Dr. D. Woolacott—The Interglacial Problen. 25 
agree. I propose briefly to summarize these, and subsequently to 
discuss more controversial and indefinite subjects. The most: 
important of the former are :— . 
(1) In Preglacial times—probably starting with the Miocene— 
the surfate of Northumberland and Durham was eroded by a series 
of easterly-flowing streams, which were not adjusted to the present 
coastline The maximum proved depth of the Preglacial valleys 
beneath sea-level is 169 feet, occurring at Dunston, west of Gates- 
head, near the junction of the ““ Wash ”’ 2 and the “ Tyne’’.? These 
mature watercourses probably were considerably and unevenly 
deepened by glaciation. Those which lay in the same direction as 
that of the ice-movement had a series of rock basins developed in 
them. In my paper onthe superficial deposits I prove that the slope 
of the bed-rock of the “ Tyne ”’ is of a switchback nature,* a feature 
probably due to the scooping out of the softer beds by the Tyne 
glacier.” In valleys such as the “ Wash”, which lay across the 
direction of the ice-flow, the slope of the Preglacial Thalweg is, 
however, continuously in one direction.® The depth of the “ Tyne ” 
at its mouth is not so great as it is further inland nor as that of the 
“Wash ”’, and I am of the opinion that this is in part due to the 
uplift that produced the Postglacial raised beaches having been 
more accentuated in the coastal region. It would appear certain 
that at some time prior to the Glacial period the country was more 
elevated and that the constructional shore-line lay far to the east 
and north of the present one,’ but there is no evidence in the 
two north-eastern counties as to the position of the coastline 
immediately prior to the oncoming of the Scandinavian ice-sheet.” 
(2) Before this great outflow, Teglian, Cromerian, and other 
deposits were laid down on the North Sea area, and some of these 
were pushed forward by the advancing ice.” 
(3) The first ice to reach the east of Durham was that from 
1 Geogr. Journ., July, 1907. 
2 Tn this paper all Preglacial valleys are denoted by inverted commas. 
3 “ Note on Borings at Derwenthaugh and Dunston’”’: Proc. Univ. Durham 
Phil. Soc., 1909. 
4 Quart. Journ. Geol. Soc., vol. lxi, 1905, p. 76. 
> Merrick, who has studied the Tyne valley very minutely, has also come 
‘to the conclusion that rock-basins were developed along it. 
6 “The Preglacial Wash’’: Proc. Univ. Durham Phil. Soc., vol. ii, 1906, 
5 Ds 
” Geogr. Journ., July, 1907, p. 37. 
6 The buried Chalk cliff and associated deposits at Sewerby, near Flam- 
borough Head, is a little above sea-level. Lamplugh states “ that they prove 
that at the beginning of glacial times the North Sea held possession of its basin, 
and with a surprisingly slight difference from the present level’. I have always 
- doubted that the level at the beginning of Glacial times was the same as the 
present. I consider it to have been more elevated. It is not certain that the 
Sewerby raised beach is not an Interval-deposit. (Or, as suggested by 
Trechmann, op. jam cit., p. 190, an Interglacial one.) 
9 Trechmann, Quart. Journ. Geol. Soc., vol. Ixxv, pt. iii, 1920, p. 193. 
