John Milne — Geological Notes on Cairo. 361 



The entrance to this valley is narrow, being bounded on the right 

 and left by cliffs of limestone, which dip at a low angle up the 

 valley, those on the right being about 50 feet in height, and those on 

 the left from 20 to 30 feet. As the valley gradually widens, to a 

 breadth of about half a mile, the cliffs and hills which form a scarp to it 

 become lower. Covering the ground over which you walk are frag- 

 ments of gypsum sparkling in the sand, as mica often does in the 

 gravels of our streams, which probably indicate the presence at some 

 point higher up the valley of the sand-beds seen above the Citadel 

 Quarry. Opposite to the termination of the tramway, which is 

 about half a mile up the valley, upon the right-hand side of the 

 road, there is a knoll of black stones, in the distance something like 

 a low volcanic cone. This is made up of a similar but darker 

 coloured rock to that of Jebel Achmar, and in fact apparently marks 

 the eastern boundary line of this red quartzose formation, which 

 forms several outcrops, and appears to run up the right-hand side of 

 this valley. 



Keeping to the right hand at all junction of tracks, you pass 

 along the foot of the limestone hills, whilst opening out upon the 

 left there is a wide flat plain, which shortly narrows into a flat 

 valley. Near the head of this, many black masses of quartzite, 

 similar to the one just mentioned, are seen, covering portions of the 

 hills. If a line were drawn passing through these heaps of debris, 

 it would take a N.W. direction towards the Eed Hills. 



At the first of these mounds there is a ridge of the material, which 

 is apparently turned on end, the left-hand side of which is quite a 

 dark-coloured flint ; whilst the right-hand side cannot be distinctly 

 seen, from the quantity of debris which has fallen from above upon 

 it, amongst which there are several large fragments of silicified 

 wood. 



Standing up from a sandy rock on the west or Cairo side of this 

 ridge, there are a number of short cylinders, averaging six inches in 

 length to one inch in diameter, formed of concentric layers of sand, 

 the structure of which is seen in a transverse fracture. 



Near the head of this valley, at the entrance to a small cutting 

 into the hills upon the right, the relation of the limestones *to one of 

 these siliceous ridges is to be seen. This, like the others, strikes in 

 the direction of the Red Hills, dipping at an angle of about 80° to 

 the N.E., upon that side it is a fine-grained siliceous rock, from 

 which it graduates in a thickness of only two feet through a pudding- 

 stone, into a soft quartzose sandstone upon the N.E. 



Coming down the cutting upon this side are some narrow bands 

 of limestone, overlying beds of sand, also dipping to the N.E., but 

 only at about 5° or 6°, which, but for the intervention of a few feet of 

 sandy material, would apparently be seen to abut against the up- 

 turned ridge. 



A short distance beyond this last-mentioned ridge the track turns 

 sharply to the right, and enters, between sloping masses of red rock, 

 into a large opening, resembling a shallow sand-pit, above which is 

 the Petrified Forest. 



