ON SOME I'LATF.AU DEPOSITS AT KEI.STEAD AND STEI'.HING. 1.^7 



wliich this wearing away has occurred, therefore, represents the least 

 time whicli has elapsed since the I')C)uIder Clays were altered into loam. 



Another deposit of quite a different character must now claim 

 our attention. This is at Stebbing Downs, a little north of the 

 village, or " Dunes," it might have been written, for the greater part 

 of the upland of that place is a large sand-dune (that is, a heap of 

 blown sand). Overlooking the Mount, and near to the brickyard, a 

 pit has been worked for sand, and a notice of the underlying Westlc- 

 ton Gravel, etc., has already appeared in the Essex N.viuralist 

 (vol. v., page 210). The upper six feet of sand, however, is a very 

 singular deposit, and its age and true character were not at first 

 apparent. An implement made out of a piece of conglomerate and 

 a fragment of Roman pottery having lately been found in it, its age 

 is not so uncertain.'^ Indeed, until quite recent times (of improving 

 agriculture) the formation must have been still in progress. A close 

 examination of its structure and material shows the bed to be a 

 [)roduct of dry denudation, all of it having been drifted by the east 

 wind. Small pieces of chalk from the size of a shot upwards, and 

 almost always rounded, are collected in masses in different places. 

 These were supplied by the Boulder Clay, whilst the sand was 

 supplied by the Westleton Beds, both formations being exposed 

 on the somewhat higher grounds to the east and north-east. The 

 drifting of the sand is peculiar, and much resembles " false-bedding." 

 Towards the south of Stebbing village, and on the same side of the 

 brook, there is another upland deposit of sand differing slightly from 

 that of the Downs, but probably of the same age. The sand here is 

 cemented into masses by a ferruginous deposit. 



Any attempt to jud^e of the ages of the three deposits of which 

 we have treated is affected by difficulties which concern relative as 

 well as absolute time. AVe may judge with a poor approximation of 

 the rate of denudation now in progress ; but we cannot say that it was 

 the same in comparatively recent times, although times of greater 

 sterility as shown by the Stebbing sands. Much less can we say any- 

 thing of the times when those Plateau loams were made. With a 

 lower winter temperature there was a greater erosion during thaw ; but 

 there were longer intervals of rest during frost, and we do not know 

 whether the debris was removed at the same rate as at present or not. 



The same difficulty is increased in judging of the early Post 

 Glacial Plateau Gravels ; erosion then was prodigious, but it may 



5 I li.ive (May 7th) since founil a small bed of charc<.al ashes under six feet of blown sand. 



L 



