536 EVENING DISCOURSES 



river channel at Shippea Hill between Ely and Mildenhall. Here no 

 fewer than three archsological horizons were discovered stratified into the 

 fen deposits. 



Broadly speaking the fenland history has shown alternating phases of 

 marine invasion and of fresh-water conditions. The first fresh-water 

 phase in the present fens extended through the Mesolithic and Neolithic 

 periods, and for much of this time the fens were covered with alder-birch 

 fen woods. It was probably about the end of the Neolithic period that 

 marine invasion caused formation of the fen clay. In the Bronze Age 

 which followed, fen woods grew extensively, but these must have been 

 dry enough for occupation by prehistoric man, since Bronze Age remains are 

 found abundantly in the fen peats. It is probable that the fens became 

 too wet for occupation in the Iron Age. 



In the Roman period marine invasion once again dominated the fenland 

 history. All the silt of the Wisbech-Spalding area was laid down and its 

 surface intensively cultivated. Along the tidal rivers silt banks were built 

 up, and stood above the surrounding peat land as habitable areas. 



After the Romans left Britain the fens were not exploited until the drain- 

 age which began seriously in the seventeenth century. As it became 

 effective the shallower lakes such as Whittlesea Mere, Soham Mere and 

 Benwick Mere disappeared. The ground level sank by shrinkage and 

 wastage of the peat, often by as much as one inch per year, and the silt 

 banks of the Romano-British watercourses began to appear as raised banks, 

 or ' roddons ' crossing the peatland. 



Dr. Godwin suggested that there was no reason to suppose that the land 

 and sea movement which had played so much part in former fenland history 

 should now have ceased entirely, and said that there was some evidence 

 that recent drainage troubles in the fens were due in part to sinking of the 

 coast. He suggested that the subsidisation of work like that of the Fenland 

 Research Committee would be of value not only to science, but to such 

 scientific applications as the drainage of our fenlands. 



References. 



1935 Journ. Ecology, 23 (with M. E. Godwin and M. H. Clifiord). ' Controlling 



factors in the formation of fen deposits as shown by peat investigations at 



Wood Fen, near Ely.' 

 1938 B.A. Ann. Rept., Appdx. 17. 'The post-glacial deposits of Fenland.' 



Phil. Trans. Roy. Soc. B, 229, 562, pp. 323-406 (with M. H. CHfford). 



' Studies of the post-glacial history of British Vegetation." 



SECOND EVENING DISCOURSE 



Monday, August 22, 1938. 



THE CONTRIBUTION OF THE ELEC- 

 TRICAL ENGINEER TO MODERN 

 PHYSICS 



BY 



PROF. M. L. OLIPHANT. F.R.S. 



The Discourse was reported in Engineering, 319-20, Sept. 16, 1938, and " 

 in Nature, 142, 3592, 444-5, Sept. 3, 1938. 



