ON SOME PLATEAU DEPOSITS AT FELSTEAD AND STEBBING. 133
occupy the highest ground. That is to be found about a furlong to
the north-east, and is about six feet higher, and is of Boulder Clay.
The gravel is about sixty to seventy feet above the river.
This gravel rests upon the Boulder Clay, and as in its composition
it has, so far as I can see, no bond of connection with that deposit,
it could not well have been derived from its waste. It does, how-
ever resemble local Glacial Gravel (that underlying Boulder Clay), and
may, therefore, reasonably be supposed to have been derived directly
from it. But when we come to inquire how the transport was effected,
and from what direction it came, we are met with a great difficulty.
The promontory at the time of the deposition of the Boulder Clay was
here probably surrounded on three sides by a considerable valley.1
We should, therefore, be taking an unwarrantable position in sup-
posing the Boulder Clay to have filled up the valley here, and so to
have formed a bridge over which the gravel could pass, although it
may have done so. It would be better to suppose that the gravel
came from the west, where Glacial Gravels are now exposed at a
mile distance, but at a somewhat less elevation.
The forces engaged in this transport must have been prodigious,
whether submarine or due to melting ice after the elevation of land
(there would certainly seem to be a hiatus between the underlying
Boulder Clay and the gravel as shown by the sharpness of the
juncture). Whatever may have been the agency, it was sufficient to
transport boulders of upwards of seven pounds in weight.2
The onus rests with me to show that the Post-Glacial has no
bond of connection with the Boulder Clay. This is difficult to prove,
but the same difficulty applies to the Gravel underlying Boulder Clay.
Anyone well conversant with the two deposits cannot possibly mis-
1 This I infer from the circumstance that the stream now occupies a depression in the London
Clay, and that Boulder Clay in at least two places extends to nearly the bottom of this depression
on Molehill Green, and at the same elevation London Clay is reached at a depth of less than ten
feet. Continuing down the valley, but more towards the west, Boulder Clay extends nearly to
the bottom. On the opposite side of the river, at Willows Green, at about the same elevation
as at Molehill Green, London Clay is exposed as shown on the map, and at a little north-west of
this, at a much less elevation, Boulder Clay rests on the slope. [On this statement Mr. Whitaker
remarks as follows :—" This is clearly a case showing the irregular deposition of Boulder Clay,
which cuts into London Clay in a sort of irregular channel. But the valley has been worn out
since the deposit of Boulder Clay, and is cut through it and the gravel to the London Clay. The
mapping distinctly makes the gravel underlie the Boulder Clay. Of course there may be later
gravel also.--W. Whitaker."] That marked on map as Glacial Gravel at this spot, is probably
thinly spread at places. In the absence of sections which did not then exist, it
could hardly have been marked otherwise than as Glacial. That at Peak's Hall, a little further
up stream, I cannot as yet determine.
I may mention that I have notes of similar depressions in the London Clay which are partly
occupied by Boulder Clay, extending along the present bed of the Chelmer. I hope to put them
on record later.
2 I only found one stone weighing as much as forty pounds, and it is possible that this may
have been dug from the underlying Boulder Clay, but I feel quite sure that this was not so.
Although I broke the Boulder, I could make nothing of it, as it did not agree with any rock that
I had before seen.