378 CRETACEOUS. 



include Waldhciinia iamarindus, W. Woodivardi, Tcrchrahila depressa, 

 RhynchoncUa latissima, Ostrca macroptera, Trig07iia alccformis, Opis 

 Neocomiensis, Cyprina Sedgivickii, Pleiirotomaria gigantea, and (at 

 Upware) the Sponge Elasmostoma aciitimargo} 



Iron-ore was formerly worked in the sands in the neighbourhood 

 of Leighton Buzzard ; and this locality has yielded Cycadiies Yatesii, 

 (described by Mr. Carruthers).^ Pinites has been obtained from 

 the Potton Beds. 



Prof. Bonney observes that the ' coprolites ' consist of wood, mineralized by 

 phosphate, casts of Mollusca, bones, and shapeless lumps ; they are worked for 

 manure. The Potton phosphatic nodules, to which attention was first directed by 

 the Rev. P. B. Brodie, yield from 30 to 50 per cent, of phosphate of lime, while 

 those of the Cambridge ' Greensand ' yield 5S to 61 per cent. The occurrence of 

 phosphatic nodules at the base of the sands at Brickhill was made known in 1873 

 by Air. Teall. The Upware district was first described by Mr. J. F. Walker, and 

 there phosphatic nodules occur in the Lower Greensand and also at the base of the 

 Gault.'* 



In the neighbourhood of Woburn the Woburn Sands (termed by the Rev. John 

 Michell in 1 7S8 the ' Sand of Bedfordshire ') are about 220 feet in thickness, and 

 here at Wavendon and other places fuller's earth has been dug for the past 150 

 years.* The fuller's earth occurs rather below the middle part of the sand, as 

 follows : — 



Sand 1 30 feet. 



Fuller's Earth 12 ,, 



Sand about 80 ,, 



The fuller's earth is now obtained by sinking shafts, at Aspley Heath. The 

 water thrown out by this bed is said to be very pure and sweet, and Mr. A. C. G. 

 Cameron states that blocks of the earth have been placed in wells to purify the 

 water. At Ampthill the thickness of the Lower Greensand is upwards of 30 feet, 

 while at Potton it is over 100 feet ; at these localities, as well as at Sandy and 

 Woburn, the Lower Greensand contains much iron-ore in the form of ochre, etc. 



Prof. Bonney remarks that at Sandy, in Bedfordshire, the Lower Greensand 

 strata form a remarkably picturesque escarpment on the right bank of the Ivel ; 

 between that place and Potton, they are cut through by, and well seen from the 

 railway between Bedford and Cambridge. They consist of Carstone and buff or 

 ochreous brown sand, often showing false-bedding, and with many cakes and 

 concretions of brown iron-oxide. So sterile is the land in places that it can support 

 little but the Scotch fir ; still the extraordinary productiveness of the market- 

 gardens in the Ivel valley above Sandy is largely due to the admixture of this light 

 warm sand in the alluvial soil.* 



1 J. F. Walker, Ann. Nat. Hist. (3), xviii. 31, 381, xx. 118; H. G. Seeley, 

 Ibid, xviii. iii, xx. 23; and Index Woodwardian Museum, p. ix ; Brodie, G. 

 Mag. 1866, p. 153 ; J. J. H. Teall, The Potton and Wicken Phosphatic Deposits ; 

 Bonney, Cambridgeshire Geology, p. 22. 



• G. Mag. 1867, p. 199. 



^ G. Mag. 1867, p. 454 ; 1868, p. 399. See also W. Keeping, The Fossils, etc., 

 of Upware and Brickhill, 1883. 



* Fitton, T. G. S. (2), iv. 295 ; Rev. B. Holloway, Phil. Trans, xxxii. 419 

 (1723) ; Conybeare and Philhps, GeoL Eng. and Wales, p. 138; A. C. G. 

 Cameron, G. Mag. 1885, p. 91, Brit. Assoc. 18S5. 



^ Cambridgeshire Geology, p. 22. 



