CHAPTER V. 



VALLEY GRAVELS OF THE EARLY RIVER SYSTEM. 



In the higher parts of the tributary valleys, as well as in other 

 localities nearer Cambridge, there exist certain patches of 

 gravel and loam, regarding the age of which there has lately 

 been much difference of opinion among Cambridge geologists, 

 and the relations of which could perhaps hardly have been 

 ascertained until the country was mapped in some detail. 



Although similar in composition to the gravels previously 

 described, they occur mostly at much lower levels and are 

 entirely separated from the glacial deposits ; they appear to 

 have a distinct relation to the valley systems in which they lie, 

 and they behave in all respects like ancient river gravels. 

 The correspondence of these deposits with the direction of the 

 present valleys is not however preserved in their lower pro- 

 longations, indeed so great is the divergence that near Cam- 

 bridge they strike across the Cam Valley almost at right angles 

 to its present course ; at the same time their fluviatile origin 

 becomes more apparent, for they preserve a definite line across 

 the country, forming a nearly continuous ridge, which may be 

 followed with few interruptions far into the regions of the Fens. 

 We are thus led to the inference that these old gravels indicate 

 the course taken by the first river system of the district, and we 

 may expect them therefore to throw much light upon the 

 history of its denudation, and upon the relative age of some of 

 its principal physical features. 



The southernmost patches of these old valley gravels are to 

 be found in a curious hollow among the Chalk Hills near 

 Royston, called Wardington Bottom. The beds of the lower 

 Chalk are here affected by a remarkable disturbance which has 



