1868.] BAUEEMAN AEABIA PETRiEA. 27 



350 to 400 feet more. The top of the hill is capped by a thin lime- 

 stone, from 8 to 15 feet in thickness, which is tolerably persistent on 

 the northern side of the district. It is usually grey or light brown, 

 very crystalline, and at times much resembling spathic iron-ore. It 

 contains a few obscure fossils, chiefly encrinite stems and rings, with 

 a few imperfect sections of cups ; and, according to Mr. Etheridge, 

 these are to be referred to Triassic forms. Mr. Salter, on the other 

 hand, states that they are Carboniferous, including forms of the ge- 

 nera JRhodocrinus and Poteriocrinus, and that they are associated with 

 the spiral imivalves Murcliisonia and possibly Eulimci. 



The thin limestone-beds are covered by other sandstones similarly 

 false-bedded to those below, but of a lighter colour, and they form 

 the highest rocks in the IS'asb district ; but further south, in "Wady 

 ISTagb el Bedra, they are succeeded by beds of Cretaceous age. 



Age of the Sandstone. — The same series of sandstones has been 

 described by other geologists as occurring in Egypt and ISTubia under 

 similar conditions, i. e. between older crystalline schists below and 

 undoubted Cretaceous beds above. Eussegger calls it " Nubian Sand- 

 stone," colouring and describing it as Lower Cretaceous in his maps 

 of Egypt, Nubia, and Arabia Petrsea. The text, however (Reisen, 

 vol. ii. pt. 1. p. 570), contains no positive statement to the above 

 effect, but only says that the beds in question are not younger than 

 the Lower-Cretaceous period. 



Figari Bey describes the tripartite arrangement of the series (two 

 great masses of sandstone, mth a thin limestone between them) as 

 occurring in Egypt, Sinai, and in the neighbourhood of Akaba ; and 

 in the latter place he states the total thickness to be about 850 feet *. 

 He assigns the whole to the Trias, taking the limestone as repre- 

 senting the Muschelkalk, although the evidence for this determina- 

 tion (other than lithological character) is not very clear. The only 

 fossil mentioned is a goodi-sizeA Ammonite, not named specifically, but 

 said to approximate in character to a Triassic form f. I have con- 

 formed to this view, without, however, wishing to express any very 

 decided opinion on the subject, owing to the great want of evidence. 



Manganese-bed of Nash. — The thin limestones capping the hill are, 

 on the western side of Wady Nasb, thrown down to the bed of the 

 watercourse by a fault running nearly north and south. On both 

 sides they are commonly associated with ores of iron and manganese, 

 which run in a nearly continuous bed of varying thickness, as a chain 

 of pockets or lenticular deposits, over the greater j)art of the district. 

 The mineral usually consists of a compact brown hoematite, jDassing, 

 by admixture of quartz, into an iron -jasper or extremely ferruginous 

 sandstone. Some of the larger beds, which are from 5 to 8 feet 

 thick, contain compact and mammillated brown hsematite in large 

 masses, with small, but beautifully transparent, crystals of gothite 

 in the hollows. Pyrolusite is also found in considerable quantities 

 in places, usually in large nodular masses, enclosed in the iron-ore 

 and associated with psilomelane. The base of the cliff, throughout 



^' Studii scientifici suU' Egitto e sue adjaccnze, torn. ii. p. 550. 

 t Ibid. torn. i. p. 14G. 



