Manchester Memoirs, Vol. Ixii. (1918), No. 



IX. The Association of Facetted Pebbles with Glacial 



Deposits. 



By J. Wilfrid Jackson, F.G.S. 



(Assistant Keeper of the Manchester Museum [Geological Department ) 



[Read January 2.2nd, 1918. Received for publication May 7th, 1918.) 



INTRODUCTION 



The object of this paper is to place on record some recent dis- 

 coveries of facetted and wind-eroded pebbles in Lancashire and 

 Cheshire, and to discuss the interesting association of such pebbles 

 with Glacial deposits. 



Wind-worn and facetted pebbles have been regarded as some- 

 what rare in the British Isles ; but this may be due to their being 

 overlooked. The records of their occurrence, especially in association 

 with the Drift, are certainly scanty. 



Probably the earliest discovery in England was made by the late 

 Mr. R. D. Darbishire, of Manchester, nearly fifty years ago, when 

 a beautifully facetted pebble of quartzite was obtained from the 

 Glacial sand and gravel of Bowdon, Cheshire. This specimen was 

 an exceedingly perfect and characteristic example of the pyramid 

 pebbles or " Dreikanter," such as are found in the " Diluvium " of the 

 North German plain. It was exhibited by Dr. F. A. Bather before 

 the Geological Society of London in 1899, and was fully described by 

 him later in the Proceedings of the Geologists' Association of London. 1 

 The same writer has since described another distinctly facetted 

 pebble of micaceous sandstone found by Mr. W. D. Brown, of 

 Burscough, near Ormskirk, Lancashire, in gravelly soil overlying 

 Boulder-clay at about 3 feet below the surface in the Burscough 

 Brick Company's clay pit. 2 



In 1912 Mr. Brown recorded a number of other examples from 

 the same clay-pit, including a large specimen, 8 by 8 inches, and 4 

 inches high, weight ii| lbs., which he states " was found in situ 

 embedded in the clay, 40 feet from the land surface." 3 This speci- 

 men is distinctly three-edged and is almost identical in form to the 

 Bowdon pebble. It has been presented to the Manchester Museum 

 by Mr. Brown. The depth at which it was found is remarkable. 

 The facet angles appear to be somewhat rubbed, as if the specimen 

 had been rolled about after the facetting. 



1 F. A. Bather, "Wind-Worn Pebbles in the British Isles," Proc. Geol. 

 Assoc, XVI., June, 1900, pp. 396-420, PL XI. 



2 Geol. Mag., August, 1905, pp. 358-359; and W. D. Brown, Lancashire 

 Naturalist, October, 1912, p. 259. 



3 Brown, op. cit., p. 259 and plate. 



