STEVENSON— INTERRELATIONS OF FOSSIL FUELS. 475 



rence of several vertical stems in a mine near Charleroi ; but these 

 seem to be transported fragments ; there is no reason for supposing 

 that they are sur place. 



Schmitz'^ in 1895 found 33 stumps of erect trees in the roof of 

 the Grande Veine at Grand Bac in the Liege district, where the coal 

 seam is vertical. The glossy, brilliant basal surface of the roof is 

 exposed in the wall throughout and observers could determine the 

 circular markings, indicating bases of the trunks. In almost every 

 case, the cylinders of these petrified trees retained the bark, coalified, 

 sometimes a centimeter thick, under which were leaf scars showing 

 that they are Sigillaria. As the stems are vertical to the stratifica- 

 tion, detailed study of their surface was impossible. The exposure 

 is on the north wall of the gallery, 2 by 93 meters, giving to each 

 stem a space of 5-6o square meters, a condition favoring belief that 

 they are in loco natali. But the stems are distinctly cut off sharply 

 at approach to the coal. Most of them show the swelling which 

 belongs near the roots, but no trace of roots appears. It is clear 

 that the rooting of these trees could not be in the toit, for that is 

 merely a few centimeters of carbonaceous shale. This thin toit con- 

 tains many impressions of plants and stalks of lycopods and equise- 

 tacese, all lying flat. Four of these were seen passing across the 

 base of a trunk, which proves that the stems are not in loco natali. 



But the whole condition indicates rather that the overlying rock, 

 penetrated by the trunks, has slipped on the coal during the disturb- 

 ance. This polished the surface at the plane of contact and cut off 

 the stems as sharply as though they had been sawed. Schmitz, in a 

 later article, recognized this condition and regarded the forest as in 

 loco natali. Long ago, Breton," in his description of the Concession 

 of Dourges, stated that, in some mines, Calamites were found normal 

 to the bed, in the place where they grew. The roots often rest on 

 the coal and the stems traverse the roof. In the pit, Ste.-Hermite, 

 one can see in a gallery, 60 meters long, a number of Calamites, 

 resting by their thin part on the coal, the stems penetrating the over- 



''^ G. Schmitz, " Un banc a troncs debout," etc., Bull. Acad. Roy. de 

 Belg., III., t. XXXI., 1896, pp. 260-266. "Formation sur place de houille," 

 Rev. des Quest, Scient., April, 1906, p. 31. 



" L. Breton, op, cit., pp. 383, 389. 



