GEOLOGY 553 



centred in the south temperate zone about the present site 

 of South Africa, there is no more difficulty in comprehending 

 its glaciation than the Pleistocene glaciation of parts of the 

 northern hemisphere, or the present glaciation of Antarctica 

 and Greenland. 



This point of view is taken in A. du Toit's elaborate review 

 of the " Carboniferous Glaciation of South Africa " (Trans. 

 Geol. Soc. S. Africa, 24, 192 1, pp. 186-227). Wegener's views 

 are also adopted in du Toit's paper on " Land Connections 

 between the Other Continents and South Africa in the Past " 

 [South African Journ. Sci., December 192 1, pp. 120-40). 

 The Dwyka ice-sheet, which came into being in the Uralian 

 (Upper Carboniferous), was an extensive body formed by the 

 coalescence of ice radiating from several distinct centres, namely, 

 Namaland, Griqualand West, Transvaal, and Natal. Subse- 

 quently to the Triassic Gondwanaland was forcibly disrupted, 

 and the fragments moved apart until they were brought up 

 in the Tertiary against the ring of earth-folds developed in 

 that era. 



Mr. P. Lake gives a critical review of Wegener's hypothesis 

 in the Geol. Mag. (59, 1922, pp. 338-46). Lake points out 

 numerous discrepancies in Wegener's joinings of the land 

 masses, and shows that in many cases Wegener has ignored 

 the geological history of the land masses thus brought into 

 contact. " He [Wegener] has suggested much, he has proved 

 nothing." A like scepticism pervades the discussion on 

 Wegener's hypothesis at the Hull meeting of the British 

 Association {Nature, January 6, 1923, pp. 30-1), and Prof. 

 G. A. J. Cole's review {Nature, December 16, 1922, pp. 798-801). 



An interesting symposium on the topic of isostasy has 

 recently been conducted by the Geological Society of America. 

 The following list of papers published in their Bulletin (vol. 

 xxxiii, 1922, pp. 273-410) will give an idea of the nature and 

 range of the subjects discussed : W. Bowie, " Theory of 

 Isostasy^ — A Geological Problem " ; G. R. Putnam, " Condi- 

 tion of the Earth's Crust and the Earlier American Gravity 

 Observations " ; H. O. Wood, " Some Considerations touching 

 on Isostasy " ; H. F. Reid, " Isostasy and Earth Movements " ; 

 J. F. Kemp, " Isostasy and Applied Geology " ; Sir Sidney 

 Burrard, " Folding of Mountain Ranges — the Argument from 

 Isostasy " ; A. C. Lawson, " Isostatic Compensation con- 

 sidered as a Cause of Thrusting " ; A. C. Lane, " Weight of 

 Sedimentary Rocks per Unit Volume " ; B. Willis, " Role of 

 Isostatic Stress " ; H. S. Washington, " Isostasy and Rock 

 Density." 



It is only possible here to touch upon a few interesting 

 points in this discussion, as, for example, the connection of 



