28 The Ancient Fauna of Essex.
[and also the brick-earth, H. W.] is not of definite age, but
may have been forming at any time since the last emergence
of the country from the sea (and its consequent subjection to
atmospheric agents) to the present time."
This theory of the atmospheric origin of the clay with flints,
and so of the brick-earths of the chalk-area, was put forward
by my friend, Mr. W. Whitaker, B.A., F.G.S., in the Geo-
logical Survey Memoir to Sheet 7, 1864, and I thoroughly
endorse his views.
This brick-earth would be slowly formed upon the upper
watershed of the Thames and all its tributaries, and by rains
and floods would be washed off the surface and brought down
into the quiet reaches, together with the bones of land-
animals, and land-snails.
The story of the Thames Valley brick-earths is the same as
that of the "red-earth" of our ossiferous caverns in limestone
districts. The carbonate of lime is dissolved away by the
percolation of rain-water charged with carbonic acid, eating
out those great swallow-holes, chasms, and caves for which
the Mendip Hills, the Peak in Derbyshire, and the limestone
districts of Lancashire and Yorkshire are so famous. This
red-earth of the caves is only the insoluble (aluminous)
residuum of the limestone in which, as in our brick-earths,
the relics of prehistoric man and of the animals he saw and
hunted have been found.
The following is a list of the Mammalian remains from
Ilford, from the collection of the late Sir Antonio Brady,
F.G.S., now preserved in the British Museum of Natural
History:—
Felis spelaea.
Canis vulpes.
Ursus ferox.
Elephas primigenius.
,, antiquus.
Rhinoceros leptorhinus.
,, megarhinus.
,, tichorhinus.
Equus fossilis.
Megaceros hibernicus.
Cervus elaphus.
„ sp.
Bison priscus.
Bos primigenius.
Miscellaneous Ruminant re-
mains.
Hippopotamus.
Undetermined species.