on the Orgcmic Composition of Chalk a?id Chalk Marl, 375 



taken place, that the whole of the limestones of Benisuef, 

 Siout and Thebes, on the western bank of the Nile, and of 

 Cairo and Kineh (including the gray marl near Kineh), on 

 the eastern bank, and which inclose the Nile at an elevation 

 of frequently 100 to 300 feet above its level, extending along 

 the river full sixty German miles in length, are, like the 

 Nummulite limestone, composed of an inconceivable accumu- 

 lation of microscopic calcareous-shelled animalcules, which 

 are of precisely the same genera and species as those which 

 constitute the chalk of Europe. The table-land formed by 

 these calcareous rocks extends far westward into the Desert, 

 and it is perhaps principally composed of them. 



A new and unexpected light is thus thrown on these exten- 

 sive regions. The phaenomena apparent in Egypt may be 

 connected with those of Western Africa. It has been already 

 shown that the same animalcules constitute the territory of 

 Oran, stretching far along the foot of the Adas; and when we 

 consider the equality of surface which prevails in the plain of the 

 Great Desert, or Sahara, of the North of Africa, and compare 

 it with what I have myself seen along the whole extent of its 

 eastern border, as well as on a large portion of its northern, we 

 may he well permitted to think of a similarity of composition. 



But these distinct indications of a similar organic influence 

 extend not merely to the west but also to the east of Cairo, 

 expanded into Asia. The specimens collected by Dr. Hemp- 

 rich and myself from Hamam Faraun, and Tor in the Sinaian 

 portion of Arabia, which I had formerly considered as ash- 

 gray marl and yellowish-gray limestone of the tertiary epoch, 

 were now proved, by the new method of examination, to con- 

 sist of quite the same microscopic chalk animalcules as con- 

 stitute the hilly masses of Upper Egypt. And from hence 

 this formation appears to be continued eastward far into the 

 interior of the Great Desert plain, trending toward Palestine ; 

 but on the Arabian coast of the Red Sea we did not find it 

 further south than Tor, which locality alone, among all the 

 points of the east, yielded flints similar to those which occur 

 in the European chalk. 



We have here to remark on the absence of siliceous animals 

 in this limestone and marl formation, while the so-called 

 Egyptian pebbles and jaspers occupy the same position in 

 horizontal layers as the flints in the North of Europe, appear- 

 ing as their substitute. But in these jaspers the organic sili- 

 ceous elements are no longer to be distinctly found by reason 

 of their intermixture with other substances, and their conse- 

 quent opacity, giving rise to dendritic and other delineations. 

 It seems as if the solution and conversion of the organic into 

 the inorganic in the Egyptian pebbles {Cailloiix (T Egypt e) 



