Lieut. Newbold on the Geology of Egypt. 223 
mediate vicinity; and 2ndly, the gravel beds which cover the raised 
coral beach of Kossier and the limestone clifls of the Red Sea near 
the Jaffatine group, also the detritus resting on the elevated platform 
of the Libyan desert near Dendera, the materials composing the 
whole of which consist of far-transported plutonic and metamorphic 
pebbles, intermingled with others derived from adjacent formations. 
8. Volcanic Rocks.—After alluding to the supposed volcanic 
cones or extinct craters in the desert between Cairo and Suez, and 
to others said to exist in the vicinity of Dakkeh, situated in the 
Nubian desert 69 miles from Syene, Mr. Newbold proceeds to de- 
scribe the trap and porphyry dykes which in Upper Egypt penetrate 
all the rocks from the lower sandstone to the granite, and have been 
already noticed in the account of the formations through which they 
pass; the author, however, observes in addition, that the relative age 
of the trap is defined by the upper or fossil-wood sandstone being 
undisturbed, and by its sometimes containing pebbles of the trap. 
Granitic or syenitic rocks are of rare occurrence in Egypt, ap- 
pearing only at the cataracts of Syene, and in the desert between the 
Nile and the Red Sea, forming the anticlinal axis(lat. about 26° N.); 
and according to M. Trivin, stiJl 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 
