80 
discovered any adequate source of the motion. The 
polefluchtkvaft is too feeble; it is purely meridional 
in direction and is inconsistent with the existing 
distribution of the land. It is probably ineffective. 
A differential soli-lunar attraction on the emergent 
features of the continents is obviously inadequate. 
The fact is Wegener works out the theory on the 
basis of a westerly drift of the continents. In doing 
so I think he is in error. An adequate force appears 
available provided an easterly drift is postulated ; 
and so far as I can see the theory grows in probability 
when examined from the new point of view. 
According to Sir George Darwin, the tidal effects 
of sun and moon acting on ‘‘a stiff yet viscous 
planet ’’ (‘‘ The Tides,’’ p. 277) must produce a 
retardation of the surface crust relatively to the 
interior. He states that this is speculative as regards 
the earth ; but this was written twenty-five years ago. 
The great fact of the isostatic compensation of the 
continents, proving their flotation in a viscous 
magma, was not then supported by such strong 
evidence as Hayford and others have since adduced. 
I assume that the differential motion exists (or formerly 
existed) and that the floating continents possess a 
slightly less rotational velocity than the deeper parts 
of the underlying magma, the velocity of which 
continues to increase downwards until a more rigid 
interior is reached. 
The consequence of this assumption is that the 
eastern velocity of every land area on the globe 
depends to some extent upon its downward penetration 
into the sustaining magma. A continent upon which 
a great geosynclinal loading is progressing becomes 
acted upon by the faster moving layers and is exposed 
to a force which is continuous and relentless, and the 
intensity of which depends on the area and depth 
of the protuberance. Whether the resultant motion 
of the continent will be due east, relative to the 
surface crust, or whether it will take up a turning or 
rotational motion, will depend on the location of the 
applied force. If excentric a rotational movement 
must ensue. If uniform over the continental area— 
as in the case of a great ‘‘ revolution ’’ or oceanic 
invasion—the drift will be towards the east. 
According to this view, America did not leave 
Europe and Africa but was left behind by them. 
Their increased easterly velocity was, possibly, 
ascribable to the great Laramide submergence of 
South Europe, South Asia, and North Africa. (The 
tidal effect is greatest in equatorial regions.) In a 
similar manner New Zealand left Australia: the 
force in this case being plainly referable to the 
isostatic compensation demanded by the lofty ranges 
of New Zealand. So also Ceylon was torn from 
Peninsular India; the fracture line of the eastern 
Asiatic coast was produced, etc. 
As regards mountain elevation it is evident that, 
while from the present point of view mountain 
building is in every case ultimately referable to tidal 
forces, mountains may develop in different circum- 
stances. They may, in central continental areas, 
be conditioned partly by magmatic pressure from 
beneath, partly by crustal pressure. In such a case 
as the western mountains of America the magmatic 
pressure eastwards must be the principal agent. The 
continental movement gives rise, in this case, to a 
depression of the bordering ocean floor—a ‘‘ wake.”’ 
But, again, continental movements may give rise to 
mountain chains by the direct pressure between land 
masses. In this manner the Himalayan chains prob- 
ably originated. The force arising out of the com- 
pensation required by the great and lofty central 
plateaus of Asia sufficiently accounts for a turning 
movement around the more stationary features of 
Peninsular India and the Arabian Plateau. This is 
NO. 2777, VOL. 111] 
NATURE 
[JANUARY 20, 1923 
in harmony with the current view that the fold- 
mountains of Asia were diverted by the resistance of 
those massive earth blocks. J. Ouse 
Trinity College, 
Dublin, December 31. 

SINCE my return from the Falkland Islands a few 
months ago I have followed with great interest the 
course of the discussion in the columns of NATURE 
which has ensued upon the publication by Prof. 
Wegener of his revolutionary views on the flotation 
and drifting of continental masses. During my 
recent geological survey of the Falkland Islands I 
was very greatly impressed by the extraordinary 
similarity of the geology of the Islands to that of Cape 
Colony. The geological succession comprises rocks 
ranging in age from Archean to Permo-Carboniferous, 
although rocks of Cambrian, Ordovician, and Silurian 
age appear to be absent. The oldest rocks closely 
resemble some of the Archean rocks of Cape Colony; 
and from the Devonian to the Permo-Carboniferous 
the lithological and paleontological succession is 
practically identical in the two areas. The post- 
Triassic dolerite dykes of the Falklands are also 
very like the intrusions of the same age in Cape 
Colony. The east and west folding so evident 
in the southern part of Cape Colony makes the most 
conspicuous feature in the Falkland Islands. The 
only notable point of difference in the two areas is 
that whereas in Cape Colony the lowest division of 
the Cape System (Devonian), namely the Table 
Mountain Series, is much folded, the corresponding 
rocks in the Falkland Islands have escaped such 
disturbance and lie almost horizontal, or with only a 
gentle dip, over an area of many square miles. The 
equivalents of the middle and upper members of 
the Cape System (Bokkeveld Series and Witteberg 
Series) are, however, intensely folded in the Falkland 
Islands. 
From the orthodox point of view one has to believe 
in the persistence, in minute detail, of a strati- 
graphical sequence representing the passage of a 
great period of geological time, across the 5000 miles 
of ocean which separate Cape Colony from the Falk- 
land Islands, and, in face of the array of facts 
marshalled into such an orderly and effective host 
by Wegener and again by Du Toit, this becomes, on 
a sudden, an unexpected strain upon one’s faith. 
In discussing the ice-fields of Gondwanaland in his 
very interesting paper, ‘‘ Land Connections between 
the Other Continents and South Africa in the Past ” 
(S. Afr. Journ. Sci., pp. 120-140, Dec. 1921), Dr. 
Du Toit states that in the Falkland Islands the centre 
of origin of the ice is unknown. I was able, during 
my survey of the Islands, to note that wherever the 
glacial tillite at the base of the Permo-Carboniferous 
sequence was adequately exposed it was always 
possible to collect a varied assortment of rocks 
occurring as erratic boulders in the deposit, and 
certain types, such as pegmatite, a coarse granite, 
and a pink quartzite, never failed to occur. The one 
and only exposure of Archzan rocks in the Colony 
occurs at Cape Meredith, the southernmost point of 
West Falkland, and when I examined that area I 
readily recognised the pegmatite, granite and 
quartzite occurring there as similar to the ubiquitous 
boulders of the tillite. Subsequent microscopic 
examination confirmed the identity of the rocks. 
With regard to the direction of the strie on 
glaciated surfaces underlying the tillite, I never came 
across a really convincing exposure, but in a few 
places on both East and West Falkland I noted, on 
the smoothed surface of the quartzite beneath the 
tillite, what I regarded (although with some doubt) 
as glacial striz, and in every case the markings ran 

