STEVENSON— INTERRELATIONS OF FOSSIL FUELS. 483 



with long flame, but it varies greatly. One finds it passing from 

 coal to cannel, boghead, bituminous shale and even to sandstone or 

 conglomerate. Sometimes it is clean from floor to roof, 15 or 20 

 meters ; at others, it is divided by intercalated shale, sandstone or 

 conglomerate, up to several meters thick. This great mass of coal 

 is at 500 to 800 meters above the base of the formation, near which 

 are some irregular deposits of anthracite. 



The conditions are similar in les Ferrieres, where the principal 

 deposit, apparently contemporaneous with that of les Pegauds, has 

 a curved outcrop and thins to disappearance at both extremities. 

 The coal has less volatile than that in the other sub-basin. 



Fine sandstone prevails in les Pegauds, but coarse material is not 

 wanting. One remarkable mass, marking the course of a violent 

 flood, was formed shortly before the beginning of the Grande 

 Couche. It is coarsest midway, where some blocks are of enormous 

 size, but it shades away on each side into fine sand. Another coarse 

 deposit is intercalated in the Grande Couche, but it is only a few 

 hundred meters long and passes into the coal at each extremity of 

 its outcrop. Fragments of Coal Measures rocks are found in all 

 parts of the section. Those of shale, by their form, suggest to Fayol 

 that they were plastic when enclosed. The pebbles of coal usually 

 resemble in composition the coal nearest to them ; those of the basal 

 portion are anthracitic; those of les Ferrieres are maigre but in 

 deposits overlying the Grande Couche the pebbles are usually of coal 

 with long flame, though rare specimens of anthracite occur. 



The coal occurs in films and in seams. Calamites are rare in 

 the roof of Grande Couche but Calamodendron abounds. The flora 

 is the same throughout and continues into the Permian; but there 

 is distinct localization of forms. Lepidodendron and Stigmaria are 

 present in the southwestern portion but are wanting in the eastern. 

 Knflrria, Lepidophloios, Lepidostrohus are in the roof at western 

 localities. Fish and insect remains are abundant in some portions. 

 Renault studied many specimens of trunks and branches enclosed in 

 the fine sands. Their coal is derived from decomposition of vege- 

 table material ; there is no evidence of enrichment by infiltration, as 

 the enclosing sand contains neither coal nor bitumen. At times a 



