358 Dr. F. A. Bather— A Wind-icorn Pebble in Boulder Clay. 



Eadiolaria in South Wales between the Carboniferous Limestone and 

 the Millstone Grit proves that conditions suitable for their formation 

 occurred at no great distance from Carboniferous land, and goes far 

 to disprove the view put forward by Messrs. Hinde and Fox that 

 the Lower Culm beds of Devonshire are " deep-water representatives 

 of the shallower-formed calcareous deposits to the north of them," ' 



IIL — A Wind-worn Pebble in Boulder Clay. 

 By Dr. F. A. Bather, M.A., F.G.S., British Museum (Natural History). 



NEARLY forty years ago Mr. E. D. Darbishire obtained from the 

 Glacial gravel of Bowdon, Cheshire, a facetted pebble, which 

 I afterwards had the privilege of describing (Proc. Geol. Assoc, xvi, 

 pp. 396-420, pi. xi, June, 1900). The conclusion then reached was 

 that the pebble bore witness to the action of blown sand at a period 

 during or not long before the deposition of that particular bed of 

 Glacial Drift. Since, however, the pebble was in other respects 

 similar to pebbles common in the Bunter beds, and since some had 

 supposed the existence of desert conditions in those Triassic times, 

 there remained the possibility, and to some minds the probability, 

 that the pebble in question had received its facets during the 

 Triassic epoch. It may, therefore, be useful to draw attention to 

 a distinctly facetted pebble from the Boulder Clay within twenty- 

 five miles of Bowdon. This was found by Mr. W. D. Brown, of 

 Burscough (north-west of Ormskirk, Lancashire), at about three feet 

 below the surface in the Burscough Brick Company's clay pit. The 

 pebble is composed of a greyish micaceous sandstone, weathering 

 yellow, and too coarse and loose in texture to be capable of taking 

 a polish. The facets on it, however, are clearly cut, and do not 

 appear to have undergone much, if any, subsequent abrasion. Its 

 greatest length is 37-5 mm. ; greatest width, 29*5 mm. ; greatest 

 thickness, 7"9 mm. What was probably its uppermost surface, 

 during the latest period of its exposure to wind action, shows a flat 

 central area, of irregularly pentagonal outline, surrounded by five 

 facets, of which one is slightly concave, one rather irregular, two 

 slightly convex, and the last markedly convex and probably retaining 

 the original curved surface of the pebble. The greater part of the 

 under side seems to preserve the original rounded, presumably 

 water- worn, shape, but about two-thirds of this side is bevelled at an 

 angle of about 45° by two facets which are not clearly separated 

 from one another. The number of facets on the upper side suggests 

 that the stone was, perhaps more than once, shifted I'ound its vertical 

 axis, while the under side indicates that it was at one time blown 

 over into a different position of equilibrium. Nothing, however, 

 would be gained by further speculation : the real value of the find 

 seems to lie in its confirmation of the view that abrasion by blown 

 sand did take place in the north-west of England during the later 

 Glacial age. Mr. Brown tells me that he found another facetted 



1 Quart. Journ. Geol. Soc, vol. li, p. 609 (1895). 



