44 



of these Cambridge Coprolites more than 200 feet above the 

 level of their outcrop on the north and north-west. 



Prof. Sedgwick in 1861 mentioned similar gravel on the 

 "Stapleford Hills" — by this he probably meant the height 

 called Little Trees Hill to the south of the main road ; only 

 about a foot of gravelly soil however is now to be seen at the 

 top of the chalk-pit. Pipes filled with stones and gravel are 

 shown in the Shelford clunch pits on Steeple Hill. 



Again, on Missleton Hill to the N.W, of the Gog-Magogs 

 there are hollows from which similar gravel has been obtained ; 

 flints and other stones are to be seen impacted into the upper 

 few feet of the rock in the chalk-pit on this hill. 



Besides the series of outliers just described, I am not aware 

 of any other gravels in Cambridgeshire which occupy a similar 

 position; they appear to form a group by themselves, capping 

 all the hills in the vicinity which rise above the limits of a 

 certain inclined plane. This plane slopes from a height of 330 

 feet on Barrington Hill to a level of about 240 on the Gog- 

 Magogs, and where the gravels descend below this plain or fill 

 up hollows, as near Abington, we may suppose that these 

 existed previously, as irregularities of the surface, or that they 

 were excavated out of the Boulder Clay during the period when 

 the gravels were formed. The latter is probably the more correct 

 view, and the subordination of such hollows to a given plane 

 certainly suggests marine action. 



In the neighbourhood of Newmarket, however, there are 

 some gravels which resemble those on the Gog-Magogs in being 

 newer than the Boulder Clay, and in resting either on it or on 

 the Chalk ; but I have not been able to work out the relations 

 of the several patches to one another, and will therefore simply 

 describe the sections I have seen. 



First are the gravel pits half a mile S.E. of Newmarket 

 Station, where about 18 feet of gravel and sand are shown, the 

 lower six feet consisting of fine gravel and sand interbedded, the 

 upper twelve feet of rougher and coarser material, flints being 

 the chief component ; the gravel appears to occupy the southern 

 slope of the valley, and from its character and position, I am 

 inclined to think that it most probably belongs to the series of 

 old valley gravels, which will be presently described. 



