C.—GEOLOGY 79 
accept 1,000 metres as the thickness of the ice sheet—a figure not incom- 
patible with known observations of former ice sheets. Ocean currents 
would be checked, and still further increase of the ice cap would result. 
Depression of the lands, however, would have the reverse effect. Beyond 
any doubt, periods of mountain building and of marine incursions have 
occurred, but Ramsay admits that there are difficulties that he cannot 
fully explain. His theory is, however, only a development of that put 
forward by Lyell in his letter to Darwin, and later published in his 
Principles of Geology. 
Now all these theories abound in conditional phrases, and the geologist 
hardly knows what to accept. Personally I favour Brooks’ theory, for it 
demands far less disturbance of the conditions we are inclined to consider 
normal. ‘The earth so far as we can see has always been solid and rotating 
at an enormous rate—a gyroscope, in fact. If we are to assume wholesale 
melting of the sub-surface rocks, then the speed of rotation would soon 
play havoc with the crust. It would no longer be a case of continental 
‘drift,’ there would be a continental ‘surge.’ I cannot accept such whole- 
sale continuous movements of continents as Wegener envisages, but I do 
accept something along the lines of Joly’s periodic local softening of the 
sub-stratum, differential foundering of the continental blocks, even slow 
separation of the continents, and a rotation of the blocks round parts 
where softening had not taken place. In consequence, the continents 
are not aggregated round the equator, where they ought to be on Wegener’s 
hypothesis, and there has not been any serious slip of the skin on 
the core—Wegener’s definition of shifting of the poles—at any one time. 
The Atlantic I consider a young ocean, but, like Tate Regan,** believe that 
it was a wide ocean by Eocene times. In fine that the so-called tremen- 
dous earth storms are really very local. It is true that the ‘ Alpine’ storm 
of Miocene date looms very large in north-west and central Europe, but 
look on a globe at the area involved and see how small it is relatively—a 
mere trifle as compared with the opening up of the Atlantic ocean. I 
feel that our maps have much to do with our defective appreciation of 
world conditions. Mercator has a deal to answer for, as a result of his 
“ projection,’ and until we get back to studying a globe, instead of a 
sheet of paper, our ideas will remain distorted, especially when the areas 
involved are in the temperate and northern regions—precisely those 
regions where geological research is most abundant to-day. 
Now how are we going to test these several hypotheses? One of the 
neatest possible tests has been applied by Mrs. Reid and Miss Chandler 
in their work on the London Clay Plants.5* This flora has puzzled people 
since Parsons’ work in 1757. (We may say that the presence of Nipa 
at Sheppey and Artocarpus in Greenland are two of the most difficult 
palzobotanical facts to arrange in their proper setting.) 
These ladies set out, first of all, by establishing the principle that 
with flowering plants, at any rate, and confining their attention to living 
forms, the great bulk (70 per cent. at least) showed little power of adapta- 
bility to different climatic zones—they are tropical or extra-tropical as 
55 ‘Discussion on Geological Climates,’ Pyoc. Roy. Soc., 1930. 
58 London Clay Flora, British Museum, 1933. 
