140 Notes on the Geological Position of the Human
notice the similarity between the sections there given of the
alluvial deposits of the estuary of the Severn and those of
Tilbury. The former are given as consisting of—
Upper Clay.
Upper Peat.
Lower Clay.
Lower Peat.
Sands and Mud.
Gravel.
Of course, as at Tilbury, they show much local variation.
He estimates the amount of subsidence, as measured by the
present position of the lowest (Severn) peat-bed, as about
20 feet, an amount nearly coinciding with that given by the
lower of the two Tilbury peaty Seams interbedded with the
inundation-mud—the lowest peaty bed being excluded for the
reasons just given. We must not forget, however, that
the present surface of Tilbury Marsh near the Docks is, as
Mr. Pinker told us, between seven and eight feet below high-
water mark, the shrinking being the result of the embankment
and consequent drainage. The real amount of the subsidence,
therefore, is greater by seven or eight feet than measurements
to the present surface would give. Evidence of recent
subsidence to a similar extent abounds around our shores.
The facts as regards Essex have been noticed by Mr. W. H.
Dalton in the 'Geological Magazine' for 1876, pp. 491-3.
The newspaper reports that I have seen describe the
Tilbury skeleton as having been found at the top of the sand,
at the depth of 32 ft.;6 the beds in which it was discovered
being said to be of Pleistocene age. This term Pleistocene
seems to me objectionable in this case on two grounds. For
it is not only unnecessarily vague as compared with the more
precise term Alluvium, but it implies a much greater antiquity
than that to which the skeleton is really entitled. Sir Charles
Lyell, indeed, its inventor, proposed the disuse of the word
Pleistocene more than twenty years ago, on account of the
confusion it was found to cause, from the various meanings
attached to it by different writers. Now, while it may be of
5 See note at end of paper.