O34 Correspondence—Prof. J. Prestwich. 
them at Lebrusch, on the flanks of the Moabite hills above the shore 
of the Dead Sea. I supposed, therefore, that Dr. Schweinfurth had 
found what we had failed to notice. But, on reading further, the 
matter was set at rest. It is somewhat unfortunate, and tending to 
confusion, that there are two Arabah valleys, one in the eastern part 
of upper Egypt, opening out on the Gulf of Suez, and the other con- 
necting the Gulf of Akabah with the Dead Sea and Jordan Valley. 
The former is that referred to by the African explorer, and is of 
special importance as helping to connect the geology of the Upper 
Nile Valley with that of Arabia Petreea. Dr. Schweinfurth recog- . 
nizes the identity of the beds he describes with those of the Wadi 
Nasb in the Sinaitic Peninsula, where limestone containing fossils 
of Carboniferous Limestone age, first discovered by Mr. Bauerman, 
are interposed between crystalline rocks and sandstones and other 
strata of Cretaceous age. These beds were afterwards examined by 
Col. Sir Charles Wilson and by the Members of the Expedition of 
1883—84, and the fossils brought home by them were determined 
by Prof. Sollas.' Of this identification of the beds of the Wadis Nasb 
and Arabah there can be no question, as the genera of the fossils are in 
most cases identical, and the species characteristically Carboniferous. 
The following is a section of the beds in the escarpment of the 
southern flank of the plateau of north Galala, descending to the 
bottom of the Wadi Arabah, in Upper Egypt, as given by Dr. 
Schweinfurth :— 
Summit of Escarpment ; 1400 m. above the sea. 
300 m.—Terraines Tertiaires du Parisien. 
200 m.—Terraines Tertiaires Londinien (?). 
200 m.—Banks of débris covering Cretaceous-beds of Stages Up. and Lr. Senonien, 
50 m.—Argillaceous and Marly ochreous Limestone and sandy beds with Ammonites. 
Senonien inferieur. 
250 m.—Escarpment of red Nubian Sandstone. (TZerrains Crétacés d incertains 
étages). 
(Geat Geological hiatus. ) 
2m.—Dark Sandstones with silicified wood (Araucarioxylon). Lower Carboni- 
JSerous. 
60 m.—Solid and soft Sandstones and Marls, with fragments of Crinoids, and 
Spirigera. 
1 m.—Bed of hard blue Limestone—with Crinoids, Productus, Spirifer, etc.— 
(Carboniferous Limestone). 
40 m.—Marls and Sandstone partly fossiliferous. 
Lower Carboniferous. 
(Details of beds below this not given.) 
GzoLocicaL SurvEY Orricr, Dusiin, 23 May, 1888. E. H. 
THE ATMOSPHERE OF THE COAL PERIOD. 
Str,— From the silence of your reviewer, I presume that he is 
unable to verify the assertion so often made that experiments had 
proved the improbability of plants living in an atmosphere contain- 
ing an excess of carbonic acid. As I before remarked, very few 
definite experiments had been made besides the one I have quoted 
in my work. I might, however, have referred to those made by 
1 <« Physical Geology of Arabia Petreea and Palestine,’’ Mem. Palestine Exploration 
Fund, p. 48. 
