74 



from the gravel of Waterbeach the Woodwardian Museum has 

 the vertebrae of a whale, which from its preservation was 

 evidently contemporaneous with the bed." It would be desira- 

 ble to know whereabouts in Waterbeach this was found, whether 

 in gravel under alluvium or in the higher series westward of the 

 town, for the village itself is situated mainly on a strip of gault 

 which separates the two sets of gravels. The gravel and sand 

 underlying Waterbeach Fen and bordering the alluvium near 

 Chesterton and Milton are comparable with the low level 

 deposits previously mentioned. 



Wilbraham Fens. To enter upon a general description of 

 the Cambridgeshire Fens would be beyond what I understand 

 to be the scope of the subject proposed, and would certainly 

 prolong this Essay to an inordinate length. There is however 

 one isolated tract that merits description here, inasmuch as its 

 origin is connected with that series of ancient river-gravels 

 which form so noteworthy a feature in the vicinity. This is the 

 fenny district which stretches southward from Quy between 

 Wilbraham and Fulbourn, and is known as Wilbraham Fen; 

 its history appears to have been somewhat as follows. 



When the drainage of the country was carried off by the 

 ancient river above referred to, this fen could have had no 

 existence, and the springs which now rise near Wilbraham and 

 Fulbourn were then probably at a higher level and contributed 

 their supply to the river itself ; but when the drainage ceased 

 to take this course, and the hills were gradually cut back south- 

 ward, the springs would retire also in that direction, while the 

 old river-course remaining as an elevated ridge prevented the 

 outflow of these waters to the north, and caused the formation 

 of a shallow lake in the same way as the moraine of an old 

 glacier ponds back a mountain stream. The level of this lake 

 would rise until the water overflowed the gravel ridge and made 

 an outlet for itself where Quy- Water Bridge now stands. This 

 outlet having once been made, the lake probably drained itself 

 to a certain extent until it was reduced to the condition of a fen 

 with pools or meres in the deeper portions of the area : in this 

 state it remained until attempts were made to bring it under 

 cultivation, the streams being banked up and carried along in 

 definite channels. 



