790 
Nile and the Red Sea, forming the anticlinal axis (lat. about 26° N.); 
and according to M. Trivin, still further north in the same desert, in 
about the latitude of Benisuof (29° 10’N.). This locality, Mr. New- 
bold thinks, may be that mentioned by Savary. Sir G. Wilkinson has 
likewise traced them to lat. 28° 26’, where they form the peak of Gebel 
Tenaset; and the same author states that the extreme height attained 
by these rocks in Gebel Gharib (lat. 28° 10’) is 5000 feet above the 
sea. 
Respecting the relative period of their elevation, Mr. Newbold is 
of opinion that it was subsequent to the deposition of the inferior 
sandstone and limestone which occur on their flanks in inclined strata, 
and prior to that of the superior horizontal sandstone. He is like- 
wise of opinion that the plutonic rocks were upheaved through once 
continuous solid strata of sandstone and limestone, on account of the 
absence of granitic veins in those deposits and the occurrence of 
breccias along the junction line of the igneous and sedimentary for- 
mations. He carefully examined the limestone and sandstone for 
imbedded pebbles derived from the granite or syenite, but without 
success. Granitic veins penetrate the gneiss. 
9. Alluvial Accumulations.—These deposits Mr. Newbold describes 
under, Ist, the mud of the Nile, and 2ndly the Delta; but he alludes 
also to the vegetable soil of the Oases, to the detrital soil washed 
down from the rocks, and to the greyish soil accumulated generally 
around the ruins of ancient cities, due partly to the decay of animal 
and vegetable matter, partly to the mouldering ruins ; likewise to the 
ammoniacal and nitrous salts formed in the deserts where caravans 
have halted, and which have been collected from the earliest times. 
(i.) Mud of the Nile-—This accumulation varies with the nature 
of the formations over which the Nile flows, and is therefore, Mr. 
Newbold. observes, not merely the result of the spoils of Abyssinia. 
To this cause he also ascribes the discrepancies in the analyses of the 
mud. Above Thebes, below the granitic and sandstone formations 
of Nubia, and on the southern limit of Egypt, it contains more silex 
and less calcareous or argillaceous matter than at Cairo, which stands 
on the great limestone deposit, and in the Delta, which rests on that 
formation. It varies also in texture and composition, according to its 
position relative to the main channel of the river and the force of 
the current. The finest mud, as that of Ghennah, is generally dark 
brown passing to lighter shades; it is also highly tenacious, reten- 
tive of moisture, effervesces, and fuses per se, with extrication into 
a greenish glass. The annual deposit or layer varies in thickness in 
the same situation from an inch to a few lines, the upper part being 
generally lighter than the lower; and each layer is separable from 
that above or beneath it; but the deposition of one year is frequently 
removed by the flood of the next. 
Mr. Newbold does not knowif the thickness of the mud in the centre 
of the river’s bed has been ascertained; the greatest accumulation in 
a transverse section being near the stream’s channel ; but in Upper 
Egypt he has measured clifis composed of it forty feet in height; 
and the average thickness in Middle Egypt is thirty feet, while at 
