53 



readied ; these show 6 or 8 feet of chalky and somewhat clayey 

 gravel, containing patches of light sand, and covered in places 

 by a reddish-brown sand ; the whole is apparently made up of 

 waste from Boulder Clay, it contains many rounded pebbles of 

 chalk, many flints (mostly angular), pieces of limestone, sand- 

 stone, quartzite, red chalk and derived fossils. This patch lies 

 on the slope of the hill, and similar sand and gravel may be 

 traced northward along the ridge and also down the slope into 

 Wratting Valley ; half the hollow of the ancient watercourse is 

 therefore preserved, while the opposite slope has been worn 

 back, but once stood, no doubt, over the ground of the present 

 valley, as shown by the dotted line in Fig. 3. The same feature 



Fig. 3. Section across Wrattiug Valley. 



a = chalk. 



b — gravel. 



was remarked near Duxford Grange in the " Wardington 

 Bottom " series, in both cases the gravels lying half on the hill 

 and half in the valley. In both cases also the present valley or 

 " bottom " only coincides with the line of the ancient watercourse 

 in its upper and deeper portions, while lower down the old 

 gravels gi'adually get up on the slopes of the valley, and 

 eventually deserting it altogether they form long ridges raised 

 above the level of the country beyond ; such behaviour indicates 

 at once their great antiquity, and the enormous amount of 

 denudation which has taken place since the period of their 

 formation. 



In the present case this feature is very marked, the next 

 outlier of gravel occurring along the high ridge which is cut 

 through by the junction of the old and new railways to 

 Newmarket. 



A chalk pit near its southern extremity shows about 8 feet 

 of hard chalky sand containing scattered flints, but few chalk 

 pebbles of any size ; the sandy matrix is an intimate mixture of 

 chalk grains and flint sand, but the former has been dissolved 

 from the uppermost foot or two, leaving the flints embedded in 



