Descriptive Report.
77
and afterwards ran turbid with suspended matter for about
two hours, after which it resumed its original clearness.
At Cross Farm, a little over a mile E.N.E. of W. Mersea,
the disturbance opened another small E. and W. crack, from
which two little fresh-water streamlets spouted forth and
trickled down towards the house for 8 or 9 hours, and then
ceased to flow. The farm stands on London Clay, about 54
feet above the sea, and the streamlets, which were about 10
yards apart and one inch wide, were charged with a reddish-
coloured sand. A specimen of this sand which had been
collected was kindly forwarded to me by Dr. Alexander
Wallace, of Colchester, with the following remarks :—"Plenty
of water just beneath soil. Sand like this not found about
these parts when digging foundations." Some of the sand
was kindly submitted to microscopical examination for me by
Prof. T. G. Bonney, F.E.S., who has been good enough to
supply the following observations :—
" The bulk of it consists of quartz grains, varying from
rather angular to moderately rolled, commonly about .008"
diameter, i.e., a little less than .01''. I do not notice evi-
dence in them of a composite structure, but this, under the
circumstances, might readily be overlooked. There are a few
dull green rather rounded grains, probably a glauconite
mineral, and some minute opaque nodules, perhaps iron
peroxide, or possibly phosphatic. The sand, as is often the
case, is stained of a warm buff colour, being coated by a
pellicle of hydrous iron peroxide. I do not profess to have
made a special study of sand, but I doubt whether any con-
clusion could be founded on this. It has clearly been derived
at the first from a granitoid rock, but that may be said of
numbers of other sands. It is no doubt post-cretaceous in
its date of transport to these regions; the materials may
have for a while rested in Thanet or in Bagshot beds. I
should say they had been for a time in deposits belonging to
the Crags, from which, or from one of the sands derived from
them, they have no doubt immediately come. A strong spring
of water might easily bring up sand of this fineness from a
depth of several yards."
At a well near these streamlets the water was made to rise
about two feet, and was rendered turbid.