Hyland — On some Specimens from Wady-Halfa. 441 



tute. 1 A remarkably fine palaeolithic stone implement of the true 

 river-drift type has been described by H. Stopes. 2 The locality 

 given is half-a-mile from the Spring of Moses, near Cairo ; the 

 greatest length is 5*5 in, width 3*8, and thickness 1*5. It is made 

 of " conglomerate " precisely similar to that found at Jebel 

 Ahmar. Sir "W. Dawson 3 holds, however, that all such remains 

 of man are superficial and modern, and considers that there is no 

 certainty as to the human origin of the implements stated to have 

 been discovered by Greneral Pitt Rivers in the old indurated 

 gravels near Thebes. 



Many of the implements before me are highly polished and 

 unevenly corroded. The agency to which this is generally ascribed 

 is Eolian. It is, in fact, a well-known observation in Egypt that 

 this action goes on upon the large scale — strata being deeply 

 grooved and ploughed by the sand-charged blasts of the desert. 4 

 The unevenness in the corrosion is due to differences in the com- 

 position and hardness of the various layers. Professor V. Ball 5 

 has recently suggested that the appearance is probably due to the 

 solvent action of a supersaturated solution of carbonate of soda 

 upon the silica. Incrustations of sodium carbonate are abundant 

 in India, whilst in Nubia the soil is impregnated with salts. In 

 Equatorial Africa nitrate of soda makes its appearance, and covers 

 huge plains to the N.W. and S. of the Kilima-Ndjaro. 8 Hence, 

 considering the known solvent action of such alkaline salts, it 

 seems necessary for us to ascribe to this agent a part in the process 

 of corrosion — though a minor one as compared with that of blow- 

 ing sand. A. Irving 7 regards the humus-acids furnished by the 

 desert- scrub as the more likely solvent. 



1 Dawson, I. c, p. 483 ; also, inter alia, Haynes, Silex acheuleens de l'Egypte, 

 Bull. Soc. Anthrop. Paris, ser. 3, tome i., 1-878, p. 339 ; E. Desor : Notice sur les 

 silex prehistoriques des bords du Nil. Bull. Soc. Sci. Nat. Neuchatel, vol. xii., 1882, 

 pp. 435-438 : 1 pi. 



2 On a Palaeolithic Stone Implement from Egypt. Eep. Brit. Ass., 1880, p. 624. 



3 Transactions of the Victoria Institute, 1884. 



4 Cf. J. D. Enys, " On Sand-worn Stones from N. Z.," Q. J. G. S., Lon., xxxiv., 

 p. 86. 



5 On some Eroded Agate Pebbles from the Soudan, ibid., March 28, 1888, p. 368. 



6 Hyland, I. c, p. 211. 



7 Metamorphism of Rocks : London, 1889, p. 104. 



2L2 



