22 president's address. 



(3) A. L. du Toit, " Land Connections between the other Continents 

 and South Africa in the Past." South African Journal of Science, XVIII, 

 120-139. 



(4) A. Daubree, " Etudes synthetiques de Geologie Experimentale," 

 1879, p. 256. 



(5) The effects of climate on rock formation are discus.sed in many 

 works ; a comprehensive discussion of moderate length is that liy Joseph 

 Barrell, " Relations between Climate and Terrestrial Deposits," Journal 

 of Geology, XVI, 1908. Johannes Walther in " Einleitung in die Geologie," 

 1893-4, especially Vol. Ill, treats of the subject in detail; in " Denudation 

 in der "Wiiste," 1891, and " Das Gesetz der Wiistenbildung in Gegenwart 

 und Vorzeit," 1900, he deals specially with dry climates. 



(6) W. M. Davis in a paper entitled " The G-eographical Cycle in an 

 Arid Climate." Journal of Geology XIII, 1905 (reprinted in " Geographical 

 Essays " 1909), discusses the question at length, and in the volume of 

 collected papers will be found admirable presentations of the evolution of 

 surface forms through various agents. 



(7) Prof. J. W. Gregory considers the term " Inselberg " unnecessary 

 (" The Rift Valleys and Geology of East Africa," 1921, p. 35) and would 

 call the hills residual mountains, which they are, tors or monadnocks. He 

 says that the term would be more appropriate for an inlier like the Isle 

 of Ely ; it seems to me unlikely that anyone having a recollection of that 

 place ' and seeing the Inselberge of South Africa would use the same name 

 for them as physical features. Brent Knoll, rising abruptly from Sedgemoor, 

 would be a closer analogue to some of the island mountains of Bushman- 

 land and the southern Kalahari, for their bases are certainly buried, sand 

 taking the place of the alluvium of Sedgemoor. But there is a great 

 difference in appearance owing to the fact that the island mountains are 

 made of hard rocks and owing to the difference between the agencies of 

 erosion and transport in the two regions. Rocks like the soft Jurassic 

 clays and limestones of Brent Knoll would scarcely become Inselberge in 

 the Kalahari. It sems convenient to retain Bornhardt's term, which has 

 become widely known through its adoption by Passarge, for a special class 

 of residual mountains, just as certain other residual mountains witli their 

 bases buried in ice are called nunatakkr. Inselberge lack the curved 

 profile produced by stream erosion, their profile is chiefly made up by 

 straight lines, in which again they resemble nunatakkr and for analogous 

 reasons, disintegration by change of temperature and transport of the 

 fragments chiefly by gravity and wind, almost without the co-operation 

 of running water. 



(8) " Die Kalahari." pp. 636-7. Descriptions of several of the plains 

 are to be found in this book; that of the Kwabe district on p. 114 and 

 previous pages is one of the best. It must be remembered that work 

 further south has proved two periods of erosion of pre-Cretaceous age, one 

 of early Nama and the other of early Karroo age. It is scarcely possible 

 without detailed work to be assured that in any particular instance we 

 are concerned with the results of the latest of these three periods alone. 

 At the time of Passarge's work in this country (1896-8) the widespread 

 occurrence of Karroo outliers north of the Orange River had not ))een 

 recognised, and very little was known of the nature of the pre-Nama floor. 



(9) It would be convenient to confine the term " pan " to depressions 

 lacking outlet, but the local usage is not uniform ; the largest depression 

 in this country is Haakschien Vley, while one of the largest depressions 

 connected with a river is called Verneuk Pan, though ordinarily what are 

 called pans have no outlet and a vley is part of a valley. 



(10) Descriptions of Haakschien Vley and other pans lacking outlets are 

 given in Ann. Rep. Geol. Comm. for 1907, pp. 110-120; of Verneuk Pan. 

 with outlet, in Trans. Rov. Soc. S.A. 1911, pp. 79-82. Also in the Reports 

 for 1906, pp. 82-5; and 131-4; for 1907, pp. 190-2; for 1910, pp. 13-6. 



See also Passarge, " Die pfannenformigen Hohlformen der suedafri- 

 kanischen Steppen," Pet. Mitt. 1911. 11, Heft 2. H. Michaelsen. '• Zur 

 Kenntnis der Kalkpfannen des oestiichen Damaralandes." Naturw-ssen- 



