WOODRUFFE-PEACOCK : NATURALISTS AT BOURNE. 295 



of the various strata, pointing out that the Oxford clay terminated at 

 the foot of Stamford Hill. The steep eastern and northern escarp- 

 ments of this hill, as welt as the plateau of the Brunswald, are 

 composed of the boulder clay, which overlies the Oxford clay and 

 the corn brash, obscuring these formations in many parts, and thus 

 rendering local investigation somewhat difficult. The base line of 

 this glacial deposit slopes gradually eastward with the dip of the 

 Oxford clay towards the border of the Fenland, where it is covered 

 by a newer sheet of boulder clay. These boulder clays pass 

 beneath the Fen beds, the only part of Fenland not so underlaid 

 being the border extending to Dyke, Hacconby, Dowsby, and 

 Dunsby. The included fragments comprise flints, chalk, and stones, 

 and blocks from local Jurassic strata. The boulder clay rises from 

 the plains, covers the hill slopes, and rests on the higher parts of 

 the hills in this portion of the county. It is not disposed as in 

 moraines, but it is spread out as a universal mantle. It appears to 

 have been banked against the southern slopes, and bedded in the 

 valleys open to the south. It would seem, therefore, that the ice 

 must have moved from the southward, or have formed as coast-ice 

 along the border of a sinking shore line. Mr. A. J. Jukes-Browne, 

 in his geological memoir, inclines to the view that the boulder clay 

 had its origin in coast-ice. He says : — ' We have only to suppose 

 a gradual submergence of the land till the ridges formed by the 

 cretaceous and Jurassic escarpments became a succession of long, 

 low islands, round whose shores coast-ice was accumulated every 



* 



winter. The ice-foot which grew beneath the faces of the escarp- 

 ments would receive a specially heavy freight of debris, and when 

 broken up into floes during the summer thaws, the distances to 

 which they were carried would depend upon the weight of the load, 

 and on the varying direction of the currents among the islands. 

 This process being continued until the movement of depression 



submerged the highest points of land, the resulting deposit of 



boulder clay would have been spread gradually over the older rocks, 

 and, when the sea-floor was again raised, would appear as we now 

 find it, making allowance, of course, for post-glacial denudation/ 



Attention was also directed to the partial ring of the Upper 



Estuarine Series overlying the Lincolnshire limestone in the 



am valley, at the foot of the northern escarpment of the 

 Brunswald. These bands of clay and fibrous limestone w 

 accumulated under alternate marine and freshwater conditions such 

 as prevail in the estuary of a great river. In the lower part of this 

 series at Little Bytham clays are dug for very hard and durable 



bricks, locally termed clinkers. The fibrous limestone of the Upper 



Oct. 1396. 



