xvm. ILFORD. GRAYS. 471 



Section of Uphall Pit south side. 



ft. in. 



Soil, dark, sandy, with scattered pebbles . . . ' . . 3 o 

 Thick bed of' Uncallow,' consisting of gravel, brickearth, loam, and sand, 

 in horizontal, curved, and aggregated masses ; the gravel containing 

 much flint and some quartz ; some of the pebbles placed with the 

 long axis vertical ; general colours pale, ochraceous, and ferruginous 10 o 



Brickearth, pale, bluish, and ferruginous 26 



Sanda, mostly ferruginous, tinted in parallel but disturbed layers (5 



or 6 feet seen) ..60 



(Green sands said to occur below.) 



The shelly clays, sands, and gravel-beds thus associated are 

 found at many places on both sides of the valley below London, 

 and present endless small variations, even in single brickfields ; 

 they evidently belong all to one geological period, and one set 

 of variable physical conditions. Their geological date, judged 

 by these conditions, would seem to be post-glacial, if the upper 

 beds, deposited in disturbance, may be regarded as re-composed 

 from the glacial deposits on the neighbouring hills. This ex- 

 planation is suggested by the case at Grays, where over the chalk 

 and its covering sands, which form elevated ground, appears very 

 much such a mixture as the ' Uncallow' in the lower grounds of 

 Ilford and Grays ; and it seems to ' tail down' from the high ground 

 to the low, where it is collected in such a way as it may be supposed 

 hasty floods and ice disturbance often repeated might occasion. 

 It is not likely to have been produced by ordinary free fluctuation 

 of water, because of the confusion of bedding, want of horizontal 

 sorting, mixture of specific gravities, inequality of masses, and 

 sudden local changes. 



!S*.. 



Diagram (7(7/7. Section across the Vale of Thames from Erith to Grays-Thurrock. 



C. Chalk. T. Thanet sand. W. Woolwich beds. D. Hill-drift. 



D'. Cyrena or Valley-drift. 



But for these circumstances one might fancy the deposits of shells 

 in the places of their growth more ancient than the earliest distribu- 

 tion of the gravels of the vicinity ; that they were pre-glacial, and 

 only inferior in age to the Forest-bed of the Norfolk coast *. 



1 In considering this question Mr. Tylor's careful Sections should be consulted. 

 Geol. Proc. vol. xxv. 1869. 



