24 J. MILNE ON THE SINAITIC PENINSULA AND N.W. AKABIA. 



Rocks from between Akaba and the Till Plateau : — 



1. Quartz porphyry with a green felsitic base, through which crystals of 



porphyry are disseminated. 



2. Red porphyry. 



3. Brown felsitic quartz porphyry. 



4. Reddish brown porphyry. 



5. Light-green porphyry. 



6. Reddish purple porphyry. 



7. Porphyry like ISo. 6, but with white crystals of felspar. 



8. Basalt, of a dark green colour and thoroughly degraded. 



9. Red quartz porphyry. 



10. Greenish grey porphyry, much decomposed. 



11. Altered pyromeride, of a yellowish colour, and with a mamillated surface. 



A short distance further up this wady, at an elevation of about 

 1200 feet, the road suddenly turns to the left through a narrow 

 gorge of chalk cliffs, and then ascends by a steep, zigzag, artificially 

 formed pathway to the plateau of the Tih. 



Both on the right and left side of this defile good exposures of 

 cliff-sections are to be seen, in which there are several inaccessible 

 cave-like openings. The rock, as before, is lithologically a chalk, 

 containing numerous bands of flint. 



These bands, which can be broken out in large slabs, the upper 

 and lower surfaces of which are gently rounded into smooth un- 

 dulating surfaces, average about 4 inches in thickness, and occur at 

 about the same distance apart. Although they can be detached in 

 large flat masses, through the number of vertical cracks by which 

 they are traversed, they split into fragments when struck. 



On the surface of this chalk rock, in one or two places, a slight 

 efflorescence of common salt can be detected — an indication, perhaps, 

 of the existence of larger quantities in the neighbourhood. 



About 80 or 100 yards up the gorge the chalk rocks suddenly 

 terminate, and abut against the almost perpendicularly downturned 

 beds of a yellowish rusty-looking limestone, the juncture of the 

 two apparently marking the line of a N.N.E. fault. 



In these yellow limestones flints were seen, and fragmentary 

 fossil remains were common. All exposed surfaces of this rock are 

 much eroded and weathered. In several large blocks which had 

 fallen from some bands in the upper portion of this cliff-like 

 exposure, small crystals of brown oxide of iron (pseudomorphs of 

 iron pyrites in combinations of the cube and octahedron) were 

 common. 



At an elevation of 1800 feet, or 600 feet above the gorge, a 

 bluish grey, compact, fine-grained limestone is met with, in which 

 numerous sections of Nerinoea are to be seen. A few small cavities 

 filled with minute scalenohedral forms of calcite indicated the exist- 

 ence of other fossil forms. 



At 2000 feet there is an exposure, about 40 feet in thickness, 

 of yellowish earthy bands, containing narrow veins of gypsum from 

 1 to 2 inches in thickness, forming a cap to the Nerincea-limesione. 



Prom this there is a descent of about 100 feet into a small open 

 plain, in which there are numerous exposures of a pinkish red (or 



