'9"] STEVENSON— FORMATION OF COAL BEDS. 93 



fundamental jelly. Each ball of gelose yielded a little mass of 

 glassy, transparent gold-yellow hydrocarbon. 



The bituminous matter found in all is wholly dilTerent from the 

 fundamental material. There is proof of its intervention, for it 

 follows clefts made by contraction of the fundamental material, 

 which it does not color. The coalilied stems of Vcrtcbraria on 

 Joadja creek are humefied vegetable material charged with bitumen. 

 There is no evidence that this bituminous enrichment was due to 

 condensation of resinous matter held in suspension by the funda- 

 mental material ; nor is there any evidence that the fundamental 

 material originated from alteration of the enclosed bodies. 



The accumulation could be made with remarkable rapidity. A 

 few good days with low water would suffice. All the accidental 

 bodies, enveloped in a humic coagulum, make a raft on the abso- 

 lutely tranquil water. A very slight cause, colder weather, more 

 water, would hinder formation of gelose and cause descent. The 

 precipitation of brown matter was continuous but formation of 

 gelosic matter was fortuitous ; with check of algic growth, the deposit 

 passes over to a humic coal or organic shale. The vegeto-humic 

 deposit was fixed at once and remained unaltered. The fossiliza- 

 tion was in the presence of bitumen, which became altered so as to 

 be insoluble in the ordinary solvents of asphaltum.*** 



Bertrand's charbons humiques differ from the charbons gelo- 

 siques in that the fundamental matter is not diluted with foreign 

 bodies. They are typified by the Broxburn shales of Scotland, con- 

 taining, according to Cadell, about 75 per cent, of ash. Accidental 

 bodies, such as algse, spores, pollen, vegetable debris are in small 

 proportion. Bitumen penetrated through the fundamental jelly and 

 enriched the shale. Bertrand finds no evidence that this bitumen 

 is a leakage or exudation from a fermenting vegetable mass ; he 

 believes that it was in the water and that it penetrated the accidental 

 bodies only with difficulty. 



'* After the memoir was read in the Paris congress, de Lapparent asked 

 what is to be understood by the term " bitumen." Bertrand replied that " the 

 term bitumen implied for him the idea of a substance charged with carbon 

 and hydrogen, intervening wholly formed in the rock.'" 



9a 



