THE PRINCIPLES AND OBJECTS OF GEOLOGY.


                      MINISTRY OF FINANCE, EGYPT.
                               * * * * *
                          SURVEY DEPARTMENT.
                               * * * * *

                                  THE
                   PRINCIPLES AND OBJECTS OF GEOLOGY
                       WITH SPECIAL REFERENCE TO
                        =THE GEOLOGY OF EGYPT,=

                                  BY
                   W. F. HUME, D.SC., F.R.S.E., ETC.
                 DIRECTOR, GEOLOGICAL SURVEY OF EGYPT.

                               * * * * *

     _Technical Lectures delivered in the Survey Department, Giza,
                on January 20, and February 10, 1910._

[Decoration]

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                               * * * * *
                                 1911.

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                            ILLUSTRATIONS.
                               * * * * *


                                                                 PAGE.

  Fig. 1. — Two Anticlines and a Syncline                            6

   „   2. — Overfolding of Strata                                    7

   „   3. — Unconformity exhibited in the Fayûm                      8

   „   4. — Fault exhibited by a Coal-seam                           8

   „   5. — Sand-erosion of Sandstone Cliff at
            Gebel el Tunb                              Facing       10

   „   6. — Water-worn Amphitheatre in Side-valley
            of Um Leseifa                                 „         10

   „   7. — Denudation Effects in a District of
            Sedimentary Rocks                             „         11

   „   8. — Denudation Effects in a District of
            Igneous Rocks                                 „         11

                               * * * * *




                =THE PRINCIPLES AND OBJECTS OF GEOLOGY=
                       WITH SPECIAL REFERENCE TO
                        =THE GEOLOGY OF EGYPT.=

                               * * * * *

                              I.—GENERAL.


The systematic examination of the geological structure of Egypt,
carried out by the Geological Survey during the last thirteen years,
has, in conjunction with previous studies, revealed the fact that
the surface of the country is composed of very varied materials:
limestones, sands, clays, sandstones, granites, schists, etc. The
co-ordination of view as to the distribution of these rocks[1]
presented by a geological map has further shown that they are not
arranged in a random manner, but that certain very definite relations
exist between them. If, for instance, the Moqattam hills behind
the Citadel be ascended, the lower part of the scarp is found to be
composed of white limestone, which is capped by a series of sandy
limestones and clays differing alike in colour and in the rapidity
with which they are worn away by the streams, due to the rare but
destructive winter rains. Finally, the summit is crowned by beds
in which boulders of flint and quartz play the most important part,
the matrix of sand which bound them together having long been removed
by the action of the wind.

Similarly, if we were to go southward towards Aswan, a change would
be noted in the character and composition of the rocks which form
the cliffs bordering the Nile Valley. From Cairo to Qena, limestones
predominate; but from thence southward to Esna, clays play a large
part at the base of the limestones, and the slipping of the latter
over these softer members has given rise to the “tumbled” country
which is so conspicuous a feature between Armant and Matana. South of
Esna the clays in their turn disappear, while the sandstone which is
seen underlying them near Mahamid becomes the dominant constituent
of the hills from near Edfu to the neighbourhood of Aswan; at this
locality the sandstone itself vanishes, except in so far as it forms
isolated caps on the granite, which is the principal rock in the
well-known district of the First Cataract.

The same lesson as to the order of succession of the rocks in Egypt
is forced home if we move from Qena eastward to the Red Sea hills,
or south-westward to Kharga Oasis. East of Qena the clays are a
conspicuous feature at the base of the outlying limestone hills (Abu
Had, etc.), and in their turn rest on sandstone, which forms striking
plateaus seamed by deep ravines giving entry to the heart of the Red
Sea hills. On traversing these gorges, a confused hill-country of
granite (worn into boulders on the surface), or dark-green schists is
entered, on whose summits the sandstone occurs as isolated outliers
near the main sandstone mass, but to the east disappears altogether.

Similarly, going westward and crossing the great limestone desert, on
reaching the edge of the scarp which bounds the oases, clays appear
from under the limestones, and in their turn overlie sandstones
forming the floors of the oasis depressions. Closer examination
reveals the fact that in the upper part of the sandstone series seams
of clay alternate with the sandy layers, and in that part of the cliff
where clay bands predominate, beds of limestone alternate with them.

In broad outline, it may be stated that in southern Egypt, limestone
rests on clays alternating with limestone, these on sandstones which
in their upper part alternate with clay, and the sandstone on granite
and metamorphic rocks (slates, schists, etc.). The inclination or dip
of the various beds is such that should a boring be made through the
limestone near Cairo, one might expect to reach first a succession
of beds where clay was predominant, followed by beds of sandstone,
and finally the series of which the granite of Aswan is a conspicuous
member.[2] In northern Egypt, the conditions are reversed, sandstones
and clays _overlying_ the limestones near Cairo, but never attaining
the extent and importance of those exposed to view in the south.

These facts require an explanation—the one furnished by the science
of Geology, being briefly as follows: Each of the rocks observed
has a definite origin or formation; the nature of their present
distribution is due to subsequent movement, or deformation; the
various meteorological agencies at work lead to the transformation of
the original structures, resulting in the formation of a new series
of rocks composed of materials derived from the wearing away of the
older deposits.


                   II.—ORIGIN OR FORMATION OF ROCKS.


The simplest illustration of the formation of a rock is one which
may be observed by the dweller in Egypt every year during the Nile
flood. The “red water” of the Nile, if collected during this
period, and evaporated to dryness, leaves behind it the fine-grained
sediment, or Nile mud, forming the soil to which this land owes its
fertility; while in the central portions of the river, the coarser
material, consisting largely of sand-grains, is being transported by
the stronger current. As a result, the river flows for the main part
over a sandy bed, the clays being restricted to the sides where the
water is moving less swiftly, or to the fields on which the finer
sediment is deposited. This “red water” has been traced step by
step to its parent source, and has been proved to be derived from
the wearing away of the widely-spread volcanic rocks of Abyssinia,
disintegrated by differences of temperature, etc., and denuded
by the destructive rainstorms which break over that region in the
early summer. It is equally a matter of experience that on drying,
this sediment passes from the condition of a soft and sticky mud
to a hard and resistant clay, which, drying during the heat of the
summer, cracks in every direction. The fluviatile character of these
clay deposits is often revealed by the presence of the river shells
enclosed in them, and in each succeeding year slight differences
in composition in the material brought down are indicated by the
layers being sharply marked off from one another, and so presenting
the familiar stratified appearance. Again, much sand and clay is
being carried seaward and deposited, the former, in general, nearer
the land on account of its greater specific gravity and less finely
divided character.

These clays and sands are forming both on the land and in the sea,
a point which does not need elaboration, but when considering the
origin of the limestones, and how it is that they seem at times to
be built up of fossil shells, as a rule the general student would
be at a loss for an answer. The researches in the great oceans,
which have been carried on with such assiduity during recent years,
have shown that the upper layers of their waters are crowded with a
vast number of living organisms, apparently simple in structure, but
having the power of extracting the carbonate of lime in solution and
constructing shells of complicated and beautiful form. As the animals
die, these tiny shells rain down to the bed of the ocean, slowly
forming a muddy white calcareous paste which encloses the sea-urchins
and other marine animals living in the depths of the sea. Thus, step
by step, muds (which on drying are as genuine limestones as any now
forming the cliffs and scarps of Egypt) are laid down on one another,
separated into strata whenever some external change, such as the
addition of some clayey matter transported from a river in flood,
slightly alters the composition. The alteration is subsequently
indicated either by variation in tint or by differing resistance
to the wearing influences of the meteorological agencies. But how
are these argillaceous muds transformed into the solid clays, the
sands into sandstones, and the calcareous muds into fossiliferous
limestones? How have these loose materials become consolidated so
as to form the compact rock-masses with which we become acquainted
in the most casual study of the physical structure of Egypt?


                      III.—DEFORMATION OF ROCKS.


Examination of the rock exposures at many localities in the
neighbourhood of Cairo bears witness to the fact that the strata of
limestone which were laid down horizontally upon the bed of the sea
are no longer in the position they once occupied, but are now inclined
to the horizontal plane at angles which are easily perceptible. This
is especially noticeable in the two shallow cuttings under the
Great Pyramid, where the strata are inclined 5 degrees to the
south, revealing the reason why the whole Pyramid slope descends so
rapidly in the southward direction. Again, if standing at the base
of the same mighty structure, the gaze be allowed to wander over
the broad expanse of the Nile Valley to the scarp of the Moqattam
hills behind the Citadel, it will be seen that the white limestone
of their lower slopes forms, not a long horizontal wall, but an arch,
sloping strongly both north and south of the Citadel. There has been
obviously change of form, but how has it taken place?

We learn with surprise that an earthquake shock in distant San
Francisco or in the inhospitable regions of Turkestan has recorded
itself through the delicately-poised recorder at Helwan, long before
the dire news of destruction has flashed along the telegraph wire
to the same destination. There is a realization of the instability
of the earth’s crust, in spite of the solidarity of its component
parts, but though the sudden shocks bring home this truth, it is
not so readily grasped that day by day and hour by hour parts of the
earth’s crust are slowly rising and others sinking, offering stern
problems to the dwellers on the shores where these changes are most
markedly taking place. On the eastern shores of England, towns and
forests are being submerged beneath the relentless advance of the sea;
on the coasts of the Scandinavian peninsula, etc., on the other hand,
beaches formerly beneath the sea now stand high above the influence of
its waves, and in Egypt coral-reefs which once grew beneath the waters
of the Red Sea rise in places to over two hundred metres above it in
bold hills or steep-sided terraces. Though possibly of far greater
importance and significance than the sudden convulsions which have
left so deep an impression on the mind of man, these movements are
nevertheless so imperceptible that they arouse little attention.

A second type of deformation is noted where heavy masses of one
rock rest on other and softer materials. The underlying beds are
then often compressed and contorted; clays, for instance, are
drawn out into thinner laminæ, giving rise to shales, while the
massive rocks above either slip on the surface of the lower ones,
if these be impermeable, and so permit of a water-layer forming
along the junction, or else descend by sheer weight, producing a
confused area of mixed materials in front of the still unshattered
cliffs. Examples of this nature abound in Egypt wherever the Eocene
limestones rest on the Cretaceous clays; on the railway from Armant
to Matana the resulting effects are well observed near Shagab. Here
in the main cliff the massive limestones are seen resting on the
soft bluish clays, while in front is a wilderness of low hills in
which limestones and clays are mixed, broken and contorted. But while
these deformations may be irregular and local, there remain greater
pressure-effects which have been regional in character, and by whose
agency the solid rocks have been folded in the most remarkable manner,
strata once horizontal being thrown into arches, or anticlines,
and basin-like curves, or synclines. The importance of these changes
cannot be over-estimated, and some of the marked features of Egyptian
scenery depend directly on these effects. Reference has already been
made to the slope of the Pyramid plateau, but the character of Egypt
in far broader outline depends on the results of these pressures and
the foldings so produced. A glance at the map suffices to show that
many of the salient features in this country present a remarkable
similarity and parallelism. The eastern cliff-wall of Kharga Oasis
preserves a notable parallelism to a portion of the Nile Valley,
though the latter be separated by many kilometres of wild desert
plateau from the oasis; another portion of the Nile Valley also
agrees with the Gulf of Suez in the broad outlines of its trend.

[Illustration: Fig. 1.—Two Anticlines and a Syncline.[3]]

A section taken from Baharia or Kharga Oasis to the shores of the
Red Sea reveals the fact that Egypt proper is bounded on the west
by a low flat arch which has brought the underlying sandstones
nearer to the surface, giving rise to the great oases.[4] These
are mainly present in the sandstone areas, and are in part bounded
by cliff-walls composed in many instances of clays at the base and
limestones at the summit. To the east, on the other hand, rise the
Red Sea hills, the central core of a steeply inclined arch in which
the resistant granites and schists now rise high above the low-lying
sandstone country which flanks them. Between these two arches is
the flat-bedded syncline in which the nummulitic limestone is the
conspicuous member, the strata in central Egypt having in consequence
a half cup-shaped form, of which one half, the northern, may have
disappeared by fracture beneath the waters of the Mediterranean
Sea. This cup-like structure may be due to Egypt having not only
been folded in a north-west and south-east direction but also almost
at right angles, this latter folding giving rise to such remarkable
features as the Wadi Araba, the Qena bend, and possibly affording the
fundamental explanation for the great S-shaped bends of the Nile. In
other and more mountainous regions, such as the Alps and Himalayas,
these solid earth-waves may be under such immense pressure that their
crests begin first to turn over like those of an advancing wave of
the sea, and then may be broken in such a way that mighty masses
of strata are rent asunder, those portions which are uppermost
being thrust for great distances over the underlying beds. These
extreme folds ending in fracture, or overthrusts, are as yet but
little known in Egypt, though Dr. Ball has reported an interesting
case from the neighbourhood of Abu Harba, and some of the phenomena
of dislocation observed near the borders of the Gulf of Suez may
possibly be explained as resulting from movements of this nature.

[Illustration: Fig. 2.—Overfolding of Strata.]

These intense movements become masked under the influence of the
denuding hand of time, the contorted strata may again sink beneath the
sea, new beds are laid down horizontally on the upturned edges of the
older series and the result is the production of an unconformity
between the two members, which differ in age, in inclination,
and in fossil character. Sometimes rolled fragments of the older
stratum are interposed between it and the new overlying beds, further
revealing the activity of denudation before the newer member began
to be deposited.

If fracture by overthrust be unknown in Egypt, another type of
fracture has produced effects of a far-reaching character. In certain
regions of the earth, folding is no longer the conspicuous method
by which the rock-components of its crust are displaced with regard
to one another. In many instances small fissures have been observed
in which the beds on one side have been thrown down to a lower level
than they are on the other. These faults are frequently the result of
great earthquakes, many striking examples of such occurrences having
been noted during the major earth-movements within the last hundred
years. It is probable, indeed, that many of the most important of
these, such as the destructive earthquake of Messina, are due to
further settling of the strata in relation to fracture-lines already
determined. Naturally, this implies that there are certain spaces
formed deep beneath the earth’s surface, which permit of these
efforts to restrengthen the weak spots by filling up the gaps. In the
extreme outskirts of Egypt these fault-lines have produced marvellous
and striking effects, the most conspicuous being the remarkable
depression which, commencing at the Gulf of Aqaba, penetrates far
into the continent of Asia, giving rise to the Dead Sea (many hundred
metres below the level of the Mediterranean), to the Jordan Valley,
to the Lake of Tiberias, and the valley which continues this line
northward. I have had the opportunity of personally studying some
of these fault-lines in the Sinai peninsula, tracing them from an
arched fold in the north, whose sides were being let down by faults
in a series of steps, to a trough-fault, in which the younger strata
are displaced bodily between the older ones. Where undisturbed, the
succession in Sinai shows sandstone lying on granite, and limestone
(containing definite groups of fossils) on sandstone. In the valleys
due to these trough-faults, the granite hills tower 500 metres on each
side, capped by small outlying fragments of the overlying sandstone,
whereas in the valley itself the only rocks visible are limestones
and sandstones often tilted at high angles, and thus revealing the
tremendous displacement to which they have been subjected.

[Illustration: Fig. 3.—Unconformity exhibited in the Fayûm.]

[Illustration: Fig 4.—Fault exhibited by a Coal-seam.]

Considering the earth-movements of Egypt as a whole, the evidence
shows folding to have been the more important type of displacement on
its western side, and intense faulting to have been most conspicuous
in the east, while between these two extremes, the relative importance
of folding and faulting will remain a contested point. The discussion
will only close when the borders of the Nile Valley and the Gulf
of Suez have been mapped with the accuracy and precision of a
Geological Survey in Europe—a pious aspiration, whose realization
can scarcely be hoped for while the broad geological picture is
still being filled in.

Egypt, then, has passed through a long history, of which the
following seems to be the record put in dogmatic form. The ancient
schists and granites which form the central core of its eastern
arch, or anticline, the Red Sea hills, are witnesses to a period
of sedimentation, of volcanic action, and of the influence of
deep-seated molten igneous masses. Step by step these were revealed
by denudation, becoming part of an ancient continent. In addition to
a brief marine invasion during the Carboniferous period, there was a
second advance of the sea in Cretaceous times, which is represented
first by the deposit of such coarse detrital materials as the sands
composing the Nubian sandstones. Then, as the depression increased,
only the finer clayey materials reached the Egyptian region, and
finally the sea covered, if not the whole, at least the greater
part of its area for a lengthened period. With the close of the
Eocene epoch a reverse movement set in, by which the pure white
marine limestones of the Moqattam hills were capped by the sandy
limestones and clays forming the brown-tinted beds of their upper
portion, the whole being, in its turn, covered by the coarse flint
and quartz gravel which containing silicified trees[5] is the chief
desert-former in the immediate neighbourhood of Cairo, as also of
a large area in north-west Egypt. Any gain by the sea since this
period has been comparatively local and limited, and the present
conditions suggest that the land is gaining on the sea rather than
the reverse. The great fold-movements which we have seen to determine
so many important features are relatively of very late date in this
series of events, on their nature and position depending the present
character and visible extent of the different formations.


                 IV.—PHYSICAL TRANSFORMATION OF ROCKS.


The geological features of Egypt as presented to-day are the results
of the formation through varying conditions and the subsequent
deformation of the rocks composing its solid crust; we may next
consider the varied agencies through whose action these are now
undergoing transformation. A comparatively small portion of this
country is undergoing erosion by the sea, and if elevation be still
taking place, there is rather gain from the sea than destruction
by it.

Very different, however, are the meteorological agencies which are
at work fashioning the land as a whole, the effects of wind-blown
sand, rain, and river being of prime importance. Different in these
respects are the Eastern and Western Deserts of Egypt. If the western
border of the river be examined in Southern Egypt, and especially in
Nubia, the sight of huge masses of golden-tinted sand filling every
wind-sheltered hollow might well leave the impression that the vast
desert plain behind was covered by a pall of sand. Closer study
has shown that these wind-swept expanses afford no protection or
resting-place for the finer sands and that consequently their floor
must be formed of the more solid materials which wind cannot carry
before it. If this be realized, no astonishment will be felt that
the Libyan Desert surface is composed of limestone, or of coarse
gravels from between whose larger fragments all the finer sand has
been swept away.

[Illustration: Fig. 5.—Sand-erosion of Sandstone Cliff at Gebel
el Tunb. Wadi Qena, Eastern Desert.]

[Illustration: Fig. 6.—Amphitheatre in Side-valley of Um Leseifa,
north-east of Qena, due to erosion of Limestone by the action of
Temporary Torrents.]

                                                       [Facing p. 10.]

However, the wind-borne sand leaves its mark on the limestones,
which in some places are seamed by delicate grooves parallel to
the sand-blast, and in others, where they are softer, have been
sculptured into low hummocks often scattered over immense tracts
of country. The sand itself has a strangely local distribution,
advancing across the desert in lines of enormous length, and usually
trending in an almost meridional direction. The supply does not come
from the south or south-west, as might at first sight be expected,
but from the north, and most of the great dune-systems, which occur
around and beyond the great oases, have their termination in the
southern direction. Even the series of dunes, over 100 metres high,
which prevented the Rohlfs party advancing westward from Dakhla to
Kufra, come to an end further to the south, leaving the wide sandstone
plains bare.[6] In the oasis of Kharga the dominant longitudinal type
is replaced by huge crescentic dunes which, separated by broad spaces
clear of sand, follow one another along a north-south line, and are
not stopped in their onward march even by ridges of considerable
size. The reasons have still to be found for these lines of special
sand aggregation, though when studying the cataract district of Amara,
the initial formation of a dune-system was seen to be determined by
a local depression, which had given sufficient protection for the
formation of a sandy base on which the dune could then be built up.

[Illustration: Denudation Effects in a District of Sedimentary Rocks.

Fig. 7.—Um Leseifa camp (looking west). The harder beds of limestone
form precipitous ledges.]

[Illustration: Denudation Effects in a District of Igneous Rocks.

Fig. 8.—View of Diorite Hills near Gebel Sobeir, Eastern Desert
of Egypt.]

                                                       [Facing p. 11.]

Not only are limestones grooved and seamed, but certain areas of
the Western Desert are covered with curious melon-shaped masses,
harder concretionary portions remaining after the softer materials
of the beds have been carried away by wind-action, whereas in the
region to the east of the Nile these concretions are still enclosed
in the softer limestones.

Still more striking is the effect of the wind-blown sand in the
sandstone and granitic regions. Here the complex composition of
the granite has made it a ready victim. The softer felspars and mica
having been worn by the impact, leave the quartz grains loose upon the
surface, and give the rock a “frittered” appearance. Holes have
been formed in the windward side of the blocks, and the sand contained
in them clearly shows the agency to which they owe their origin.

Near the eastern edge of the Western Desert the effects of
water-action become more conspicuous, on the borders of the Fayûm
terrace-formation being a marked feature, and there is a transition
to the dominant characteristics which mark the limestone country
eastward of the Nile. Here, deep and intricate valley-systems have
been cut out from a plateau which a few kilometres from the Nile
is as flat as the great western plains. One of the best known
examples is the Wadi Hof, near Helwan, with its ramifications,
terminating in steep cliff-faces having all the appearances of “dry
waterfalls.” Any doubt as to the active agent in their production
is set at rest by an examination of the excellent photographs taken
by various observers during the great storms which almost annually
burst over this region. (The lecture was illustrated by a series of
slides showing Wadi Hof in flood, and the cascades descending the
“waterfalls” which terminate its side-channels, these being most
kindly lent to the writer by Herr Züst, of the Electrical Service,
Ministry of Public Works). The great annual and diurnal temperature
variations (over 50° C.) aid in the work of denudation by preparing
an immense amount of broken material through the contraction and
expansion which they produce. As every material expands and contracts
according as it is heated or cooled, so the different component
parts of the rocks composing the earth’s crust are in constant
movement with regard to one another, and the less homogeneous they
are the greater the effect in breaking them up into small masses or
particles. These loosened fragments which cover the surface of the
desert are thus ready to be swept away by the rain-waters, and as we
have already seen, it is owing to these effects, superadded to more
subtle changes next to be considered, that the old volcanic rocks
of Abyssinia yield the rich silt or mud of the Nile Valley. It would
be difficult to estimate the rapidity with which these wild ravines
are being deepened by any comparison with water-wearing effects in
Europe. Any beds of soft sands and clays are rapidly dissected by
the torrent waters, a feature which readily explains the absence
of conspicuous hills in the Eastern Desert east of Esna, where the
Cretaceous clays form the dominant constituent in the geological
structure of the country. Whatever the effects of sand-erosion in the
Western Desert or rain-erosion in the hills and on the plateaus of
the Eastern Desert of Egypt, they come relatively but little under
the notice of the dweller on the Nile, to whom the river-erosion
and the reformation of new materials become of primary importance.

Even the powerful agency of frost cannot be entirely dismissed from
consideration in Egypt. Owing to the expansion of water when converted
into ice, the rocks in whose cracks the water has collected are split
asunder, and as we have recently noted, temperatures lower than 2°
C. have been recorded in Cairo during the present winter (1910). On
the great desert plateau which extends from Kharga Oasis to the Nile
Valley, temperatures of 24° F. and 30° F. were also observed, and
in the Red Sea hills and Sinai frost must be of common occurrence,
as one mountain in the latter peninsula was ascended in snow, and
the higher peaks are frequently covered in a white pall.

The nature of a river system need not be dealt with in much detail
here, as I have already discussed this subject in “Survey Notes”
for April, 1907, under the title of “River Characteristics as
illustrated by the Nile.” It may be well, however, to recall that a
normal river passes through three distinct phases of activity. In its
mountain tract (for most large rivers arise in the higher altitudes)
there is maximum erosion and backward growth of the river system. In
its central portion, or valley tract, the stream is acting as a
transporter of eroded material, and such erosion as there is, is
downward rather than sideward. Finally, the plain tract is the region
of deposition of the materials so carried, erosion being lateral,
and the growth of the stream bed forward in the form of a fan-shaped
delta where the transported sands and clays enter the sea.

But this general succession may be further complicated by
circumstances depending upon the geological conditions. In Egypt and
the Sudan the Nile passes from areas where it flows peacefully and
quietly, usually of considerable breadth and bounded by fertile lands,
to others in which it is restricted, dashing down steep slopes in
rapids and cataracts. A geological examination has shown that in
the first case the river is flowing over and between sedimentary
homogeneous rocks, such as the limestones and sandstones, while in
the second instance it has entered regions composed of heterogeneous
igneous and metamorphic rocks, such as the granites, gneisses and
schists. The production of these rapids is due to the combination of
steep slope and the difference between harder and softer materials,
the rapidly-moving waters wearing away those more easily denuded,
while the compact members remain as obstacles to their advance,
and are only slowly worn away along joint-planes and other lines of
weakness. In the Third Cataract, hard bars of granite rising through
softer gneiss at right angles to the river course have produced the
main rapids; elsewhere, as at the Bab el Kebir, near Wadi Halfa, the
river has taken advantage of a thin dyke of soft rock traversing an
extremely hard diorite, so that the stream has worn a narrow gully
between steep rock-walls, where the intensity of the rush of water
is greatly exaggerated owing to its being restrained and fettered
by the narrowness of the passage. In some cases the same result has
been produced owing to the existence of a line of fracture, or fault,
across the stream, the waters taking advantage of this line of least
resistance. The general erosion in these rapids is accompanied
by great local effects where eddies and whirlpools are produced,
and the sand and rocky fragments act as abrading agents. Pot-holes
are formed in the solid rock, and rapidly deepened by the intense
effects of this nature produced during times of flood, the result
being splendidly illustrated in some of the smaller islands of the
First Cataract at Aswan.

A river is, in fact, the main agent combining the effects of
transformation and reformation, new strata being produced in its
plain tract as the result of the eroding activities in its upper
reaches. Much of the detrital material is also carried seaward to
form deposits of marine sands and muds along the shore-lines of the
continents, these themselves becoming, should subsequent differential
movement of land and sea take place, the sandstones and clays of
future continental areas.

But there are other agencies at work as transformers on and within
the earth’s crust. There are in most rocks a series of divisional
planes, which may be either vertical or inclined, and to which
the name of joints has been given. These may arise from various
causes. Both in sedimentary and igneous rocks they are in part
due to contraction during consolidation—in the former when they
lose their contained water, in the latter when they solidify from a
molten condition. Joints may also be called into being by the effects
of internal pressures and movements within the earth’s crust,
such structures having been experimentally reproduced by Daubrée
in materials under stress by torsion and by simple pressure. The
granite of Aswan displays such jointing to a marked degree, giving
rise to remarkable hills composed of huge boulders of granite piled
on one another.


                 V.—CHEMICAL TRANSFORMATION OF ROCKS.


Besides the mechanical effects of river, rain, and wind, other changes
whose wide-reaching significance cannot be over-estimated, are taking
place on and below the earth’s surface. Chemical action is slowly
at work producing effects of the first importance to man. Rain-water
has the power of absorbing important quantities of carbonic acid
gas and oxygen from the atmosphere. On the average, rain-water
contains 1·77 per cent by volume of dissolved carbonic acid gas,
and 33·76 per cent of dissolved oxygen. In passing through the soil,
rain-water also absorbs the organic acids formed by the decomposition
of plant remains. These dissolved gases and organic acids render rain
an active chemical agent in the alteration of rocks, its effects
being conveniently classified under the headings: (1) Oxidation;
(2) Solution; (3) Formation of Carbonates; and (4) Hydration.

(1) Oxidation results in the formation of thin crusts on the
surface of rocks, the compounds of manganese and iron so frequently
present in them being also rusted or hydrated by the action of the
rain-water. Nothing is more striking than the presence of the dark
films on the desert limestones in regions which are liable to a
certain amount of rainfall, and nothing more convincing as to their
origin than their absence in those portions of the south-western
desert of Egypt where rain is of great rarity. Near the Nile, the Red
Sea and the Mediterranean, dew may take the part of rain in action,
and in a sense the results of its activity may appear more intense,
as rain is liable to wash away the products of its own handiwork.

(2) The effects of Solution are of the greatest importance,
limestone being soluble to the extent of about 1 part in 1,000 in
water saturated with carbonic acid. In many limestone countries of the
world the solution effects are marked by the production of underground
caves and channels and in some parts of the north-eastern desert of
Egypt, where chalky limestones are the main constituent, this action
has produced remarkable results—large caves, cylindrical channels,
and natural bridges being of not uncommon occurrence.

(3) Formation of Carbonates. Owing to the rains in Egypt being of very
brief duration, but nevertheless extremely active while they last,
the soluble material in the condition of the unstable bicarbonate
of lime is carried only a short distance, and losing its loosely
combined carbonic acid is redeposited in the cracks of the rocks,
as veins of carbonate of lime, or as the cementing material by
which broken fragments are consolidated into compact breccias. This
action may be seen in the cliff face south of the Pyramids, near the
Sphinx, where the sandy limestones forming the top of the hill have
been attached by the rain containing carbonic acid. The calcareous
tests of the shells in the sandy limestones have been dissolved away,
leaving only the sandy internal casts of the shells behind, and the
material so removed has been redeposited in intricate interlacing
veins in a clayey band immediately below. A vein may sometimes grow
by the accretion of successive layers, which, owing to local causes,
such as the relative content of iron oxide, etc., may display slightly
different colours, one of the results being the production of so
interesting a rock as the Egyptian alabaster, which is a carbonate
of lime. As a rule, the term alabaster is applied to the sulphate
rather than to the carbonate of lime. Probably much carbonate of
lime is also carried in solution to the sea, and there forms the
source of the material which hundreds of living animals seize upon
for the production of the shells in which they dwell. I was much
struck last year, during a journey from the Pyramids to Wasta, to
note how the oyster-beds of one age (the Pliocene) formed themselves
upon oyster-beds of a long preceding period (the Eocene), probably
on account of the greater amount of carbonate of lime at those
localities, present owing to solution of the earlier shell-structures.

That veins of carbonate of lime should be present in limestone
districts is, in view of the above statements, not surprising,
but it does appear somewhat startling at first sight, to find
marked deposits of carbonate of lime lining the floors and sides of
torrent-beds in districts entirely composed of igneous or volcanic
rocks of complicated mineral structure. Experience has shown,
however, that the lime silicates, so abundant in the more basic
members of the igneous series, such as diabases and diorites, are
liable to the attack of the rain-waters containing carbonic acid,
carbonate of lime being produced by the reaction.

(4) Of the results of Hydration, the most striking examples in Egypt
are the formation of kaolin near Aswan, due to the absorption of water
by the felspars of the granitic and gneissose rocks, and the thick
zone of decomposition (kaolinic) products, which was cut through in
excavating the navigation canal in the syenite which forms the main
rock at that locality.

The total effect of all the above-mentioned meteorological influences
results in the weathering of the rock-surface, involving the softening
and crumbling of the harder materials, but sometimes leading to
the solidification of materials previously loosely aggregated by
substances left as cementing agents when the water containing them
in solution has evaporated.

In addition to the various direct results of the meteorological
activities upon the earth’s surface, there are others which
indicate more subtle changes. Perhaps amongst the most interesting
of these is the formation of concretions—bodies composed of one
material aggregated in more or less rounded or irregular form in a
rock of another composition. Among the most interesting and abundant
of these are the layers of flint, which form bands of strikingly
parallel character in the limestones of Upper Egypt. These have not
yet been submitted to the detailed study which similar concretions
have received in Europe, but there is little doubt that they,
in large measure, represent the aggregation of gelatinous silica
round decomposing organic materials, the shells of organisms and the
framework of siliceous sponges often forming their centre. In some
cases, as in the fossil trees, the replacement appears to have taken
place molecule by molecule, as the outlines of every cell of the once
woody fibre are now replaced in silica. By a well-known transition,
this once gelatinous material has now become one of the most solid
of substances.

Ferruginous concretions, composed of oxide of iron, are present in
many of the Egyptian sandy clays, some of the beautifully-tinted
purple, yellow and red ochres being found in this form; and
the natives collect them for the use of the women as ornamental
coloration.

Of greater importance to the world at large are the gradual changes
which vegetable matter (collected under specially favourable
circumstances free of all sandy and clayey admixture) has undergone
through vast periods of time, causing the slow evolution of the
oxygen, hydrogen and nitrogen, originally present, with a gradual
predominance of the carbon. This passage from vegetable matter to coal
has been noted in Egypt in connection with the Nubian sandstone,
beds of carbonaceous material deserving the name of lignite or
even bituminous coal having been found at various localities. The
deposits found up to the present time are of such tenuity that it
is not possible on the evidence available to express optimistic
opinions as to the probable occurrence of workable coal in Egypt,
but still they are of sufficient interest to be kept constantly in
mind while the Geological Survey is prosecuting its researches. From
time to time the finding of coal-seams has been reported at Edfu,
in Kharga, at Saqiet el Teir and Abu Radham[7] in the Eastern Desert,
but the efforts hitherto made have resulted in failure.

The evidence thus far available shows that great rivers were entering
the sea in Nubia during an early geological period (the Cretaceous),
typical fresh-water shells having been found south of Aswan covered
with marine worm-tubes; leaf-imprints are abundant in some of
the sandy layers, and in isolated instances they have collected
in sufficient quantity to give rise to lignite and bituminous
coal-layers of extreme thinness, showing that this interesting
and important change has taken place, at least to some extent,
in Egypt itself. The study of coal-producing regions tends to show
that the change to coal of high commercial value requires not only
conditions favourable to the loss of the more volatile gases, but
also that the beds must have been involved in great earth-movements,
which have hastened the tendency to their being enriched in carbon,
both favourable conditions of deposition and marked disturbance of
the strata being thus required to obtain the much-desired result.

Other internal chemical activities are at work, producing changes
which are still the cause of debate and earnest study. The origin of
petroleum must undoubtedly be traced to chemical transformations of a
complicated character, if we may judge by the number of experimental
methods which yield petroleum as a product. All opinions agree that
the mineral oil is derived by some form of chemical action, though
whether it arises from the decomposition of organic remains or whether
it be of inorganic origin is still matter of dispute. Geological
students have on the whole ranged themselves on the side of the
first-named view, pointing out that the petroleum fields are all
associated with sedimentary strata, whether sands or limestones. The
inorganic view has been held as tenaciously by a number of men
experienced in the search for oil, and it is capable of argument
that sulphur dioxide and sulphuretted hydrogen, if being produced
simultaneously, may result in the alteration of limestone to gypsum,
free sulphur and petroleum being also obtained in the reaction.

In this connection it is interesting to note that gypsum, sulphur
and petroleum are associated at Jemsa, on the Gulf of Suez.

One of the most interesting features in connection with petroleum is
the phenomenon presented in most oil-fields of oil-wells separated
perhaps by only thirty metres emitting oil under pressure at the
same time; also the great pressures indicated by the remarkable
fountain flows which are of constant occurrence in the principal
petroleum fields.[8]


                  VI.—THE FORMATION OF IGNEOUS ROCKS.


The external and internal transforming agents are therefore of
the deepest interest and of the highest economic importance,
and the further study of the deep-seated changes leads directly
to a consideration of the formation and sustained activity of the
molten materials which find their main present-day expression in the
phenomena of volcanoes. Their extension in the past is also revealed
by the wearing hand of time in the wide distribution of coarsely
crystalline granites and other igneous rocks, once deep-seated,
but now exposed in regions which are either the cores of ancient
continents or centres of exceptional deformation.

Igneous action and movements of the earth’s crust stand in intimate
relation to one another, a point which has been clearly stated by
Dr. Harker[9] as follows:—“Setting aside operations conducted in
hypothetical intercrustal magma-basins, or generally in the unknown
depths of the earth’s crust, we recognize the actual manifestations
of igneous action chiefly in the forcing outward of molten magmas from
a lower to a higher level within the crust or through the crust to the
surface.” This study has led directly to the recognition of three
phases of igneous action, of which two are intrusive, being phases in
which the molten materials are raised from a lower to a higher level
within the earth’s crust, and an extrusive phase, in which these
materials are raised to the surface and poured out there as lavas.

Study in all parts of the world has further shown that these events
follow a definite sequence or cycle of igneous activity, volcanic
phenomena marking its commencement, followed by the movement of
deep-seated igneous molten magmas (representing the plutonic phase),
and closing with a number of minor intrusions, which may seam both the
volcanic, plutonic, and sedimentary strata. Egypt clearly illustrates
this remarkable succession, and thus gives additional grounds for
believing that it is of fundamental importance. Volcanic activity
was developed on a gigantic scale when the most ancient sediments
of Egypt, now forming the folded and altered slates and schists
of the Red Sea hills, were being laid down. To this part of the
cycle belong some of the most interesting rocks of the country,
the imperial porphyry of Dokhan, the dark andesites that crown
the highest summits in Sinai, and the country-rock in which some
of the most ancient of Egypt’s gold-mines are situated. Here,
too, belong the banded and columnar lavas of the Sixth Cataract,
and the fragments of volcanic rocks which play an important part in
the characteristic conglomerates of the Eastern Desert.

Still more conspicuous is the phase of plutonic activity, vast
masses of granite, diorite, and other highly crystalline rocks
as molten magmas having been in contact with or intruded into the
overlying sediments and volcanic materials. From Sinai to the Sudan
there is a geographical complex due to the intermingling of these
deep-seated igneous rocks with the older and metamorphosed volcanic
and sedimentary members. Desolate volcanic hills of dull-green shade,
whose sides are covered with weathered debris of irregular outline,
alternate with broad plain, out of which rise rounded masses
of granite, or with mountain ranges, whose precipitous sides and
serrated outlines constitute some of the most striking features of
the Red Sea hill scenery.

The final phase, that of the minor intrusions, is admirably
illustrated in Egypt, large areas of the desert consisting of low
ridges formed of parallel bands or dykes of hard rocks, which have
seamed the softer granite, the latter having subsequently been worn
down by erosion. In other cases the dyke is of more basic composition
and more easily denuded than the adjacent rocks.

When these evidences of past igneous activity are examined, they
reveal the interplay of such varied and complicated chemical and
physical effects that a large volume would be required to set forth
the great body of facts observed. Of these only a bare statement of
the most incomplete order must suffice. Igneous rocks are of very
variable chemical composition, and for the purposes of discussion of
their complex relationships have been subdivided into three series
according to the amount of silica they contain, viz.:—The Acid
Rocks with 50 to 70 per cent silica; The Intermediate Rocks with 50
to 60 per cent silica; The Basic Rocks under 50 per cent silica. As a
whole, the igneous rocks are compounds of the silicates of alumina,
magnesia, lime, potash and soda, with oxide of iron; the silicates
of alumina, soda and potash are most abundant at the acid end of
the scale, and those of lime, magnesia, with the oxides of iron
and phosphates at the basic extreme. In consequence, the basic
rocks are usually darker in colour and heavier than the more acid
varieties. Not only have the igneous rocks a varying composition,
but also a varying structure depending on the differences of
origin and position. We may note their history as involving several
stages, viz.:—(1) Solidification from the initial molten magma;
(2) Deformation when under the influence of great earth pressures;
(3) Transformation under the meteorological influences, at or near
the earth’s surface. In addition there are the contact alterations
produced near their junctions with the overlying strata, both within
themselves and in the beds affected by the molten material.

A molten magma varies greatly in its behaviour according to
its position, the solidification of that portion which remained
deep-seated in the hidden reservoir beneath the earth’s crust
taking place slowly and imperceptibly. A rock such as granite is
not formed suddenly by instantaneous cooling, but step by step
individual minerals are crystallized from the complex solution, and
tend to develop as regular and often most beautiful crystals. It
is a source of surprise to most to learn that the greater number
of mineral substances, if free to develop from solution without
external hindrances, tend to form solid bodies which are fashioned on
geometrical principles, constituting one of the most interesting and
mysterious problems with which scientific thought has to deal. The
minerals, as a rule, tend to crystallize out directly in the order
of their basicity, the oxides of iron with their eight-sided crystals
being among the first, so that their octahedral outlines are usually
well preserved. The other minerals of the rocks follow in succession;
sometimes complicated intergrowths occur owing to two crystals of
different composition starting their formation at the same time in the
same portion of the solution. Finally, the last-formed minerals have
to occupy the interspaces left by their consolidated neighbours, and
in the more acid rocks this unenviable position is usually reserved
for the free silica, forming _quartz_. These deep-seated masses,
slowly solidified and entirely crystalline in their structure,
have been called the _Plutonic_ rocks, the example familiar to all
dwellers in Egypt being the red Aswan, or monumental granite. In it,
the felspars and micas or hornblendes present tend towards their
true crystal form, while the quartz occupies the interspaces.

Intermediate between the extruded volcanic rocks, and the highly
crystalline varieties of the internal reservoirs of molten material,
are the dyke or hypabyssal rocks, which as narrow vertical or nearly
vertical intrusions pass in all probability from the deep-seated
source towards the surface of the earth, when they reach it giving
rise to volcanic effects. The dykes have a tendency to be parallel to
one another, and in some regions are the most conspicuous features,
if harder than the surrounding rock giving rise to marked ridges
separated in many cases by comparatively shallow valleys. Not a few
of the main summits in the Red Sea hills and Sinai have assumed their
present form and outline owing to the unequal denudation of one of
these hard bands, while many an ascent, which otherwise would have
been by no means free from danger, is simplified by the formation of
gullies due to the wearing away of the softer and more basic members
of this series.

In the hypabyssal varieties, as well as in surface flows, an
examination of hand-specimens often reveals the presence of
larger crystals (usually termed porphyritic crystals) scattered
in a ground-mass in which no definite structure is visible except
under the microscope. These may in part have been formed before
the molten magma of the rock had begun its upward ascent, but in
general they and the finer-grained base, have crystallized under
similar conditions. Examinations of the ground-mass microscopically
also shows it to be entirely crystalline in its nature, but the
individual components are of very small size.

In the extruded volcanic rocks, on the other hand, the porphyritic
crystals are probably of much earlier date than the ground-mass in
which they are present, the latter being solidified above-ground,
where cooling was rapid, pressure suddenly reduced, and many of
the gaseous constituents were free to escape readily. As crystals
require a certain temperature and a slow liberation of the heat for
their formation, in many volcanic rocks the rapid cooling results
in the production of a glass instead of a crystalline aggregate,
so that the presence of a glassy matrix is in itself evidence of a
quick loss of heat.


               VII.—THE FORMATION OF METAMORPHIC ROCKS.


All materials, both sedimentary and igneous, composing the earth’s
crust, are liable to be involved in movements of deformation, becoming
subject to pressures and chemical agencies, which are often intense
in character and productive of far-reaching internal changes. The
result is the formation of a series of rocks, which may be of divers
origins, but which having lost their original characteristics,
may be grouped as metamorphic. By the action of compression
and dislocation not only are the major masses folded or broken,
but their individual constituents are brought into new relations
both as regards their external conditions and internal molecular
arrangement. Where lateral pressure has been active as regards the
finer-grained rocks, such as clays, the individual particles arrange
themselves with their longer axes at right angles to the pressure,
the result being the production of a fissile structure or cleavage,
totally distinct from the original bedding-planes of the strata.

Clays under such circumstances pass into slates, in which no very
definite mineral banding is observed, or into schists, in which there
is a tendency for the separate minerals, such as mica and quartz, to
have a pseudo-stratified appearance, though the individual layers,
if closely examined, are found to be lenticular, not parallel in
shape. These schists and slates are developed on a large scale in
the Red Sea hills and Sinai.

The extent to which compression and tension has been carried in
these ancient sedimentary strata is well indicated in Sinai, where
rounded pebbles of quartz have been fractured, the two broken parts
somewhat separated, and the whole re-cemented in a schistose matrix.

In many instances, besides mechanical stress, another factor of
metamorphism of rocks has to be invoked to explain the phenomena
observed. Mineral changes take place in these rocks which are due
to the superadding of thermal action, consequent on their direct
contact with molten masses of granitic and other plutonic rocks. In
Sinai, for instance, new minerals are called into existence by
these contact effects, members of the _andalusite_ group, which
are formed at high temperatures, being produced near the junctions,
garnets being present in the mica-schists in a zone somewhat further
removed from the contact area, while beyond these is a belt where the
slaty strata show only traces of the formation of the new minerals
in the presence of ill-defined knots, or segregations forming the
so-called “Knotenschiefer” of the Germans.

It is possible to trace the influence of these contact and dynamic
effects, not only in the sedimentary rocks, but also in those of
plutonic origin. An excellent example of such changes, known as
foliation, can be observed in the Dal Cataract, where a granite is
present containing large crystals of red felspar. It is possible
to trace the change of this rock into a variety which instead
of being massive, is banded, the bands containing the larger red
felspars all tending to lie in one plane. These are not parallel,
but lenticular, certain of the minerals, especially the felspars,
remaining comparatively unaffected as “eyes,” round which the
other minerals appear to sweep. The quartz in many instances is
found to be crushed into a mosaic of small grains, and the plates
of mica have been dragged out and separated from one another by
the shearing. These rocks, having a general composition resembling
the granites, have been termed gneisses, and in some cases, similar
effects have been produced by the intrusion of veins of granite along
the horizontal planes of a more basic rock already banded. This result
is well seen in the Third Cataract, where a foliated rock composed of
a white felspar and mica has been pierced by veins of highly quartzose
granite, which has then spread along the laminæ of the older member.

Similarly in Sinai, the granite, where in contact with the schistose
sedimentary beds, has in certain favourable localities penetrated
between the schistose layers, producing a banded rock which approaches
a gneiss in character.

In Egypt, we are not at present acquainted with such gigantic
overfolding, fracture, and pushing of whole masses of strata one
over the other, as have been studied, for example, in the North-West
Highlands of Scotland, but there is in Egypt itself, a vast series
of gneisses, crystalline schists, marbles and dolomites whose
origin is but dimly understood, and which may represent changes
long anterior those exhibited by the ancient rocks of which we have
been speaking. Developed in the untrodden wastes of the Sudan, in
the wilder stretches of the Cataracts, in the desolate regions of
the Etbai Desert of Egypt, their study is attended with difficulty
and all our hypotheses must depend on the comparison of isolated
specimens with similar rocks from more favoured regions.


                               SUMMARY.


1.—Every rock originates either from the solidification of
molten material or of sediments, these constituting the Igneous and
Sedimentary Rocks respectively.

2.—These may undergo deformation due to movements of the earth’s
crust, such movements according to their intensity determining
the re-arrangement of the constituents with the development of new
structures, producing the Metamorphic Rocks.

3.—These varied rocks, when exposed at the earth’s surface, are
brought under the influence of the agents of transformation, such as
frost, contraction and expansion due to variations of temperature,
the mechanical action of rain, sand borne by wind, and running
water in the form of streams. In addition to these purely physical
activities are others of a chemical nature, either proceeding from
changes outside the terrestrial surface (carbonic acid dissolved in
rain, etc.), or from processes operating within the earth’s crust
(production of petroleum, coal, mineral veins, etc.).

4.—The chemical and physical activities deep within the earth’s
crust result in the formation of the plutonic rocks solidified from
molten solutions, intimately associated with them being the external
manifestations of the working of these hidden forces as revealed in
volcanoes and their associated phenomena.

5.—By the surface changes on the consolidated igneous and other
rocks, the materials are supplied for the formation of some of the
members of the sedimentary series, the sands and clays, while the
limestones in large measure owe their origin to the property possessed
by living animals of constructing shells from the carbonate of lime
brought in solution to the oceans, etc., these shells, after the death
of the animals, contributing to the formation of the calcareous rocks.


FOOTNOTES:


[Footnote 1: In geology, the term _rock_ is applied alike to the soft
and hard materials composing the earth’s crust, as sands may pass
into solid sandstones, soft muds become the most tenacious of clays,
and hard basalt originate as a molten lava.]

[Footnote 2: This statement may not absolutely apply to Cairo itself,
seeing that in the disturbed region of Abu Roash sandstone is actually
at the surface, and the clays are less conspicuously developed than
is the case to the south.]

[Footnote 3: Figs. 1, 2 and 4 are based on photographs of localities
in Great Britain and Ireland taken for the Geologists’ Association
collection of photographs.]

[Footnote 4: Farafra is an exception to this rule, the depression
being due to the wearing away of soft Cretaceous beds higher than
the sandstone.]

[Footnote 5: The well-known Petrified Forests.]

[Footnote 6: From information given by Mr. Harding King.]

[Footnote 7: At Abu Radham a dark layer of purple iron ochre seems
to have been the cause of the investigation.]

[Footnote 8: For further details, see my paper “Petroleum:
Its occurrence and origin,” Cairo Scientific Journal, No. 48,
pp. 205-218.]

[Footnote 9: “The Natural History of Igneous Rocks,” p. 23.]




                            SHORT CATALOGUE
                                OF THE
                    =MAPS, PLANS, AND PUBLICATIONS=
                             ISSUED BY THE
            SURVEY DEPARTMENT, MINISTRY OF FINANCE, EGYPT.
                               * * * * *

                           =MAPS AND PLANS.=
                               * * * * *

The following is a general list of the maps and plans offered for
sale by the Survey Department. A booklet giving details of all sheets
printed may be obtained free, on application either personally or
by letter at the Headquarters of the Department, Giza (Mudiria),
or at the Geological Museum, Public Works Ministry Gardens, Cairo,
where all maps and plans are for sale, or through any bookseller.

Except where specially stated, the price of each map-sheet is 50
milliemes on paper, and 65 milliemes on cloth, and they are sent
post free by the Department.

The reference marks denote: (*) map is in Arabic only; (†) map is in
English only; (*†) map bears place-names both in Arabic and English;
(*) (†) map can be obtained either in Arabic or English.


                             =Town Maps.=


The following list gives particulars of the maps published. The
map of Alexandria, on the scale of 1:1,000 will be completed during
1911. The survey of Cairo on the scale of 1:1,000 is in progress.

  Cairo (*†), 30 sheets, scale 1:1,000 (in preparation).

  Alexandria (*†), 147 sheets, scale 1:1,000.

  General map of Alexandria Municipality (French and Arabic), 10
  sheets, scale 1:6,000.

  Mit Ghamr (*†), 4 sheets, scale 1:1,000.

  Mansura (*†), 16 sheets, scale 1:1,000.

  Suez (*†), 20 sheets, scale 1:1,000.

  Suez (*†), 1 sheet, scale 1:2,500.

  Sohag (*†), 6 sheets, 1:1,000.

  Tanta (*†), 15 sheets, scale 1:1,000.

  Girga (*†), 6 sheets, scale 1:1,000.

  Aswan (*†), 23 sheets, scale 1:1,000.

  Port Said (in French), 1 sheet, scale 1:5,000.

  Zagazig (*†), 20 sheets, scale 1:1,000.

  Damanhur (*†), 14 sheets, scale 1:1,000.

  Benha (*†), 25 sheets, scale 1:1,000.


                           =Cadastral Maps.=


These are maps of the villages showing each _hod_ and plot of
land. They are printed in Arabic only. In ordering, the name of
the village and the numbers of _hod_ and plot should be given. The
following list gives the particulars of the maps for each mudiria
(province):—

  Beheira mudiria (*), 3,300 sheets, under survey, scale 1:2,500.

  Gharbia mudiria (*), 3,460 sheets, scale 1:4,000 and 1:2,500.

  Daqahlia mudiria (*), 2,237 sheets, scale 1:2,500.

  Sharqia mudiria (*), 2,974 sheets, scale 1:2,500.

  Menufia mudiria (*), 2,173 sheets, scale 1:4,000 and 1:2,500.

  Qaliubia mudiria (*), 778 sheets, scale 1:2,500.

  Giza mudiria (*), 766 sheets, scale 1:4,000.

  Fayum mudiria (*), 2,263 sheets, scale 1:2,500.

  Beni Suef mudiria (*), 942 sheets, scale 1:2,500.

  Minia mudiria (*), 1,635 sheets, scale 1:2,500.

  Assiut mudiria, including Kharga Oasis (*), 2,273 sheets, scale
  1:2,500.

  Girga mudiria (*), 1,313 sheets, scale 1:2,500.

  Qena mudiria (*), 1,568 sheets, scale 1:2,500.

  Aswan mudiria (*), 1,076 sheets, scale 1:2,500.


                         =Topographical Maps.=


Scale 1:10,000 (10 cm. = 1 kilometre; 6·3 inches = 1 mile).—The
names on these maps are in most cases in Arabic and English. The
following table shows the number of sheets published:—

  Beheira mudiria (*), 260 sheets.

  Gharbia mudiria (*†), 213 sheets.

  Sharqia mudiria (*†), 29 sheets.

  Daqahlia mudiria (*†), 11 sheets.

  Menufia mudiria (*†), 73 sheets.

  Qaliubia mudiria (*†), 65 sheets.

  Giza mudiria (*†), 90 sheets.

  Fayum mudiria (*†), 126 sheets.

  Beni Suef mudiria (*†), 21 sheets.

  Assiut mudiria, including Kharga Oasis (*†), 72 sheets.

  Aswan mudiria (*†), 63 sheets.

  Aswan or First Cataract (†), 6 sheets.

  The Nile Valley from Aswan to Korosko(†), 36 sheets (paper only,
  25 milliemes each).

Scale 1:25,000 (4 cm. = 1 kilometre; 2·5 inches = 1 mile).—A
provisional map of Northern Gharbia has been published on this scale,
pending the publication of the 1:10,000 sheets of this area. There
are 91 sheets.

Scale 1:50,000 (2 cm. = 1 kilometre; 1·3 inches = 1 mile).—These
maps are printed in three colours. Names are given in English,
and as a rule in Arabic as well. This series is completed for the
whole of the cultivated area of the Nile Valley and Delta. There
are 145 sheets.

Scale 1:1,000,000 (1 cm. = 10 kilometres; 1 inch = 16 miles).—The
six sheets of this map, covering the whole of Egypt, have now been
published. The names are in English. The price of each sheet is 50
and 65 milliemes for paper and cloth editions respectively, or the
whole can be obtained mounted on cloth, varnished, and fitted with
rollers for 550 milliemes.


                   =Special Maps on Various Scales.=


  Map of the Delta (†), 4 sheets, scale 1:200,000. Price, 75 milliemes
  per sheet, or the complete map mounted on cloth, varnished and fitted
  with rollers, 700 milliemes.

  Lower Egypt and the Fayum, 1904 (latest edition) (†), 1 sheet,
  scale 1:500,000.

  Lower Egypt, showing lines of communication (†), 1 sheet, scale
  1:500,000.

  Northern Gharbia (*†), 1 sheet, scale 1:200,000.

  Kharga Oasis (†), 1 sheet, scale 1:500,000.

  Dakhla Oasis (†), 1 sheet, scale 1:500,000.

  Baharia Oasis (†), 1 sheet, scale 1:500,000.

  Farafra and Iddalia Oases (†), 1 sheet, scale 1:500,000.

  Provisional map of the Eastern Desert of Egypt, East Qena-Aswan to
  Red Sea (†), 20 sheets, scale 1:100,000.

  Provisional map of the Eastern Desert of Egypt, between Qus, Sayala
  and Red Sea (†), 2 sheets, scale 1:500,000.

  Provisional map of a part of the Eastern Desert Oilfield (†),
  1 sheet, scale 1:100,000. Price, 100 milliemes on paper and 150
  milliemes on cloth.

  Provisional map of a part of the Eastern Desert Oilfield, showing
  registered prospecting areas (†), 1 sheet, scale 1:100,000. Price,
  100 milliemes on paper and 150 milliemes on cloth.

  Red Sea and Sinai Oilfield, showing registered prospecting areas
  (†), 1 sheet, scale 1:316,800. Price, 100 milliemes on paper and
  150 milliemes on cloth.

  Jemsa Oil Zone (†), 1 sheet, scale 1:75,000 and 1:250,000. Price,
  50 milliemes.

  Mersa Matruh chart (†), 1 sheet, scale 1:4,500.

  Mersa Matruh topographical map (†), 1 sheet, scale 1:10,000.

  Mersa Matruh and Ras Allam Rum (†), 2 sheets, scale 1:25,000.

  Aqaba-Rafa, 1906 (*†), 3 sheets, scale 1:100,000.

  Aqaba-Rafa, 1906 (*) (†), 1 sheet, scale 1:500,000 (paper, 25
  milliemes; cloth, 40 milliemes).

  The Nile Valley from Aswan to Sudan boundary (†), 1 sheet, scale
  1:250,000.

  Port d’Alexandrie (French), 3 sheets, scale 1:4,000.


                   =Wall-Maps, for use in Schools.=


The price of each map is 700 milliemes, except that of the
Mediterranean Basin, which is 500 milliemes. Each map is mounted on
cloth, varnished, and fitted with rollers. The following list gives
the maps published and in preparation:—

  Africa (physical) (*), scale 1:6,000,000.

  Africa (political) (*), scale 1:6,000,000.

  The Nile Basin (*) (†), scale 1:2,500,000.

  Egypt (*) (†), scale 1:750,000.

  The Delta and the Fayum (*), scale 1:200,000.

  Mediterranean Basin (*), scale 1:3,000,000.

  Western Europe and the British Isles (*), scale 1:1,500,000.

  Asia (physical) (*), scale 1:6,000,000.

  Asia (political) (*), scale 1:6,000,000.

  Europe (physical) (*), scale 1:3,000,000.

  Europe (political) (*), scale 1:3,000,000.

  The World (*) (Mercator’s projection).

  The Hemispheres (Eastern and Western) (Airy’s projection)

  British Isles, scale 1:750,000.

  North America (*) (physical) 1:6,000,000.

  North America (*) (political) 1:6,000,000.

IN PREPARATION:—

  South America (physical) 1:6,000,000.

  South America (political) 1:6,000,000.


                          =Geological Maps.=


Geological map of Egypt, scale 1:1,000,000. English. Six sheets,
70 × 58 cm. Price, 100 milliemes per sheet. Complete map, mounted
on cloth, varnished and fitted with rollers, 850 milliemes.

Geological map of Egypt, scale 1:2,000,000. English. One sheet,
68½ × 67 cm. Price, 200 milliemes on paper, and 300 milliemes
mounted on cloth and fitted with rollers.

A number of maps have been published in the various Geological
reports. Further information may be obtained under the respective
headings in the list of Geological Reports, pp. V and VI.


                            =PUBLICATIONS.=
                               * * * * *


The following is a general list of the publications of the Survey
Department, and a few others which are for sale at the Headquarters
of the Department, Giza (Mudiria), and at the Geological Museum,
Public Works Ministry Gardens, Cairo. A booklet giving full details
can be obtained, on application either personally or by letter.

Except where specially stated, the publications are 8vo, and in
English, and are supplied post free by the Department. They can also
be obtained through any bookseller.


                             =Archæology.=

                    ARCHÆOLOGICAL SURVEY OF NUBIA.


BULLETIN 1.—Dealing with the work (archæological and anatomical)
from September 20 to November 30, 1907. English. 39 pp., 27
illustrations. (Out of print).

BULLETIN 2.—Dealing with the work (archæological and anatomical)
from December 1, 1907, to March 31, 1908. English. 69 pp., 52
illustrations. Price, 100 milliemes.

BULLETIN 3.—Dealing with the work (archæological and
anatomical) from October 1 to December 31, 1908. English. 52 pp.,
5 illustrations. Price, 100 milliemes.

BULLETIN 4.—Dealing with the work (archæological and
anatomical) from January 1 to March 31, 1909. English. 28 pp.,
2 illustrations. Price, 100 milliemes.

BULLETIN 5.—Dealing with the work (archæological and
anatomical) from October 1 to December 31, 1909. English. 35 pp.,
5 illustrations. Price, 100 milliemes.

BULLETIN 6.—Dealing with the work (Archæological and
anatomical) from January 1 to April 15, 1910. English. 30 pp.,
8 illustrations. Price, 100 milliemes.

ANNUAL REPORT OF THE ARCHÆOLOGICAL SURVEY OF NUBIA, SEASON
1907-8. VOL. I: by GEORGE A. REISNER. Price, with volume of plates,
L.E. 2.

ANNUAL REPORT OF THE ARCHÆOLOGICAL SURVEY OF NUBIA, SEASON
1907-8. VOL. II: Report on the Human Remains, by Dr. G. ELLIOT SMITH,
F.R.S., and Dr. F. WOOD JONES. Price, with volume of plates, L.E. 2.

PHILÆ,—REPORT ON THE ISLAND AND TEMPLES OF, by CAPT. H. G. LYONS,
with introductory note by W. E. GARSTIN. 1896. English. 67 pp.,
78 illustrations. (Out of print).

PHILÆ,—REPORT ON THE ISLAND AND TEMPLES OF, by
CAPT. H. G. LYONS. 1908. English. 4to, 32 pp., 14
illustrations. Price, 200 milliemes.


                             =Geography.=


RIVER NILE AND ITS BASIN—PHYSIOGRAPHY OF THE, by
CAPT. H. G. LYONS. 1906. 411 pp., 14 maps, 34 illustrations. Price,
400 milliemes.

TURCO-EGYPTIAN BOUNDARY BETWEEN THE VILAYET OF THE HEJAZ
AND THE PENINSULA OF SINAI—THE DELIMITATION OF THE, by
E. B. H. WADE, together with additions by B. F. E. KEELING and
J. I. CRAIG. 1906. (Survey Department Paper, No. 4). 89 pp., 2
maps. Price, 150 milliemes. See also Geology.


                              =Geology.=


ABU ROASH, NEAR THE PYRAMIDS OF GIZA—CRETACEOUS REGION OF,
by H. J. L. BEADNELL. 1902. 48 pp., 2 maps, 19 illust. Price,
200 milliemes.

ARSINOITHERIUM ZITTELI (Beadnell), FROM THE UPPER EOCENE STRATA
OF EGYPT—PRELIMINARY NOTE ON, by H. J. L. BEADNELL. 1902. 4 pp.,
6 illustrations. Price, 50 milliemes.

ASWAN (FIRST) CATARACT OF THE NILE—DESCRIPTION OF, by
DR. BALL. 1907. 121 pp., 5 maps, 28 illustrations. Price, 200
milliemes.

BAHARIA OASIS, ITS TOPOGRAPHY AND GEOLOGY, by DR. BALL and
H. J. L. BEADNELL. 1903. 84 pp., 8 maps, 2 illust. Price, 200
milliemes.

BLACKENED ROCKS OF THE NILE CATARACTS AND OF THE EGYPTIAN DESERTS,
by A. LUCAS. 1905. 58 pp. Price, 100 milliemes.

BUILDING STONES IN EGYPT—DISINTEGRATION OF, by A. LUCAS. 1902. 17
pp. Price, 75 milliemes.

BUILDING STONES OF CAIRO NEIGHBOURHOOD AND UPPER EGYPT, by
DR. HUME. 1909. 92 pp., 9 illustrations. Price, 150 milliemes. Survey
Department Paper, No. 16.

CAIRO AND SUEZ—TOPOGRAPHY AND GEOLOGY OF THE DISTRICT BETWEEN,
by T. BARRON. 1907. 133 pp., 2 maps, 14 illustrations. Price,
200 milliemes.

CATALOGUE OF THE GEOLOGICAL MUSEUM, CAIRO, by DR. HUME. 1905. 37
pp. Price, 25 milliemes.

DAKHLA OASIS, ITS TOPOGRAPHY AND GEOLOGY, by
H. J. L. BEADNELL. 1901. 107 pp., 9 maps, 7 illustrations. Price,
200 milliemes.

EASTERN DESERT OF EGYPT, CENTRAL PORTION—TOPOGRAPHY AND GEOLOGY OF,
by T. BARRON and DR. HUME. 1902. 331 pp., 10 maps, 30 illust. Price,
400 milliemes.

EASTERN DESERT OF EGYPT, BETWEEN LATITUDES 22° AND 25°
N.—PRELIMINARY REPORT ON GEOLOGY OF, by DR. HUME. 1907. 72 pp., 4
maps, 5 illust. Price, 150 milliemes. Survey Department Paper, No. 1.

FARAFRA OASIS, ITS TOPOGRAPHY AND GEOLOGY, by
H. J. L. BEADNELL. 1901. 39 pp., 8 maps. Price, 150 milliemes.

FAYUM PROVINCE OF EGYPT—TOPOGRAPHY AND GEOLOGY OF, by
H. J. L. BEADNELL. 1905. 101 pp., 2 maps, 22 illustrations. Price,
300 milliemes.

FORÊTS PÉTRIFIÉES DES DÉSERTS DE L’EGYPTE—NOTE SUR L’ÂGE
DES, par M. R. FOURTEAU. 1898. French. 8 pp. (Out of print).

IRON ORES IN EGYPT—DISTRIBUTION OF, by DR. HUME. 1909. 16 pp.,
1 map. Price, 50 milliemes. Survey Department Paper, No. 20.

JEBEL GARRA AND THE OASIS OF KURKUR—TOPOGRAPHICAL AND GEOLOGICAL
RESULTS OF A RECONNAISSANCE-SURVEY OF, by DR. BALL. 1902. 40 pp.,
2 maps, 5 illustrations. Price 150 milliemes.

KHARGA OASIS, ITS TOPOGRAPHY AND GEOLOGY, by DR. BALL. 1900. 116 pp.,
19 maps, 16 illustrations. Price, 250 milliemes.

MAMMALS—PRELIMINARY NOTE ON SOME NEW—FROM THE UPPER EOCENE OF THE
FAYUM, EGYPT, by C. W. ANDREWS and H. J. L. BEADNELL. 1902. 9 pp.,
4 illustrations. Price, 100 milliemes.

PÉTROLE DE LA MER ROUGE—RAPPORT SUR LES RECHERCHES DU, par
J. BAROIS. 1885. French. 16 pp., 1 map, 10 illustrations. Price,
100 milliemes.

PETROLEUM DISTRICTS SITUATED ON THE RED SEA COAST—REPORT ON,
by COL. C. E. STEWART. 1888. 25 pp. Price, 100 milliemes.

PETROLEUM INDUSTRY AT BAKU—SKETCH REPORT OF, by
J. H. TREVITHICK. May, 1886. 22 pp. Price, 100 milliemes.

PHOSPHATE DEPOSITS OF EGYPT, by SURVEY DEPARTMENT, 2nd edition
1905. 35 pp., 3 maps. Price, 50 milliemes.

SINAI PENINSULA (SOUTH-EASTERN PORTION)—TOPOGRAPHY AND GEOLOGY
OF, by DR. HUME. 1906. 280 pp., 5 maps, 23 illustrations. Price,
300 milliemes.

SINAI PENINSULA (WESTERN PORTION)—TOPOGRAPHY AND GEOLOGY OF,
by T. BARRON. 1907. 241 pp., 2 maps, 13 illustrations. Price,
300 milliemes.

SOIL AND WATER OF THE FAYUM PROVINCE—PRELIMINARY INVESTIGATION OF,
by A. LUCAS. 1902. 17 pp. Price, 75 milliemes.

SOIL AND WATER OF THE WADI TUMILAT LANDS UNDER RECLAMATION, by
A. LUCAS. 1903. 26 pp., 1 map, 5 illustrations. Price, 100 milliemes.

SUBSOIL WATER IN LOWER EGYPT—PRELIMINARY NOTE ON THE, by
H. T. FERRAR, M.A., F.G.S. 1910. 16 pp., 3 illustrations. Price,
50 milliemes.

THE MOVEMENTS OF THE SUBSOIL WATER IN UPPER EGYPT, by H. T. FERRAR,
M.A., F.G.S. Survey Department Paper, No. 19. English. 74 pp.,
32 illustrations and 16 maps. Price, 150 milliemes.

TERTIARY VERTEBRATA OF THE FAYUM, EGYPT—DESCRIPTIVE CATALOGUE OF,
by C. W. ANDREWS. 1906. 319 pp., 124 illustrations.

TORTOISE—LAND—FROM THE UPPER EOCENE OF THE FAYUM,
EGYPT—PRELIMINARY NOTICE OF, by C. W. ANDREWS and
H. J. L. BEADNELL. 1903. 11 pp., 3 illustrations. Price, 50 milliemes.


                            =Meteorology.=


DAILY WEATHER REPORT.—Issued daily by the Survey
Department. Contains the readings taken at 29 stations in Egypt and
the Sudan, and five stations in southern Europe, with a map showing
the distribution of pressure. Post free, 200 milliemes quarterly,
including short monthly summary.

SUMMARY OF THE WEATHER IN EGYPT, SUDAN, AND THE SURROUNDING
REGION. Monthly.—Contains a brief report on the weather for
the month, with maps showing the pressure-distribution for each
day. Price, post free, 300 milliemes per annum.

ANNUAL METEOROLOGICAL REPORT.—Contains all the meteorological
readings made during the year in Egypt and the Sudan. Also the
readings of the various Nile gauges.

  Years 1898-1899, 1900, 1901, 1902,
  1903                                      Price, 250 mill. each.

  Years 1904, 1905 (in two parts:
  Part I containing the readings
  taken at Helwan Observatory, Part
  II containing the readings for the
  rest of Egypt and the Sudan)              Price, 100 mill. each part.

  Year 1906 (Part I, Helwan)                Price, 100 mill.

  Year 1906 (Part II, Rest of Egypt
  and the Sudan)                            Price, 150 mill.

  Year 1907 (Parts I and II)                Price, 150 mill. each part.

  Year 1908 (Parts I and II)                Price, 150 mill. each part.


                             =Nile Flood.=


MEASUREMENT OF THE VOLUMES DISCHARGED BY THE NILE DURING 1905
AND 1906, by E. M. DOWSON; WITH A NOTE ON RATING FORMULÆ FOR
CURRENT-METERS, by J. I. CRAIG. (Survey Department Paper, No. 11). 82
pp., 6 illustrations. Price, 100 milliemes.

RAINS OF THE NILE BASIN:—

In 1904, by CAPT. H. G. LYONS. 25 pp., 1 map, 5 illustrations. Price,
50 milliemes.

In 1905, by CAPT. H. G. LYONS. 40 pp., 4 maps, 5 illustrations. Price,
50 milliemes.

RAINS OF THE NILE BASIN AND THE NILE FLOOD:—

In 1906, by CAPT. H. G. LYONS. (Survey Department Paper, No. 2). 70
pp., 5 maps, 11 illustrations. Price, 100 milliemes.

In 1907, by CAPT. H. G. LYONS. (Survey Department Paper, No. 9). 50
pp., 1 map, 11 illustrations. Price, 100 milliemes.

In 1908, by CAPT. H. G. LYONS. (Survey Department Paper, No. 14). 69
pp., 1 map, 8 illustrations. Price, 100 milliemes.

In 1909, by J. I. CRAIG. (Survey Department Paper, No. 17). 55 pp.,
1 map, 8 illustrations. Price, 100 milliemes.


                   =Special Papers on Meteorology.=


ATMOSPHERIC ELECTRICITY—DISCUSSION OF THE OBSERVATIONS
ON—AT HELWAN OBSERVATORY, FROM MARCH 1906 TO FEBRUARY 1908, by
H. E. HURST. (Survey Department Paper, No. 10). 65 pp., 2 maps,
8 illustrations. Price, 100 milliemes.

CLIMATE OF ABBASSIA, NEAR CAIRO, by B. F. E. KEELING. (Survey
Department Paper, No. 3). 1907. 61 pp., 1 map, 7 illustrations. Price,
100 milliemes.

EVAPORATION IN EGYPT AND THE SUDAN, by B. F. E. KEELING. (Survey
Department Paper, No. 15). 1909. 29 pp., 1 illustration. Price,
100 milliemes.

PLATINUM-RESISTANCE THERMOMETERS—REPORT ON THE USE OF—IN
DETERMINING THE TEMPERATURE OF THE AIR AT THE HELWAN OBSERVATORY,
by E. B. H. WADE. 1905. 20 pp., 5 illustrations. Price, 50 milliemes.


                             =Surveying.=


ALTITUDES—THE DETERMINATION OF—BY LEVELLING, by
E. M. DOWSON. (Technical Lecture). 1908. 23 pp., 6
illustrations. Price, 50 milliemes.

CADASTRAL SURVEY OF EGYPT, 1892-1907, by CAPT. H. G. LYONS. 1908. 421
pp., 30 maps, 16 illustrations. Price, 400 milliemes.

CADASTRAL SURVEY OF EGYPT—COMPARISON OF—WITH THOSE OF
SOME EUROPEAN COUNTRIES, by CAPT. H. G. LYONS. (Technical
Lecture). 1909. 24 pp., 8 maps. Price, 50 milliemes.

ERRORS OF OBSERVATION, by T. L. BENNETT. (Technical Lecture). 1908. 27
pp., 3 illustrations. Price, 50 milliemes.

LONGITUDE—DETERMINATION OF, by E. B. H. WADE. (Technical Lecture)
1908. 39 pp., 2 maps, 1 illustration. Price, 50 milliemes.

LONGITUDES—A FIELD METHOD OF DETERMINING—BY OBSERVATIONS OF THE
MOON, by E. B. H. WADE. (Survey Department Paper, No. 5). 1907. 47
pp., 9 illustrations. Price, 100 milliemes.

MAP-PROJECTIONS, by J. I. CRAIG. (Technical Lecture). 1909. 25 pp.,
1 map, 25 illustrations. Price, 50 milliemes.

MAP-PROJECTIONS—THE THEORY OF—WITH SPECIAL REFERENCE TO THE
PROJECTIONS USED IN THE SURVEY DEPARTMENT, by J. I. CRAIG. F.R.S.E.,
(Survey Department Paper, No. 13). 1910. 77 pp., illustrated. Price,
200 milliemes.

RELIEF ON MAPS—THE REPRESENTATION OF, by
CAPT. H. G. LYONS. (Technical Lecture). 1909. 19 pp., 5 maps. Price,
50 milliemes.


                       =Terrestrial Magnetism.=


MAGNETIC OBSERVATIONS IN EGYPT, 1895-1905, WITH A SUMMARY OF PREVIOUS
MAGNETIC WORK IN NORTHERN AFRICA, by B. F. E. KEELING. (Survey
Department Paper, No. 6). 1907. 65 pp., 4 maps. Price, 100 milliemes.

MAGNETIC OBSERVATIONS MADE FROM APRIL TO DECEMBER, 1907, AT HELWAN
OBSERVATORY. 8 pp. Price, 25 milliemes.

MAGNETIC OBSERVATIONS MADE DURING 1908 AT HELWAN OBSERVATORY. 11
pp. Price, 25 milliemes.

THE SAME FOR 1909. 11 pp. Price, 50 milliemes.

STANDARDIZATION OF THE MAGNETIC INSTRUMENTS AT HELWAN OBSERVATORY
DURING 1907, by H. E. HURST. (Survey Department Paper,
No. 8). 1908. 45 pp., 4 illustrations. Price, 100 milliemes.


                           =Miscellaneous.=


ANNUAL REPORTS ON THE WORK OF THE SURVEY DEPARTMENT, by the
Director-General, as follows: 1905, 120 milliemes; 1906, 1907,
1908 and 1909, 100 milliemes each.

CHEMISTRY OF THE RIVER NILE, by A. LUCAS, 1908. (Survey Department
Paper, No. 7). 78 pp., 1 map, 1 illustration. Price, 150 milliemes.

COLLECTION OF STATISTICS OF THE AREAS PLANTED IN COTTON IN 1909,
by E. M. DOWSON and J. I. CRAIG. 1909. English or Arabic. 77 pp.,
8 illustrations. Price, 150 milliemes each.

COLLECTION OF STATISTICS OF THE AREAS PLANTED IN COTTON IN
1910. 1910. English or Arabic. Price, 50 milliemes each.

PRESERVATIVE MATERIALS USED BY THE ANCIENT EGYPTIANS IN EMBALMING,
by A. LUCAS, F.I.C. (Survey Department Paper, No. 12). 1911. 59
pp. Price, 100 milliemes.

                               * * * * *


[Footnote: £ 1 = 975 milliemes; $ 1 = 200 milliemes; Mk. 1 = 48
milliemes; Fr. 1 = 38 milliemes.]


                               * * * * *
                      Imp. Nat. 4323-1910-250 br.
                               * * * * *