202 Dr. W. F. Humc—Geolocji/ of Eastern Sinai. 



above sea-level, so that, if its marine origin be admitted, a differential 

 movement of at least 2,000 feet has taken place in the southern end 

 of the peninsula during comparatively recent times. 



(c) Gravels cemented by Calcite. — At the mouth of Wadi Nasb, 

 near Dahab, the gravels composed of igneous rocks are cemented 

 together by crystalline calcite developed in scalenohedra (dog-tooth 

 spar), while in the hills themselves the igneous fragments are 

 enclosed in well-marked travertine, especially in the smaller water- 

 courses. 



The theoretical deductions which maj' help to explain the presence 

 of the various types of gravels are thus summarized : — 



1. In South-Eastern Sinai earth-movements have produced three 

 high watershed lines, only one of which is now broken through. 

 If these were formed at the same period all the water draining into 

 the basin enclosed by them would collect to form nan-ow lakes. 

 This would account for — 



(a) The flat character of the plateaux. 

 (&) The absence of marine organisms. 



2. A marine depression, resulting in the invasion of the sea, and 

 amounting to at least 700 metres, is also suggested, and might 

 account for — 



(c) The oolitic beds of Wadi Hashubi. 



{d) The manganiferous gravels of Sherm. 



(e) The travertines of the higher valleys. 



(/) The calcite-cemented gravels of Nasb. 

 This hypothesis would also account for their flat character, and only 

 the absence of marine organisms prevents the absolute acceptance of 

 the view that many of these gravels were laid down beneath the 

 surface of the sea. Indeed, it is of interest to note that Mr. Beadnell 

 has obtained these calcite-cemented gravels and travertines in his 

 Nile Valley lacustrine series, thus affording an additional reason for 

 not arriving at hasty conclusions regarding the marine origin of those 

 in Sinai. 



3. A subsequent elevation, accompanied by earth - movements 

 resulting in the uptilting of the older coral-reefs, brought the 

 formation of these special features to a close, the gravels subsequently 

 formed being now distributed irregularly over the surface, in places- 

 overlying the oolite beds, and being interbedded with the younger 

 Pleistocene coral-reefs. 



II. Coral Eeefs and Raised Beaches. — This portion of the 

 paper opens with a correction of Professor Waltber's statement that 

 the Gulf of Akaba is poor in coral-reefs, it being pointed out by the 

 author that his colleague, Mr. Skill, had now practically mapped 

 continuous reefs from Dahab to Ras Muhammed. This Fringing Reef 

 and the isolated coral terraces, up to 25 metres high, standing only 

 a little way back from the sea-shore (viz. the Loioer Coral Series) , 

 are first considered, and shown to be typically Pleistocene, the 

 raised beaches which in many places line the shore being closely 

 associated with them. The Upper Coral Limestone or Older Fossil 

 Eeef of Walther, though apparently overlying the lower one, is- 



