530 RECENT. 



brought down by the rivers may be left out of account, for the bulk of it is pro- 

 bably deposited on their alluvial flats long before it reaches the estuary. More 

 mud seems to be carried into the rivers by the tide than comes down them." 



The silt consists of upwards of 70 per cent, of very fine sand, about 10 per cent, 

 of alumina, and the remainder of carbonates of lime, magnesia, oxide of iron, and 

 organic matter. This mud or warp is largely deposited between tide-marks, "thus 

 tract after tract gradually rises to near the level of high-water, and is then protected 

 by embankments and added to the area of the cultivated land." The rise and 

 embankment of Sunk Island, now part of the mainland, is fully described by 

 Mr. Reid.i 



The tidal warp forms some of the richest land in Holderness. Large areas in 

 the neighbourhood of the Humber have been raised and improved by artificial 

 warping. 



The deposits of the Fenland, including the Bedford Level, comprise a variable 

 accumulation of sands and gravels, silts, and clays, with intercalated layers of 

 peat. These deposits where they come to the surface give distinct characters to 

 the landscape, the areas of silt and gravel being marked by numerous villages, 

 while the peat presents a more even surface ; it is for the most part devoid of 

 hedgerows and no villages are situated on it.^ In places, as between the Rivers 

 Witham and Glen, the following general succession of beds may be traced : ^ — 



Soil, peat, silt, or clay. 

 Peat or peaty clay. 

 Blue clay often ' buttery.' 

 Bottom peat. 

 Sand or gravel. 



The gravels, clays and silts are marine, and thus the beds indicate changing 

 conditions, the sea at one time having the mastery, and then there occurred changes 

 during which land-surfaces appeared, for the newer peat, which is 3 or 4 feet thick, 

 contains buried trees at its base. The silt and Buttery clay (so named from its 

 consistency) contain Scrobiciclaria plana, Tellina Balthica, Cardium edide, and 

 Littorhm littorea. Marine gravels occur near Tattershall and Bourn. (See 

 sequel.) 



The Cambridgeshire peat has yielded remains of Brown Bear, Beaver, etc., and 

 at Burwell Fen, about 10 miles from Cambridge, remains of Bos priniigeiiiiis were 

 obtained, in the frontal bone of which animal a Neolithic implement was partially 

 embedded.* Peat has been dug near Chatteris, at Coveney and Burwell Fen, also 

 at Billinghay between Sleaford and Tattershall. 



TERRESTRIAL PHENOMENA. 

 Springs. 



The occurrence of freshwater at different levels beneath the 

 surface of the earth is dependent upon the rainfall and geological 



^ Geol. Holderness, pp. 105, etc. ; see also E. Tindall, Geologist, iii. 40. 



'* Skertchly, Geol. Fenland (Geol. Survey) ; and The Fenland Past and Present, 

 by S. H. Miller and S. B.J. Skertchly, 1S78. 



2 A. J. Jukes-Browne, Geol. S. W. Lincolnshire, pp. 98, 106 ; Science Gossip, 

 1879, pp. 242, 265 ; Penning and Jukes-Browne, Geol. Cambridge, p. 112 ; Rev. 

 E. Trollope, Proc. Geol. and Polyt. Soc. W. Riding, iii. 637. 



* Dr. H. Woodward, G. Mag. 1869, p. 64 ; J. Carter, G. Mag. 1874, p. 492 ; 

 see also Bonney, Cambridgeshire Geology, p. 58 ; Rev, L. Jenyns (Blomefield), 

 Brit. Assoc. 1845. 



