115 



PROCEEDINGS 



OP 



THE GEOLOGICAL SOCIETY. 



POSTPONED PAPER. 



Geological Description of the First Cataract, Upper Egypt. 

 By JoB2f Clarke Hawkshaw, Esq., B.A., F.G.S. 



(Eead December 5, 1866*.) 



[Plate IV.] 



The following remarks are written with a view to describe the geo- 

 logical features of the First Cataract, and to illustrate the locali- 

 ties of the accompanying specimens f ? which, with the exception of a 

 few from the neighbourhood of Cairo and a few from other places, 

 were collected by the author during a month's stay on the Island of 

 Sehayl, at the First Cataract of the Nile, near Assouan, Upper Egypt, 

 in the spring of 1865. The accompanying map (PI. lY.) is for the 

 most part taken from a survey of the district made during the author's 

 stay there, the river WHq being represented at a time when it was 

 nearly at its lowest level. 



The First Cataract commences at the southern extremity of the 

 Island of Hesseh, and includes the portion of the river extending 

 thence to the Island of Elephantine opposite Assouan, a distance 

 of about six miles : throughout this district the river is generally 

 divided into two principal branches by the Islands of Hesseh, 

 Sehayl, Soulujie, and Elephantine. One branch, that to the east- 

 ward, flows at a higher level than the other or western branch ; and 

 the two communicate by some considerable streams and by innumer- 

 able small ones until they unite for a time at the southern end of 

 the Island of Sehayl, where the actual rapids cease. The difference 

 of level between the two branches at the north of the Island of Hesseh 

 is 10 feet ; and at this point an artificial cut was made by Mohammed 

 Ali, the faU being distributed over a length of about 200 yards. 

 The whole faU of the river from the south of the Island of Hesseh 

 to the south of Sehayl, a distance of upwards of four miles, is 15 

 feet at low Nile and 12^ feet at high Nile. In no one of the rapids 

 which form the so-called ^' Cataracts " of the Nile does the faU 

 exceed 3| feet, which is spread over a length of 20 yards or more, 

 with the exception of Mohammed All's cut mentioned above. Many 



* For the other communications read at this Evening-meeting, see p. 38. 

 t Deposited in the Society's Museum. 



