STEVENSON— INTERRELATIONS OF FOSSIL FUELS. 473 



ent in the Grande Veine of Centre, that of Charleroi, Dix-Paumes, 

 Gros Pierre, Caillette and other seams. Some have been discovered 

 in partings, in the roof and in the mur. The largest weighs 25 

 kilogrammes and most of them are sandstone. Stainier thinks that 

 these pebbles must have been entangled in roots of trees, floated 

 into the sea. 



Schmitz^^ asserts that rolled pebbles are not so rare as some 

 v/riters have supposed ; they are not exceptional but are of common 

 occurrence throughout the coal formation. He thinks that they 

 confirm sympathy for the French doctrine, which assumes that the 

 plant materials were changed into coal before burial in deltas. He 

 suggests that, on the shores of coal lagoons, movements of water 

 more or less rapid had brought fragments of rock with the vegetable 

 alluvium; a long voyage in the bouillie vegetale would bring about 

 the coating of coal. 



Barrois's'^^ exhaustive stiidy was based upon a collection of more 

 than 300 pebbles made in the Veine-du-Nord at mines of the Com- 

 pagnie d'Aniche. The seam is regular and, though thin, 0.45 to 0.60 

 meter, it has been mined profitably for a long time. The coal is of 

 excellent quality, demi-gras, with 13 per cent, of volatile and com- 

 paratively little ash. The mur has abundance of rootlets and at half 

 a meter below the coal there are many large rhizomes of Stigniaria 

 with appendages. The roof is fine shale, without animal fossils, 

 has no erect stems but has impressions of Lepidodendron and Cala- 

 mites. The faux-toit is shale and coal, never more than a half meter 

 thick. 



The pebbles vary greatly in shape and are distributed irregu- 

 larly in the coal from mur to toit. Their position indicates that 

 they were not brought in by currents and some have salient angles, 

 which would have been destroyed by even gentle rubbing. The 

 crust is coal, laminated and brilliant, often with pyrite, derived from 

 the coal. It is adherent, is removed only with difficulty and contains 

 more volatile than is found in the surrounding coal. 



■^2 G. Schmitz, " A propos des cailloux roules du houiller," Ann. Soc. 

 Geo!. Belg., t. XXL, 1894, Bull., pp. Ixxi-lxxv. 



''^3 C. Barrois, " Galets trouves dans le charbon d'Aniche (Nord)," Ann. 

 Soc. Gcol. du Nord, t. 36. 1907, pp. 248-330. 



