404 Sir H. H. Howorth—The Mammoth and the Glacial Drift. 



Wye, Mr. Symonds found a stratified red sand and silt, 3 or 4 feet 

 thick, containing pebbles, one of which was greenstone ; and he adds : 

 " Every one of those pebbles out of that red sandy deposit must have 

 been derived from Silurian and Trap rocks which are not to be 

 found in situ until after we have traversed the long tract of Old Red 

 Sandstone through which the Wye passes between Coppel Wood 

 Hill, near Eoss and Trewerue, above Hay or Breconshire, a distance, 

 by the river of 70 or 80 miles" (Geol. Mag. Vol. VIII. p. 436). 



The evidence of this cavern therefore completely supports that 

 from North Wales. 



If we now leave the area where true Glacial drift is supposed to 

 occur and enter the Thames Valley, the evidence seems to me to be 

 equally conclusive. 



In the Thames Valley Boulder-clay is not found, but I suppose 

 it is generally agreed now that the Trail of Mr. Fisher represents it. 

 Now, there can be no doubt that this Trail overlies the Mammalian 

 and Palaeolithic gravels of the Thames Valley. 



Dr. Falconer, in discussing, in 1857, the deposits at Gray's 

 Thurrock, and the lower beds at Brentford, in the Thames Valley, 

 " inferred that they were of an earlier age than any part of the 

 Boulder-clay or Till " (Q.J.G.S., vol. xiv. p. 83). " It appears," 

 says Mr. Symonds, "that these Thames brick-earths are covered by a 

 Glacial deposit of ice-borne debris, as is the Forest Bed by Boulder- 

 clay " (Geol. Mag. Vol. V. p. 420). 



Professor Boyd Dawkins, in his paper on the age of the Lower 

 Brick-earths of the Thames Valley in 1867, gives a section from 

 the Uphill Pit at Ilford, in which the famous head of the Mam- 

 moth now in the British Museum was found. The bed in which 

 it occurred was covered by several beds of loam, clay, gravel, 

 and sand, of one of which Professor Dawkins says : " By the com- 

 parison of its bedding, the admixture of clay with sand and gravel, 

 and the presence of pebbles of chalk and of large transported 

 boulders of grey weathers and of flint, is proved beyond doubt 

 to be of Glacial origin — to have been carried down by the ice 

 and deposited on its melting, upon the eroded top of the fluvatile 

 deposits below." In regard to Mr. Prestwich's notion that the bed 

 was partially formed from gravel derived from the Boulder-clay, 

 Mr. Dawkins says, "a careful examination compels me to believe 

 that there is no proof of the derivation of this Glacial deposit from 

 the wreck of the Boulder-clay " (Q.J.G.S., vol. xxiii. p. 93). 

 Turning to Gray's Thurrock, he argues that we have precisely the 

 same superposition, there being bed numbered 6 on the section 

 which from the irregular size of its pebbles, its tabular flints, its 

 contortions, and its irregular deposition, owes its presence to ice in 

 some form or other. Its sandy nature may be owing to the Thanet 

 sand having been caught up by the ice and deposited on its melting, 

 just as the clayey nature of the Trail at Ilford was probably owing 

 to portions of the London Clay being in like manner transported 

 (id. p. 95). This bed was distinctly superimposed on the gravel 

 containing Mammalian bones. At Crayford he gives a section 

 in which a similar bed, number 7, consisting of an irregular 



