38 



being found in a dark lead-coloured sand with chalk pebbles 

 underlying about 20 feet of clay ; this sandy gravel is prabably 

 a similar bed to that which forms the base of the Boulder Clay 

 near Had stock and other places, see p. 31, the materials being 

 exactly the same as those in the Boulder Clay, but without the 

 compact clayey matrix.] 



§ d. The Isle of Ely. We have already found that as we 

 proceeded northward the Boulder Clay descended to lower and 

 lower levels; its edge at Lolworth and Boxworth is about 120 

 feet above ordnance datum, and near Ely its base is about 60 

 feet lower. 



The low ridges or hills which stand out of the surrounding 

 fens, and constitute what was of old the Isle of Ely, are capped 

 by the Chalky Boulder Clay except where they rise higher than 

 70 or 80 feet above the sea-level, as at Haddenham and south- 

 ward towards Aldreth. Possibly the Glacial Clay was originally 

 banked round the outliers of Gault and Neocomian here, as it 

 was round the latter at Potton and Sandy, 



Ely Cathedral and most of the city is situated upon the 

 Neocomian Sand, which is underlaid by the Kimmeridge Clay 

 (here however of no great thickness). Boulder Clay first comes 

 on near the Union House and stretches southward till it spreads 

 out over the high ground between Witchford and Thetford. It 

 caps the long ridge which extends westward from Witchford by 

 Wentworth to Sutton ; it covers Sutton Field, but Mr Skertchly 

 informs me that the town itself stands on a patch of gravel which 

 appears to be intercalated in the Glacial Clay and that the 

 materials composing this gravel are the same as those found in 

 the neighbouring Boulder Clay ; so that as sometimes we have 

 Boulder Clay without the boulders, vv^e have here Boulder Clay 

 without the clay. 



North of Ely, Boulder Clay is found at Little London and 

 Boslyn Hill, whence it runs down in the form of a long tongue 

 through the clay-pit called Boslyn or Roswell Hole. Here it 

 lies in a long hollow which has been scooped out of the Kim- 

 meridge Clay, and contains at the particular place where the pit 

 was first opened a large boulder of gault and chalk ; this has 

 been brought by the agency of ice from some point to the east- 



