Yol. 68.] LATE GLACIAL STAGE IN THE YALLEY OF THE LEA. 213 



12. On a Late Glacial Stage in the Valley of the River Lea, 

 subsequent to the Epoch of Eiver- Drift Mait. By S. 

 Hazzledine WARREiif, F.Gr.S. With Reports on the Organic 

 Remains and on the Mineral Composition of the Arctic Bedy 

 hy various Authors. (Read January lOth, 1912.) 



[Platks XV-XVII.] 



Contents. 



Page 



I. The Discovery of the Arctic Bed 213 



II. The Stratigraphy of the Arctic Bed 215 



III. The Climatic Evidence furnished by the Arctic 



Bed 218 



IV. The Correlation of Pleistocene Deposits 219 



V. The Correlation of the Arctic Bed 221 



VI. The Eelation of Palaeolithic Man to the Glacial 



Period 225 



VII. The Holocene AUuYium of the Eiver Lea 226 



VIII. The Reports upon the Fauna and Flora of the 



Arctic Bed 227 



IX. The Mammalia of the Arctic Bed and the 



Associated Grravels 227 



Appendices I-VII 229 



I. The Discovery of the Arctic Bed. 



For some few years past the Great Eastern Railway Company 

 have been obtainiog remains of the Mammoth from a large ballast- 

 pit, known as the Pickett's Lock pit, at Ponder's End (Middlesex). 

 Many of these remains, through the instrumentality of Mr. A. 

 Atkins, of the Engineers' Department of the Company, have been 

 carefully preserved, and are placed in the Board Room at Liverpool 

 Street Station, the London terminus of the Great Eastern Railway. 



The Pickett's Lock pit at Ponder's End is an extensive one, 

 and it is situated in the Low-Level River-Drift of the Lea Valley. 

 The surface of the ground lies at about 43 feet above Ordnance 

 datum, and is but slightly raised (to an amount of 2 or 3 feet) 

 above the present alluvial flood-plane of the river. The pit 

 exhibits a very fine section, chiefly composed of gravel and sand, 

 showing the effects of strong current- action. There is a subordinate 

 capping of brickearth, which does not exceed 4 feet in thickness, 

 and is usually less. The greatest total thickness of the Drift 

 amounts, I believe, to 22 feet ; but towards the western side of 

 the pit the underljdng floor of London Clay gradually rises, and 

 the thickness of the Drift is much less. 



When I first visited the pit, Mr. Guy Leonard, the engineer in 

 charge of the works, pointed out to me a dark bed, from 1 to 2 



