198 GREYWETHERS AT GRAYS THURROCK, ESSEX.
Tertiary beds the softer portions of which have been removed
by denudation from the places where these blocks are now seen,
and as their distribution is extremely irregular, their occurrence,
when seen, is well worth noting from a geological point of
view.
But greywethers are not necessarily to be seen only on the
surface of a district. Mr. Whitaker remarks that they
"occur somewhat rarely in our River Gravel."2 For the
changes in the courses of rivers occasionally involve the
imbedding in river deposits of blocks once some little distance
from the banks of the stream. At an excursion of the Geologists'
Association to the British Museum of Natural History on
March 15th, 1902 (Proc. Geol. Assoc, vol. xvii., pp. 365-6) the
members inspected a large Sarsen stone discovered in Thames
Gravel when the foundations of the Victoria and Albert Museum-
were being excavated. It was presented to the N. H. Museum
by Colonel C. K. Bushe, F.G.S., a member of the Association,
who saw it taken out. It is now in the Eastern Gardens of the
Museum.
In the Geological Magazine for 1867 there is a very short paper
by the late Professor John Morris, once a much esteemed
honorary member of the Essex Field Club, "On the Occurrence
of Grey-Wethers at Grays, Essex." It occupies little more than
a page (pp. 63-4). He remarks that the occurrence of Sarsen
stones "has not, I believe, been generally noticed in this locality."
The various chalk, &c., pits, when he wrote, had not been worked
so far back northward as they now are by a considerable
distance. He states that "the Sarsen stones (of which some may
be still seen lying about the large chalk pit) I have noticed
during the progress of the workings as occurring on the upper
surface of a bed of disturbed chalk, above the solid chalk, and
covered by a blackish, or carbonaceous clay containing fresh
water shells. They are of various sizes, some very large, and
more or less waterworn."
He adds that the position of the Sarsen stones seen by him
was "about midway between the back of the present workings
and the entrance to the pit." The grey wethers were evidently
in old river deposits, though it is not now easy even to identify
the exact pit of which Prof. Morris writes. But as the spot
2 Geology of London and of part of the Thames Valley, vol. i., p. 330.