1868.] BATJEKl^rAX — AEABIl PETE2EA. 21 



bushes recall strikingly the sage-barrens of the desert in the Columbia 

 Yalley on the west side of America. 



The hills along the northern portion of the desert present no par- 

 ticular features of interest, but form a long and tolerably uniform 

 line of escarpment, not unhke that of the English Oolites or other 

 flat-bedded limestones, and are probably not more than 300 or 400 feet 

 in height. The only marked point is that known as Gebel Sudder, 

 called in addition, on the Admiralty chart, Barn Hill, which rises 

 above the entrance of Wady Sudder. 



The hills in the middle distance are those of the gravel-topped allu- 

 vium already mentioned as occurring in the same position behind 

 Moses's Wells. 



xllong the gravel-plain many detached crystals of gypsum, of small 

 size, are met with. They are tolerably perfect, and of the compound 

 arrow-head type, but usually opake in places. This may be due 

 either to exfoliation, attended probably with a partial dehydration, 

 or to a molecular change alone. 



I'^ear Wady Amara the raised beach is accompanied by patches of 

 a kind of oolite, made up apparently of rolled fragments of shells, and 

 consolidated into an extremely hard conglomerate, with a decided 

 dip towards the sea. These beds are peculiarly interesting, as bear- 

 ing on the distribution of organic remains in limestones, and appear 

 to explain why fossils are found so irregularly in diiferent quarries 

 in the same bed. In this case it is evident that the shells imbedded 

 in these consoKdated deposits have a much better chance of being- 

 preserved than those that are lying about exposed to the air and the 

 sand in the unconsolidated beach all around them. The consolida- 

 tion is probably due to the joint action of the air and the sea-water ; 

 and it is owing to the latter agent that the deposit has a seaward 

 dip. In future times, after submergence and upheaval, these coarse 

 shelly oolitic patches will most hkely appear as lenticular or false- 

 bedded masses in a more compact limestone. The consolidated 

 beaches, with Tridacna gigantca, recall forcibly to the mind of the 

 observer the Calcaire grossier of France. 



Alabaster Senes. — Approaching Wady Gharandel from the north, 

 the ground becomes more broken as the hills come nearer the sea, and 

 a line of cliff is formed by blue shaly clays, weathering to a rusty 

 brown, filled with nodules and iiTCgularly bedded masses of gypsum, 

 both in the form of selenite and dull granular alabaster. The tumbled 

 surface of the marls has been repeatedly rearranged by the forma- 

 tion of fresh masses of gypsum, deposited from solution in the same 

 manner as already noticed in describing the marls near Moses's Wells, 

 but on a much larger scale. 



The gypseous series is underlain by calcareous strata at the mouth 

 of Wady Gharandel, but extends for a considerable distance up the 

 valley. 



Wachj Taragi. — About two miles to the north and a little to the 

 eastward of this point, there is a remarkable section in a small val- 

 ley caUed by the Bedaween Wady Taragi. This is about 200 feet 

 deep, and in places more, with a breadth at the bottom of only 



