24 I'kksidkxt's addiikss. 



falls into the period between upper Cretaceous and upper Pliocene, including- 

 upper Cretaceous." 



(24) E. Kaiser, " Bericht uel)er geologische Studien waehrend des 

 Krieges in Suedwestafrika," Ahh. der Ciesener Hochschulgesellschaft, II, 

 1920. The oldest of the superficial deposits yet found in the Namib would 

 seem to be very considerably younger than those containing Dinosaur bones 

 at Kangnas ; the observations so far recorded do not require the assumption 

 of a wet climate in the Namib in Miocene times ; they point, as Prof. 

 Kaiser remarks, to the Miocene being the latest date to which the setting 

 in of arid conditions there can be ascribed. 



(25) The chalcedonic rock near Komgha which contains Chara and 

 mollusca is not of quite the same kind as those referred to ; it is a rock in 

 which silica has replaced other substances rather than being cemented 

 sand, and it is more like the rocks described by Mr. Bullen Newton from 

 Rhodesia in Ann. and Mag. Nat. Hist., March, 1920, to which he tentatively 

 assigned an uppei- Cretaceous age, which seems scarcely justified by the 

 evidence. 



(26) E. Kalkowsky, " Die Verkieselung der Gesteine in der noerdlichen 

 Kalahari," Mitt. a.d. Koenigl. Mineral. -Geolog. Museum, etc., in Dresden, 

 1901, pp. 66-7. Passarge, in " Die Kalahari," p. 509, points out that the 

 facts from that region are not explicable on such grounds, but that another 

 source must be looked for and suggests silica brought in by springs. These 

 discussions relate rather to silicified (verkieselte) rocks than to rocks made 

 of sand grains cemented (eingekieselte) by silica. 



(27) In " The Geology of Cape Colony," 1904, p. 363, Kalkowsky's 

 explanation is said to fit in with the sporadic occurrences of the rock, but 

 many other occurrences do not support it, notably the extensive silcretes 

 on the flanks of Zwartberg and elsewhere (e.f/., Schwarz, Ann. Rep. Geol. 

 Com. for 1905, p. 51), the small masses of similar rock associated with 

 ferricretes at Woyenthin, Transvaal (" Explanation of the Geol. Map of 

 the Country near Heidelberg," 1922, pp. 69-70); and such instances as 

 that near Moorreesburg Station described and figured in " Geology of 

 Cape Colony," 2nd edition, 1909, p. 382, which are irregularly shaped bodies 

 of the quartzite formed in or just below the soil. 



(28) Pasisarge, " Die Kalahari," pp. 285, 350, 370, 473, 582, and Chapter 

 XXXV. Opaline silica is much more abundant in the rocks described by 

 Passarge than in those of the west and south of the Cape Province, and 

 that is also the case with the southern Kalahari and Bechuanaland occur- 

 rences (Ann. Rep. Geol. Com. for 1907, pp. 81-2) ; G. W. Lamplugh, in 

 " Geology of the Zambesi basin," Q.J.G.S., vol. 63, pp. 198-200, suspects 

 that the formation of the Zambesi silcretes goes on at the base of sands 

 where it is exposed, and shows that it is not so extensive as the sands 

 themselves. 



(29) E. Kaiser, " Bericht ueber geologische Studien, etc.," 1920, pp. 

 20 and 33. 



(30) In the wet years 1917-8 the deposition of iron oxides at the surface 

 of the ground was conspicuous in Heidelberg, Tvl., at places where there 

 is generally no seepage. The rainfall, as Mr. Stewart tells me, was 44 

 and 40" 8 inches in the two years, while the average is about ^8. " Explana- 

 tion " of the Geological Map of Heidelberg, 1922, p. 69. These deposits 

 are not quite like the iron pans formed in soils, of which a good account 

 is given in R. H. Rastall's " Agricultural Geology," 1916, pp. 140-3. The 

 ironstone of the Cape Flats is a pan formed under sand. 



(31) W. J. Wybergh, " The Limestone Resources of the Union," 

 Geological Survey Memoir No. 11, pp. 14-17, and vol. II, pp. 32-35. 



(32) An instance of the formation of three feet of tufa in 27 years at 

 a place where water oozes out is quoted in Ann. Rep. Geol. Com. for 1906, 

 p. 79. 



(32a) Instances are Water Pan in Vryburg (Ann. Rep. Geol. Com. for 

 1907. p. Ill); Klein Chwaing (the same for 1906, p. 83); and the Britten 

 Salt Pan. where the slielly tufa occurs several feet above tlie level of the 

 pan. 



