346 JOURNAL OF THE WASHINGTON ACADEMY OF SCIENCES VOL. 13, No. 15 
spondence in occurrence of coastal sodie rocks on both sides might be 
considered favorable to the Wegener hypothesis, but on the other hand 
the generally markedly sodic character of the South Atlantic islands 
may be interpreted with equal plausibility as indicating a generally 
sodie character for the magmas that underlie the South Atlantic basin 
and that the coastal occurrences are but marginal effusions from this. 
The lack of correspondence between the Guiana-Ceara coast and that 
of Guinea, sodic rocks being absent from the one and quite abundant 
in the other,.seems to constitute more positive and more decisive evi- 
dence against the hypothesis. In addition to this is the rather fre- 
quent occurrence of charnockitic rocks along the African side of the 
Atlantie and their absence from the American side. The balance 
of the petrographical evidence, may, then, be regarded as adverse to 
Wegener’s hypothesis. 
Before leaving the southern part of the Atlantic split another 
feature should be considered. In the Transvaal and Cape Colony, and 
extending north into Rhodesia, enormous areas are covered with the 
plateau basalts of the late or post-Karroo (Triassic) Stormberg or 
Drakensberg series, and what are probably analogous plateau flows of 
about the same age are found in the Kaokoveld, near the coast, in 
northwestern ex-German Southwest Africa. Across the South At- 
lantic, in the states of Parand, SAo Paulo, Santa Catarina, and Rio 
Grande do Sul in Brazil, in Uruguay, and in southern Argentina 
(Patagonia), enormous areas are covered with similar plateau basalts 
of generally Triassic age. These vast flows have not been sufficiently 
studied, as yet, to permit any detailed chemical or petrographical 
correlation. But their occurrence as a petrographical feature of 
the first magnitude common to both sides of the South Atlantic is of 
great interest and is apparently favorable to the Wegener hypothesis, 
To judge from their geologic age they would seem to have been ex- 
truded on both sides, in general, shortly before the beginning of the 
split, if I understand Wegener correctly. If his hypothesis be true, 
however, we would expect, on the analogy of the Thulean basaltic area 
of the North Atlantic, to find many basaltic islands in the ocean 
between the two sides of the fracture, because of the relief of pressure 
and exposure of the underlying basaltie substratum brought about 
by the westward sliding of the American continental mass. This, 
however, is not the case. There are very few islands in the South 
Atlantic and these show dominantly sodic and not sodi-caleic (basaltic) 
characters. These vast plateau extrusions of probably similar basalts 
in South Africa and in southern South America seem to me more 
justifiably interpreted as belonging to a general and widespread 
event or cyclical incident in the earth’s history, strictly analogous 
