R. H. Rastall — Minerals of Barrington Bone-bed. 253 



and Recent age in this district, with, a view to ascertaining whether 

 the character and possible derivation of the smaller mineral grains 

 might tlirow any light on the correlation of these puzzling deposits. 

 Some of the results have been already published/ while other groups 

 are still under investigation. Since the Barrington Bed is so widely 

 known, and so peculiar in character, it seemed advisable to accord it 

 separate treatment. 



The earliest detailed description of the lithological character of the 

 bone-bed appears to be that given by the E,ev. 0. Fisher in 1879 '^i 

 it is as follows : — 



"The materials of which the bone-bearing deposit consists are 

 peculiar. The matrix is a grey sand with a slight admixture of clay. 

 The pebbles consist of flint in subangular pieces of no great size, 

 sometimes ochreous, sometimes grey, sometimes black. These are 

 not rounded, but have their surfaces worn, polished, and the angles 

 rubbed off. There are rolled lumps of Chalk-marl and a considerable 

 admixture of ' coprolites ', as might be expected, seeing that the 

 coprolite-bed is abraded by the deposit itself. The remaining pebbles 

 are well-rounded pieces of crystalline rocks, consisting of quartz, 

 quartzite, syenite, jasper, and trap. These old rocks conti'ibute 

 a large part of the pebbles, so that the material cannot be called 

 a flint-gravel, in that it appears to consist of the least destructible 

 parts of the Boulder-clay, mixed with materials from the Chalk-marl 

 and Greensand. 



" There appear to be very few remnants of the Oolitic rocks among 

 the pebbles, except a few fragments of Qryplicea. The pebbles are, 

 for the most part, not at all decomposed, as those are which one now 

 picks up in the neighbouring ploughed fields, and the glacial scratches 

 are well preserved." 



The foregoing description was penned at a time when the facilities 

 for a thorough examination were greater than at present exist. The 

 section is described as extending for 70 yards from north to 

 south, and workings were then in active operation. It only remains 

 to add, what is not perhaps there made sufficiently clear, that many 

 of the so-called ' pebbles ' are large stones, weighing as much as 

 14 or 161b., and that large, well-rounded boulders of hard white 

 Chalk are common. It is, however, mainly with the finer material of 

 the beds that we are here concerned, and the characters and origin of 

 the larger constituents, though a topic of great interest, cannot be 

 further discussed.^ 



Since the deposit shows a good deal of variation from top to bottom, 

 several samples were collected from different parts, and of these three 

 are here more particularly described. 



1. This specimen was obtained about two feet from the top of the 

 bed. It may be described as a white chalky gravel and sand, 



' ' ' The Mineral Composition of some Cambridgeshire Sands and Gravels ' ' : 

 Proc. Camb. Phil. See, vol. xvii, pp. 132-43, 1913. 



^ " On a Mammaliferous Deposit at Barrington, near Cambridge " : Quart. 

 Journ. Geol. See, vol. xxxv, pp. 670-7, 1879. 



* For the most recent description see Hughes, " Excursion to Cambridge and 

 Barrington" : Proc. Geol. Assoc, vol. xxii, pp. 268-78, 1911. 



