48 



direction of tlie old river course may be traced by the gravelly 

 surface of the ground. 



Further still another large mass of gravel is met with, 

 covering the country north of Chrishall Grange ; about a mile 

 N. of this place it has been excavated for road material, and 

 when seen in 1875 the pit disclosed 8 feet of rough chalky 

 gravel underlaid by 3 feet of fine chalky. sand, with a lenticular 

 bed of fine gravel composed entirely of small chalk pebbles. 

 The gravel was roughly stratified, and one layer was stained 

 black by manganese or iron ; a few large boulders occurred, and 

 many subangular flints, some of them standing on end ; there 

 were also two or three small patches of contorted loam enclosing 

 shells (Succinea and Pupa ?), these appeared to have been 

 contemporaneously interbedded, and if so, they would indicate 

 clearly the fluviatile origin of the gravel. 



This pit is situate on a flat or gentle slope, but the base of 

 the gravel appears to be uneven, and to rise towards the North, 

 for it runs out into the high ground, which extends as a gravel- 

 covered ridge northward towards Thriplow, but bends eastward 

 before reaching that village, and points towards the mass of 

 loam and gravel to be next described. 



This is first seen in a gravel-pit near the main road about a 

 mile west of Whittlesford station, but the best section is to 

 be found in a large pit close to the station on the south side of 

 the road. Along the eastern face of this a sandy buff-coloured 

 loam is seen which is underlaid at the southern end by fine 

 chalky gravel, containing on a rough calculation about 50 per 

 cent, of chalk pebbles, the rest being chiefly flints ; a small cave 

 here excavated in the gravel is roofed by the overlying loam. 



Turning back and descending into the lower part of the pit, 

 we find it worked in roughly bedded gravel, chiefly composed of 

 small stones, but with occasional layers of coarser material, 

 made up of flints and large chalk stones, with quartzites, shelly 

 oolites and fragments of Gryphsese ; several pieces of laminated 

 loam with shelly partings were also found. Farther on the 

 gravel becomes strongly false-bedded, with intercalated patches 

 of fine sharp sand, and the whole is cut into by a descending 

 scoop of the overlying loam, which is strong and clayey near the 

 base, but vellow and sandv above. 



