12 THE PRESIDENTIAL ADDRESS 
This view, outlined by others, has been emphasised by Wegener 
and dealt with by him in full detail in his work on The Origin of 
Continents and Oceans, and it now plays a leading part in what is 
known as the Wegener theory of continental drift. The hypothesis 
is supported by the close resemblances in the rocks and fossils of 
many ages in western Europe and Britain to those of eastern North 
America; by community of the structures by which these rocks are 
affected ; and by the strong likeness exhibited by the living animals 
and plants on the two sides, so that they can only be referred to 
a single biological and distributional unit, the Palearctic Region. 
The hypothesis, however, did not stop at this ; and in the South 
Atlantic and certain other areas Wegener and his followers have 
also given good reasons for believing that continental masses, once 
continuous, have drifted apart. 
Broad areas in southern Africa are built of rocks known as the 
Karroo Formation, of which the lower part, of late Carboniferous 
age, is characterised especially by species of the strange fern-like 
fossil plants Glossopteris and Gangamopteris. Associated with 
them are peculiar groups of fossil shells and fossil amphibia and 
reptiles. Similar rocks, with similar associations and contents, in 
Peninsular India have been named the Gondwana Formation. 
Comparable Formations also occupy large regions in Australia, 
Tasmania and New Zealand, in Madagascar, in the Falkland Islands 
and Brazil, and in Antarctica. 
The correspondence between these areas is so close that Suess 
supposed they must at that date have been connected together by 
lands, now sunk beneath the sea, and he named the continent thus 
formed Gondwanaland after the Indian occurrences. The break-up 
of this land can be followed from a study of the rocks, and it was a 
slow process, its steps occupying much of Mesozoictime. Dr. A. L. 
du Toit’s comparison of South African rocks with those of Brazil 
and elsewhere in South America favours even a closer union than 
this between the units now scattered. 
One of the most remarkable features shown by these rocks in all 
the areas mentioned, but to varying extents, is the presence of con- 
glomerates made of far-travelled boulders, scratched like those borne 
by the modern ice-sheets of Greenland and the Antarctic, associated 
with other deposits of a glacial nature, and often resting upon 
typical glaciated surfaces. ‘There is no possible escape from the con- 
clusion that these areas, now situated in or near the tropics, suffered 
an intense glaciation. ‘This was not a case of mere alpine glaciers, 
for the land was of low relief and not far removed from sea-level, but 
of extensive ice-sheets on a far larger scale than the glaciation of the 
northern parts of the new and old worlds in the Pleistocene Ice Age. 
I have never seen any geological evidence more impressive or con- 
