34 



§ c. Western District. The greater portion of the third 

 district, lying to the west of the Cam Valley, is likewise over- 

 spread with a broad and often thick covering of Boulder Clay, 

 which has filled up the pre-existing hollows and now forms an 

 elevated plateau or upland ; there is however hardly any gravel 

 either above or below this clay, and there are few sections that 

 merit description. I will therefore simply point out the limits 

 and the ' behaviour' of the Glacial Clay. 



The hills above Haslingfield, Harlton and Orwell are capped 

 with it everywhere above a height of 200 or 220 feet, but as 

 they nowhere rise above 250 feet, a long narrow ridge of Boulder 

 Clay is the result, probably not more than 30 feet thick at any 

 spot; it stretches from Haslingfield chalk-pit to Orwell may- 

 pole, and thence to Cobb's Pound and Eversden Wood, a dis- 

 tance of four miles, and may be seen in many of the quarries 

 between the above places ; it is shown to be a stiff grey clay, 

 full of chalk fragments, but only containing a sprinkling of other 

 rocks, such as Red Chalk, quartzites, and nodules from the 

 Cambridge Greensand. 



It spreads out westward and descends to a lower level, 

 closely following the outcrop of the chalk about Wimpole and 

 Arrington ; indeed the position of this outcrop and the general 

 features of the country have clearly been determined by the 

 presence of the Boulder Clay, and its power of resisting denuda- 

 tion has no doubt been the means of preserving this outlying 

 area of chalk marl, with the underlying coprolite bed, from the 

 destruction to which they must otherwise have been exposed. 



Its former extension is indicated by the occurrence of stones 

 and boulders over the fields far beyond its present limit ; a very 

 large boulder stands in Lord Hardwicke's grounds at Wimj)ole. 



From Arrington the Boulder Clay continues to cap the high 

 ground bounding the north side of the Rhee Valley by Croydon 

 to Tadlow and Wrestlingworth, overlapping the Chalk Marl on 

 to the Gault ; its boundary passes eastward of Sutton and Potton, 

 to the neighbourhood of Gamlingay. There is a small outlier 

 capping Sutton Hill, and another on the hill just S. of Potton 

 Church. From Gamlingay Wood the boundary is continued by 

 Waresley and Gransden to Eltisley and Croxton, the numerous 

 little streams which flow off the neighbouring high ground having 



