to insert these Drifts and Gravels. This work has been in 

 progress ever since, and has been completed over most parts of 

 the South-eastern counties. The only maps yet published, 

 however, are sheets 1, 2, 7, -18, S.E. and G4 of the Ordnance 

 Survey and the excellent map of London and its environs. 

 Two descriptive Memoirs have also been published, one by Mr 

 Whitaker, entitled " A Guide to the Geology of London," the 

 other, on the Fenland, by Mr S. B. J. Skertchly, Memoirs on 

 the other sheets are likewise in course of preparation. 



Having thus indicated the history of opinion regarding the 

 Post Tertiary beds, I will proceed to the consideration of such 

 portions of these deposits as are found in the county of Cam- 

 bridge, and form the subject of this essay. 



