456 



DE. J. E. LEES0N AND ME. G. B. LAFFAN ON [Aug. 1 894, 



There can be no 

 doubt that this layer 

 of dark-blue loam is 

 purely a local one. In 

 two well- sections at 

 Isleworth, quoted in 

 Whitaker's ' Geology 

 of London,' Mem. Geol. 

 Surv. 1889, vol. ii. 

 p. 121, no mention 

 of it is made ; and, 

 coming nearer home, 

 we find that it is 

 also absent in a 

 recent well-section at 

 Messrs. Burrows and 

 Cole's Brewery, near 

 Twickenham Railway 

 Station, | mile east 

 of the present section 

 (op. cit. vol. ii. p. 170) ; 

 while the description 

 of an extensive cutting 

 in the Thames Valley 

 Railway, | mile to 

 the westward (op. cit. 

 vol. i. p. 394), does 

 not mention anything 

 about it. These facts, 

 in conjunction with 

 what will be shown 

 farther on from the 

 seeds found in the 

 loam, appear to indi- 

 cate that we are deal- 

 ing with the deposit 

 of a small local lake 

 lying in the midst of 

 the Thames gravels, 



Fig. 3. — Sections of the sump-holes in the 

 gravels at Twickenham. 





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Made 

 ground. 



Coarse 

 reddish- 

 yellow 

 gravels. 



.Discoloured 

 gravels. 



Dark loam- 

 bed. 



Coarse 

 gravel. 



Made 

 ground. 



Coarse 

 reddish 

 yellow 



Discoloured 



I 



Dark loam 

 bed. 



Coarse 



[Vertical Scale : 1 inch = 4 feet.] 



while the fact of its erosion and its unconformability to the gravels 

 above indicate that we are dealing later on with an old land- 

 surface. 



Our interest in the deposit was aroused by finding, in the first 

 instance, reindeer-horns in the gravels, near the commencement of the 

 cuttings. The London Clay then cropped up for some distance, and 

 nothing more was found, till a \ mile farther on the bones of Bison 

 and Bos longifrons (or Bos taurus) were discovered lying on the top 

 of what proved to be our < dark loam ' layer. A diligent search 

 was made in this loam for some further evidences of organic 

 remains, but without success ; and thinking that its dark colour 



