256
THE ESSEX NATURALIST.
suppressed, and from this point of view the disappearance
of chert in the gravels is not difficult to explain. It is, however,
impossible to explain the absence of the typical Greensand
minerals. It is also to be noted that the Warley Gravels, as
they now exist, do not possess the structure of a river-gravel; nor
indeed that of any water-laid deposit. This might be attributed
to subsequent modification but the idea is too hypothetical to
carry much weight. A little reflection on the problem of the
Warley Gravel soon convinces one that speculation is largely
futile. There are too many conditional elements in every
hypothesis suggested, and it is evident that more facts must
be sought. For the present an uninspiring agnosticism must
be maintained, though there is hope that it will be temporary
only.
Before leaving the subject, mention must be made of a
deposit, apparently associated with the Warley Gravels locally,
but differing from them lithologically. It is best seen in a small
pit on the east of the road between Pilgrim's Hatch and South
Weald and within the area marked "Camp" on the map. Here
some 10 ft. of coarse red-brown sand, massive and imbedded,
are seen. Above is a thin pebbly soil, but there are no stones
in the sand. The latter contrasts markedly with the local Bag-
shot Sands, which are fine in grain and pale in colour. Its mass
characters show a considerable resemblance to those of the
Diestian Sands, though this fact in itself is of little weight in the
question of correlation. The suite of heavy minerals obtained
from it is interesting and varied, containing abundant kyanite
and staurolite of Lower Greensand type. Taken as a whole
the suite bears comparison with that of the chert-bearing
Pebble Gravel of Hertfordshire, though the proportion of kyanite
is higher than in the latter. It also shows considerable
resemblance to the Diestian suites of Surrey in respect of its
dominant mineral species, but the characteristic accessories of
the Diestian assemblage are absent or very rare. Close by,
on the other side of the road, is the site of the famous section at
Langtons which revealed the true Bagshot Pebble Bed, followed by
the Warley Gravels. The relation of the red sands to the Warley
Gravels is not easy to make out; probably they rest upon them.
Similar sands have been noted by the writer in a temporary
exposure at the northern edge of Parsons Spring Wood near