On the Arabian Frontier of Egypt. 19 



theory, which was most satisfactorily refuted by MM. Le 

 Perc and Dubois- Aynie ; who produced the results of actual 

 measurements in their appendix. Descr. de I'Eg. vol. xviii., 

 Pt. i. 



A brief sketch of the physical structure of the Isthmus of 

 Suez, may here be of interest to such as are not familiar with 

 the characteristic features of this remarkable though inhos- 

 pitable tract. The survey of Messrs J. M. and G. Le Pere, 

 St Genis, and Chabrol,* furnishes the data for the dia- 

 gram illustrating this subject, Section No, 1. shewing the 

 line of tlie lowest points across the Isthmus of Suez, from 

 the present head of the Gulf to the north side of the plateau 

 in question. This line is the bottom of a valley, flanked on 

 both sides by a table-land of bai-ren rock and sand. It forms 

 an irregular trough, loner than the Red Sea in every part, ex- 

 cepting two low plateaus of very small extent. Both of these 

 w€re once only shoals extending across a narrow strait, f 

 along which the Mediterranean and Red Seas mingled their 

 waters, which then had the same level. At some period more 

 remote than historical records can reach, the gradual eleva- 

 tion of the laud must have brought up the central shoal to 

 eight feet above the water's surface, by which a natural dyke, 

 about five miles across, was formed, separating the two seas. 

 TLe northern half of the Isthmus, and the whole Delta, owe 

 their existence as dry land to the formation of this barrier. 

 For, the Mediterranean having thereby become a lai'ge in- 



tlie Ked Sea liad reached the limits assigned to it by M5I. Dubois-Ayr.ie and Le 

 Pere, it would have gone farther, and submerged all lower Egypt. Ho there- 

 fore concludes of the theory " C'est une hypothese ; tandis que Vabaisgement du 

 plateau est nn fail positif ; en effet, qu' importe le reste ?" 



In answer to M. Uoziiire, M. Le Pere gave the measurement of every station 

 of the survey across this plateau, 12 in number, jiroving that it rises 8 ftet alove 

 the liighest tides of the Red Sea; so that the elevation of that critical point, and 

 not its ilcpression, is the ^' fait positif ." Thus the sea could, and did, for perhaps 

 thousands of years, reach that limit, without the disastrous effects predicted by 

 M. Koziere. The result of these measurements are given in the section No. I., 

 wlicre the principal stations only are delineated. On so small a scale, more de- 

 tail would have produced confusion. 



* iJcscr. do TEgypte, Kt Mod., vol. xi., and App., vol. xviii., pt. 1. The lins' 

 of both sections is coloured on the map. 



t LycU's Pr, of Geology, book ii., p. 1., chap. viii. 



