64 Dr. D. Woolacott—The Interglacial Problem. 
whether foreign rocks do occur in the Kaims in any quantity,! as if 
so it would undoubtedly lend support to the argument in favour of 
the formation of a shore-line, as the loose materials of such a deposit 
would be much more easily removed than the stiff Scandinavian 
Drift. 
(3) It has also been suggested that the valleys of “ Hesleden ”’, 
“Castle Eden’, and ‘“‘ Hawthorn”, which are now filled with 
boulder-clay containing Scottish, Cheviot, and Lake District erratics, 
and which I have described as Preglacial, were eroded between 
the deposition of the Scandinavian and the overlying British Drift. 
I considered these valleys when I first described them to be mature 
Preglacial waterways, and I am not aware of any evidence which 
proves they were formed during an Interval-in-the-Glaciation or 
were modified in such a period. We cannot be certain that some of 
them do not contain Scandinavian Drift at their base,? and if it was 
a lobe of this ice that reached the Durham coast they may be Pre- 
glacial and yet not have foreign boulder-clay in them. These 
valleys should, however, be examined as opportunity permits for the 
occurrence in them of Scandinavian Drift, and for their possible 
formation during a Glaciation-interval. 
It has been further suggested that there was an interglacial 
episode during the deposition of the Main or British drifts. 
Trechmann has noticed the occurrence of.clay filling a depression 
at Hartlepool, which contains only boulders brought from the west 
down the Tees valley ; it is also possible that such western-derived 
drift may occur at the base of the Preglacial “Tyne” or “ Sleek- 
burn”; and Smythe has shown that in Northumberland, between 
Bamburgh and the Wansbeck, there are two boulder-clays, one 
mainly derived from the west and an upper with material from the 
north (Tweed valley, etc.). There are no Interval-deposits or other 
evidence in support of this suggestion, but it is quite possible that 
there is an “ Interval-in-the-Glaciation ” between the formation of 
these two drifts, as the supposed later glaciation which brought the 
material from the north was undoubtedly the greater, and so may 
1 Flint and Chalk are, as I shall show, so peculiarly distributed in the Super- 
ficial Deposits that I do not regard them as all having been brought by the 
Scandinavian ice to the area. 
2 About 1903 Mr. Bell, of Bishop Auckland, sent to me two or three small 
pieces of rock which he had obtained from material dug up in excavations 
in Castle Eden Dene. One was a fragment of Laurvik syenite. I visited the 
locality shortly afterwards, and decided that it had been obtained from a gravel 
deposit and not from boulder-clay. I did not, therefore, record it at the time. 
In 1910 I saw a boulder of Laurvik syenite cemented in the foot of the cliff 
north of Castle Eden near Warren House Gill, and at the same time saw other 
evidence—that Dr. Trechmann has since, along with much new material, 
fully described—which convinced me that the Scandinavian ice had reached 
the Durham coast and thatthe boulders were trueerratics. I therefore recorded 
the boulders in the Boulders Com. Report of the Univ. Durham Phil. Soc. 
(Proc. Univ. Durham Phil. Soc., vol iv, pt. ii, 1910-11, pp. 89-90) and in Proce. 
Geol. Assoc., 1912. 
