Dr. D. Woolacott—The Interglacial Problem. 61 
Trechmann has brought forward evidence in favour of an Interglacial 
Period between the deposition of the Scandinavian and the British 
(or Main) Drift, and has suggested a possible Interglacial episode 
between the formation of the boulder-clay with only western 
erratics in 1t, and the more northerly derived deposit with Scottish, 
Cheviot, and other rocks.! 
I have already discussed my views regarding the Interglacial 
controversy, and propose to examine the subject from the stand- 
point stated. The evidence for an Interval-in-the-Glaciation 
which may possibly be Interglacial in character between the 
Scandinavian and British Drift is much stronger than that for even 
a Glaciation-interval between the two British Drifts. The general 
sequence of the boulder claysin Northumberland and Durham stated 
by Dr. Trechmann is correct. Along the coastal region of Northum- 
berland and Durham this sequence is (a) Scandinavian Drift, (b) Drift 
with western erratics,? (c) Drift with Scottish, Cheviot. and Western 
boulders. The Scandinavian Durham basement clay is overlaid by 
the Tweed-Cheviot-Lake District boulder-clay with Interval-deposits 
between at Warren House Gill; the evidence proves that the western- 
derived clay was deposited along the coastal region of South 
Northumberland, and was then removed by the southerly moving 
Tweed—Cheviot ice, hence the mixture of Lake. District, Cheviot, 
and Scottish erratics along the Durham coast. Clay with only 
Lake District-Tees Valley boulders has been proved to occur in 
a depression at Hartlepool,? and the western-derived clay can be 
seen under that from the north along the Northumberland coast 
between Bamburgh and the Wansbeck.* 
The main difficulty in accepting that there was an Interglacial 
period between the deposition of the Scandinavian and the British 
Drift near Castle Eden is that the hypothesis seems to demand that 
there was no British ice on the east of Durham during any stage of 
this, the maximum, extension of the Scandinavian ice-flow. It 
seems hardly possible that this ice could occupy the greater part of 
the North Sea area, without there being a concurrent gathering of 
ice on the uplands of Scotland and England and therefore a flow 
at the same time across the North of England.> It has always been 
1 Op. jam cit., 1920, p. 198. 
* There is, however, distinct evidence that ice bringing Scotch erratics 
reached the Northumberland coastal region before that from the Lake 
District. 
* Trechmann, Quart. Journ. Geol. Soc., vol. Ixxv, pt. iii, 1920, p. 192. 
4 Smythe, Glacial Geology of Northumberland, p. 94. 
° The difficulty introduced by this is seen when the Basement clay of 
Holderness and the Scandinavian Drift of Durham are compared. The former 
contains English and Scottish erratics mixed with foreign rocks (‘‘ Geology of 
Holderness ’’: Mem. Geol. Surv., pp. 18-19), the latter only such boulders as 
could be brought by the passage of an ice-sheet from Norway. The Durham 
Basement clay must therefore on this hypothesis belong to an earlier period 
of glaciation than that of Yorkshire with an Interglacial period (or possibly 
two such intervals between). This is, however, not impossible, but it is evident 
