306 H. H. Howorth—A Great Post-Glacial Flood. 
of the Norfolk and Norwich Naturalists’ Society,) has specially alluded 
to my opinions respecting the dependence of upheaval and of subsi- 
dence upon the denudation and the deposition of materials ; and has. 
also re-directed attention to the subject in a favourable manner by 
a letter in the Georocican Macazinu.? Having formerly (1878) 
criticized my views adversely, these recognitions of them must be 
considered to be greatly enhanced in value. 
TV.—Tracets oF A Great Post-GuactaL Foon. 
Part 6. Ture Evipence oF THE RottED GRAVELS AND THE SANDS: 
By Henry H. Howorrn, F.S.A. 
N a previous paper of this series I endeavoured to show that the 
| so-called Marine Drifts found at high levels, on both sides of 
the Irish Sea and elsewhere, are proved by their testaceous contents 
to have had no connection with the Glacial Age; while the mode 
of their distribution shows that ice in no form can have distributed 
them as we find them, nor yet are they consistent with the sub- 
mergence of the land for any considerable time beneath the sea; and 
T concluded that the only power known to us capable of distributing 
them is a wide-spread flood of water. I now propose to carry my 
argument considerably further, but before doing so, as it 1s so easy 
to be misunderstood, I must guard myself against the supposition 
that in what I have said or mean to say Iam minimizing the Great 
Glacial Age. 
Any one who will cursorily examine the present distribution of 
the Pliocene deposits, their disintegrated and broken character, the 
wide areas which are now entirely free from them, and yet the very 
specialized fauna and flora which characterize the broken fragments, 
will agree that a gigantic denuding agency has swept over the whole 
northern hemisphere, occupied by a continuous land surface in 
Pliocene times. This apart altogether from the more direct evidence 
of denuding forces we have in the products of the Glacial age. ‘That 
Glacial age which intervenes between Pliocene and Post-Glacial 
times, and is such a marked and complete barrier between them, 
was no doubt the distinctive era when not only Pliocene but . 
earlier Tertiary beds were scoured out and torn to mere shreds of 
their former extension. As we cannot suppose that the forces of 
Nature working on the same materials could have worked in a 
different fashion to that they work in now, we are driven, in view 
of the very greatness of the effects, to postulate that these forces, 
although precisely like those now current in form, were immensely 
different in degree. This is quite plain, whether we belong to the 
extreme school of Glacialists or no. It seems equally clear that a 
large portion of the work done was done by ice: we know of no 
other agency competent to do it. The smoothed and rounded rocks 
and other proofs of denudation that prevail so widely in the land- 
scapes of the high latitudes ‘of Europe and America are explainable 
1 The Scenery of Norfolk, vol. iii. p. 460. 2 Dec. II. Vol. X. p. 93, 1883.. 
