480 TRANSACTIONS OF SECTION C. 
is further shown that the outer and uncrystalline margins of these masses all 
trend roughly north-east and south-west. The best known is that forming the 
south-eastern margin of the crystalline area, which the author has followed, 
where present at the surface, almost the whole distance from Stonehaven, on the 
east coast of Scotland, to Omagh in the north of Ireland. Recent work suggests 
that this margin is also present on the west coast of Ireland. 
This outer margin of crystallisation is not confined to Scotland; it is also 
present in Anglesea, where the margin of the crystalline massif is seen along 
a portion of the Menai Straits. It also occurs in the Isle of Man, where the 
old rocks are identical with those of the lower aureoles of thermometamorphism 
in the southern Highlands. In both cases the trend of this outer margin is the 
same—north-east and south-west. Wherever this margin can be examined it 
has been found to be a great line of resistance, and the folding in the adjacent 
palzozoic, and, at times, even newer rocks, is found to be parallel to it; it is in 
fact the cause of the strike of the folding; under carth-stresses the softer rocks 
have buckled up against a great resisting crystalline mass. 
Thus, strictly speaking, there is no such thing as a Caledonian Movement; 
there are a series of resisting masses with parallel margins; the folding in 
North Wales is determined by the Anglesea Archean Rocks; Caledonia has 
nothing whatever to do with it. : 
If, now, we turn to the area in the south of Britain, we find another system 
of folding; this, too, the author believes to be due to a similar cause. The 
outer margin of the old crystalline rocks in Cornwall seems to be roughly east 
and west; it certainly is not north-east and south-west. It now remains to do 
in the north-west of France what the author has done in North Britain—i.e., to 
trace out the outer margins of crystallisation and prove that the so-called 
Hercynian system means simply that the boundaries of the resisting crystalline 
masses, against which the newer rocks buckle up, now trend east and west. If 
these facts are once grasped we have an explanation of the local departure of 
the strike of the folding in the north of England; the lines of resistance locally 
depart from their usual trend and the subsequent folding does the same. 
5. The Division between the Lower and Upper Avonian. 
By Dr. A. Vauacuan. 
6. The Harlow Boulder Clay* and its Place in the Glacial Sequence of 
Kastern England. By A. Irvine, D.Sc., B.A., and P. A. 
Irvine, B.A. 
(1) In the light of Professor Bonney’s Presidential Address at Sheffield 
(1910) and the known intersection of the East Anglian chalk range by the pre- 
glacial Stort-Cam Valley (well-sections at Elsenham and Quendon), it is sub- 
mitted that the facts recorded last year point legitimately to the conclusion that 
the (roughly) East and West line of high country about two miles south of 
Harlow (Essex) represents the terminal moraine of the southernmost prolonga- 
tion (through the Elsenham Gap) of the ‘inland-ice.’ Its till-like character, 
the contained fossils and erratics (with the failure to detect any rock-fragments 
of Scandinavian origin), suggest that the Mercian ice-sheet was the confluent 
mass of two contributing sheets, one on either side of the Pennine mountain- 
chain, with smaller contributory glaciers from that region, sweeping the Mid- 
lands of débris from such districts as Charnwood, during the early Pleisto- 
cene maximum (alpine) elevation of the more northerly portions of the British 
area. Such considerations further suggest synchrony between the deposits (so 
similar in character) at Harlow, Cromer, and Saffron Walden; antedating 
the ‘Chalky Boulder Clay’ of East Anglia by the interglacial period of the 
glacial shingle (with remains of Hippopotamus, Hlephas antiquus, Bos primi- 
1 B.A. Reports, Dundee Meeting (1912), pp. 132 ff.; Nature, June 20 and 
August 22, 1912. 
