256 John Hogg, Esq., on the Geography and 



Where it is so, it generally contains imbedded nodules o^ flint, 

 which are often black, in regular and almost horizontal layers, 

 conforming to the stratification. In other localities, it is 

 usually of a cream or buff colour, and close in texture- 

 Among its numerous fossils are found ostrese, echini, madri- 

 porse, and pectines. Rocksalt and gypsum occur in layers." 

 The calcareous ridges of Gebel Wardan, Hamam, Araba, 

 Hemam, and some " ranges on the eastern coast, appear to 

 be spurs and outliers from El Tyh.'' 



" The central region around (the monkish) Mount Sinai presents 

 a magnificent outburst of granitic and porphyritic rocks, which have 

 uplifted and thrown into confusion a zone of hypogene rocks, prin- 

 cipally liornhhndeschist and gneiss^ all penetrated by great dykes of 

 greenstone, which present a singular feature in this extraordinary 

 tract, passing through and over high bare mountains of red granite 

 in dykes and walls. 



" The nearest approach of the granite to the western coast is near 

 its north-west angle to the south of 29° north latitude. At Tur it 

 is about eight miles distant. It spreads out, breaking up the horn- 

 blendeschist to the eastern coast, where it forms a range from 800 

 feet to 2000 feet above the sea. Emerging on the north from the 

 sandy plain of Debbet-el-Ramleh, it disappears to the south under 

 (the sandstone and) the tertiary f'ossiliferous limestone of Has 

 Mohammed. 



" Sandstone is seen resting on the borders of the granitic and 

 hypogene areas, and sometimes entangled in them, the limits of 

 which it is difficult to define. On the north, it appears to be 

 bounded by the limestone of El Tyh, and is visible near the coast 

 of the Red Sea, in the vicinity of Burdes, a little south of the lime- 

 stone of Gebel Hamam, and forms the cliffs of Wadi Mukatteb, El 

 Naszb, Sarbut-el-Chadem, and the Mountain of ' the Bell' El Narkus, 

 south of which it disappears under the (secondary) limestone of 

 Gebel Hemam and El Kaa, near Tur." 



Again, further south, it is found bordering on the granitic 

 formation, as well on the western as on the eastern sides of 

 the extremity of the Gebel-el-Turfa. 



" Near the east coast it caps the hornblende rock at Ograt-el- 

 Faras (Hillock of the Horse), and thence to Wadi Murrali and El 

 Hadhera. It caps the granite of Gebel Samghy (Gummy), and 

 northerly it is seen occasionally resting on the granitic rocks, as at 

 Wadi Mezarik and Wadi-el-Musry, near the head of the Akaba 

 Gulf. In lithologic character it varies from a compact reddish quartz 

 rock, as at the western mountain, near Gebel Hemam beyond Tur, 



