25 



In the supplementary notes further details are given of the 

 Post-glacial Gravels, the higher series having been found to 

 run down the escarpment and to overlie the Boulder Clay at 

 several points. He is inclined to consider all of them as having 

 resulted from the action of rivers on the newly emerged land, 

 but the series described as indicating the ancient course of the 

 Cam he regards as representing the latest stage of all, previous 

 to the present system of drainage. He points out that in many 

 cases the gravels occupy hollows along the top of ridges, the 

 gravel deposited in the old channel having preserved the clay or 

 chalk immediately beneath, and that many of these ridges run 

 up into coomb-like valleys among the hills. 



[1877. A Memoir on the Geology of the Fenland, by Mr 

 S. B. J. Skertchly, was published in this year by the Geological 

 Survey ; the greater part of this book is occupied by an account 

 of the newer Post-glacial beds, but the Gravels and the Boulder 

 Clay are also described. 



Mr Skertchly classes the Fenland Gravels under three heads: 

 (1) Ancient Valley Gravels. (2) Marine Gravels, forming beaches. 

 (3) " Flood-Gravels," which run down from the hills into the 

 Beach-Gravels. In describing these deposits, however, he treats 

 them geographically, and not according to their age or mode of 

 formation. In Cambridgeshire he notices the Fossiliferous 

 Gravels occurring near Peterborough, Whittlesey and March, 

 and gives a list of the shells which they contain. 



The sections described under the head of Boulder Clay are 

 mostly in Lincolnshire, but a full account is given of the well- 

 known pit near Ely, which will be referred to again in the 

 sequel.] 



