1868.] BATJERM AN— ARABIA PETR^A. 37 



view is furnished by the decided unconformity of the limestone upon 

 the greensand in the Gharabi escarpment — although too much stress 

 must not be laid on this point, owing to the number of faults run- 

 ning parallel with the escarpment, some of which may have some- 

 thing to do with the apparent unconformity. The ordinary rule of 

 geological reasoning would perhaps be best satisfied by putting the 

 whole of the chalky beds with flints into the Nummulitic series, as, in 

 addition to the Nummulitic form near Gharandel, the few small fossils 

 found in Wady Taibe, Wady Husseid, and the Marcha are, for the 

 most part, when recognizable, Tertiary forms. As far as I can gather 

 from books, a somewhat similar difficulty is experienced in Eg}^3t, 

 where the upper line of the chalk is rather arbitrarily drawn at 

 certain soft limestones which are not very different in character, ex- 

 cept as regards their fossils, from the lower IsTummulitic beds imme- 

 diately next in succession. This makes it probable that the transi- 

 tion from the Cretaceous to the Tertiary period in these regions was 

 not marked by any great break physically, the beds immediately 

 before and after the change having been accumulated under similar 

 conditions ; and probably in the Eed Sea at the present day the beds 

 accumulating are of an essentially chalky nature. In more recent 

 times, however, a great break must have occurred between the JSTum- 

 muKtic and the flint- conglomerate formations, as the latter is entirely 

 made up of the waste of the rocks immediately preceding it ; and 

 how considerable this waste must have been is evidenced in the 

 ridge of Abooalagha, where a mass of strata, about 600 feet thick, 

 is about half composed of conglomerates, none of which contain a 

 single pebble that can be referred to the New Red Sandstone, all 

 being of flints. 



After leaving the New Red Sandstone in Wady Ferran, the whole 

 of the country up to the convent of St. Katherine, in Sinai, with the 

 exception of the fossiliferous alluvium in Wady el Scheick, is made 

 up of crystalline and metamorphie rocks, which will not be further 

 alluded to here, as I hope to make them the subject of a future 

 communication to the Society. 



Conclusion. — The order of succession of the rocks mentioned in 

 the foregoing account may be summarized as follows, in ascending 

 order: — 



1. Gneiss and granites. 



(1. Lower E,ed Sandstones, 

 2. Limestone with encrinites. 

 3. Upper Brown Sandstone. 



3. Cretaceous rocks. Green saiids with Echinoderms, sandy limestones, and 



shales. 



[■ Lower part possibly Cretaceous. 



4. White Hmestone with flints. •< Upper part bituminous, with Nummu- 



L lites. Eocene. 



5. Flint-conglomerate with corals. Miocene. 



6. Great gypseous series of Wady Taragi. 



7. Reconstructed gypseous series and conglomerates. 



8. Raised beaches and Miliolitic Limestones. 



9. Alluvium and Desert Drift. 



Yolcanic rocks appear at two periods ; the older are post-Triassic 



