94 STEVENSON— FORMATION OF COAL BEDS. [April i8, 



to coke, to coal changed by dikes of igneous rock. He is certain that 

 this fibrous coal could not have come from spontaneous decomposi- 

 tion of fibrous twigs, for in that case it would be like the enclosing 

 coal. It is remarkably like the ordinary wood charcoal made by 

 fire and it dififers from coal as well as from anthracite by the struc- 

 ture and the volatile content. The ash varies from a trace to 70 

 per cent. He thinks that this fibrous coal is evidence of fires and 

 refers to a great conflagration in 1844 near Saint-Leon in Landes, 

 which was caused by lightning and destroyed 100 hectares of forest. 

 In the discussion, A. Pomel dissented from Daubree's conclusions 

 because the quantity of this anthracitic fibrous material is too great 

 to be the result of forest fires. 



Dawson in 1878 summed up his conclusions which had been 

 published in various forms in the interval from 1846. There is no 

 possibility of accounting for a substance, so intimately mixed with 

 the coal, by the supposition of conflagrations or of subterranean heat. 

 The only satisfactory explanation is that afforded by the chemical 

 changes experienced by woody matter, decaying in the presence of 

 air, as described by Liebig. Mineral charcoal results from sub- 

 aerial decay, the compact coal from subaqueous putrefaction, more 

 or less modified by heat and exposure to air. 



Grand'Eury^^ found fusain present in great quantity scattered in 

 small patches throughout the coal. Stems of Mednllosa and Dad- 

 o.vylon are often carbonized and whole trunks of Calainodcndyon 

 have been found converted into fusain enclosed in a crust of coal. 

 Fusain is like charcoal ; but some of it was exposed to moisture and 

 dryness alternately. The subdivision of the material suggests the 

 breaking up of wood in dry air; he thinks it indicates an extreme 

 climate, for one does not find fusain in recent lignite or in swamps 

 of today, but he has seen it in the older lignites. In any case it came 

 at first from disintegration in air; other causes cooperated, but 

 maceration does not give fusain. 



\'on Giimbel's conclusions are similar ; the mode of occurrence, 

 its peculiar disintegration and its loose structure show that it was in 

 completely converted condition when taken up by the coal. He is 



"" C. Grand'Eury, " Memoire sur la formation," etc., pp. 106, 113-115. 



