president's address. 27 



in Ann. Rep. Geol. Com. for 1906, pp. 68-71). The wind, working much 

 more frequently than flood-water, obliterates bedding, and is not sufficiently 

 constant to impose generally the strongly marked current bedding found 

 in sections through sand dunes. 



(44) Ann. Rep. Geol. Com. for 1907, p. 95 ; on Pepani, a farm south 

 of Morokwen. Passarge records a probable local depth of 160 feet, 

 •' Suedafrika," p. 142. 



(45) The Clanwilliam sand veld and the Zand Leegte are described in 

 Ann. Rep. Geol. Com. for 1903, pp. 158-167. 



(46) The large pan on Poortje and Meintjes Kraal, north of the Tanqua 

 Karroo is in an abandoned course of the Bosch River (Ann. Rep. Geol. 

 Com. for 1900, pp. 40-1) and is not strictly comparable to such a place as 

 Haakschien Vley, but, like Verneuk Pan, it is a flat--cut part of a valley 

 widened and devoid of vegetation. The bare patches of flat ground 

 covered with mud in wet weather in the Great Karroo have ill- defined 

 boundaries, though they are flooded with rain water for a few hours at 

 a time They may well be pans in the making, but they lack the depression 

 and well-defined borders of the northern pans, and bush stretches irregularly 

 into them. 



(47) The rainfall maps given by Mr. Charles Stewart in evidence before 

 tlie Select Committee on Droughts in 1914, and printed in " Senate S.C. 

 ■"2 — 1914 " are most convenient maps showing average and seasonal rainfall 

 within the Union A large collection of figures is given in Chapter II, 

 " Climate and Meteorology," in Memoir No 4 of the Botanical Survey of 

 South Africa, " A Guide to Botanical Survey Work," 1922, together with 

 maps of average and seasonal rainfall. The older work of Buchan, " A 

 Discussion of the Rainfall during the Ten Years, 1885-1894," Capetown, 

 1897, is very useful for the Cape Province. I may here acknowledge my 

 indebtedness to Mr. Stewart for so freely giving me the benefit of his 

 great store of information. 



(48) A. Penck. " Die Morphologic der Wuesten," Geographische 

 Zeitschrift, XV, 1909, p. 556. 



(49) One of these pans, on the south-western part of Maraisdrift, has 

 found an outlet to Riet Spruit, though the stream only partly drains the 

 pan ; this appears to be an instance of a pan which has overflowed its 

 limits or has been breached by headward erosion of a stream and is in 

 process of destruction through stream erosion. It holds water in its deeper 

 part only after heavy rain. 



(50) Passarge, "Die Kalahari," p. 648, and Chapter XXXVII; also in 

 " Suedafrika." 



(51) A. Penck, " Climatic Features of the Pleistocene Ice Age," 

 Addresses and Papers read at the joint meeting of the British and 

 t^.A.A.A.S. in 1905, vol. II, pp. 1-9, also Geographical Journal, Feb., 190B, 

 and in " Die Alpen in Eiszeitalter," pp. 1142-7. 



(52) A. Penck, " The Shifting of the Climatic Belts," Scottish 

 Geographical Magazine, June, 1914, pp. 281-283. Related questions are 

 dealt with in Publication No. 192 of the Carnegie Institution, Washington, 

 1914, by Huntington and others, but I have not seen it; "The Climatic 

 Factor, as Illustrated in Arid America." A review in Am. Journ. Sci. series 

 IV, vol. 38, 1914, p. 563, shows that the work includes a discussion of 

 the interpretation of terraces and the means of distinguishing those due to 

 earth-movements from those dependent on change of climate, the bearing 

 of the growth rings in the great Sequoias on the climate of the last 2,000 

 years and many other things connected with post-Pleistocene fluctuations 

 of climate. 



(53) R. Chudeau. " Les Changements de Climate du Sahara pendant le 

 Quarternaire," C. R. Ac. Sci., March 7th, 1921, T. 172, p. 604. 



(54) J. W. Gregory, " The Rift Valleys and Geology of East Africa," 

 1921. p. 149. and references there given. 



