158 W. S. Gredey — A Coal Pebble in a Coal-scam. 



base of the Pennant Series, and to a coal pebble the size of a hen's 

 egg in the roof of the ' Rock Eawr ' coal-seam near Bridgend 

 (Q.J.G.S., vol. xxxiii, p. 932). 1 In the roof of the ' JS'anaimo ' 

 coal, in Yancouver Island, a coal pebble in a conglomerate was 

 recorded in 1906. Several instances of water-worn lumps of coal 

 have been mentioned in the volumes of the second Geological Survey 

 of Pennsylvania as having been found in the semi-bituminous and 

 Pittsburg regions. 



PehUe of Coal in Coal. 



Having collected all available notices of rolled pebbles and of 

 angular or travelled rock-fragments discovered in seams of coal, or 

 in the floors and roofs of coal-beds, as well as in the Coal-measures 

 generally, for a period of twenty-five years, the writer has just met 

 with the only instance known to him of the occurrence of a rounded 

 fragment of coal actually embedded in a seam of coal. If this 

 specimen does happen to be unique, the circumstances of its occur- 

 rence need create no wonderment, since rounded fragments of almost 

 every other Coal-measure roch would seem to have turned up either 

 actually in or near to seams of coal in one coalfield or another. 



Location, etc., of the Coal Pehhle. 



Found, lying flat, in about the middle of the ' Little Coal ' 

 seam, in the Donisthorpe Colliery, in Overseal, Derbyshire, in the 

 Leicestershire and South Derbyshire Coalfield, and at a depth of 

 about 900 feet. The seam is about 4 ft. 10 in. in height, and is 

 believed to lie at about the middle of the Middle Coal-measures.^ 

 The character of the seam is what may be called ordinary house- 

 coal, but the lower half of it is, on the whole, much harder or more 

 'spirey' than is the upper portion, which, for the most part, is ' dicey ' 

 or soft. ITow, it was just within the bottom of the dicey layers that 

 this coal pebble was discovered, the discovery being made in this way : 

 A workman on the ' screens ' at the surface, in order to separate an 

 ordinary lump composed of part soft and part hard coal, split the same 

 with a pick and thus exposed the pebble. The specimen was handed 

 to the foreman, who presented it to the writer a few days afterwards. 



Parenthetically it may be stated that a few years ago the Manager 

 of this colliery (Mr. J, Armson) gave the writer a well-rounded 

 pebble of pale-brown, fine-grained quartzite, which had been found 

 in the clay floor of this same ' Little Coal ' at this same colliery ; 

 also that, some thirty-five years ago now, a much larger quartzite 

 boulder occurred in the same horizon (in the underclay) at a 

 colliery about 3 miles north of Donisthorpe. For a description 

 of this, as well as of other smaller erratics in these Coal-measures, 

 see the author's paper on "The occurrence of Boulders and Pebbles 

 in the Coal-measures" (Trans. Manchester Geol. Soc, 1888). 



^ [See also remarks by W. Sanders and H. Cossham on pebbles of coal in the 

 Bristol Coalfield. The pebbles found in the Upper Measures were stated to be 

 anthracitic, proving their derivation from the Lower Measui-es. (Geol. Mag., 1865, 

 p. 134.)— Ed.] 



2 There are, approximately, 1,000 feet of Coal-measures above and 1,000 feet 

 beneath this seam. 



