8 Dr. John Ball— The Gulf of Suez. 



2. The occurrence of Pholas borings, discovered by Professor 

 Schweinfurth, in the slopes of the Mokattam Hills, near Cairo, at an 

 altitude of about 60 metres above the present sea-level. 



3. The occurrence of sands with an Erythraean fauna of Pliocene 

 age, near the pyramids of Giza, 64 metres above the present sea-level, 

 as shown by Beyrich and T. Fuchs. 



4. The mingling of Mediterranean and Erythraean faunas in the 

 shell-beds near Suez, as proved by the researches of Issel. 



5. The occurrence of alluvial deposits with Nile shells on the 

 Isthmus of Suez. 



6. The traces of an ancient sea-level, 60 metres above the present 

 one, near Suez, observed by Professor Hull. 



7. The raised beaches of Pleistocene age on the shores of the Gulf 

 of Suez, some of which are 158 metres above the present sea-level, 

 according to Barron and Hume's measurements. 



I shall show that all these various facts can be explained easily and 

 naturally as consequences of erosion and secular oscillation of tbe 

 earth's crust, without invoking the aid of any such catastrophic 

 changes as the letting-down of large tracts by trough -faults. 



Accepting the erosive origin of the Gulf of Suez as sufficiently 

 indicated by the considerations I have already given, we may first 

 inquire into the probable antiquity of the valley whose submergence 

 gave rise to the gulf. It cannot be older than the Miocene, for 

 Miocene beds cap hills on both coasts, and appear to have undergone 

 the folding which I have mentioned as evidence of the anticlinal 

 structure of the gulf. The earliest date possible for the commence- 

 ment of the erosion must be the latter part of the Miocene period, 

 when a great rise of the crust took place in North-East Africa, with 

 folding and faulting. This folding and faulting, far from producing 

 the Gulf of Suez by subsidence, raised the land-surface over its present 

 site. The folding probably had some part in determining the course 

 of the drain age -lines, by weakening of the folded strata; but the actual 

 valley, whose submergence at a later date was to give rise to the gulf, 

 was yet to be excavated by river-action. The erosion of the valley 

 may well have gone on during the latter part of the period of elevation, 

 as well as after it. The drainage down what is now the gulf would 

 continually cut backwards (i.e. northwards, towards what is now the 

 isthmus), gradually lowering the land-surface ; but it is clear that so 

 long as the gulf was a river- valley, the Isthmus of Suez must have 

 been relatively high land. The length of the gulf from north to south 

 is roughly 300 kilometres. Assuming that when the valley had cut 

 itself back as far as Suez, it had an average slope of 1 in 5,000 (which 

 is about twice as steep as the slope of the Nile between Cairo and 

 Aswan), the land at Suez must have been at least 60 metres above sea 

 so long as the gulf remained unsubmerged. 



Now while the Gulf of Suez was thus being eroded as a river- 

 valley, the Nile would be cutting its channel. The amounts of 

 erosion evidenced in the Nile Valley and in the gulf are of the 

 same order of magnitude, and the two valleys were most likely 

 approximately contemporaneous in origin. And if the rise of land 

 to 60 metres or more above its present level was general over the 



