Pleistocene Deposits at Ilford. 391 



In some places, as pointed out by Mr. Prestwicli/ fragrnents of 

 these ancient fluviatile deposits have been preserved as older river- 

 valley terraces ; in other spots, as in the neighbourhood of Ilford, 

 they still form wide sheets, covering a considerable low-lying tract, 

 which probably has been elevated and depressed more than once 

 since its original deposition. 



The bottoms of the valleys are for the most part occupied by 

 more modern prehistoric deposits seldom raised much above the 

 level of the stream. (See Geol. Mag. 1869, Vol. VI. p. 385.) 



But even where their actual relative elevation is an uncertain 

 guide, there is always a marked difference between the older and 

 newer deposits as regards the materials of which they are composed. 



The prehistoric as well as the present alluvia are mostly composed 

 of clays, more or less stiff, and the gravels of pebbles more or less 

 evenly sorted, both having been formed under conditions of climate 

 not very different from those at present existing. 



The Pleistocene Bi-ick -earths, on the other hand, very seldom 

 consist of stiff clays, and the gravels contain large and small pebbles 

 and angular blocks confusedly mixed together, clearly indicating 

 that the transporting power of the rivers at that period was greater 

 in certain seasons than at the present day, and that freshets were 

 probably of more frequent occurrence. 



But perhaps the most striking difference which they present is 

 offered by the remains of the fauna associated with each : for 

 whereas the prehistoric and modern deposits of our river- valleys are 

 characterized by stone-implements and other relics of human in- 

 dustry, associated with remains of animals at present indigenous to 

 our island, or which are known to owe their extermination to man's 

 agency, the Pleistocene Brick-earths and gravels of the Thames 

 reveal no trace of man's presence," but present us with a fauna 

 almost wholly dissimilar from that now living in Europe, and most 

 if not all of the species of which are extinct. 



The brick-pits of the neighbourhood of Ilford have long been 

 celebrated for the wonderful variety of extinct Mammalian remains 

 which they yield. So long ago as May, 1824, Mr. Gibson, of Strat- 

 ford, obtained from the brick-field on the London turnpike-road a 

 large portion of the skeleton of an elephant, Mr. Clift and Prof. 

 Buckland being present at the exhumation of the bones. Prof. 

 Morris refers to Mr. Gibson's Collection in an article on " Deposits 

 in the Valley of the Thames containing Mammalian Eemains " (see 

 Magazine of Nat. Hist., 1838, vol. ii. new series, p. 540). He 

 mentions the " remains of the horse, elephant (a tusk 12ft. Gin. 

 long), rhinoceros, deer, and two species of oxen; the bones are found 



^ Phil. Trans., vol. cliv. 



2 It is true that the Eev. 0. Fisher communicated to the Geol, Mag. that he 

 had found an undoubted implement in the gravel at the base of the Crayford Brick- 

 earth ; see Geol. Mag. Vol. IX. p. 268 ; see also Mr. Boyd Dawkins, in Quart. 

 Journ. Geol. Soc. Lond., vol. xxviii. p. 414. These may, however, and probably did 

 helong to a later date, the deposits in which they occur having been subsequently, iu 

 part perhaps locally, disturbed and re-assorted. 



