ON SOME PLATEAU DEPOSITS AT FELSTEAD AND STEBBING. 135
in the Plateau loams, a general description of which has already
been quoted from the Survey Memoir.
At Causeway End, Felstead, three-quarters of a mile S.S.E, of
church (marked erroneously on the old one-inch map as "Cobbler's
Green"), a loam of this description has been worked for many
years for bricks. It is over eight feet thick in one place, and it
everywhere rests on Boulder Clay. Some curious facts have come
out in the working of this deposit. The entombed flints are nearly
all broken and, after the fracture occurred, they have at times sunk
to the bottom of the loam. At other times, after the fracture, the
pieces have separated laterally, sometimes as much as three inches
of loam intervening, and those corresponding pieces may now be
brought together and fitted again. Moreover, every piece has, since
its fracture, been coated with a brownish-yellow deposit. A grada-
tion in the character of the loam is also discernible, it becoming
stronger in proportion to its approach to the Boulder Clay. Bricks
made from the upper portion of the loam (but not so near to the
surface as to be affected by modern weathering) cleave with facility.
Those from the lower portion, in spite of much artificial working of
the clay, are much more refractory.
At Great Saling Gravel Pit (near the church) a similar loam
occurs, having some of these peculiarities, and, in addition, nodules
of Boulder Clay retaining their chalk are enveloped in the mass.
Fundamentally these loams appear to differ only from Boulder Clay-
in the angular character of their flints, and in the almost or complete
absence of chalk; a result which may be brought about by weathering
alone, and that this was the agency there seems to be good evidence.
The cleavage of the rocks, and their juxtaposition in the loam
points to the exertion of molecular forces such as those brought
into play by the action of frost and thaw. Their position alone
testifies to the changes having been made in place. That chemical
agencies, giving rise to the yellow coating of the flint fragments, have
been at work the following instance will show. A flint was found
which had been broken into two pieces, which, although still in contact,
had slid laterally. These were afterwards joined together by a siliceous
cement which could only have been the result of chemical agencies.
The fracture of the flints by frost is easily explicable to those
conversant with the fragile character of recently dug flints. They
are then full of quarry water, upon which the least frost acts. The
behaviour of soils under the action of frost and thaw is familiar to