Chapter XLIX: Appendix: (A, p. 239.)

_Observations on the Discovery, by_ Professor LEPSIUS, _of
Sculptured Marks on Rocks in the Nile Valley in Nubia; indicating
that, within the historical period, the river had flowed at a
higher level than has been known in Modern Times._ By LEONARD
HORNER, Esq., F.R.S.S. L. & E., F.G.S., &c. (_This paper is here
reprinted[376] at the request of_ Professor LEPSIUS.)

The recent archaiological researches of Professor Lepsius in Egypt, and the Valley of the Nile, in Nubia, have given a deserved celebrity and authority to his name, among all who take an interest in the early history of that remarkable portion of the Old World. While examining the ruins of a fortress, and of two temples of high antiquity at Semne, in Nubia, he discovered marks cut in the solid rocks, and in the foundation-stones of the fortress, indicating that, at a very remote period in the annals of the country, the Nile must have flowed at a level considerably above the highest point which it has ever reached during the greatest inundations in modern times. This remarkable fact would possess much geological interest with respect to any great river, but it does so especially in the case of the Nile. Its annual inundations, and the uniformity in the periods of its rise and fall, have been recorded with considerable accuracy for many centuries; the solid matter held in suspension in its waters, slowly deposited on the land overflowed, has been productive of changes in the configuration of the country, not only in times long antecedent to history, but throughout all history, down to the present day. Of no other river on the earth’s surface do we possess such or similar records; and, moreover, the Nile, and the changes it has produced on the physical character of Egypt, are intimately associated with the earliest records and traditions of the human race. Everything, therefore, relating to the physical history of the Nile Valley must always be an object of interest; but the discovery of Professor Lepsius is one peculiarly deserving the attention of the geologist; for he does not merely record the facts of the markings of the former high level of the river, but he infers from these marks that since the reign of Mœris, about 2200 years before our era, the entire bed of the Nile, in Lower Nubia, must have been excavated to a depth of about 27 feet; and he further speculates as to the process by which he believes the excavation to have been effected.

It will be convenient, before entering upon the observations I have to offer upon the cause assigned by Professor Lepsius for the former higher levels of the Nile indicated by these marks, that I should give the description of the discovery itself, by translating Dr. Lepsius’s own account of it, in letters which he addressed to his friends, Professors Ehrenberg and Böckh of Berlin, from the island of Philæ, in September, 1844[377].

“You may probably remember, when travelling to Dongola on the
Lybian side of the Nile, and in passing through the district
of Batn el hagér, that one of the most considerable of the
cataracts of the country occurs near Semne, a very old fortress,
with a handsome temple, built of sandstone, in a good state of
preservation; the track of the caravan passing close to it,
partly over the 4000-year-old artificial road. The track on the
eastern bank of the river is higher up, being carried through the
hills; and you must turn off from it at this point in order to
see the cataract. This Nile-pass, the narrowest with which I am
acquainted, according to the measurement of Hr. Erbkam, is 380
metres (1247 English feet) broad[378]; and both in itself, and
on account of the monuments existing there, is one of the most
interesting localities in the country, and we passed twelve days
in its examination.

“The river is here confined between steep rocky cliffs on both
sides, whose summits are occupied by two fortresses of the most
ancient and most massive construction, distinguishable at once
from the numerous other forts, which, in the time of the Nubian
power in this land of cliffs, were erected on most of the larger
islands, and on the hills commanding the river. The cataract
(or rapid) derives its name of Semne from that of the higher of
the two fortresses on the western bank; that on the opposite
bank, as well as a poor village lying somewhat south of it, is
called Kumme. In both fortresses the highest and best position is
occupied by a temple, built of huge blocks of sandstone, of two
kinds, which must have been brought from a great distance through
the rapids; for, southward, no sandstone is found nearer than
Gebel Abir, in the neighbourhood of Amara and the island of Sai
(between 80 and 90 English miles), and northward, there is none
nearer than the great division of the district at Wadi Halfa (30
miles distant).

“Both temples were built in the time of Tutmosis III., a king
of the 18th dynasty, about 1600 years before Christ; but the
fortresses in which they stand are of a more ancient date. The
foundations of these are granite blocks of Cyclopian dimensions,
resting on the rock, and scarcely inferior to the rock itself
in durability. They were erected by the first conqueror of the
country, King Sesurtesen III., of the 12th Dynasty, in order
to command the river, so easily done in so narrow a gorge. The
immediate successor of this king was Amenemha III., the Mœris of
the Greeks: he who accomplished the gigantic work of forming the
artificial lake of Mœris, in the Fayoum, and from whose time—the
most flourishing of the whole of the old Egyptian kingdom—the
risings of the Nile in successive years, doubtless by means of
regular markings, as indeed Diodorus tells, remained so well
known, that, according to Herodotus, they were recorded in
distinct numbers from the time of Mœris. It appears that this
provident king, occupied with great schemes for the welfare of
his country, considered it of great importance that the rising
of the Nile on the most southern border of his kingdom should be
observed, and the results forthwith communicated widely in other
parts of the land, to prepare the people for the inundations. The
gorge at Semne offered greater advantages for this object than
any other point; because the river was there securely confined
by precipitous rocky cliffs on each side. With the same view
he had doubtless caused Nilometers to be fixed at Assuan and
other suitable places; for without a comparison with these, the
observations at Semne could be of little use.

“The highest rise of the Nile in each year at Semne, was
registered by a mark, indicating the year of the king’s reign,
cut in the granite, either on one of the blocks forming the
foundation of the fortress, or on the cliff, and particularly
on the east or right bank, as best adapted for the purpose. Of
these markings eighteen still remain, thirteen of them having
been made in the reign of Mœris, and five in the time of his two
next successors. These last kings discontinued the observations;
for, in the mean time, the irruption of the Asiatic pastoral
tribes into Lower Egypt took place, and well-nigh brought the
whole kingdom to ruin. The record is almost always in the same
terms, short and simple: _Ra en Hapi en renpe_ ... mouth or gate
of the Nile in the year.... And then follows the year of the
reign, and the name of the king. It is written in a horizontal
row of hieroglyphics, included within two lines—the upper line
indicating the particular height of the water, as is often
specially stated—

“The earliest date preserved is that of the sixth year of the
king’s reign, and he reigned 42 years and some months. The next
following dates are, the years 9, 14, 15, 20, 22, 23, 24, 30, 32,
37, 40, 41, and 43; and include, therefore, under this king, a
period of 37 years. Of the remaining dates, that only of the 4th
year of his two successors is available; all the others, which
are on the west or left bank of the river, have been moved from
their original place by the rapid floods which have overthrown
and carried forward vast masses of rock. One single mark only,
that of the 9th year of Amenemha, has been preserved in its
original place on one of the building stones, but somewhat below
the principal rapid.

“We have now to consider the relation which these—the most
ancient of all existing marks of the risings of the Nile—bear to
the levels of the river in our own time. We have here presented
to us the remarkable facts, that the highest of the records now
legible, viz., that of the 30th year of the reign of Amenemha,
according to exact measurements which I made, is 8·17 metres (26
feet 8 inches) higher than the highest level to which the Nile
rises in years of the greatest floods; and further, that the
lowest mark, which is on the east bank, and indicated the 15th
year of the same king, is still 4·14 metres (13 feet 6½ inches):
and the single mark on the west bank, indicating the 9th year, is
2·77 metres (9 feet) above the same highest level.

“The mean rise of the river, recorded by the marks on the east
bank, during the reign of Mœris, is 19·14 metres (62 feet 6
inches) above the lowest level of the water in the present day,
which, according to the statements of the most experienced
boatmen, does not change from year to year, and therefore
represents the actual level of the Nile, independently of its
increase by the falls of rain, in the mountains in which its
sources are situated. The mean rise above the lowest level,
at the present time, is 11·84 metres (38 feet 8 inches); and,
therefore, in the time of Mœris, or about 2200 years before
Christ, the mean height of the river, at the cataract or rapid of
Semne, during the inundation, was 7·30 metres (23 feet 10 inches)
above the mean level in the present day.”

Such are the facts recorded by Dr. Lepsius; and then follow, in the same letter, his views as to the cause of the remarkable lowering of the level of the river.

“There is certainly no reason for believing,” he says, “that
there has been any diminution in the general volume of water
coming from the south. The great change in the level can,
therefore, only be accounted for by some changes in the land,
and these must also have altered the whole nature of the Nile
Valley. There seems to be but one cause for the very considerable
lowering of the Nile; namely, the washing out and excavations of
the catacombs (_Auswaschen und Aushölen der Katakomben_[379]);
and this is quite possible from the nature of the rocks
themselves, which, it is true, are of a quality that could not
well be rent asunder, and carried away by the mere force of the
water, but might be acted upon directly by the rising of the
water-level, and the consequent effects of the sun and air on
the places left dry, causing cracks, into which earth and sand
would penetrate, which would then give rise to still greater
rents, until, at last, the rocks would of themselves fall in, by
having been hollowed out, a process that would be hastened in
those parts of the hills where softer and earthy beds existed,
and which would be more easily washed away. But that, in
historical times, within a period of about 4000 years, so great
an alteration should take place in the hardest rocks, is a fact
of the most remarkable kind—one which may afford ground for many
other important considerations.

“The elevation of the water-level at Semne must necessarily have
affected all the lands above; and, it is to be presumed, that
the level of the province of Dongola was at one time higher, as
Semne cannot be the only place in the long tract of cliffs where
the bed of rock has been hollowed out. It is to be conceived,
therefore, that not only the widely-extended tracts in Dongola,
but those of all the higher country in Meröe, and as far up
as Fasogle, which, in the present day, are dry and barren on
both sides of the river, and are with difficulty irrigated
by artificial contrivances, must then have presented a very
different aspect, when the Nile overflowed them, and yearly
deposited its fertile mud to the limits of the sandy desert.

“Lower Nubia also, between Wadi Halfa and Assuan, is now arid
almost throughout its whole extent. The present land of the
valley, which is only partly irrigated by water-wheels, is, on
an average, from 6 to 12 feet higher than the level to which the
Nile now rises; and although the rise at Semne might have no
immediate influence upon it, yet what has occurred there makes
it more than probable that at Assuan there was formerly a very
different level of the river, and that the cataracts there, even
in the historical period, have been considerably worn down. The
continued impoverishment of Nubia is a proof of this. I have no
manner of doubt that the land in this lower part of the valley,
which, as already stated, is at present about 10 feet above the
highest rise of the Nile, was inundated by it within historical
time. Many marks are also met with here, that leave no doubt
regarding the condition of the Nile Valley antecedent to history,
when the river must have risen much higher; for it has left an
alluvial soil in almost all the considerable bays, at an average
height of 10 metres (32 feet 9 inches) above the present mean
rise of the river. That alluvial soil, since that period, has
doubtless been considerably diminished in extent by the action
of rain. On the 17th of August Hr. Erbkam and I measured the
nearest alluvial hillock in the neighbourhood of Korusko, and
found it 6·91 metres (22 feet 7 inches) above the general level
of the valley, and 10·26 metres (33 feet 7 inches) above the
present mean rise of the river. That rise, which at Semne, on
account of the greater confinement of the stream between the
rocks, varies as much as 2·40 metres (7 feet 10 inches) in
different years, varies at Korusko less than 1 metre (3 feet 3
inches).

“Near Abusimbel, on the west bank, I found the ground of
the temple 6·50 metres (21 feet 2 inches) above the highest
water-level. This temple, it is well known, was built under
Rameses the Great, between 1388 and 1322 years before Christ.
Near Ibrîm there are, on the east bank, four grottoes excavated
in the vertical rock that bounds the river, which belong partly
to the 18th and partly to the 19th Dynasties; the last, under
Rameses the Great, is also the lowest, and only 2·50 metres (8
feet 1 inch) above the highest inundation; the next in height is
2·70 metres (8 feet 9½ inches) above the former, and was made 250
years earlier, under Tutmes III. Although I only measured the
present level of the valley near Korusko, nevertheless it appears
to me that, during the whole of the new kingdom, that is, from
about 1700 years before Christ to this time, the Nile has not
reached to the full height of the low land of the valley.

“It is, however, conceivable that, at the time when the present
low land of the Nubian Valley was formed, the cataracts at Assuan
were in a totally different state; one that would, in some
degree, justify the overcharged descriptions of the ancients,
according to whom they made so great a noise that the dwellers
near them became deaf. The damming up of the inundation at Assuan
could have no material influence on Egypt, any more than that at
Semne, or the land from thence to Assuan.”

It appears, therefore, from the above statements, that at the time mentioned, the Nile, during the inundations, stood 26 feet 8 inches higher than the highest level to which it now rises in years of the greatest floods; and that, to account for this, Professor Lepsius conceives that, between the time of Mœris and the present day, the bed of the Nile, from a considerable distance above Semne to Assuan, must have been worn down to that extent. In the index to the volume of the Berlin Monatsbericht, in which the letters of Professor Lepsius are inserted, there is the following line:—

“NIL, _senkung seines Bettes um 25 Fuss seit 4000 Jahren_.”

“_Nile_, sinking of its bed about 25 feet (Paris) within the last
4000 years.”

Rivers are, undoubtedly, among the most active agents of change that are operating on the earth’s surface; the solid matter which renders their waters turbid, and which they unceasingly carry to the sea, afford indisputable proof of this agency. But the power of rivers to abrade and wear down the rocks over which they flow, and to form and deepen their own bed, depends upon a variety of circumstances not always taken into account; and although the great extent of that power, in both respects, is shown in the case of many rivers, to conclude, as some have done, from these instances, that all rivers have excavated the channels in which they flow, is a generalisation that cannot be safely assented to. The excavation of the bed of a river is one of those problems in geological dynamics which can only be rightly solved by each particular case being subjected to the rigorous examination of the mathematician and the physicist. The solid matter which rivers carry forward is in part only the produce of their own abrading power; and the amount of it must be proportional to that power, which is mainly dependent on their velocity; they are the recipients of the waste of the adjoining lands by other combined agencies, and the carriers of it to the lower districts and to the sea. They often afford the strongest evidence of the vast lapse of time that must be included between the beginning and close of a geological period; and, when they flow through countries whose remote political history is known to us, they supply a scale by which we may measure and estimate that lapse of time. This is especially so in the case of the Nile.

When so startling an hypothesis as that now referred to, viz., that the entire bed of so vast a river as the Nile, for more than 250 miles, from Semne to Assuan, has been excavated, within historical time, to a depth of 27 feet, is made by a person whose name carries so much weight in one department of philosophical inquiry, the statement involves such important geological considerations, that it becomes the duty of the geologist to examine, and thoroughly test, the soundness of the explanation, in order that the authority of Professor Lepsius for the accuracy of the facts observed, may not be too readily admitted as conclusive for the correctness of his theory of the cause to which they owe their existence. That there has been such an undoubting admission, appears from the following passage in the work of one of the latest writers on Nubia:

“The translation of the name of this town (Aswán) is ‘the
opening;’ and a great opening this once was, before the Nile had
changed its character in Ethiopia, and when the more ancient
races made this rock (at the first cataract) their watch-tower
on the frontier between Egypt and the south. That the Nile has
changed its character, south of the first cataract, has been made
clear by some recent examinations of the shores and monuments
of Nubia. Dr. Lepsius has discovered water-marks so high on the
rocks and edifices, and so placed as to compel the conviction
that the bed of the Nile has sunk extraordinarily by some great
natural process, either of convulsion or wear. The apparent
exaggerations of some old writers about the cataracts at Syene
may thus be in some measure accounted for. If there really was
once a cataract here, instead of the rapids at the present day,
there is some excuse for the reports given from hearsay by Cicero
and Seneca. Cicero says, that ‘the river throws itself headlong
from the loftiest mountains, so that those who live nearest are
deprived of the sense of hearing, from the greatness of the
noise.’ Seneca’s account is: ‘When some people were stationed
there by the Persians, their ears were so stunned with the
constant roar, that it was found necessary to remove them to a
more quiet place[380].’”

The learned author of an article on Egyptian Chronology and History in the “Prospective Review” for May, 1850, in referring to the contributions of Professor Lepsius to Egyptian history, says: “He has discovered undescribed pyramids, equal in number to those known before; has traced the Labyrinth, and ascertained its founder. _He has detected inscriptions on the banks of the Nile, which show that its bed has subsided many feet in historic times._” _9th June, 1850._

In the assumption of an excavation of the bed of the river, we have no small amount of wear to deal with, for the distance from Semne to Assuan, following the course of the river, is not less than 250 miles; and if, as Professor Lepsius supposes, the excavation extended to Meröe, we have a distance, between that place and Assuan, of not less than 600 miles.

Although these records of a former high level of the Nile at Semne had not been noticed by any traveller prior to Professor Lepsius, we may rest fully assured of the accuracy of his statements, from the habitual care and diligence, and the established character for fidelity, of the observer. The silence of other travellers may be readily accounted for by this, that none of them appear to have remained more than a very short time at this spot—not even the diligent Russegger—whereas we have seen that Professor Lepsius passed twelve days in the examination of this gorge in the Nile Valley.

The theory of a lowering of the bed of the river by wearing, involves two main considerations, viz., the power of the stream, and the degree of hardness of the rocks acted upon. The power depends upon the volume and velocity of the river—the velocity on its depth, and the degree of inclination of the bed: the hardness of the rocks we can form a tolerable estimate of when we know their nature. To judge, therefore, of the probability of the hypothesis of Professor Lepsius, we must inquire into the physical and geological features of the Nile Valley, in Nubia.

In the observations I have now to offer, my information has been derived of course entirely from the works of other travellers, particularly those of Burckhardt, Rüppell, and Russegger[381], and especially the latter, who travelled in Nubia in 1837; for he not only enters far more into the details of the natural history of the country, but he is the only traveller in Nubia who appears, from previous acquirements, to have been competent to describe its natural history with any degree of accuracy—I refer more particularly to the physical and geological features of the country. Besides full descriptions in his volumes, he has given a geological map of Nubia, and also several sections, or what may more properly be called _vertical sketches_—a term that would, perhaps, be a more appropriate designation for all sections that are not drawn to a true scale, or at least when the proportion of height to horizontal distance is not stated.

_The Physical Geography of Lower Nubia[382]._

Russegger informs us[383], that he believes he was the first traveller who had succeeded in making a series of barometrical measurements along the Nile Valley, from the Mediterranean to Sennaar and Kordofan, and thence to the 10th degree of north latitude. He gives the following altitudes, above the sea:

Paris Feet. English Feet.

The upper part of the Cataract of Assuan 342 = 364·37
Korusko, on the right bank of the Nile, in Nubia 450 = 479·43
Wadi Halfa 490 = 522·00
New Dongola 757 = 806·52
Abu Hammed 963 = 1026·00

I shall now give the length of the Nile along its course from Abu Hammed to the island of Philæ, at the head of the cataract of Assuan. I employ for this purpose the map in the atlas which accompanies the work of Russegger, which bears the date of 1846, and which, doubtless, was constructed on the best authorities. He mentions a map of General von Prokesch with great praise[384]. It flows:

German M. English M.

From NE. to SW., from Abu Hammed to Meröe, about 31 = 150

It makes a curve between Meröe and Old Dongola,
of about 16 = 77

It flows between Old and New Dongola, from SE.
to NW., about 16 = 77

Then, with some short windings, nearly due north
to the island of Sais, for about 30 = 145

And from Sais to the island of Philæ, from SW.
to NE., about 68 = 327
--- ---
Making the whole length of the course, from Abu
Hammed to Philæ, about 161 = 776

Ascending the river, we have, between Philæ and Korusko, a distance of 24 German, or 115½ English miles, and without any rapid, except one near Kalabsche. Korusko being 115 feet above the head of the cataract of Assuan, at Philæ, we have an average fall of the river between these two places of a foot in a mile.

Between Korusko and Wadi Halfa there is no rapid. The distance being 20 German, or 96⅓ English miles, and the difference of altitude being 42½ feet, we have an average fall throughout that part of the river’s course of not more than 5·3 inches in a mile.

This very inconsiderable fall need not surprise us; for the average fall of the Nile in Lower Egypt, at the lowest water, is little more than one-third of that now stated. At the time of the highest water the surface of the Nile, at Boulak, near Cairo—that is, about 116 miles in a direct line from the coast—is only 43·437 English feet above the level of the Mediterranean, and at the time of the lowest water, only 17·33 feet. Thus, in the first case, there is an average fall of about 5·00 inches; in the second, of not more than 1·80 inches in a mile[385].

Between Wadi Halfa and Dale, a distance of about 94 miles, six cataracts, or schellals, as they are called in the language of the country, are marked in Russegger’s map. And here, it may be as well to notice, that there are no cataracts, in the ordinary sense of the term, on the Nile; no fall of the river over a precipice; all the so-called cataracts are rapids, where the river rushes through rocks in its bed; the rapids varying in their length and degrees of inclination. We have no measurements of their lengths or of their falls, except as regards the first and second cataracts. The former, according to Russegger, has a fall of about 85 English feet in a distance of about 8 miles; and he describes the latter as extending from 5 to 6 _stunden_; that is, from 12 to 14½ miles, but he does not give the height. Speaking of the schellals above Semne, Russegger says, that all may be passed in boats without difficulty for about six weeks, or two months in the year. This is the case also at the cataract or rapid of Assuan. But between Wadi Halfa and Dale, with some inconsiderable spaces of free navigable water, in the ordinary state of the river, there is an almost uninterrupted series of rapids. We have no measurement of the height of Dale above Wadi Halfa, near to which the second great cataract of the Nile occurs; but this is the part of the river’s course where the fall is greatest, and from Semne to Dale there are about 45 miles of this more rapid fall.

From Dale to New Dongola, a distance of 35 German, or about 168 English miles, only three rapids are marked on Russegger’s map—the highest being at Hannek, about 26 English miles below New Dongola. New Dongola being 806 English feet above the sea, and the distance from that place to the rapid of Hannek being 26 miles only, we may with probability estimate the surface of the river at the rapid of Hannek at 780 feet above the sea. Now, Wadi Halfa being 522 feet, we have a difference of height, between these two last-named places, of 258 feet; and the length of the river’s course between them being 236 miles, we have an average fall of 13·12 inches in a mile; that is, in the part of the river’s course where nine rapids occur, in the provinces of Batn-el-Hadjar, Sukkôt, and Dar-el-Mahass, where the river flows over granite and other plutonic rocks; gneiss, mica-schist, and other hard rocks, which Russegger considers to be metamorphic. But between Semne and the head of the second cataract at Wadi Halfa, there is not a continuous rapid stream; for Hoskins says, that about two miles above that cataract, the river has a width of a third of a mile, and, when he passed it, the water was scarcely ruffled[386].

From the rapid of Hannek to Abu Hammed the distance is 329 English miles, and the difference of altitude is 246 English feet. We have thus an average fall in that distance of 9·00 inches in a mile.

Thus, in the 776 miles between Abu Hammed and Philæ, we have an average fall of the Nile

Of 9·00 inches in a mile, for a distance of 329 miles.
Of 13·12 ” ” 236 ”
Of 5·30 ” ” 96 ”
Of 12·00 ” ” 115 ”

_Of the Breadth, Depth, and Velocity of the Nile, in Nubia._

Our information is very scanty respecting the breadth and depth of the river, either at the time of lowest water or during the inundations. About two miles above Philæ, it is stated by Jomard[387] to be 3000 metres, or nearly two English miles wide. At the second cataract, or rapid of Wadi Halfa, it spreads over a rocky bed of nearly two miles and a quarter in width (2000 klafter)[388], but contracts above the rapid to a third of a mile. Russegger also states, that the Nile, near Boulak, in Lower Egypt, is 2000 toises, nearly two-and-a-half English miles in breadth, and yet that it is considerably wider in some parts of Southern Nubia; but Burckhardt says that the bed of the Nile in Nubia is, in general, much narrower than in any part of Egypt. Near Kalabsche, about 30 miles above Philæ, the river runs through a gorge not more than 300 paces wide, and its bed is full of granite blocks. It shortly afterwards again widens for some distance; but near Sialla, 78 miles above Philæ, it is contracted by the sandstone hills on both sides coming so near each other, that the river’s bed is again not more than from 250 to 300 paces wide. It is about 600 yards broad about two miles above the second cataract near Wadi Halfa, but is again very much contracted in the rocky region of Batn-el-Hadjar. At Aulike it is only 200 paces broad[389].

I have not met with any measurements of the depth of the river in any part of its course in Nubia; but Hoskins describes it as being so shallow at the island of Sais, 327 miles above Philæ, on the 9th of June, which would be before the commencement of the inundation, as only to reach the knees of the camels[390]. Near Derr, about 86 miles below the Cataract of Wadi Halfa, Norden, in January, found the river so shallow that loaded camels waded through it, and his boat frequently struck the ground. In May, Burckhardt found the river fordable at Kostamne, 53 miles above Philæ; and Parthey states, that between Philæ and the island of Bageh, to the west of it, the river is so shallow before the commencement of the inundation, that it may be waded through[391]. Burckhardt says, that from March to June the Nile-water, in Nubia, is quite limpid[392]. Miss Martineau, who visited Nubia in December and January, speaking of the river above Philæ, says, that it “was divided into streamlets and ponds by the black islets. Where it was overshadowed it was dark-grey or deep blue, but when the light caught it rushing between a wooded island and the shore, it was of the clearest green[393].” At the second cataract she describes the river as “dashing and driving among its thousand islets, and then gathering its thousand currents into one, proceeds calmly in its course[394].”

Although we have no accurate measurements of the velocity of the Nile in Nubia, we may arrive at an approximate estimate of it by comparing its fall with that of a river well known to us.

I have stated the fall of the Nile in different parts of its course to be 5·30, 9·00, 12·00, and 13·12 inches in a mile. The fall of the Thames from Wallingford to Teddington Lock, where the influence of the tide ends, is as follows:

+-----------------------------------+---------+----------+----------+
| | Length | | Fall in |
| | of | Fall. | Inches |
| | Course. | | per Mile.|
| +---------+----------+----------+
| |Miles. F.| Feet. in.| |
| | | | |
|From Wallingford to Reading Bridge | 18·0 | 24·1 | 15·72 |
|From Reading to Henley Bridge | 9·0 | 19·3 | 25·68 |
|From Henley to Marlow Bridge | 9·0 | 12·2 | 16·20 |
|From Marlow to Maidenhead Bridge | 8·0 | 15·1 | 22·32 |
|From Maidenhead to Windsor Bridge | 7·0 | 13·6 | 23·16 |
|From Windsor to Staines Bridge | 8·0 | 15·8 | 23·52 |
|From Staines to Chertsey Bridge | 4·6 | 6·6 | 17·28 |
|From Chertsey to Teddington Lock | 13·6 | 19·8 | 17·40 |
| +---------+----------+----------+
| | 77·4 | 125·11 | |
+-----------------------------------+---------+----------+----------+

“In general, the velocity may be estimated at from half a mile to two miles and three-quarters per hour; but the mean velocity may be reckoned at two miles per hour. In the year 1794, the late Mr. Rennie found the velocity of the Thames at Windsor two miles and a half per hour[395].”

It will thus be seen that the velocity of the Nile is probably greatly inferior to that of the Thames; for it appears that, except during the inundation, for more than half the year the depth is inconsiderable. The average fall when greatest, that is, including the province of Batn-el-Hadjar, where the rapids chiefly occur, is considerably less than that of any part of the above course of the Thames; so that there must be long intervals between the rapids where the fall must be far less than 13 inches in a mile. The breadth of the Nile is vastly greater; but supposing the depth of the water to be the same as that of the Thames, on account of the friction of the bed, the greater breadth would add very little to the velocity. If we assume the average depth of the Thames in the above distance to be 5 feet, and that it flows with an average velocity of 2 miles in an hour, and if we assume the average depth of the Nile in that part of its course where the fall is 13·12 inches to be 10 feet, when not swollen by the rise, the velocity would be 2⅘ miles nearly in an hour[396], if the fall were equal to that of the Thames. We shall probably come near the truth, by assuming the velocity of the Nile on this part at 2 miles in an hour. That it must be considerably less in the other divisions of the course I have named, and especially in that part immediately below the second cataract, where the average fall is only 5·30 inches for a distance of 96 miles, is quite evident.

The power of a river to abrade the soil over which it flows, so far as water is by itself capable of doing so, must depend upon its volume and velocity, and the degree of hardness of the material acted upon. The power is increased when the water has force enough to transport hard substances. But even transported gravel has little action on the rocks with which it comes in contact, when it is free to move in running water, unless the fall be considerable, and, consequently, the velocity and force of the stream great. When stones are firmly set in moving ice, they then acquire a great erosive power, cutting and wearing down the rocks they are forcibly rubbed against; but this condition never obtains in Lower Nubia, as ice is unknown there.

_Geological Structure of Lower Nubia._

One kind only of regularly stratified rock occurs in the 776 miles from Abu Hammed to Philæ; viz., a silicious sandstone, similar to that which occurs to a great extent on both sides of the Nile in Upper Egypt, and which Russegger, after a very careful examination of it there, considers to be an equivalent of the greensand of the cretaceous rocks of Europe. The tertiary nummulite limestone, so abundant in Egypt, has not hitherto been met with in Nubia.

The Nile flows over this sandstone for nearly 426 miles of the entire distance, but not continuously. At Abu Hammed, it flows over granitic rocks, and these continue from that place for about 120 miles. There is then about 215 miles of the sandstone, which is succeeded by igneous and metamorphic rocks, that continue for 195 miles without any interruption, except a narrow stripe of sandstone of about 15 miles near Amara. It is in this region of hard igneous rocks that nearly all the rapids occur, between that of Hannek and the great or second cataract at Wadi Halfa. From the latter place there is sandstone throughout a distance of about 196 miles, and then commences the granitic region of the Cataract of Assuan, through which the Nile flows about 35 miles. Thus we have about 350 miles of igneous and metamorphic rocks, and about 426 of sandstone.

The general hard nature of the igneous and metamorphic rocks, over which the Nile flows for about 155 miles above Semne, and for about 40 immediately below it, will be recognised by my naming some of the varieties described by Russegger, viz., granites of various kinds, often penetrated by greenstone dykes; sienite, diorite, and felspar porphyries; gneiss, and clay slate, penetrated by numerous quartz veins.

The siliceous sandstone is very uniform in its character; and in Nubia, as in Egypt, the only organic bodies which it has as yet been found to contain, are silicified stems of wood. Occasionally, as in the neighbourhood of Korusko, interstratified beds of marly clay are met with[397].

When, therefore, we take into account the hard nature of the siliceous sandstone, the durability of which is shown by the very ancient monuments of Egypt and Nubia, that are formed of it, and the still greater hardness of the granites and other crystalline rocks, it is manifest that the wearing action of a river flowing over so gentle a fall, can scarcely be appreciable. If the occasional beds of marly clay occur in the bank of the river, they may be washed out, and blocks of the superincumbent sandstones may fall down; but such an operation would have a tendency to raise rather than deepen the bed of the river at those places; unless the transporting power of the stream were far greater than can exist with so moderate a fall, especially in that part of the river below Semne, where, for 96 miles, it is not more than 5·3 inches, and for 115 miles below that, not more than 12 inches in a mile. Even if we suppose the river to have power to tear up its bed for some distance above Semne and below it, as far as the rapid of Wadi Halfa, it is evident that the materials brought down would be deposited, except the finest particles, in that tranquil run of 96 miles, which may be almost compared to a canal. The drains in Lincolnshire are inclined 5 inches to a mile[398]. When the annual inundations commence, the water of the Nile comes down the rapid at Assuan of a reddish colour loaded with sand and mud only; whatever detrital matter of a larger and heavier kind the Nile may have brought with it, is deposited before it reaches that point.

From all these considerations, therefore, I come to the conclusion, that the bed of the Nile cannot have been excavated, as Professor Lepsius supposes, since the date of the sculptured marks on the rock at Semne. He says, “Es lässt sich kaum eine andere Ursache für das bedeutende Fallen des Nils denken, als ein Auswaschen und Aushölen _der Katakomben_.” By the word _Katakomben_[399] he can only mean natural caverns in the rock; but such caverns are rarely, if ever, met with in sandstones, and only occasionally in limestones. If the course of the Nile were over limestone instead of sandstone, we could not for a moment entertain the idea of a succession of caverns for 200 miles beneath its bed, sometimes two miles in width, the roofs of which were to fall in; and where the igneous rocks prevail, this explanation is wholly inapplicable.

But besides the objections arising from the nature of the rocks, and the inconsiderable fall of the river, there is still another difficulty to overcome. It is to be borne in mind, that this lowering of the bed of the Nile, from Semne to Assuan, is supposed to have taken place within the last 4000 years. Between the first cataract at Assuan and the second at Wadi Halfa there are numerous remains of temples on both banks of the Nile, some of very great antiquity. “From Wadi Halfa to Philæ,” says Parthey, “there is a vast number of Egyptian monuments, almost all on the left bank of the river, and so near the water that most of them are in immediate contact with it[400].” We may rest assured that the builders of these would place them out of the reach of the highest inundations then known. Although we have many accurate descriptions of these monuments, the heights of their foundations above the surface of the river are not often given; they are, however, mentioned in some instances. I shall describe the situations of some of these buildings relatively to the present state of the river’s levels, and shall begin with those on the island of Philæ.

This island, according to the measurements of General von Prokesch, is 1200 Paris feet (1278 English) in length, and 420 (447) in breadth, and is composed of granite. Lancret informs us, that, “à l’époque des hautes eaux, l’île de Philæ est peu élevée au-dessus de leur surface: mais, lorsqu’elles sont abaissées, elle les surpasse de huit mètres.” It was formerly surrounded by a quay of masonry, portions of which may be traced at intervals, and in some places they are still in good preservation. The south-west part of the island is occupied by temples. According to Wilkinson, the principal building is a temple of Isis commenced by Ptolemy Philadelphus, who reigned from 283 to 247 years before Christ; and he adds, that it is evident an ancient building formerly stood on the site of the present great temple. Lancret, in referring to this more ancient building, says:—“Il y a des preuves certaines d’une antiquité bien plus reculée encore, puisque des pierres qui entrent dans la construction de ce même grand temple, sont des débris de quelque construction antérieure.” Rosellini considers that it was built by Nectanebus. The first king of Egypt, of the Sebennite Dynasty of that name, ascended the throne 374 years B.C., the second and last ceased to reign about 350 years B.C.[401]

Rosellini[402] informs us, that on the island of Bageh, opposite to Philæ, there are the remains of a temple of the time of Amenophis II., and a sitting statue of granite representing him. He was a king in the earlier years of the 18th Dynasty, which, according to the Chevalier Bunsen[403], began in the year 1638, and ended in 1410 B.C.

GAU[404], in describing a temple at Debu, about 12 miles above Philæ, which he visited in January, and consequently during the time of low water, states that he discovered under the sand, at the edge of the river, the remains of a terrace leading towards a temple.

A short distance north of Kalabsche, about 30 miles above Philæ, at Beil-nalli, Rosellini[405] speaks of a small temple in the following terms:—“Among the many memorials that still exist of Ramses II., the most important, in a historical point of view, is a small temple or grotto excavated in the rock!” and Wilkinson mentions it “as a small but interesting temple excavated in the rock, of the time of Ramses II., whom Champollion supposes to be the father of Sesostris or Rameses the Great[406].” He was the first king of the 19th Dynasty, which began in the year 1409 B.C.[407]

Gau[408] thus describes a monument at Gerbé Dandour:—“La chaîne de montagnes qui borde le Nil est, dans cet endroit, si approchée du lit de ce fleuve, qu’il ne reste que très peu d’espace sur la rive. Cet espace est presque entièrement occupé par le monument, et la rivière, dans ses débordemens, arrive jusqu’au pied du mur de la terrasse.”

Parthey informs us that the temple of Sebûa is about 200 feet distant from the river, in which distance there are two rows of sphinxes, and that the road between them, from the temple, ends in wide steps at the water’s edge; and he adds that Champollion refers this temple to the time of Rameses the Great[409].

It thus appears that monuments exist close to the river, some of which were constructed at least 1400 years before our era; so that taking the time of Amenemha III. to be, as Professor Lepsius states, 2200 years B.C., the excavation of the bed of the Nile which he supposes to have taken place, must have been the work, not of 4000 years but of 800. If the erosive power of the river was so active in that time, it cannot be supposed that it then ceased; it would surely have continued to deepen the bed during the following 3000 years.

At all events, the buildings on the island of Philæ demonstrate that the bed of the Nile must have been very much the same as it is now, 2200 years ago; and even a thousand years earlier it must have been the same, if the foundation of the temple on the island of Bageh, opposite to Philæ, be near the limit of the highest rise of the Nile of the present time; so that there could be no barrier at the Cataract of Assuan to dam up the Nile when they were constructed; and thus the deafening sound of the waterfall recorded by Cicero and Seneca must still be held to be an exaggeration.

The existence of alluvial soil, apparently of the same kind as that deposited by the Nile, in situations above the Cataract of Assuan, at a level considerably above the highest point which the inundations of the river have reached in modern times, to which allusion is made by Professor Lepsius, has been noticed by other travellers, and even at still higher levels than those he mentions. Whether that alluvial soil be identical with, or only resembles the Nile deposit, would require to be determined by a close examination, and especially with regard to organic remains, if any can be found in it. There is no evidence to show that it was deposited during the historical period, and it may be an evidence of a depression and subsequent elevation of the land antecedent to that period. It may not be of fresh-water origin, but the clay and sand, or till, left by a drift while the land was under the sea. For remote as is the antiquity of Nubia and Egypt, in relation to the existence of the human race, it appears to be of very modern formation in geological time. The greater part of Lower Egypt, probably all the Delta, is of post-pliocene age, and even late in that age; and the very granite of the Cataract of Assuan, that of which the oldest monuments in Egypt are formed, and which, in the earlier days of geology, was looked upon as the very type of the rock on which the oldest strata of the earth were founded, is said to have burst forth during the later tertiary period. We learn from Russegger, that the low land which lies between the Mediterranean and the range of hills that extends from Cairo to the Red Sea at Suez, and of which hills a nummulite limestone constitutes a great part, is composed of a sandstone which he calls a “Meeresdiluvium,” a marine diluvial formation, and considers to be of an age younger than that of the sub-appennines[410]. This sandstone he found associated with the granite above Assuan, and covering the cretaceous sandstone far into Nubia. It appears, therefore, that, in the later ages of the tertiary period, this north-eastern part of Africa 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 described by Russegger:

“We arrived at a plateau of the Arabian Chain south-east of
Assuan. 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 supposing 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[411].’”

An eruption of a true granite during the period of the sub-appennine formations, one possessing the same mineral structure as that we know to have been erupted during the period of the palæozoic 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 Professor 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 narrow gorge of the river below Semne, a place had been described by any traveller, where, 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, as it was more distant from Semne, a bar that, in the course of a few centuries, might have been gradually washed away, I might have ventured to suggest such a solution of the problem. But without any information 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 Assuan, 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 difficulty.

_7th April, 1850._

_Translation of a Letter from Dr. Lepsius to Mr. Horner, dated Berlin the 12th of April, 1853._

DEAR SIR,—I observe from a letter of your daughter, that she is
desirous of adding to her translation of my Letters a note upon
the height of the water of the Nile, with reference to your paper
in the “Edinburgh Philosophical Journal.” I wish that you would
get reprinted in that note the whole of the small memoir, as it
possesses great interest, and abounds in data not easily brought
together; for in that case the subject may probably be further
discussed.

I will, at all events, avail myself of this opportunity to
make some remarks, which you may, if you like, propose to have
introduced into the contemplated note.

I must first remark that the word _Katakomben_ was entirely a
typographical error for _Katarakten_, as was unfortunately the
case in many other instances in those things which were printed
during my absence.

But in respect of the explanation of the observed facts, my
views are perhaps less different from yours than you imagine.
You imagine a natural or artificial barrier which has broken
down, but this appears to me of insufficient magnitude; I too
imagine barriers to have existed, and natural ones, but that
there must have been several of them. I do not, moreover, regard
it as impossible, that at certain periods, when the country was
in its most flourishing condition, artificial dams may have been
constructed in order to obtain a higher rise of the water within
a particular space, such as was necessary for an overflowing. But
if we imagine an entire dam thrown across the river, this, if
I am not mistaken, could only hold back the current for a very
short way, namely, where there is a greater general fall. If,
for example, we imagine a barrier at Assuan, it would require to
be several hundred feet high to have any effect on the height
of the water at Semneh, and then the whole valley from Philæ to
Wadi Halfa would be a great lake, as it may indeed have been in
geological time.

If we imagine a succession of barriers which would be especially
formed where veins existed in the primitive rock, then the
present entire physiognomy of the Nile valley seems to be more
easily explained. The river-bed, amidst granitic or other
upheaved rock, is not level, like a chalk or sandstone channel,
but forms sometimes lakes, sometimes barriers. The force of
the swollen current at these last, of which there is one at
Semneh itself, does not act in the mean proportion of a space
of considerable extent, but with immense effects, exceeding all
calculation, especially when, in addition, there is a contraction
of the sides, as at Semneh. Immediately below this barrier the
bed again spreads out, and the rocks disappear in the current.
The colossal rock-fragments on that bank, whose inscriptions
sometimes show that above 4000 years ago they were still not
broken loose, display the Titan force of a current thus hemmed
in, and allow us to conceive how at that spot it gradually washed
out its bed, sometimes to a great depth, but sometimes also to
a greater breadth, which has the same effect, and how all that
is broken away, or that during the time of low water splits to
a considerable depth in the bed of the river from the summer
heat, rolls away, until arrested by falling into hollows. But
if these single barriers are only washed away in the course of
thousands of years, then the whole river must receive an equable
fall, and it will never rise in the very rocky districts, but can
only continue to be still more excavated, and will only again
deposit the heavier portions it bears along with it, below the
cataracts, where every obstruction disappears. The monuments can
hardly be cited in opposition to the view of a gradual sinking
of the bed of the river in the higher districts. All of them
lie tolerably far above the region of the rise of the Nile—for
example, the temple on the island of Bigeh, to which there is a
considerable ascent. Philæ has only been built upon since the
time of Nectanebus, and there is nothing to indicate buildings
of an earlier date. The sinking of the surface of the water even
at Philæ and Assuan must also have been far less than at Semneh.
Nevertheless, special researches with respect to the relative
condition of the ancient temple and rock-inscriptions to the
present surface of the water would certainly be of the greatest
utility.

Herr von Humboldt, after reading some observations on the same
subject by Wilkinson in the Nouv. Ann. des Voyages, i., without
recollecting my views, wrote to me as follows:

“Breaches in dams, I imagine, cause only temporary rises of
water, unless in earlier times (for which I see no reason)
there was a greater accumulation of water in the valley of the
river, from meteorological causes. Primeval conditions, where
broad valleys were filled with waters, are not applicable to
periods when there were inscriptions. Does it not seem to you
more probable, that the height of the water was at one time at a
greater elevation, on account of the bed of the river not having
been so much furrowed out, because at an earlier period the
bottom of the river was not at _c d_, but at _e f_.

“There are rivers whose beds are elevated and rendered more
shallow by deposition, others which furrow out their bed _qui
creusent un lit plus profond_.”

With sincere respect, your faithful,

R. LEPSIUS.