40 PKOCEEDINGS OF THE GEOLOGICAL SOCIETY. [DcC. 9, 



2. On the Occurrence of Celestine in the Nummulitic Limestone of 

 Egypt. By H. Bauerman, Esq., E.G. S, and C. Le Neve Eoster, 

 D.Sc, B.A., E.G.S. 



The fact of the occurrence of sulphate of strontia in the Eocene rocks 

 forming the great escarpment of Mokattam to the east of Cairo has 

 already been noticed by geologists, the latest and most complete 

 account being that contained in Dr. Eraas's description of the Tertiary 

 strata of Egypt *. The object of the present communication is to 

 furnish some additional particulars in connexion with the position 

 and mode of occurrence of the mineral. 



The Mokattam escarpment forms a long connected line of cliff, for 

 the most part nearly inaccessible in front, but which can be easily 

 ascended from some of the numerous lateral ravines. The 

 highest point even commands the old citadel, and has therefore been 

 fortified. The height is probably about 800 feet above the Nile ; 

 that of the citadel being 567 feet, by a single barometrical observation. 

 The beds are almost flat, having but a slight dip towards the desert. 

 In a northerly direction the hill diminishes rapidly in height until it 

 is covered by the red quartzose millstone -rock of Jebel Aehmar. 



Apart from palseontological considerations, the NummuHtic escarp- 

 ment, owing to a well-marked physical division, may be divided into 

 two parts, the white and the brown beds, the latter being the higher 

 member of the group. The lower, or white beds, are said by Dr. 

 Eigari Beyt, to rest upon tufaceous and slightly argillaceous lime- 

 stone, representing the upper part of the Cretaceous formation. 



The foUovnng is the observed section in ascending order, com- 

 mencing in a quarry at the back of the Tombs of the Caliphs, where 

 the ridge is not quite so high as it is behind the citadel $ : — 



f 1. Soft white Hm est one, compact and without joints over ft. in. ft. in. 



^ I the entire quarry-bank. Itis worked for flooring-slates 10 4' 



■^12. Buff and brown limestone, more fossiliferous than No. 1 14 10 



W J 3. Sandy marl parting 5 



4. Bluish-grey limestone with Nautili and large Nummulites 48 }- 1 16 7 



5. Eubbly oyster-bed, thickness variable 4 



6. Soft shelly beds, covered by quarry-rubbish 9 



7. White limestone, seamed with brown streaks 30 0^ 



8. Compact brown sandy limestone, the upper part cindery, 

 containing celestine 4 



9. Marls, with fibrous gypsum (have been worked) 4 5 



10. Hard, brown, sandy limestone, with casts of fossils 3 9 



1 1 . Variegated yellowish-brown and white sand 4 



I ■{ 12. Hard, brown limestone, much honeycombed 5 3 . r-y, « 



^ 13. Sand and shale...... 2 0^^^ ^ 



14. Hard brown stone, like No. 12 3 10 



15. Brown honeycombed limestone, irregularly bedded, with 

 sand and brown iron-ore interspersed 22 5 



\^ 16. Brown beds like No. 15, but more calcareous 5 J 171 



* Aus dem Orient, Stuttgart, 1867. 



t Studi scientifici sull' Egitto, vol. i. p. 136. 



t The character of these rocks varies rapidly in a short distance. The height 

 of the section in the escarpment behind Old Cairo is about 400 ft. ; and the 

 white and brown beds are separated by nearly 100 ft. of gypseous shales with 

 nodules of pyrites, which have been changed into brown iron-ore and gypsum. 

 The dip is generally N. 70° E. at an angle of from 3° to 5°. 



