328 IME. T. H. BURTOX OS THE MICEOSCOPIC [vol. Ixxiii, 



10. The MicEoscoPic Material of the Bu>"tee Pebble-Beds 

 o/'XoTTi^"GHAMSHiEE, and its Peobable Solece o/Oeigix. 

 By Thomas Haeets Buetox, F.G.S. (Read May 2Dd, 

 1917.) 



Contexts. t, 



Page 



I Introduction 328 



II. Physical Characteristics of the Sand 328 



III. Description of some of the Simple Minerals 329 



lY. Conclusions as to the probable Direction of the Sediment- 

 bearing Currents, and as to the Sources of the Mineral 



Grains 331 



I. Ixteoductiox. 



Samples of sand were carefully collected from all the principal 

 exposures on the outcroj) of the Pebble-Beds in Nottinghamshire. 

 It was cleaned in hydrochloric acid, sifted, and then separated by 

 means of Thoulet's Solution haying a specific gi-ayity of 2*77. 

 Enough of each sample (namely. 2 ounces) was taken to give 

 a heayy residue sufficient to weigh and to mount as permanent 

 objects for the microscope. 



II. Physical Chaeacteeistics oe the Saxd. 



The sand in the exposures is more or less coherent, in many cases 

 taking on the appearance of hard rock. It may, hoAveyer, when 

 dislodged (the cement being mainly ferric oxide) be easily ci-umbled, 

 often between the fino-ers. 



At depths of 102, 211, and 307 feet, cores at the Farnsfield 

 borehole, near the Midland Eailway Station, showed the rock to 

 be compact, hard, and yer}' calcareous Microscopic examination 

 proved this to be the only real difference when compared with 

 samples taken from the exposures. 



The sand varies in texture and colour, coarse-grained material 

 largely predominating ; but the following distinct types may be 

 recognized : — 



1. A coarse sand, whitish yellow to buff and bro-n-n in colour, found 



in most exposures. 



2. A reddish sand of medium coarseness, found in all the principal 



exposui-es. 



3. A dark brownish-red sand of fine texture, used for moulding purposes, 



found especially at Whisker Hill Quarry near Retford, and at 

 Bestwood Warren.^ 



Samples ~ were all taken from Xo. ' 2.' Ordinary bedding may 



^ 'The Geology of the Country between Newark <t Nottingham" Mem. Geol. 

 Surv. 1908, p. 34. 



^ See map (p. 332) for localities from which sand was collected for 

 ■separation. 



