STEVENSON— INTERRELATIONS OF FOSSIL FUELS. 485 



removed the roof and much of the coal along a line of 80 meters on 

 the outcrop. About 40 meters of Permian beds remain ; the suc- 

 cession is discordant. 



Fayol's conception is that the coals were deposited as transported 

 vegetable matter on the sides of the submerged deltas in the lake or 

 in the bays separating them. A remarkable feature observed in the 

 Tranchee de I'Esperance is regarded by him as due to a slide on the 

 v/atersoaked surface of the delta. The folding is very distinct in a 

 close synclinal where the rocks are different in color from those of 

 the wrinkled Coal Measures beds on one side, where exposures are 

 complete. As the coal has been mined in vast open works, the con- 

 ditions are well shown in two adjacent excavations. The locality 

 was visited by Stevenson®* in 1909, who explained the matter very 

 differently. He regarded the light colored rocks of the synclinal 

 as a deposit filling a channel-way eroded after the coal had been 

 consolidated. The distortion of the strata was caused by eruption 

 of a great mass of dioritine, the lateral thrust folding the rocks, 

 crushing the coal into polished lenses and causing shale beds between 

 sandstones to become wrinkled. This thrust produced a horizontal 

 fault under the severely flexed rocks, which is well-exposed in the 

 Tranchees Longeroux and de I'Esperance. The disturbance be- 

 comes insignificant east from the former tranchee as distance from 

 the dioritine increases. 



Autun. —Fevmian in the little basin of Autun contains the bog- 

 head, which, according to the studies by Bertrand and Renault,^^ 

 consists chiefly of algae enclosed in a " fundamental matter." It 

 closely resembles the Kerosene Shale of New South Wales. 



The deposit is thin and in limited space ; it extends north from 

 Autun for about 7 kilometers and is from 150 to 450 meters wide. 

 It disappears away from a certain depth and is represented on the 

 borders only by small lentils, irregularly scattered. The principal 

 lens is from 23 to 25 centimeters thick, but exploitation is profitable 

 as the yield of oil on distillation is very large. The boghead is 



8* J. J. Stevenson, "The Coal Basin of Commentry in Central France," 

 Ann. N. Y. Acad. Sciences, Vol. XIX., 1910, p. 198. 



85 C.-Eg. Bertrand et B. Renault, " Pila bibractensis et le boghead 

 d'Autun," Bjill. Soc. d'Hist. Nat. d'Aiitiin, t. 15, 1892, sep., pp. 1-93. 



PROC. AMER. PHIL. SOC, VOL. LIX, EE, DEC. 21, I92O. 



