191 -'J STEVENSON— THE FORMATION OF COAL BEDS. 451 



carbonaceous shale are rounded easily. The contrasts are shown 

 well by fragments in this sandstone, for the glance coal is angular 

 and the cannel rounded. Fragments of slaty coal also are rounded, 

 but the shale i^ortion resisted better than the coal portion and 

 the fragments are flatter than those of cannel. The bond between 

 coal and shale must have been, at entombment, such as is seen in slaty 

 coal now. It might be supposed that the pebbles are burie(;i frag- 

 ments of wood; but such complete penetration of wood by shale is 

 inconceivable ; there would be, moreover, so great change in volume 

 that the fragments could not retain their form. He is convinced 

 that the consistency of glance on the one hand and of cannel on the 

 other is so different as to make certain that the materials had 

 acquired their characteristics before burial. The source of the 

 pebbles cannot be ascertained, but they do not appear to have come 

 from any contiguous bed, and the only suggestion possible seems 

 to be that they have been derived from much older deposits. The 

 features of the rock carrying the coal pebbles, especially its coarse- 

 ness, in which it differs from the sandstone on each side, seem to 

 suggest that it may occupy a valley eroded in the sandstone. 



Coal pebbles are not confined to the Coal JVIeasures. Haast^^ 

 found them in Cretaceous sandstone of northern New Zealand and 

 Hutton found them abundant in a conglomerate of the same age in 

 Otago, where the rock rests on the eroded surface of a coal bed. 

 Fragments of coal have been reported by the writer from upper 

 Cretaceous sandstones of New Mexico and a large block of oolite 

 •coal was obtained in the chalk of Kent. England. A more curious 

 phenomenon is the existence of apparently rolled pebbles in the 

 coal itself. Gothan*'^' states that in the Lias area of Fiinfkirchen. 

 Hungary, there is. near Vas^s, abundance of " JMugelkohlen." round 

 to ellipsoidal fragments of pure coal, embedded in almost all of the 

 coal beds. In size they vary from nut to two fifths of a meter; 



^'J. Haast. "Report on the Geology of the Malvern Hills, Canterbury," 

 "Geol. Surv. New Zealand. 1872, pp. 50, 52, F. Hutton, " Report on the Geol- 

 ogy and Gold Fields of Otago," Dunedin, 1875. p. 106. 



*" W. Gothan, " Untersuchungen iiber die Entstehung der Lias-Stein- 

 kohlenfl()ze bei Fiinfkirchen (Pecs, Ungarn)," Sitcuiigber. d. k. preus. Akad., 

 Vol. VHI., 1910, pp. 136-143. 



