| Mineralogy and Geology. 273 
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. Ou 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 
18, 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 me ills, one or 
In the basin of the Bitter lake, shells occur like those of the Red Sea, 
mong which a species of Mactra is very common. It is pro 
basin contained water: but it was fresh water which was brought there 
by the canal joining th® Nile and Red Sea. It is a controverted question 
whether the 
