﻿Vol. 6 1.] CRETACEOUS SYSTEMS OE THE NILE VALLEY. 671 



(395 metres =1296 feet wide) of great depth, occupying the site 

 of a fault or fissure in the sandstone. 1 He considered that 

 there was certainly a cataract here at the time of the Kom-Ombo 

 lake, although if the stated identity 2 of level of the lacustrine 

 beds on either side be correct, the sandstone-block intervening 

 between the two passes of the present day was probably an island 

 in the midst of a long continuous lake. Nowadays the river 

 washes the sandstone-escarpment on both banks for a distance 

 of a kilometre (=two-thirds of a mile). The Nubian Sandstone 

 of Jebel Silsila is mostly hard and massive, and it was here that 

 much of the stone for the Egyptian temples was quarried. Bands 

 of clay are almost absent, the sandstone in places having an un- 

 broken thickness of over 20 metres (65 feet). Vertical rectangular 

 jointing occurs in the rock, and evidently full advantage was taken 

 of it in quarrying. The interior of the quarries is well protected, 

 and in many instances the tool-marked faces remain astonishingly 

 fresh. Irregular bands full of round, elongated, red ferruginous 

 concretions impart to the rock a peculiar appearance in places. 



Jebel Silsila is itself of no special geological interest, being due 

 to an excessively-hard homogeneous development of sandstone, 

 with almost entire absence of thick argillaceous bands. 



(3) SilwatoEdfu. 



Here, for the first time, the unfossiliferous Nubian Sandstones and 

 shales are capped by shelly limestones and bone-beds of Campanian 

 age ; these fossiliferous beds were first recorded by Figari Bey, 3 

 some forty years ago. The northerly dip is probably not much 

 more than the general slope of the valley, and consequently the 

 series is practically identical from Silwa to Edfu, though becoming 

 less arenaceous in character as it is followed northwards. Within 

 this region the very hard metre-thick (3| feet) sandstone-beds break 

 up, leaving considerable areas of ground strewn with big blocks of 

 irregular shape, the softer clays having been extensively denuded 

 from below. The valleys running eastwards through this district 

 are evidently cut out where soft shales have existed, the areas in 

 which sandstones are thick and predominant being occupied by 

 groups of hills and spurs abutting on the cultivated lands. 



The section described on the following page was measured from 

 the village of El Atwani, in the hills about one kilometre (= two- 

 thirds of a mile) north-east of Edfu Railway-station. The mass 

 of oyster-limestone on the top of the escarpment overlooking the 

 cultivated area must be out of place, as the same bed in its true 

 position was found farther inland, where the remainder of the 

 section was measured. 



1 Peterm. Mitth. vol. xlvii (1901) p. 9. 



2 Sir William Willcocks, ' Egyptian Irrigation ' 2nd ed. (London, 1899) p. 7. 



3 ' Studii scientifici sull' Egitto & sue Adiacenze, compresa la Penisola dell' 

 Arabia Petrea ' Lucca, 1864-65. 



