444 STEVENSON— THE FORMATION ur cOAL BEDS. [Nov. i, 



worthy records. Barrois,-* long ago, showed that the great move- 

 ment in the Cantabrian area occurred between the Middle and the 

 Upper Coal Measures. Douville had found evidence of similar 

 conditions in the Rhine country and had concluded that the move- 

 ment was general between Saxony and the Vosges. Barrois recog- 

 nized the time as one of great denudation and reworking of ma- 

 terials, for the conglomerate of Tineo came partly from Carbon- 

 iferous rocks. More recently, he has shown by stratigraphical and 

 palaeontological evidence that in the Nord basin there exist two 

 anticlinals within rocks of the lower coal terrain. 



Angular and rounded fragments of coal have been found in 

 sandstone, shale, limestone and even in the coal itself; that such 

 occurrences have an important bearing on hypotheses respecting the 

 formation of coal beds has been patent to students everywhere but 

 no systematic studies have been made by any except within very 

 recent years. The conditions deserve carefu^l consideration. 



The earliest recorded observation, found by the writer, is that 

 by Logan, "^ who referred to pebbles of coal and coal shale in the 

 Pennant as though they were familiar objects. De la Beche speaks 

 of them in the same way in his " Geological Observer." Some of 

 the pebbles are 2 to 3 inches in diameter and exhibit the definite 

 cleavage. Rounded pebbles of coal belonging to the 'lower series 

 have been found in the upper — and it is certain that the coal, in some 

 cases, was hard when removed, for at quarries in Swansea, Sigillaria 

 stems show impressions of the pebbles. Jukes, ^° in discussing the 

 evidence of unconformity between the Carboniferous and the 

 Permian of South Staffordshire, finds additional proof in the pres- 



^ C. Barrois, " Recherches sur les terrains anciens des Asturies et de 

 la Galice," Mem. Soc. Geo!, du Nord., Vol. 2, No. i, pp. 599, 600; "Expose 

 de I'etat des connaissances sur la structure geologique du bassin houiller 

 dans le Departement du Nord," Lille, 1909, p. 20. 



^^ W. E. Logan, " On the Character of the Beds of Clay lying immedi- 

 ately below Coal Seams of South Wales," Proc. Geol. Soc, Vol. IIL, 1840, 

 p. 276. 



*»J. B. Jukes, "The South Staffordshire Coal-Field," 2d ed., 1859, 

 p. 136. 



