534 CAPT. H. G. LYONS ON THE STRATIGRAPHY AND [Nov. 1 894, 



grains as readily as through, the cement, to a white, soft, friable 

 sandstone which can he crumbled between the fingers. 



In the neighbourhood of Wadi Haifa, and especially on the eastern 

 bank, lenticular deposits occur (of 2 to 5 miles and more in length) 

 of an iron-ore deposit usually strongly oolitic in character ; plant- 

 remains in the form of fragments of fossil wood occur in it, but no 

 other fossils, so far as I have been able to discover. These beds are 

 certainly lagoon deposits formed in secluded pools or backwaters 

 where marsh vegetation flourished, and the iron deposit was 

 formed similarly to the bog iron-ore deposits of the Swedish lakes. 1 

 The usual thickness of these beds is about 1| to 3 feet, and at 

 Wadi Haifa from two to three of them are exposed in the cliff- 

 section at various levels. 



Prof. Hull 2 considers that the Nubian Sandstone was " de- 

 posited within the waters of a vast inland lake, occupying the 

 greater portion of Northern Africa," but I cannot help thinking 

 that, so far as Egypt and Nubia are concerned at all events, its 

 mode of occurrence, lithological character, etc., point to an estuarine 

 deposit which was gradually invaded by the Upper Cretaceous sea 

 as subsidence continued. As I have not been able, in the area I 

 am describing, to distinguish any one part of the sandstone as being 

 of different age from the remainder, I shall consider the whole of 

 it as being Nubian Sandstone of Cretaceous age, as I believe it to 

 be, and not as being of Carboniferous 3 age in the lower part. Per- 

 haps it is only in the eastern parts of Egypt, and in the Sinai 

 peninsula and Palestine, that true Carboniferous deposits were laid 

 down. 



The better and harder varieties of this sandstone owe their 

 toughness and durability to the siliceous cement which binds the 

 quartz-grains together, and usually the darker and more iron- 

 stained is the sandstone, the more there is of the cementing silica. 

 Its origin is no doubt due to the same agency as that which has 

 replaced the woody structure of the fossil trees, to which I shall refer 

 again later. The strata are usually almost horizontal, being bent into 

 very slight anticlinal and synclinal folds, which sometimes extend 

 over such wide areas as often to render the dip barely noticeable. 



III. The Cretaceous and Eocene Strata. 



The Upper Cretaceous beds 4 which overlie the Nubian Sandstone 

 consist of the Exogyra Overwegi-series, amounting to about 500 feet 

 of alternating bands of sandstone, clay, shale, and limestone, which 

 contain a large amount of rock-salt and gypsum disseminated 

 throughout. These are succeeded by green and grey shales, which 

 are overlain in their turn by a white limestone. 



1 Geikie, ' Text-boot of Geology,' 3rd ed. 1893, p. 146 ; Both, ' Allgemeine u. 

 cheniische Geologie,' vol. i. (1879) p. 597 ; Winchell, ' Iron Ores of Minnesota,' 

 Geol. Surv. Minn. Bull. no. 6 (1891) p. 221. 



2 Trans. Victoria Inst. vol. xxiv. (1890) p. 317. 

 8 Waltker, op. Jam cit. 



4 Zittel, op. cit. pp. 61 et seqg. 





