Mineralogy and Geology. 



273 



5. On the Isthmus of Suez ; by M. Renaud, (L'Institut, No. 11*73 ) — 

 The greatest elevation of the isthmus of Suez above the Mediterranean 

 is 16 meters, and this extends along only for a few miles. Between this 

 higher part and the Gulf of Suez on the Red Sea, there are two depres- 

 sions, one, the basin of the Bitter Waters, dry ; the other, called Lake 

 Timsah, occupied with water which when flooded flows towards the Nile 

 along the Wady Toumilah. The height of land between these two ba- 

 sins is 1 1 meters above low tide in the Mediterranean ; and the height 

 between Lake Timsah and the Gulf of Peluse is but 9 meters. The dis- 

 tance across the isthmus in a straight line from the Gulf of Suez to the 

 Gulf of Peluse is 113 kilometers (70 miles). It is a sandy and nearly 

 barren region, to the north more gravelly. The southern half is com- 

 pletely sterile; the northern produces the vegetation peculiar to the des- 

 erts, on which the camels feed. Oil the borders of Lake Tismah, over 

 the dry parts of its bed, and on the channel leading to Wady Toumilah, 

 tamarinds grow in abundance. The sands of the isthmus are fixed, that 

 is, not movable, and there are therefore no dunes. In some places there 

 are minute disseminated crystals of gypsum, and also deposits of the 

 same 6 to 15 inches thick; in other places concretions of carbonate of 

 lime occur over the surface of the sand, and on some sand hills, one or 

 two beds of limestone having the appearance of quartz. 



In the north part of the basin where it was deepest, there is a deposit 

 of salt 7-J meters thick, struck in sounding No. 10 ; and in sounding No. 9, 

 salt was found covered by a bed of gypsum in fine needle crystallizations. 



In the region between the Bitter lake basin and the Red Sea, there 

 were encountered below the sand, compact clay, sandy clay, sand and 

 gravel, laminated clay, &c. In the second sounding, a band of calcareous 

 rock was found resting on one of sand. A marly clay was found in a 

 third sounding. But in general, the clays hardly effervesced at all with 

 acids. Beyond the Bitter lake basin there were only sands, excepting in 

 sounding 19, a band of marl. 



In the basin of the Bitter lake, shells occur like those of the Red Sea, 

 among which a species of Mactra is very common. It is probable that 

 these shells have not lived in the waters since the basin was shut off from 

 the tides of the Red Sea, since the hot climate, after such a separation, 

 would soon concentrate the waters by evaporation and so destroy all liv- 

 ing species. It is true that in the time of Strabo and Herodotus the 

 basin contained water: but it was fresh water which was brought there 

 by the canal joining the Nile and Red Sea. It is a controverted question 

 whether the lakes were yet a part of the Red Sea when the Jews under 

 Moses left Egypt. The affirmative accords best with the sacred text; but 

 then, the elevation of Suez must have taken place since that event. 



The banks ot the sea as well as the soil of the isthmus show no evi- 

 dence of marked change since the most remote periods. The sand and 

 shells of the present beach look very different from those of the interior, 

 and contain many shells not found in the latter. These seashore sands 

 have a width nowhere exceeding 100 meters. There is still more evidence 

 on the Gulf of Peluse that there has been no change of level since the 

 earliest historical period. 



SECOND SERIES, VOL. XXII, NO. 65. — SEPT., 1856. 



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