GEOLOGY 



brickfield, on the right hand side of the lane leading from Ilford to 

 Barking, a spot about twenty-eight feet above the river Thames. 1 



The mammals include fine examples of the mammoth or Elepbas 

 primigenius, also E. antiquus, the hippopotamus, three species of rhino- 

 ceros, the Irish elk, bison, urus, red deer, brown bear, grisly bear, wolf 

 and many others. A few flint implements have likewise been found. 

 Occasional remains of birds and fishes, and numerous land and freshwater 

 mollusca also occur in the brickearth, a deposit laid down under more 

 tranquil conditions than the gravel, and due largely to the destruction of 

 Eocene beds and Drift sands and loams. 



The gravel has been derived mainly from pre-existing gravels 

 formed of flint, with less abundant quartz and quartzite. The flint 

 pebbles were derived from Eocene pebble-beds, and the sub-angular 

 flints, quartz and quartzite mainly from the Boulder Clay or from old 

 plateau or Glacial gravels which border the Thames valley from near 

 Great Marlow to Rickmansworth, Hendon and Finchley. Occasional 

 greywethers occur, as at Grays. 1 



The sheets of gravel and brickearth which extend from Southend 

 and Shoeburyness northwards to Great Wakering, Burnham, Southmin- 

 ster and Bradwell, and occur also on Osea Island, may originally have 

 been connected with the tracts around Clacton and Little Holland. In- 

 deed, it is considered that in old times the Thames turned northwards 

 along the eastern margin of Essex, receiving the Blackwater as a tribu- 

 tary. In this region its right bank has been wholly lost by the subse- 

 quent waste of the land on that side. Thus the Thames was a much 

 mightier river than it is now, but when we contemplate the broad ex- 

 panse occupied by the old valley gravels and brickearths, we need not 

 conclude that the river ever occupied, unless in seasons of flood, the 

 entire area. Its tendency has been to alter its course, and, as pointed 

 out by Mr. Whitaker, for the most part to diverge towards the south, 

 so as to cut against the Kentish shores, while leaving broad tracts of 

 loam and gravel to the north. 8 It is difficult to say whether the land 

 was higher or lower during the earlier stages of the formation of these 

 valley deposits, if we accept the view that the lower terraces are of later 

 age where the river cut deeper into the valley. On this subject opinions 

 differ. The land originally may have been much higher, and the river, 

 more or less torrential, cut deeper and deeper into its valley before reach- 

 ing a base-level of erosion. 



In other valleys there are deposits of river gravel, as along the 

 Colne at Dedham village, and the Cam at Wenden and Great Chester- 



1 See Catalogue of the Pleistocene Vertebrata from the neighbourhood of Ilford, Etiex, in tin Colkction of Sir 

 Antonio Brady, by William Davies, 8vo, London, 1874 ; also Henry Woodward, Geol. Mag., 1864, p. 

 241, 1868, p. 540 ; and M. A. C. Hinton, Proc. Geol. Assoc., vol. xvi. p. 177. 



1 For details relating to Grays see B. B. Woodward, Proc. Geol. AIIOC., vol. xi. pp. 363, 364 

 (herein are references to the labours of all previous workers) ; see also Prestwich, Geol. Mag., 1898, 

 p. 409. 



* For a review of the literature of the Thames Valley Drift and of the origin of the Thames, see 

 Whitaker, Geology of London, vol. i. pp. 353, 496 ; Ramsay, Quart. Journ. Geol. Sot., vol. xxviii. p. 148 ; 

 Prestwich, ibid. vol. xlvi. p. 155 ; J. W. Gregory, Natural Science, vol. v. p. 97. 



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