50 



Boulder Clay, mixed with a considerable proportion of sand, and 

 an occasional chalk-pebble occurs here and there in the mass. 



This aDcient series of river deposits has now been traced 

 to a point where it is cut off by the present valley of the Cam, 

 and before proceeding to consider the direction in which it was 

 continued it will be desirable to notice some similar deposits on 

 the flank of this valley. 



The section in the railway cutting near Chesterford station 

 has long been known as exhibiting 7 or 8 feet of contorted 

 yellow and brown loam overlaid by a few feet of coarse rubbly 

 gravel. By some geologists it has been thought that the loam 

 belonged to the Mid-Glacial series, and that it was overlapped 

 by a high terrace of valley gravel. 



There is no doubt that recent valley gravel intervenes 

 between the loam and the river, but I am inclined to think that 

 this is much more recent and altogether at a lower level than 

 the gravel overlying the loam. With regard to the age of the 

 latter, its entire separation from other glacial deposits, and its 

 disposition along the slope of the valley, are sufficient to create 

 grave doubts as to the propriety of grouping it with Middle 

 Drift ; while from the great similarity of both loam and gravel 

 to the deposits above described near Wbittlesford, I am strongly 

 inclined to consider them as belonging to a similar series and as 

 having originated in a similar manner ; (indeed, a little north 

 of Ickleton inclined beds of yellow and grey loam occur, which 

 may have formed part of their continuation towards Whittles- 

 ford.) 



Southward the loam can be traced along the railway for 

 more than half a mile, and patches which have evidently once 

 been connected with it trend southward along the slope above 

 the line. It is not improbable that some of the loams and 

 gravels about Wend en and Newport may be of the same age, 

 but they are so mixed up with beds of later date as to make 

 any attempt to separate them a very difficult task. 



I think, however, that there is sufficient evidence to prove 

 that a series of deposits once existed along this valley, similar 

 in ao-e and origin to those which have been traced from 

 Wardington Bottom to Wbittlesford; but in consequence of 

 this valley having ever since continued to be a main line of 



