(j8 



the valley had no existence until the Boulder Clay had been 

 entirely removed from this district, and the springs issuing from 

 the base of the Chalk were brought into play. Opposite 

 Barrington the Rhee receives an affluent which comes down 

 from Wardington Bottom, and running through Foulmire passes 

 between Shepreth and Foxton. It will be remembered that 

 when describing the early river-system (p. 47), it was mentioned 

 that this stream had deserted the course which it took in older 

 times by Heydon Grange and the Crowley Hills to Whittlesford, 

 and that it now followed the direction above indicated. 



It is impossible to say exactly when this deviation took 

 place, but from the patches of gravel occurring along the course 

 which it now follows, it seems likely to have been a main line of 

 drainage at some period intermediate between the formation of 

 the Whittlesford gravels, and the excavation of the present 

 valley of the Rhee above Barrington. 



It may be therefore that the gravels about Foulmire and 

 Foxton were deposited about the same time as those about 

 Barnwell and Trumpington, but on the whole it seems likely 

 that they belong to a somewhat later period. 



The valley of the Bourn, on the other hand, appears to have 

 existed from very early times, and remains of the three principal 

 terraces occur along its slopes. The highest of these has been 

 mentioned by Prof Seeley as forming a ridge between Barton 

 and Grantchester\ and in all probability this was originally 

 . continuous with the Trumpington gravels, from which it is now 

 separated by the modern valley of the Granta. 



In the old pits behind Grantchester church about 10 feet of 

 fine gravel and sand was exposed in 1874, and I was informed 

 that large bones and teeth had been found here. From this 

 point the gravels extend westwards and occupy a hollow along 

 the top of the chalk ridge, bearing the same relations to a 

 previous surface as the long gravel-capped ridges previously 

 described. 



Beyond Barton the continuity of the series is interrupted by 

 a watercourse draining off the Boulder Clay on Comberton 

 Field, but a large patch again occurs in the upper part of 



* Quart. Jonrn. Geol. Soc. Vol. xxii. p. 475. 



