John Milne — Geological Notes on Cairo. 357 



Beckoning from the walls of the Citadel, near which the excava- 

 tions originally commenced, the hill has been cut back for a distance 

 of about half a mile. The workings of the quarry are carried on 

 along the face of three scarps, which, in conjunction with its semi- 

 circular form, give to it the appearance of an amphitheatre. Entering 

 the quarries from the rear of the Citadel, the road divides ; the lower 

 branch leading into what might form the arena of a theatre (Fig. 

 3, A.), the lowest part of the quarry, 350 feet below the summit of 

 the hill; the upper branch, after running a short distance towards 

 the rear of the quarries, in its turn also splitting into two branches ; 

 one of which (Fig. 3, B.) leads along the base of the second scarp, 

 forty feet above the lowest part of the quarry : whilst the other 

 (Fig. 3, C), after winding round the end of the quarry at from 

 80 to 90 feet above its lowest point, turns to the left, and passing 

 through a narrow valley opposite to the Citadel, gradually ascends 

 to the summit of the hill. 



These different roads and levels are referred to in Section Fig. 2, 

 and Plan Fig. 3, by corresponding letters. 



A striking feature in this quarry is the immense blocks of stone 

 which are scattered about in all directions. One of them, in the 

 upper road C, in measurement was found to be 57 feet long, 18 feet 

 high, and 18 feet thick, representing about 1400 tons of stone; and 

 from one point on the road I counted upwards of forty blocks ap- 

 proximating to, and in many cases perhaps exceeding, the dimensions 

 of the one just quoted. These blocks, which have been obtained by 

 the undermining of the cliff, aided by natural vertical joints, now 

 form small quarries in themselves, being more readily worked and 

 broken in upon than the upright face of the cliff from which they 

 were detached. Where these cliffs have been worked in upon, 

 several large caves have been produced, the positions of which are 

 indicated in Plan, Fig. 3. One of these shows a flat roof, about 30 

 or 40 feet in height, and 90 feet in an unsupported span. 



Standing at a distance, and looking at the range of hills in which 

 these quarries occur, it will be seen that there is a marked differ- 

 ence in colour between the rock forming the cap or head of the 

 mountains and that exposed in the cutting below — the upper strata 

 being reddish, w^hilst the lower ones are white, which at once suggests 

 the idea, which has been followed out by previous observers, of 

 dividing the beds, according to their physical aspects, into Brown 

 Beds and White Beds. The thickness of the former beds behind 

 the Citadel, as estimated by aneroid, is about 125 feet ; whilst the 

 exposure of the White Beds, from the junction with the Brown 

 Beds above to the foot of the quarry, is about 225 feet. 



These measixrements may be compared with those of a section of 

 the same beds taken about a mile and a half to the north, given in the 

 paper by Messrs. Bauerman and Foster previously mentioned, from 

 which it will be seen that behind the Citadel the Brown Beds have in 

 so short a distance more than doubled their thickness. 



Looking at these Brown Beds generally, it will be seen that their 

 surface is much weathered and decomposed, and forms a reddish soil, 



