468 Proceedings of Royal Society of Edinburgh. [sess. 
Expedition, to consist of a series of folds along an axis nearly 
parallel to the long axis of the island, i.e. a north-west and south- 
east axis. Then the soundings taken by the “ Scotia ” indicate 
that the deep water between Cape Horn and the South Shetlands 
narrows as we go eastwards into a trough-like depression of over 
2000 fathoms, passing north of the South Orkneys, then probably 
turning south-eastwards, to become continuous with the deep area 
of the Weddell Sea. 
It may be, therefore, that the Andean axis, already turning east- 
wards in Southern Patagonia and Tierra del Fuego, is continued in 
this direction south of the Burdwood bank, and then curves south- 
eastwards between the South Orkneys and South Georgia. 
If this is the case, then there is a relationship established 
between these Silurian rocks of the South Orkneys and the Silurian 
rocks occurring on both sides of the main Andean chain in Bolivia 
and Northern Argentina,* and in the province of Buenos Aires, in 
the Sierra Tandil and Sierra de la Yentana. 
More soundings in the area between the South Orkneys, Cape 
Horn, and South Georgia would probably shed further light 
on this problem ; and they are also much to be desired between 
the South Orkneys and Graham Land, where rocks of an entirely 
different type occur, viz., plutonic and metamorphic rocks on the 
Pacific side, and on the eastern side Lower Tertiary rocks, similar 
to those of Patagonia. 
At all events, the presence of isolated islands such as the South 
Orkneys and South Georgia, composed of sedimentary rocks, mostly 
inclined at high angles, and surrounded by deep water, proves a 
former much greater extension of land in this area. If they formed 
part of the Tertiary Antarctica postulated by Professor H. F. 
Osborn and many others,! to explain the floral and faunal relation- 
ships of S. America, S. Africa, and Australia, it is evident from the 
recent soundings J that the changes of level in sea and land in this 
region have been very considerable : it would now require an 
elevation of nearer 20,000 feet than the 10,000 assumed by 
Professor Osborn as necessary to unite S. America with Antarctica. 
* Cf. Suess, La Face de la Terre, yol. i. pp. 684-686. 
t H.F. Osborn, Science, 1900, vol. xi. p. 566. 
t Andersson, loc. cit., and “ Second Voyage of ‘ Scotia, 5 ” Scot. Geog. Mag., 
Jan. 1904. 
