92 STEVENSON— FORMATION OF COAL BEDS. [April 21. 



source of this infiltration ; they are convinced that it penetrated the 

 deposit, if not contemporaneously, at least very soon after its forma- 

 tion and they suggest that it may be a kind of asphaltum, like that 

 of lake Brea in Trinidad. The kerosene shale contains no animals 

 except at ^lurrurundi, where some coprolites have been discovered. 

 It is a charbon produced by unaltered gelosic organisms. 



Bertrand's''^ later studies were published in a series of papers, 

 his conclusions being summed up in a memoir presented to the 

 Geological Congress at Paris in 1900. 



The bogheads, typified by deposits at Autun of France, the Tor- 

 banite of Scotland and the kerosene shale of New South Wales are 

 charbons gelosiques of Bertrand, accumulations of fresh water algae 

 in a humic jelly, their fossilization being in the presence of bitumen. 

 The basal material of all is a clear brown fundamental jelly, the 

 dull part of the bogheads and the same as the basal material of 

 V. Giimbel's Mattkohle. Spores and pollen have undergone macera- 

 tion, but they did not liquefy. They gave two kinds of yellow 

 bodies and they condensed bitumen strongly. When they abound, 

 the coal, though dull, is brighter than mattkohle. Debris of vege- 

 table matter, also a contribution by the wind, is distributed irregu- 

 larly. The hardened tissues are usually brilliant, prismatic like 

 v. Giimbel's Glanzkohle. Wood and barks can be found as brilliant 

 coal, but this depends less on their organic nature than on the extent 

 of alteration and their capacity to imbibe bitumen. A^getation 

 along river banks yielded tree-trunks, which, after imbibing bitu- 

 men, were converted into bright coal. 



The alg?e were flcurs d'caii. They consisted of gelose and a 

 little protoplasm, which, when humefied, would condense bitumen. 

 They descended in sheets with other accidental bodies ; in times of 

 low water, the descent would be very slow, Ijeing impeded by the 



°^ C. Eg. Bertrand, i, " Xouvcllcs rcniarques sur Ic kerosene shale de 

 Nouv, Galles du Sud.," Bull. Soc. d'Hist. Nat. d'Autuii, IX., i8g6; 2, 3, "Con- 

 ferences sur les charbons de tcrre," Bull. Soc. Beige de Geol., etc., VII., 1894; 

 XI., i8f;8; (4) Caracteristiques dii kerosene shale," Assoc. Franc, pour 

 ravancon. dcs .SV;., 1807; (5) " Lcs charbons humiques et les charbons de 

 purins," Traz\ et Mem. dc rVnk\ dc Lille, W., 1898; (6) C. R. du Congres 

 Int. de Geol., Paris, igoo, pp. 458-407. 



92 



