; but the logs are 

 found in all sorts of coal, Formkohle as well as Knorpelkohle and, 

 many times, they are of enormous size. Prostrate logs are, with rare 

 exceptions, compressed, often so compressed that it would seem as 

 though only the bark remains, but erect stumps are very rarely com- 

 pressed. Leaves and the strongly compressed stems appear as im- 

 pressions on the structureless debris though occasionally, as at Bovey 

 Tracey, leaves may form the great mass as slightly compressed logs 

 do elsewhere. The logs belong mostly to conifers and they have been 

 preserved because of the resin-content. The debris, formed from the 

 Softer, more readily decomposed plants and portions of plants, con- 

 tains spores, pollen grains, bits of dicotyledonous plants as well as of 

 the softer parts of conifers. The disintegration and decomposition of 

 the material has led to enrichment in resins, as shown under the 

 microscope. Replacement of wood is common, the replacing material 

 being for the most part, silica, pyrite, calcium and ferrous carbonates ; 

 this replacement has been observed in the peaty material of the 

 debris, giving the nodules, which Gothan and Horich have termed 

 torfdolomite. 



Animal remains have been found in coal at many localities. 

 Sedgwick and Murchison, as well as Anker,- discovered bones of 

 mammals in the Eocene bogs of Styria ; Katzer saw teeth and bones 

 of mammals in the Banjaluka coal; Fournet saw abundance of land 

 and freshwater shells in the French lignite ; v. Giimbel observed 

 Helix in some layers of Pechkole in southern Bavaria. The dysodil 

 or Blatterkohle of the Lower Rhine region contains many species 

 of batrachians, fishes and insects, while that of southern France 

 is closely packed with fish remains, retaining at some localities much 

 of the original animal matter. Inorganic materials are normal con- 

 stituents of coal ; some of the admixture is due to silicious organisms. 



