Mr Nash on the Geology of Egypt. 45 



strata. This granite differs very much in quality in the same 

 rock, being in some places black and very compact, in others 

 red and porphyritic, similar to the granite of Syene. Beyond 

 this the hills diverge on either side, forming a wide amphi- 

 theatre, from which many smaller valleys proceed. This amphi- 

 theatre extends to Bir Anglaise, where the valley again contracts. 

 The left or southern boundary of this plain is composed en- 

 tirely of secondary limestone, in highly inclined strata, present- 

 ing an almost perpendicular escarpment along its whole length. 

 The dip of these strata is east, and their direction nearly north 

 and south. On the northern face this limestone is seen lying on 

 sandstone in conformable strata. This limestone contains nume- 

 rous layers and beds of flints, with an inclination conformable to 

 the stratification, and varying in thickness from a single row to 

 beds of six and ten feet deep. These flints are all fossil spon- 

 ges, alcyoniae, &c. There are also a few marine shells. The 

 similarity in the appearance of this limestone and its rows of 

 flints to the escarpments of .the chalk formation of the south of 

 England is very striking. Just before reaching Bir Anglaise is 

 a bed or dike of fossil oysters, which crosses the plain from the 

 one face of the valley to the other, rising from the surface of 

 the ground at an angle of about 35, with a dip east, conform- 

 able to the limestone, in the centre of which it was once imbed- 

 ded. This valley has, however, been traversed by a great cur- 

 rent of water, which has washed away the soft limestone rock, 

 and left the hard siliceous strata of fossils bare and solitary in 

 the midst of the plain. This dike rises in some places to the 

 height of sixty feet, while in others it is visible only a few inches 

 above the surface. 



The sandstone formation next appears, rising very distinctly 

 from beneath the limestone, having the same dip, and the same 

 angle of stratification. This sandstone varies in colour from the 

 deepest red to white, and from a hard, compact stone to a friable 

 and highly quartzose, but granular rock. In one place this 

 sandstone rests on a hill of trap, which has forced its way 

 through it, and has altered the sandstone into a dark, very crys- 

 talline rock. There is also a conglomerate of dense and silice- 

 ous blocks of sandstone, covered with a smaller pebbly conglo- 

 merate, and a stratum of grave). Beyond this sandstone come 



