454 PLEISTOCENE DEPOSITS AT TWICKENHAM. [Aug. 1894. 



bed was found at the bottom of the cutting, about 12 feet below 

 the surface of the roadway. The point where the dark bed was 

 first touched was 420 yards from the river, and throughout the 

 remainder of the section, which was continued through other roads, 

 this dark bed was found more or less at or near the bottom of the 

 cutting — at depths varying from 11 to 18 feet below the surface of 

 the ground. At two points where ' sumps ' were sunk for purposes 

 of pumping, this dark bed was cut right through, and gravel in 

 every way similar to that above was found beneath it. The 

 thickness of the dark bed at these points was found to be 2 feet 

 6 inches and 2 feet 3 inches respectively, but it must have been 

 thicker in some parts, for it was entered to a depth of 3 feet in one 

 place without reaching the bottom. 



In vol. xlviii. (1892) p. 453 of this Journal, a description is 

 given by Dr. Hicks of a dark loamy bed found beneath the gravels 

 in the bottom of excavations in the neighbourhood of Endsleigh 

 Street in which organic remains were found. The bed itself 

 appears to bear a resemblance to that found in the gravels at 

 Twickenham ; there is also considerable similarity in the flora 

 found in each, as will be shown farther on, but the dark bed in 

 Endsleigh Street was believed to lie directly on the London Clay. 

 This clearly was not the case with the dark bed found at Twicken- 

 ham ; it intervened between beds of gravel, and was itself evidently 

 of very limited thickness throughout. 



The material composing the ' dark bed ' found at Twickenham 

 varied somewhat. In some places, especially where the bed attained 

 its greatest thickness, it was of a soft, slimy nature, like river mud, 

 whereas in other places it was much coarser and somewhat sandy 

 in character. After exposure to the atmosphere the finer por- 

 tions formed into compact clayey lumps, whilst the coarser parts 

 became more disintegrated and had the appearance of earth or loam. 

 It evidently contained a large proportion of decayed vegetable matter. 

 When treated with water the finer samples left little or no residue, 

 but from the others there was a considerable amount of sandy 

 deposit. A chemical analysis gave the result tabled on p. 457. 



Immediately above the dark loamy bed there appeared to be a 

 layer of dark blue or greyish sand and gravel, which had very much 

 the same appearance as the dredgings now taken from the river, 

 and known as ' Thames ballast.' This layer of dark gravel was of 

 varying thickness, and in some places was scarcely distinguishable, 

 if not altogether absent. In no place did it attain any considerable 

 thickness, and it appeared to die gradually away into the yellow or 

 reddish gravel above it. It seemed as if the bed of dark loam had 

 discoloured to some extent the gravel in contact with it. Throughout 

 the gravels generally no organic remains were found, but the dark 

 bed of loam was very rich in indications of animal and vegetable 

 life. All the fossils found in the excavations were discovered either 

 in the dark bed of loam or in the gravels immediately above it. 



The annexed sections (figs. 2 & 3) show the structure of the ground 

 in question and the position occupied by the dark-blue loam seam. 



