22 STEVENSON— INTERRELATIONS OF FOSSIL FUELS. 



argillaceous, with abundant impressions of plants and animals, 3.30 ; 

 (3) laminated shale, argillaceous, with leaf impressions, 0.05 to 

 0.15; (4) coal, 0.25 to i.oo; (5) black-brown carbonaceous shale, 

 with great abundance of vegetable impressions, ill-preserved but 

 remarkably like modern swamp plants, such as reeds and ferns, 

 0.50; (6) marly shales with plant impressions and Posidonia, 0.90; 

 (7) shaly sandstone with remains of plants, 0.50; (8) silicious 

 fetid limestone, 3.00; total, 10.40 meters. This rests on the Lower 

 Keuper, mostly variegated marls with gypsum and salt. The dolo- 

 mite marks a notable change in conditions ; below it, the deposits 

 are micaceous and sandy, with abundant remains of plants and 

 animals ; but above it, marls predominate and remains of any sort 

 are rare. 



The coal seam varies greatly in thickness ; at times it bifurcates, 

 at others it disappears. These variations are not due to disturbance 

 as the dip is less than 3 degrees. Kidneys of dark calcareous iron 

 ore are in the coal, now concentrated under the roof but again 

 scattered throughout the seam. Pyrite is abundant. Where 

 thickest, the seam is triple, showing (i) upper bench, variable, con- 

 sisting at times of alternating bright and dull laminations, when 

 the coal is rejected as it burns badly and is not reduced to ash; 

 commonly, however, it is brilliant black and an excellent fuel ; 

 (2) middle bench, not always present ; its coal is glossy black, is 

 almost uniform, burns well and is reduced to red ash ; it encloses 

 vegetable remains, some of them root-like; (3) lower bench, has 

 brilHant black coal, yielding a brown powder. 



The quality and thickness improve toward the north. At the 

 south, near La Marche, Romain and Talliancourt, it is replaced with 

 clays containing great numbers of tree stems. Mining begins farther 

 north near la Rouville and Croinville, where the thickness is 0.15 

 to 0.30; at Norroy, it becomes 0.40 to 0.80, but at Gemmalaincourt 

 and Parey it is i meter. Fragments of shale, quartz and sandstone 

 with rounded angles occur occasionally in the coal. The lenticular 

 form of the seam is distinct. 



The same horizon has been recognized at widely separated locali- 

 ties in France, though coal is rarely present. Rouville,^^ describing 



31 P. de Rouville, Comptes Rendus, t. 48, 1857, pp. 696-698. 



