PRESIDENT S ADDRESS. 2o 



(32l>) In 1919 I looked for snails in some of the Chrissie group of pans 

 but failed to find any, though the pans were full of water and had been 

 well supplied with water for some years. Mr. T. G. Trevor tells me that 

 Lake Chrissie was nearly dry between 1903 and 1906, and that it was dry 

 at times; see a paper by him, " The Physical Features of the Transvaal," 

 in Papers read at the joint meeting of the Brit. Association and S.A.A.A.S. 

 in 1905, vol. I, pp. 335-350. 



(32c) The shells were seen at the Stinkfontein spring in June, 1913. 

 Owing to decomposition setting in amongst a large number collected in 

 weak spirit th€y were never determined. 



Vogel Vley in Calvinia has a deposit of Tomichia shells on a part of 

 its border ; the deposit is mentioned by R. Moffat, Journ. Roy. Geogr. 

 Soc, XXVIII, 1858, p. 184, as a marl bed, but its mode of occurrence has, 

 so far as I know, not been described. Specimens reached the South African 

 Museum many years ago. 



(32d) Ann. Rep. Geol. Com. for 1907, p. 119. 



(33) W. M. Davis, " Observations in South Africa," Bull. Geol. Soc. 

 of America, vol. 17, 1906, Origin of the Veld, etc., pp. 435-444. 



(34) Mr. E. H. Banks kindly measured for me the areas of parts of 

 the Orange River system above the confluence of the Molopo (Hygap) and 

 Orange. 



Square miles. 



Nossob and Auob 40,000 



Molopo (including the Kuruman River) ... ... 47,000 



Orange River, made up of the Hartebeest and 



Brak Rivers 50,000 



* Orange and Vaal Rivers 124,000 



261,000 



(The Vaal basin is 75,000 according to W. van 

 Warmelo, in " Irrigation Magazine," vol. 

 I, p. 111). 

 In choosing a northern limit for the Molopo catchment only a narrow 

 strip on the right bank above the confluence of the Nossob was included. 



(35) The condition of the Hartebeest River is briefly shown in " Verneuk 

 Pan," Trans. Roy. Soc. S.A., vol. II, pp. 79-82. 



(35a) R. Moffat, " Journey from Little Namaqualand eastwards along 

 the Orange River," Journal of the Roy. Geogr. Soc, 1858, vol. XXVIII, 

 pp. 174-187. On p. 187 he attributes the fact that the Aintas supplies 

 the river with least water of all the tributaries to the prevalence of sand 

 in the catchment. 



Thougli unconnected with my subject, I want to draw attention to his 

 statement on p. 180 that he " found ... a formation evidently subcumbent 

 to the above saliferous sliales, the lowest stratum of which was a con- 

 glomerate resting on abraded and polished granite, and filling what seemed 

 to be a depression in the metamorphic rock." He was evidently looking 

 at the Dwyka tillite, but there is no hint of its recognition as a glacial 

 deposit. This was near Jonker Water in Prieska. The paper, as well as 

 tile one printed immediately before it, by the same author, is well worth 

 reading to-day. 



(36) Ann. Rep. Geol. Com. for 1907, pp. 12 and 156. 



(37) Descriptions of the Karroo beds of the region are given in Ann. 

 Rep. Geo]. Com. for 1907, and in a paper by A. L. du Toit " Notes on 

 the Karroo System in the Southern Kalahari," Trans. Geol. Soc. S.A., 

 1916. vol. XIX, pp. 1-13, in which the structure is made out in considerable 

 detail from the results obtained in boring for water along the Kuruman 

 River. 



(38) On tlie Kaap Plateau silicified wood from the Karroo beds is still 

 preserved in a hardened gravel at Mahura Muthia at an elevation of about 

 4,600 feet above the sea; Ann. Rep. Geol. Com. for 1906, p. 77; see also 

 the same for 1907, p. 155. 



