DOI Page / Citation link:
https://doi.org/10.11588/diglit.14059#0028
18
Observations on Sculptured Marks,
must have been submerged, and that very energetic plutonic action
was going forward in the then bed of the sea. The remarkable fact
of the granite bursting through this modern sandstone is thus de-
scribed by Russegger:—
'■ We arrived at a iilateau 0f the Arabian Chain south-east of As-
suan. It is about 200 feet above the bed of the Nile, and consists of the
lower and upper sandstone, which are penetrated by innumerable granite
cones from 20 to 100 feet in height, arranged over the plateau in parallel
lines, very much resembling volcanic cones rising from a great cleft. The
sandstone is totally altered in texture near the granite, and has all the
appearance as if it had been exposed to a great heat. ' I cannot refrain,'
he says, ' from sujiposing that the granite must have burst, like a volcanic
product, through long wide rents in the sandstone, and that, in this way,
the conical hills were formed.' M*
An eruption of a true granite during the period of the sub-appen-
nine formations, one possessing the same mineral structure as that
we know to have been erupted during the period of the palasozoic
rocks, would be a fact of so extraordinary a kind, that its age would
require to be established on the clearest evidence, and especially by
that of organic remains in the sandstone.
Having thus ventured—I trust without any want of the respect due
to so eminent a person—to reject the hypothesis proposed by Profes-
sor Lepsius for the high levels of the Nile at Semne, indicated by
the sculptured marks he discovered, it may perhaps be expected that
I should offer another more probable explanation. If in some nar-
row gorge of the river below Semne, a place had been described by
any traveller, whore, from the nature of the banks, a great landslip,
or even an artificial dam, could have raised the bed to an adequate
height; that is, proportionate to the fall of the river, a^TTiTwas more
^TsSnt from Semne, a bar that, in the course of a few centuries,
might have been gradually washed away, I iftight have ventured to
suggest such a solution of the problem. But without any informa-
tion of the existence of such a contraction of the river's channel, or
any exact knowledge of the natural outlets and dams to running
water along the 250 miles of the Nile Valley, from Semne to As-
suan, it would be idle to offer even a conjecture. These marks are
unquestionably very difficult to account for, in the present imperfect
state of our knowledge of the structure of that portion of the Nile
Valley; and any competent geologist, well versed in the questions
of physical structure involved, who may hereafter visit Nubia, would
have a very interesting occupation in endeavouring to solve the dif-
ficulty.
7th April 1850.
* Keisen, Bd. II., I. Thl. s. 328.
Observations on Sculptured Marks,
must have been submerged, and that very energetic plutonic action
was going forward in the then bed of the sea. The remarkable fact
of the granite bursting through this modern sandstone is thus de-
scribed by Russegger:—
'■ We arrived at a iilateau 0f the Arabian Chain south-east of As-
suan. It is about 200 feet above the bed of the Nile, and consists of the
lower and upper sandstone, which are penetrated by innumerable granite
cones from 20 to 100 feet in height, arranged over the plateau in parallel
lines, very much resembling volcanic cones rising from a great cleft. The
sandstone is totally altered in texture near the granite, and has all the
appearance as if it had been exposed to a great heat. ' I cannot refrain,'
he says, ' from sujiposing that the granite must have burst, like a volcanic
product, through long wide rents in the sandstone, and that, in this way,
the conical hills were formed.' M*
An eruption of a true granite during the period of the sub-appen-
nine formations, one possessing the same mineral structure as that
we know to have been erupted during the period of the palasozoic
rocks, would be a fact of so extraordinary a kind, that its age would
require to be established on the clearest evidence, and especially by
that of organic remains in the sandstone.
Having thus ventured—I trust without any want of the respect due
to so eminent a person—to reject the hypothesis proposed by Profes-
sor Lepsius for the high levels of the Nile at Semne, indicated by
the sculptured marks he discovered, it may perhaps be expected that
I should offer another more probable explanation. If in some nar-
row gorge of the river below Semne, a place had been described by
any traveller, whore, from the nature of the banks, a great landslip,
or even an artificial dam, could have raised the bed to an adequate
height; that is, proportionate to the fall of the river, a^TTiTwas more
^TsSnt from Semne, a bar that, in the course of a few centuries,
might have been gradually washed away, I iftight have ventured to
suggest such a solution of the problem. But without any informa-
tion of the existence of such a contraction of the river's channel, or
any exact knowledge of the natural outlets and dams to running
water along the 250 miles of the Nile Valley, from Semne to As-
suan, it would be idle to offer even a conjecture. These marks are
unquestionably very difficult to account for, in the present imperfect
state of our knowledge of the structure of that portion of the Nile
Valley; and any competent geologist, well versed in the questions
of physical structure involved, who may hereafter visit Nubia, would
have a very interesting occupation in endeavouring to solve the dif-
ficulty.
7th April 1850.
* Keisen, Bd. II., I. Thl. s. 328.