STEVENSON— INTERRELATIONS OF FOSSIL FUELS. 469 



not fused. He remarks that the volatile decreases downward in 

 the measures but he notes also a variation along the direction of 

 strike and still more notable decrease from the disturbed southern 

 area northward into the slightly disturbed area along the northern 

 border. 



Renier®" offered a somewhat different grouping; Flenus, with 

 more than 25 per cent, of volatile; Gras, with 25 to 16; Demi-gras, 

 with 10 to II and Maigre, with less than 11. Gallet, resembHng 

 bituminous shale, is closely allied to cannel. The different benches 

 of a seam are often unlike in volatile content and there are local 

 variations w^iich are puzzling. At the same time it seems possible 

 to find a law of variation in order of superposition ; equally so in a 

 single seam along general direction of the trough, or even in a direc- 

 tion normal to the line of the trough. The downward decrease is 

 thus, Flenu, maximum, 35 per cent.; Charleroi, 24; Chatelet, 18; 

 Andenne, 15. But in the Flenu, the volatile varies from 25 to 35; 

 in the Charleroi, from 17 to 20 within Couchant de Mons, 17 to 18 

 in Centre, 10 to 18 in Charleroi, 13 in Basse-Sambre, 0.5 to 21 in 

 Liege district; the Chatelet from 6 to 10 and the Andenne from 7 

 to 15.5. He thinks that Hilt's law is practically applicable to the 

 Belgian area. But the volatile increases from north to south, that 

 is, from the less disturbed to the intensely distorted area. Finally, 

 the volatile decreases from the outcrop toward the deeper part of 

 the basin. 



Dannenberg,^^ utilizing tables of analyses compiled by Stainier, 

 makes clear that, in the Liege district, the volatile of the respective 

 faisceaux of the Charleroi decreases downward from 23.7 in th^ 

 upper St. Gilles to 6 per cent, in a seam near base of the Seraing. 

 But there are exceptional seams; one in the upper Liege faisceau 

 has abnormally low volatile, being anthracite, while one in the upper 

 portion of Seraing has 24 to 25 per cent, and is the richest gas coal 

 in the district. More important are the variations across the basin 

 from north to south. In the northern portion, the "Plateurs," 

 where disturbance is comparatively slight, the percentage is low, but 

 it increases greatly in the southern portion, where the disturbance 



^"^ A. Renier, op. cit, 1914, pp. 23-30. 

 6® A. Dannenberg, op. cit, p. 285. 



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



