Mentis. Barron ^' Ilionc — Eastrvn Desert of E<ji/iit. 



•JO 



out in a fan-shaped delta at its mouth. Although ahundant in 

 this wadi, the^'^ are unknown in the side-valleys, even where they 

 are now connected with the igneous hills. Tiie explanation of this 

 is as follows : — East of Qena the Eocene plateau has heen hrokeu 

 up into a series of outliers, which until quite recently were connected 

 by a long ridge, the sole break being that where Wadi Qena passes 

 between the main plateau and the outlier of Abu Had. Previous 

 to the formation of the latter fracture, the southern end of Wadi 

 Qena was a bay, in which flint containing conglomerates and Pliocene 

 limestones were being deposited, but when the above-mentioned gaj* 

 was formed, the drainage from the Red Sea Hills passed through to 

 the Nile Valley. Similar gravels cover the Red Sea Coast-plahi. 

 The age of these beds has now been shown to be Post-Pliocene, 

 as there is a marked unconformity between theui and the latter, 

 and also because on the Coast-plain they are found underlying and 

 overlying limestones containing Pleistocene fossils. 



This throws a strong light on the age of the Nile. Mr. Beadnell 

 found these gravels on the western side of the valley, and they are 

 apparently continuous under the Nile alluvium, thus showing that 

 the Nile as a river is later than these gravels, and could not have 

 begun to flow until late Pleistocene times. These gravels are alsa 

 suggested as the origin of the igneous pebbles reported by Professor 

 Judd in the Royal Society's boring at Zaqaziq. All the rocks 

 mentioned can be matched from the gravels near Qena. (Since thi;' 

 paper was read similar pebbles, but worn thin as by long rolling,^ 

 have been found in cuttings in the lake deposits to the north of 

 Heluan.) The theory of the derivation of the pebbles from the 

 northern part of the Red Sea Hills is untenable, as it is known that 

 Wadi Qena received all the drainage from that area in early 

 Pliocene times. 



These gravels are believed to have been deposited in a fresh-water 

 lake, a series of which were formed as the sea retreated down the 

 Nile Valley. 



1. (6) Baised Beaches and Coral Reefs.— Five series are recognized, 

 of which the youngest is below sea-level, their succession being as 

 follows : — 



(1) The coral reefs at present forming in the Red Sea. 



(2) The raised beaches and lower coral reefs which flank the coast, 



varying in height from near sea-level to 2o metres above 

 the sea. . .. 



(3) A higher coral reef series on an average four to seven kilo- 



metres from the sea, and at various levels between Ho and 

 170 metres. 



(4) A disturbed coral reef dipping 20 degrees eastward, closely 



related to the previous one. 



(5) An old coral reef in which the affinities are as mucli 



Mediterranean as Erythranvn, regarded at present as Miocene. 



Along the shore ' storm-beaches ' are common ; in some places the 



shells form well-marked zones; while the higher beaches and reels 



