,transcriber's note3 ,this article has  
been extracted and prepared from  ,the  
,geographical ,journal1 v4 #gj1 #aibg4  
,,problems ,,of ,,the ,,libyan ,,desert 
,john ,ball1 ,o4,b4,e41 ,d4,sc41        
,m4,inst4,c4,e41 ,f4,g4,s41 ,director of
 ,desert                                
,surveys1 ,egypt                        
,map following p4 #if4      ,,there can 
be few tracts of the ,earth's surface   
which present such a  number and variety
 of interesting geographical problems as
 the ,libyan  ,desert4 ,the following   
are some of the more puzzling of the    
questions  which have been asked at     
various times since ,i made my first    
acquaintance with the desert thirty     
years ago3      #a4 ,did the ,nile1 or a
 branch of it1 ever flow through the    
,libyan    ,desert to the west of the   
present ,nile ,valley8      #b4 ,by what
 natural agency were the great          
depressions in the ,libyan    ,desert   
excavated8      #c4 ,can other          
depressions in this region1 besides the 

much-discussed    ,wadi ,rayan1 be      
considered possible of utilization in   
connection with    irrigation1          
flood-protection1 or drainage of the    
,nile ,delta1 or as    sources of       
water-power for ,egypt8      #d4 ,whence
 comes the artesian water of the oases8 
#e4 ,why have not certain lakes1 such as
 ,sittra and ,bahrein1 situated as      
they are in an almost rainless region1  
long since dried up8      #f4 ,can the  
present scanty supplies of drinkable    
water derived from    local rainfall    
along the ,egyptian ,mediterranean      
,littoral be    supplemented by artesian
 borings8      #g4 ,are the artesian    
water-supplies of the oases gradually   
diminishing8      #h4 ,where shall we   
look for the mysterious 8,zerzura10 or  
8,oasis of the    ,blacks08 ,are there  
any other 8lost0 oases remaining to be  
discovered8      #i4 ,can the present   
difficulties of travel in the ,libyan   
,desert1 which    are chiefly due to    
scarcity of water1 be alleviated by the 

sinking of    new wells8      #aj4      
,where are the 8,tortoise ,marshes0 of  
,ptolemy8      #aa4 ,what determined the
 peculiar distribution of the           
sand-dunes1 some    of which extend in  
straight lines for hundreds of          
kilometres8      #ab4 ,what is the full 
extent of the distribution of flint     
implements    and pottery1 of which     
accumulations have been found in what   
are now    among the most desolate parts
 of the desert1 and what light does this
    throw on human history and climatic 
changes8    ,to most of these questions 
no completely satisfactory answers have 
as  yet been given1 though several of   
them have been the subject of           
painstaking investigations by many      
workers4 ,our knowledge of the facts    
bearing on them has1 however1 increased 
considerably during the past few  years2
 and in the present paper ,i propose    
briefly to review the various  questions
 in the light of the latest available   
data concerning them4    ,the problems1 

though they concern a variety of        
subjects1 are very much  interwoven with
 each other1 and they are mostly alike  
in that the first  difficulty in any    
attempt to solve them has always been   
the  incompleteness of our geographical 
knowledge concerning the ,libyan        
,desert as a whole4 ,if we possessed a  
series of detailed contour-maps         
covering the whole of the desert1 most  
of the problems would be in a  fair way 
of solution4 ,but the surveys which     
would be necessary for such  a result   
are impracticable at present1 mainly on 
the score of expense4    ,some fifteen  
years ago ,i essayed the construction of
 a contoured map of  the ,libyan        
,desert1 in connection with the         
,international 8,million0 map of  the   
world4 ,but ,i had to give up the task1 
finding that there were vast  areas     
without a single observation for        
altitude1 while such altitude-  data as 
did exist were open to errors of a      
magnitude intolerable for  even a       

preliminary contouring of the areas with
 which they were  concerned4 ,the       
attempt however was not without its     
value1 because it  drew attention to the
 great lack of reliable levels in the   
,libyan  ,desert1 and to the necessity  
of remedying this defect before even an 
approximately true picture of the       
general relief could be obtained4    ,in
 the interval which has elapsed since my
 former attempt1 a great deal  of       
surveying has been carried out in the   
,libyan ,desert1 and in most of  this   
work special attention has been paid to 
the matter of levels4 ,two  long chains 
of triangulation have been run westward 
from the ,nile to  ,siwa ,oasis1 one vi 
the ,wadi ,natrun and the other vi      
,baharia ,oasis2  another chain has been
 completed along the coast westward from
  ,alexandria to ,sollum1 and a         
triangulation is now being carried out  
which  will eventually connect the oases
 of ,kharga and ,dakhla with the ,nile  
,valley4 ,small local triangulations    

have also been made in certain areas1   
such as ,dakhla ,oasis and in the       
neighbourhood of ,owenat4 ,in all these 
triangulations vertical as well as      
horizontal angles have been observed1   
so that reliable trigonometric altitudes
 are now available for almost  all the  
points occupied or sighted4 ,in the     
southern and central parts of  the      
desert1 we are still dependent on       
barometric levels2 but the old          
determinations have mostly been replaced
 by later and better ones2 and  the use 
of motor-car transport1 by facilitating 
exploratory journeys in  hitherto       
untrodden regions1 has permitted of a   
large number of  additional             
determinations being made in tracts     
where no previous  observations of any  
kind existed4#a    ,owing to the methods
 employed in the latest barometric      
determinations1  the resulting altitudes
 are of a much higher order of accuracy 
than  could be hoped for in previous    
measurements of the kind2 in fact1 it is

  believed that they are not so very far
 behind trigonometric levels in         
precision4 ,this increased accuracy has 
been rendered possible by the           
collaboration of the ,egyptian          
,meteorological ,service1 which1 thanks 
to  the abundant weather-data now       
received and dealt with by it1 is in a  
position to furnish a close             
approximation to the sea-level pressure 
at  any point in the deserts at any     
given instant4 ,the aneroids used in the
  desert explorations are compared with 
the standard barometer of the           
,meteorological ,service immediately    
before the start and immediately  after 
the return of each expedition4 ,at each 
observation in the desert1  the date and
 time1 and the temperature of the air1  
are noted1 as well as  the approximate  
latitude and longitude of the place4 ,on
 the return of  the expedition1 the     
recorded reading is corrected for the   
error of the  aneroid on the standard   
barometer1 and the ,meteorological      

,service is  asked to supply the        
sea-level pressure at the particular    
place and time  of the observation4     
,from the difference of the two         
pressures and the air  temperature1 the 
height of the place above sea-level is  
then worked out  directly with the aid  
of ,jordan's table of 8,barometrische   
,hhenstufen40  ,if the place of         
observation lies considerably above     
sea-level1 a small  correction is       
applied to the observed air-temperature 
to allow for the  temperature-gradient  
in the air2 for of course it is the mean
  temperature of the air column between 
the place and sea-level which  should be
 employed in the reduction4    ,it is   
unlikely that with this procedure either
 the sea-level pressures  or those      
observed at the places can be in error  
by much more than half a  millimetre2   
and consequently1 even with some slight 
uncertainties in the  air-temperatures1 
the resulting altitudes may be expected 
to be accurate  to within about #ae     

metres when only a single observation   
has been made1  and to within much less 
than this when1 as is usually the case  
at  important points1 the altitudes have
 been calculated from a series of       
readings spread over several days4 ,that
 this degree of accuracy is  actually   
attained seems evident on comparison of 
the levels obtained for  the same places
 on different dates4 ,thus1 for         
instance1 at a camp close  to ,bir      
,terfawi1 during a stay of five days in 
,january and two days in  ,march #aibe1 
,i made in all eighteen aneroid         
observations4 ,the mean  altitude found 
was #bdd metres2 the average deviation  
of a single  observation from this mean 
was #h metres1 the maximum being #af4   
,on the  assumption that all sources of 
error are accidental1 the probable error
  of the mean resulting altitude works  
out at less than #b metres1 which is    
about the same as might be expected in  
trigonometric levelling to the  place   
from the ,nile ,valley4    ,the points  

in the interior of the ,libyan ,desert  
of which the levels are  fairly         
accurately known now number many        
hundreds1 and with the exception  of a  
large blank in the unexplored west1 and 
another between the ,nile  and ,merga in
 the ,northern ,sudan1 they are fairly  
well distributed over  the country4 ,it 
therefore seemed to me to be worth while
 to make another  attempt at a contoured
 map2 for the levels now known 7though  
still far  too few for contours to be   
drawn with any great precision7 might   
suffice  for the construction of a map  
on a comparatively small scale and with 
contours at fairly wide intervals2 it   
was felt that a provisional map of  this
 kind1 besides affording at least an    
approximate general view of the  relief1
 might help towards the solution of one 
or more of the problems  which ,i have  
mentioned above4 ,i commenced by        
sketching in the contours  at #ajj-metre
 intervals on the original sheets of the
 #a3ejj1jjj map of  ,egypt1 a revised   

edition of which is in preparation4     
,they were then  reduced to the million 
scale1 and afterwards still further     
reduced1 with  additions from my own    
recent observations around ,owenat1     
,gebel ,kissu1  and ,merga1 from        
,hassanein ,bey's records of his journey
 between ,jalo and  ,el ,fasher1 from   
the altitude-data obtained by the       
,anglo-,french ,boundary  ,commission in
 the ,sudan1#b and from the maps of     
,prince ,kemal el ,din's  expedition of 
#aibf to ,owenat and ,sarra ,well1#c to 
form the map  following p4 #if4 ,the    
attempt has1 ,i think1 fully justified  
itself1 and  more than fulfilled the    
hopes that were entertained concerning  
it4    ,probably the feature that will  
first strike the attention on glancing  
at  the contoured map is the series of  
depressions below sea-level  stretching 
westward from near ,cairo to ,jarabub4  
,the following table  gives a list of   
the principal of these depressions1 with
 the approximate  extent of the areas   

lying below sea-level1 and also 7where  
known7 the  depths below sea-level of   
their deepest parts4 ,where the lowest  
part is  covered by a lake1 the depth   
shown is that of the water-surface1 not 
that of the lake-bottom3                
,approximate area    ,approximate       
,depression4                   below    
sea-level   depth of deepest            
in sq4 kiloms4    part below sea        
in metres4      ,wadi ,natrun           
#bbj                #bc      ,faiyum    
#gjj                #de      ,wadi      
,rayan                              #bhj
                #dc      ,qattara       
7including ,moghara1          #ah1jjj   
#acd    ,qara1 and ,tebaghbagh7         
,sittra 7including ,timata7             
#cjj                #cc      ,bahrein   
7including ,nuemisa7             #aej   
#ae 787      ,watiya                    
#gj                #ae      ,areg       
#fj                #be      ,siwa       
7including ,maasir and              #hjj
                #ag    ,maraqi7         

,girba                                  
#bj                787      ,kheiba     
#dj                787      ,shiyata    
#bj                787      ,melfa      
7including ,shebat1                #bfj 
#ah 787    ,exabia1 and ,gagub7    ,as  
will be seen from the figures in the    
table1 by far the largest and  deepest  
depression in this series--seven times  
as large1 in fact1 as all  the others   
put together--is that of ,qattara1 which
 has not been shown on  any previous    
map1 and of which the existence was     
proved only last year4  ,that so deep a 
depression should exist comparatively   
near to the  ,mediterranean and to      
,cairo1 and have remained undiscovered  
until now1 is  striking evidence of how 
much has still to be learned concerning 
the  configuration of the desert        
surface4 ,the manner in which the       
discovery  was made is perhaps worth    
placing on record4 ,hearing early in    
#aiag that  a military patrol was about 
to operate in the ,qattara region1 ,i   

lent a  small aneroid to the officer in 
charge of the patrol1 and asked him to  
take readings with it at various points 
along his route1 with the object  of    
getting some idea of the altitudes in   
that region4 ,it was1 of course1        
certain that low-lying country existed  
along the foot of the ,qattara          
escarpment1 but no idea was entertained 
that any great part of it might  be     
below the level of the sea4 ,the officer
 brought back aneroid-readings  which   
seemed to indicate that the spring at   
the foot of the scarp at  ,qattara was  
about #fj metres below sea-level2 but   
the aneroid itself was  unfortunately   
lost during the return journey4 ,the    
result was too  surprising for it to be 
accepted without evidence that the      
readings of  the instrument had not been
 vitiated by accidental rough treatment1
 and  consequently ,i refrained at the  
time from placing the levels found on   
the maps4 ,but ,i resolved to confirm   
them or otherwise on the first          

opportunity4    ,that opportunity came  
last year1 when it was possible to send 
a survey-  party to triangulate         
westwards from the ,wadi ,natrun so as  
to cross the  place where the aneroid   
readings had been taken4 ,the work was  
entrusted  to ,mr4 ,g4 ,f4 ,walpole1 of 
the ,survey of ,egypt1 who had already  
distinguished himself by successfully   
carrying out a difficult  triangulation 
from the ,nile across some #ejj         
kilometres of the ,libyan  ,desert vi   
,baharia to ,siwa4 ,the result of ,mr4  
,walpole's work was not  only to confirm
 the substantial accuracy of the        
previous estimation of  the level of the
 ,qattara spring1 but to bring to light 
the existence of  a vast hollow1        
thousands of square kilometres of whose 
floor lie at even  lower levels1 and    
which at one place descends to a depth  
of no less than  #acd metres below the  
level of the sea4#d ,this last-mentioned
 spot1 some  #ajj kilometres            
south-south-west of the ,qattara spring1

 is probably the  lowest-lying point on 
the land-surface of the ,african        
continent4    ,a scarcely less          
remarkable feature is the series of     
depressions  comprising the oases of    
,kharga1 ,dakhla1 ,abu ,mungar1 and     
,farafra2 while  ,baharia occupies a    
more isolated position about midway     
between ,farafra  and the ,faiyum4 ,in  
contrast with those of the northern     
series1 these  southern depressions do  
not penetrate to sea-level4 ,the lowest 
points in  ,kharga ,oasis are probably  
at or just below the level of the sea1  
but the  general level of the ,kharga   
floor is about #gj metres above that    
datum4  ,the lowest point of ,farafra is
 somewhat higher than the general level 
of  ,kharga2 those of ,dakhla and ,abu  
,mungar are higher still1 while in      
,baharia1 though it lies farther to the 
north1 the floor-level averages  some   
#acj metres above sea4    ,a noteworthy 
thing about the larger depressions is   
that their northern  boundaries are     

formed by steep escarpments1 while to   
the south the slope  is more gradual4   
,this is the case1 for instance1 with   
the ,faiyum1  ,qattara1 ,siwa1 ,kharga1 
,dakhla1 ,abu ,mungar1 and ,farafra4    
,baharia is  unique in being entirely   
surrounded by escarpments1 as also in   
containing a large number of hills      
approximating in height to that of  the 
bounding scarps4 ,in the majority of    
cases the greater steepness of  the     
northern boundaries can be correlated   
with geological structure2 the  northern
 walls of the ,qattara and ,siwa        
depressions1 for instance1 mark  the    
southern limit of certain ,miocene      
strata1 while those of ,kharga and      
,dakhla coincide with the southern limit
 of the ,eocene limestones4    ,to the  
south-west of ,dakhla ,oasis there      
stretches a broad tract of  rising      
ground1 with the ,gilf ,kebir and the   
peaks of ,arkenu1 ,owenat1 and  ,kissu  
as conspicuous features4 ,on either side
 of this tract the general  level falls1

 on the one hand towards ,kufra and     
,cyrenaica1 and on the  other hand      
towards the ,nile4 ,the ,gilf ,kebir is 
a great broken plateau of  sandstone1   
rising very nearly to the #ajjj-metre   
contour and stretching  in a direction a
 little west of south for over #ajj     
kilometres4 ,i saw the  south end of    
this plateau from several points on the 
way from ,terfawi to  ,owenat when      
travelling with ,prince ,kemal el ,din  
in #aibe1 and fixed its  position by    
compass-bearings4 ,as seen from the     
south1 the plateau  appeared to be      
merely a flat-topped hill2 its true form
 and extent were  discovered by the     
,prince in the following year1 when he  
passed along its  eastern foot on his   
way from ,pottery ,hill to ,owenat4 ,the
 highest peak of  ,arkenu1 in about lat4
 #bb #ag1 long4 #bd #df1 ,i estimated to
 rise to  approximately #adaj metres    
above sea4 ,the altitude of ,gebel      
,owenat far  transcends ,hassanein      
,bey's previous estimate of #aajj       

metres2 a  trigonometric measurement    
which ,i made in #aibe gave its summit  
as #aijg  metres above sea4 ,the general
 level of the ground at the foot of     
,owenat  ,i found to average about #fjj 
metres1 thus agreeing with ,hassanein   
,bey's  figures4 ,gebel ,kissu1 though  
lower than ,gebel ,owenat1 is           
considerably  higher than ,gebel        
,arkenu1 and being an isolated mountain 
with a single  well-marked peak1 it     
forms a very conspicuous landmark2 my   
trigonometric  determination gave #agbf 
metres for the altitude of the peak     
above sea4    ,to the south-west of     
,kissu there are a few widely scattered 
isolated  hills1 but the country in     
general forms a rolling plain of sand   
extending to the north-east corner of   
,french ,equatorial ,africa with a      
nearly uniform level of about #gjj      
metres4 ,beyond the ,french boundary the
  ground rises towards the ,erdi ,hills1
 which attain over #ajjj metres4        
,from the corner of ,french ,equatorial 

,africa to ,merga1 a distance of #bej   
kilometres1 the country consists of     
alternations of sand-plains and flat    
stony tracts1 with a very gradual fall  
to a level of about #efj metres at  the 
edge of the ,merga depression4          
,between ,merga and ,owenat the country 
consists of sandy plains  alternating   
with broken stony ground and occasional 
hills4 ,the general  level rises from   
about #egj metres on the northern side  
of the ,merga  depression to nearly #hjj
 metres on the parallel of #bj #cj1 then
  gradually falls to about #fjj metres  
at the foot of ,gebel ,owenat4      #a4 
,did the ,nile1 or a ,branch of it1 ever
 flow through the ,libyan ,desert  to   
the ,mediterranean8      ,the idea that 
a 8dry river0 exists in the ,libyan     
,desert is a very old  one1 and seems to
 have had its origin in the fact that   
barren  depressions in that region are  
sometimes called by the local ,arabs    
,bahr  bela ma1 that is1 8sea without   
water40 ,but the ,arabic word bahr1     

which properly means a sea or a lake1 as
 in ,bahr ,lot 7the ,dead ,sea71 is     
also applied in ,egypt and the ,sudan to
 a river1 as in ,bahr el ,nil 7the      
,nile7 and ,bahr el ,azrak 7the ,blue   
,nile74#e    ,the earliest depression to
 be discovered bearing the name of ,bahr
 bela  ma was the one now known as the  
,wadi ,faregh 7the 8empty wadi071       
situated immediately south of the ,wadi 
,natrun4 ,father ,sicard1 who  visited  
the place in #agab1 correctly           
interpreted the ,arabic name to mean    
literally 8sea without water10 and      
having discovered fossil trees there1   
which he imagined to be the petrified   
remains of masts of ships1 he  inferred 
that a narrow arm of the sea formerly   
extended from the  ,mediterranean into  
the locality4#f ,at a later date        
,sicard's view that  the petrified trees
 were the masts of ships was recognized 
to be a  mistaken one2 but a greater    
error was committed by changing the     
translation of ,bahr bela ma from 8sea  

without water0 into 8river  without     
water10 as was done by ,d',anville in   
his #8,mmoires sur l',egypte1'          
published at ,paris in #agff4           
,d',anville was a great authority in his
 day1  and his translation was adopted  
by subsequent writers for over a hundred
  years4 ,general ,andreossi1 who       
commanded ,napoleon's artillery in the  
expedition of #agih and #agii1 made a   
map of the 8,dry ,river0 and the        
8,valley of the ,natron ,lakes10 in     
which both depressions are shown open   
at both ends1 instead of being closed in
 as they really are4 ,andreossi         
considered that the 8,bahr bela ma0 was 
the dry bed of an ancient branch  of the
 ,nile1 which left the present ,nile    
,valley somewhere in ,middle  ,egypt and
 entered the sea to the west of         
,alexandria2 he also thought  that the  
ancient ,lake ,moeris was probably      
formed by the damming of the  8dry      
river0 near its supposed offtake from   
the ,nile4#g ,later on1 after           

,cailliaud and other early              
nineteenth-century travellers had       
discovered  that other depressions      
existed in widely separated localities  
and bore  the same ,arabic name of ,bahr
 bela ma1 it seems to have been hastily 
assumed by the cartographers of the time
 that all the depressions  bearing the  
same name were parts of a single        
dried-up river-channel4  ,thus1 on a    
large map of ,egypt compiled by ,colonel
 ,lapin and published at  ,paris in     
#ahef1 the 8,bahar ,belah-mah ou ,fleuve
 sans eau0 is stated to  come from the  
,congo and is depicted as coursing      
through the ,oasis of  ,dakhla1 thence  
passing to the east of ,baharia ,oasis  
and on to the  ,mediterranean4 ,on      
another large map of ,egypt1 compiled by
 ,muzzi ,bey1 the  then                 
,director-,general of ,egyptian ,posts1 
and published in ,florence in  #ahgf1 a 
continuous valley is boldly shown       
leading from the mountains of  ,darfur  
to the ,mediterranean1 while            

cross-valleys1 labelled 8,old ,bed of   
the ,nile10 are depicted as connecting  
the main valley with that of the  ,nile 
at ,korosko and ,dongola4    ,the       
,rohlfs expedition of #ahgd proved that 
there was no such channel  running      
northwards through ,dakhla ,oasis2 that 
the 8,bahr bela ma0 which  had been     
crossed by ,cailliaud between ,siwa and 
,baharia was merely a  closed-in local  
depression1 and that the continuous     
empty river-beds  which were shown on   
the maps of that period had no real     
existence4#h    ,but though the         
continuous 8,bahr bela ma0 channel of   
the old  cartographers has been shown to
 be purely imaginary1 and has in        
consequence disappeared from our modern 
maps1 the belief that an old dry        
river-bed may exist somewhere in the    
,libyan ,desert has apparently          
persisted in many minds even to our own 
day4 ,only a few years ago ,i was       
called upon by the ,government to       
discuss a suggestion1 made in all       

seriousness by a person of considerable 
eminence1 that the ,nile1 or a  branch  
of it1 must at one time have followed a 
course from somewhere  near ,dongola    
through some of the ,egyptian oases to  
the ,mediterranean2  and that by tracing
 out the old channel1 and deepening it  
artificially  where necessary1 a part of
 the river might be taken off along this
 path  and its water utilized to        
irrigate the desert country on either   
side of  it4 ,to the few scientific     
travellers who have journeyed           
extensively in  the ,libyan ,desert1 it 
will doubtless appear incredible that   
such a  suggestion as this could be     
seriously made4 ,but old traditions     
concerning the geography of little-known
 regions die hard1 and this  particular 
one has probably been fostered by the   
circumstance that on  most small-scale  
maps the oasis-depressions have been    
shown without any  precise indication of
 the altitude of the intervening ground1
 as well as  by the speculations of     

geologists as to the existence of a     
river in the  region in past geological 
ages4 ,blanckenhorn1 for instance1      
published in  #aijb a series of         
small-scale maps depicting the course of
 a hypothetical  river1 the 8,libyan    
,ur-,nile10 running northwards through  
the desert in  the ,eocene and          
,oligocene periods1 and ceasing to exist
 in the  ,pliocene4#i    ,that a river  
flowed during late ,eocene or early     
,oligocene times in a  north-easterly   
direction through what is now the       
,libyan ,desert1 and  entered a sea near
 what is now the ,faiyum1 can scarcely  
be questioned2  for it is only by the   
existence of such a river that we can   
account for  the assemblage of fossil   
trees and curious remains of ,eocene    
animals  7including the ancestors of the
 elephant7 discovered by ,mr4 ,beadnell 
north of the ,birket el ,qarun and      
described by the late ,dr4 ,andrews4#aj 
,as to the size1 length1 and exact      
position of this river of the           

geological past there is very great     
doubt2 but neither its situation nor    
even its existence can be considered    
material to our present inquiry4 ,no    
one conversant with the known facts     
bearing on the general geological       
history of ,egypt during late ,tertiary 
and ,quaternary times could make  the   
mistake of thinking that the path of an 
,eocene river might be  traceable in the
 present desert relief4 ,the evidences  
of such path must  be purely of a       
geological nature4 ,in his endeavours to
 suggest what  might possibly have been 
the course of the river on whose banks  
the  ,eocene animals lived1 ,mr4        
,beadnell found in two localities       
deposits  which might have been formed  
along the ancient drainage-line2 and in 
both these localities the deposits now  
occupy the summits of hills4  ,there is 
insufficient evidence of any kind to    
justify so exact a  location of the     
,eocene river as ,blanckenhorn's maps   
would suggest1 and  none whatever of any

 relationship1 either between the       
present surface-  configuration of the  
desert and ,eocene or ,oligocene        
drainage-lines1 or  between those       
drainage-lines and the ,river ,nile4    
,the appellation 8,ur-  ,nile0 of       
,blanckenhorn is thus a misleading one4 
,if we are to look for  traces of a     
dried-up river in the surface-forms of  
the ,libyan ,desert of  to-day1 it must 
be a river which1 like the streams which
 eroded the  great wadis of the ,eastern
 ,desert1 existed in geologically recent
 times1  and which became dry either    
through the continual deepening of the  
present ,nile-channel1 with consequent  
capturing of the former drainage1  or   
through climatic changes causing a      
diminution of rainfall in the           
collecting area4    ,a study of the     
contoured map seems to me to be         
absolutely conclusive on  the question  
at issue1 for it indicates clearly that 
at no time within  the geologically     
recent period can there have been any   

such continuous  channel as has been    
supposed4 ,let us try and trace1 with   
the aid of the  map1 the most likely    
course along which the ancient ,libyan  
,nile-branch1  if ever one existed1 must
 have flowed4 ,starting from the ,nile  
in the  neighbourhood of ,dongola1 we   
observe that the lowest possible track  
is  through ,sheb towards ,kharga4 ,but 
,sheb can only be reached after passing 
over some #cej kilometres of desert     
lying well above the level of the  ,nile
 at ,dongola1 which is about #bcj metres
 above sea4 ,it is1 of course1  quite   
conceivable that even within            
geologically recent times the ,nile at  
,dongola may have been considerably     
above its present level2 so that we  may
 pass over this first difficulty as not 
being definitely conclusive  against the
 hypothesis we are pursuing4 ,from ,sheb
 to the south end of  the ,kharga       
depression there is a drop of about #afj
 metres1 so that up to  this point a    
channel may have been possible4 ,but    

from here onwards1  difficulties come   
in4 ,if we turn northwards1 we soon     
encounter the north  wall of ,kharga1   
rising to #cjj metres above sea-level2  
so there is no  continuing that way4    
,instead1 we turn westwards towards     
,dakhla4 ,but from  ,kharga we have to  
pass over ground reaching very nearly to
 the #bjj-metre  contour for some #hj   
kilometres to enter the ,dakhla         
depression1 where we  drop to a level of
 #aai metres4 ,we have to traverse some 
#ae kilometres at  altitudes above #bjj 
metres to reach ,abu ,mungar1 where the 
level is #aag  metres2 then a further   
#ab kilometres lying above the          
#bjj-metre contour  to get to ,farafra1 
where the level descends to about #ij   
metres4 ,to get  out of ,farafra1 we    
have again to traverse country lying    
over #bjj metres  above sea1 whether we 
choose a north-westerly route vi ,sittra
 to the  ,qattara depression1 or a      
north-westerly one vi ,baharia to the   
,wadi  ,rayan and the ,faiyum4 ,taking  

the first of these alternatives as being
  the shorter1 we cross some #cj        
kilometres of ground above the          
#bjj-metre  level1 and a further #abj   
kilometres lying between the #bjj- and  
#ajj-metre  contours1 before reaching   
the ,qattara depression4 ,and once we   
are in the  ,qattara depression 7the    
lowest point of which is #acd metres    
below sea71  there is no possibility of 
reaching the ,mediterranean except by   
crossing  a considerable tract where the
 ground-level is over #ajj metres above 
sea-level4    ,a section of the route   
described1 with a comparison-line       
passing through  the present            
,nile-levels in corresponding latitudes1
 is shown in the  figure below3         
,illustration3 ,profile from the ,nile  
at ,dongola through the depressions  of 
,kharga1 ,dakhla1 ,abu ,mungar1         
,farafra1 and ,qattara to the           
,mediterranean4 ,vertical scale #ejj    
times the horizontal4 ,total length of  
section about #agjj kilometres2 for more

 than half this distance the            
ground-level is seen to be above a line 
drawn through the levels of the  ,nile  
in corresponding latitudes4    ,can any 
one believe that a course of this kind  
was ever that of a river8  ,to make a   
through channel would entail deep       
cutting for more than half  the total   
distance of #agjj kilometres1 and would 
consequently involve  excavating        
hundreds of millions of cubic metres of 
rock1 much of it of  considerable       
hardness4 ,moreover1 it cannot be       
supposed1 in the present  state of our  
knowledge of the region1 that more      
favourable lines of  communication exist
 and have been overlooked4 ,many        
depressions doubtless  still remain to  
be discovered2 but these1 like those    
already known1 will  surely prove to be 
merely local basins4 ,so many           
cross-country journeys  have now been   
made in various directions through the  
desert1 that it is  inconceivable that  
any continuous channel of the kind we   

are discussing  could possibly have     
escaped notice4 ,nor can we reasonably  
suppose that  recent earth-movements    
have produced the present severance of  
the  various depressions2 such movements
 might perhaps be invoked to account    
for one or two of the separating        
elevations1 but certainly not for all4  
,we can therefore be absolutely certain 
that neither the ,nile nor any  branch  
of it ever passed through the ,libyan   
,desert to the sea4#aa    ,even channels
 of tributary streams to the ,nile1 such
 as abundantly  survive in the great    
wadis which enter the ,nile valley on   
its eastern  side1 are markedly absent  
in the ,libyan ,desert4 ,the contours on
 the map  suggest that possibly one such
 tributary stream may formerly have     
drained the south-western faces of the  
great plateau in which the  depressions 
of ,dakhla and ,kharga form bays1 and   
have entered the ,nile  somewhere       
between ,aswan and ,halfa2 but if such a
 channel ever did exist1  its actual    

traces have long since been obliterated 
by the smoothing  action of subsequent  
denudation1 and only the great          
escarpment of the  plateau which it half
 encircled remains to tell the tale4    
,photographs by ,prince ,kemal el ,din1 
,dr4 ,ball1 and ,mr4 ,walpole           
,illustration3 #a4 ,desert exploration  
with the ordinary car1 requiring  help  
even on flat ground in sandy tracts     
,illustration3 #b4 ,caterpillar cars    
carrying heavy loads over a sand-  dune 
between ,bir ,terfawi and ,gebel ,owenat
    ,illustration3 #c4 ,the western wall
 of the ,qattara depression #ce km4     
,s4,s4,w4 of ,qara ,oasis4 ,top of cliff
 about #c m4 and floor of depression    
#acc m4 below sea-level                 
,illustration3 #d4 ,ain el ,hez1        
,baharia ,oasis1 irrigated by free flow 
from well    ,illustration3 #e4         
,overlooking the ,baharia depression    
from the pass at  its southern end3 cars
 bound for ,farafra    ,illustration3   
#f4 ,northern end of ,farafra           

depression3 sandy ravine  cutting back  
into chalk plateau      #b4 ,origin of  
the ,depressions4      ,it is a marked  
characteristic of almost all true       
deserts1 that they are  regions of      
internal drainage2 and the ,libyan      
,desert is no exception to  the rule4   
,there are a few gullies draining from  
the plateau to the sea  along its       
northern edge1 and a few others draining
 into the ,nile ,valley  along its      
eastern border4 ,but none of these      
external drainage-lines  extends for    
more than an insignificant distance     
backward into the  interior of the      
country4 ,there is1 in fact1 in the     
,libyan ,desert  7especially in its     
north-eastern portion7 a marked absence 
of any  distinct drainage-lines at all2 
in their place we find extensive stony  
plains1 which either slope gradually    
down towards the various inland         
depressions1 or terminate in an abrupt  
fall where the depressions are  cut back
 into them4 ,even in the ,pluvial epoch1

 when ,europe was glaciated  and the    
deep wadis of the ,eastern ,desert on   
either side of the ,nile were  being cut
 out by great streams1 there cannot have
 been any external  drainage from a     
large part of the ,libyan ,desert2 for  
if there had been1  we should find the  
,libyan plateau far more intensely      
dissected than is  actually the case4   
,the rainfall in this region1 even      
during the ,pluvial  period1 must have  
been far smaller than in the            
neighbouring tracts of  the ,eastern    
,desert and ,sinai2 such rainfall as did
 occur was drained  into the series of  
depressions already described1 and there
 either  formed lakes or was evaporated4
 ,but the action of inflowing drainage  
waters1 carrying sand and mud in        
suspension and salts in solution1 is    
not to deepen the basins into which they
 flow1 but rather to fill  them up4     
,hence we must look to some other cause 
for the formation of  the basins        
themselves4 ,a possible cause is to be  

found in earth-  movements--either a    
local down-folding of the crust1 or an  
upraising by  faulting of the           
surrounding tracts4 ,it is not unlikely 
that such earth-  movements have to some
 extent conditioned the formation of the
  depressions2 but that the depressions 
are not simply faulted-down areas  or   
subsidences is abundantly clear from an 
examination of the bounding  scarps and 
the floors of the larger oases4 ,baharia
 is wholly1 and ,kharga  and ,dakhla are
 partially1 bounded by high escarpments1
 in many places  hundreds of metres     
high1 and the floors of these oases are 
composed of  the same rocks as are      
exposed at the base of the bounding     
escarpments4  ,it is1 in fact1 obvious  
that these great hollows are natural    
excavations1 not subsidences4 ,what was 
the excavating agency8    ,to the       
south-west of the limestone plateau     
which lies west of the ,nile  and       
extends northwards from lat4 #bc #cj    
there is fairly open sandstone  country1

 and the oases of ,dakhla and ,kharga   
occupy great bays in the  escarpment    
which marks the south-west termination  
of the plateau4 ,it  seems reasonable to
 suppose that the ,eocene and           
,cretaceous seas had  their southern    
shores somewhere about the latitude of  
,wadi ,halfa1 for  the limestones do not
 extend far beyond the tropic2 and to   
the south the  hard limestones of the   
plateau probably passed gradually into  
softer  shallow-water deposits1 which   
would lend themselves easily to         
degradation and to removal by the agency
 of streams whose traces have  long     
since disappeared4 ,we can thus possibly
 invoke water-action to  account for the
 primitive formation of the 8bays0 in   
which ,kharga and  ,dakhla are situated4
 ,but we cannot in this way explain     
either the  further deepening of these  
oases1 which converted them into basins1
 or  the excavation of the more         
northerly depressions such as ,baharia  
and  ,qattara4    ,the problem as to how

 the excavation of the northern         
depressions1 and  the deepening of the  
southern ones1 were accomplished is not 
altogether  an easy one4 ,there is1 of  
course1 no doubt that wind has been the 
main  excavating agency4 ,all the       
depressions occur in areas where soft   
rocks  are overlain by hard ones1 and   
once the hard overlying rock was removed
  at any place1 the action of the wind  
on the softer beds would soon  excavate 
a hollow4 ,the difficulty is only as to 
how the hard overlying  rock was first  
removed4 ,to some who have studied the  
question1 a  sufficient explanation is  
to be found in the general degradation1 
combined with the tectonic              
disturbances--folds and faults--which   
are known  to have affected some of the 
oasis-areas1 as1 for instance1 that of  
,baharia4 ,given an anticlinal fold1 a  
general lowering of the surface by      
wind-degradation would eventually result
 in the exposure of the soft  underlying
 beds at the highest point of the fold1 

and subsequently  continued wind-erosion
 would proceed most rapidly on these    
soft  underlying rocks4 ,others1 while  
admitting this explanation as partly    
accounting for the formation of the     
depressions1 consider that other        
factors must have assisted to cause     
penetration of the hard overlying  beds1
 especially in the areas where folding  
is not very marked4    ,of such other   
factors1 ,i can only suggest what       
appears to me to be a  possible one4    
,about twenty years ago ,i was mapping  
the ,mediterranean  coastal area in the 
neighbourhood of ,mersa ,matruh1 some   
#afj miles to the  west of ,alexandria4 
,in this area1 which has about #f inches
 of rainfall  in an average year1 there 
are numerous closed-in basins a few     
miles long  and a few hundred yards in  
width1 descending to a depth of #aj     
metres or  more in the rather soft      
limestone which forms the principal rock
 of the  locality4 ,these basins1 though
 called wadis on the maps1 are more     

usually known as 'ebs or 8bosoms0 by the
 local ,arabs4 ,i was at first  much    
puzzled to account for them2 but        
eventually ,i arrived at what ,i        
believe to be the true explanation of   
their formation4 ,the basins1 of        
course1 collect the surrounding rainfall
 in the winter1 and the drainage        
carries with it into the hollows a      
certain amount of fine loam and sand    
from the disintegration of the          
surrounding surfaces4 ,after the rains1 
the bottoms of the basins become covered
 with vegetation1 while the  surrounding
 rocky surfaces are left bare4 ,in the  
hot dry summer1  however1 the vegetation
 perishes1 and much of the loam is      
removed by the  wind4 ,we have only to  
assume 7what seems indeed likely7 that  
the  rootlets of the vegetation         
disintegrate the limestone floors of the
  hollows to form fresh soil1 and that  
more of this is removed each year  by   
the wind than is brought into the       
hollows by the drainage1 to find an     

adequate cause for a slow but           
progressive deepening of the basins4    
,the  primitive hollow may well be a    
very slight depression of the surface1  
such as might arise from greater local  
softness of the rock and  consequent    
more rapid weathering4 ,once vegetation 
has commenced to grow  in a slight      
hollow of this kind1 the action would   
lead to a slow yet  steadily progressive
 deepening year by year1 and            
sand-erosion would tend  towards an     
elongation of the depression in the     
direction of the  prevailing wind4 ,can 
such a process as this1 continued       
through vast ages  during which the     
climate was somewhat less dry than at   
present1 have  been active in the       
formation of ,baharia and similar       
depressions8      #c4 ,the ,possibility 
of ,utilization of ,depressions in the  
,libyan ,desert  for ,irrigation1       
,drainage1 or ,hydraulic ,power4        
,the depression known as the ,wadi      
,rayan1 discovered by ,mr4 ,cope        

,whitehouse about #ahhc1 situated some  
#dj kilometres west of the ,nile        
,valley and about #ajj kilometres south 
of the latitude of ,cairo1 has been  so 
frequently described and considered in  
regard to its utilization as a          
reservoir or as a flood-protection for  
,lower ,egypt1 that ,i need say  little 
about it beyond a reference to the      
principal published works  dealing with 
it4#ab ,there is no other depression in 
the ,libyan ,desert  which has received 
so much attention from the economic     
standpoint4 ,that  the ,wadi ,rayan has 
not already been utilized as a reservoir
 has depended  on a variety of          
considerations1 of which one of the     
principal has been  the doubts always   
entertained as to whether there might   
not be an  underground leakage from it1 
resulting not only in a loss of part of 
the  stored water1 but also in damage to
 the adjacent flourishing province of   
the ,faiyum4 ,these doubts will not be  
lessened by the converging lines of     

evidence which ,i shall bring forward in
 dealing with the artesian water-       
supplies1 all leading to the conclusion 
that there is an underground            
water-connection between the various    
depressions of the ,egyptian ,libyan    
,desert4 ,of late years1 however1 it has
 been proposed to make use of the  ,wadi
 ,rayan1 not as a reservoir1 but as a   
sump for disposing of the  drainage     
water of ,upper ,egypt by evaporation2  
and to this1 in  consequence of the     
lower level at which the water would    
stand in the  depression1 there is far  
less objection from the point of view of
  possible leakage or damage to the     
,faiyum4    ,the ,wadi ,natrun1 which1  
though considerably less deep1 is not   
greatly  less in extent than the ,wadi  
,rayan1 has received some consideration 
as a  possible sump for disposing of    
some of the drainage water of the       
,behera  ,province of the ,delta4 ,so   
long ago as #ahie the ,public ,works    
,department  studied the possibility of 

draining ,lake ,mariut into the ,wadi   
,natrun1  and thus doing away with the  
increasing cost of keeping down the     
level  of the lake by pumping water from
 it into the sea4#ac ,the ,wadi ,natrun 
has an area1 even at the low contour of 
#aj metres below sea-level1 of  nearly  
#ajj square kilometres1 and the average 
rate of evaporation from  an open       
water-surface within it could not well  
be much less than #c mm4  per day2 the  
wadi could therefore dispose annually of
 at least #ajj  million cubic metres of 
drainage water by evaporation alone1 and
  probably of a considerable additional 
quantity by seepage4 ,but the high  cost
 of cutting a drainage channel from     
,lake ,mariut to the wadi1 and the      
heavy maintenance charges which would be
 incurred in keeping the drain  open1   
were formidable objections to the       
scheme4 ,from a reconnaissance  carried 
out in #ahif1 ,mr4 ,verschoyle found    
that the length of the  proposed drain  
would have to be almost #hj kilometres1 

and for the  greater part of the way it 
would have to be a cutting #bj metres in
 depth  through desert and ridges of    
drifting sand2 he remarked that if it   
were  an easy matter to make the        
connection1 it would be no easy matter  
to  maintain it2 and he concluded that  
the scheme was an impracticable  one4#ad
 ,a more recent proposal has been to    
construct a partly tunnelled  channel   
instead of an open drain2 but this has  
likewise been found to be               
impracticable1 as involving too heavy an
 outlay for the benefits which  would   
result4#ae    ,illustration3 #g4 ,qasr  
,farafra1 seen from the north over plain
 of  powdery chalk forming floor of     
depression    ,illustration3 #h4        
,escarpment and 8,hattia0 of ,abu       
,mungar from the  south                 
,illustration3 #i4 ,the 8,hattia0 of    
,abu ,mungar from the east3 well on     
earth-mound on right    ,illustration3  
#aj4 ,the principal well at ,qasr       
,farafra    ,illustration3 #aa4 ,a      

street in ,qasr ,farafra1 with          
irrigation canal    ,when the great     
extent and depth of the ,qattara        
depression were  established by ,mr4    
,walpole's explorations of last year1   
hopes were  immediately entertained that
 the depression might be made to serve  
some  useful economic purpose4 ,any idea
 of its being of use as a ,nile         
reservoir was of course at once cut out1
 not only by reason of its  position and
 distance from the ,nile1 but also by   
its immense size2 for  even if we could 
turn the whole ,nile flood into it1 some
 twenty years or  more would be occupied
 in filling it to a sufficiently high   
level1#af  and the loss by evaporation  
from so large an area would be enormous4
 ,as  a receptacle for drainage water   
from the ,delta it appeared equally     
impossible of consideration1 because of 
the great length and depth of  the      
channels which would have to be cut to  
reach it4 ,a more reasonable  prospect  
seemed to be that of admitting sea-water

 from the ,mediterranean  into it by    
means of a navigable canal from the     
,arabs ,gulf2 this would  only have to  
be about #ef kilometres in length to    
reach the nearest point  of the         
depression2 and once the canal was made 
and the depression  filled1 ships might 
sail almost to ,siwa4 ,other advantages 
which might  accrue from the formation  
of this inland sea were an increased    
humidity  of the climate along the      
,mediterranean ,littoral of ,egypt1     
leading to  increased rain-crops in that
 region1 the establishment of a valuable
  fishery1 and a possible increase in   
the water-supply of the oases by the    
causing of a slight rise in the static  
water-level there4 ,another idea1  which
 rapidly followed the first one1 was to 
utilize the depression as a  source of  
electrical power for driving pumps by   
which the drainage of  the northern     
parts of the ,nile ,delta might be      
improved4 ,at first sight  this latter  
prospect looked a very attractive one4  

,the salt-marsh which  covers much of   
the floor of the depression appeared    
suggestive of a  former sea-connection1 
and if we could trace out this old      
connection1  the cutting of a canal     
along it might not1 it was thought1 be a
 very  expensive matter4 ,moreover1 it  
was apparent that evaporation from an   
inland sea or lake of so large an area  
would keep pace with quite a  large     
influx from the ,mediterranean1 so that 
if the influx were  restricted to such a
 quantity as would permit of the        
lake-surface being  maintained at a     
level considerably below that of the    
,mediterranean1  power could be         
generated continuously4 ,suppose1 for   
instance1 that we  maintained a         
permanent water-level in the lake of #ej
 metres below the  sea2 the estimated   
area of the lake at this level being    
#ijjj square  kilometres and the mean   
evaporation assumed to be #d millimetres
 a day1  an influx of no less than #cf  
million cubic metres of water per day   

could  be passed into the lake without  
altering its level1 and this with a fall
  of #ej metres would suffice           
theoretically for the continuous        
generation  of over #bgj1jjj            
horse-power4 ,of course the lake would  
gradually get more  and more saline1 but
 the power might continue to be         
maintained for very  many years before  
the lake became as rich in salt as the  
,dead ,sea4    ,but alas6 an            
investigation of the northern borders of
 the depression  showed that the        
hoped-for traces of a former connection 
with the  ,mediterranean ,sea do not    
exist4 ,the depression is entirely shut 
in from  the north1 either by great     
cliffs1 or by ground lying so high that 
the  cutting of a canal to the sea is   
utterly impracticable4 ,of the #ef      
kilometres from the sea-level contour of
 the depression to the coast  along a   
line running #ab east of north from     
,moghara ,lake 7which is the  easiest   
line hitherto found for the cutting of a

 canal71 only #af  kilometres are at    
less than #ej metres above sea2 #ca     
kilometres lie at  altitudes between #ej
 and #ajj metres2 and #i kilometres are 
above the  #ajj-metre level4 ,an open   
channel being thus put out of the       
question1 it  was next natural to       
inquire whether a tunnel1 or a channel  
partly open  and partly tunnelled1 could
 be excavated to serve for the          
conveyance of  sea-water into the       
depression4 ,but even this1 though      
perhaps not  impracticable1 would be a  
very costly undertaking4 ,the conveyance
 of the  requisite quantity of water1   
even at a relatively high velocity      
7which  of course implies a considerable
 slope71 would necessitate a tunnel or  
tunnels of very large dimensions4 ,to   
convey #cf million cubic metres a  day  
at a velocity of #e kilometres per hour 
would require a sectional  area of #cjj 
square metres--i4e4 if two tunnels were 
made1 each would  have to be #ad metres 
in diameter4 ,the cost of boring and    

lining such  tunnels would certainly be 
very great1 and it is doubtful whether  
the  value of the power generated could 
justify the capital expenditure         
involved in the excavation and other    
works which would be necessary4  ,until 
more is known of the nature of the      
strata through which the  aqueduct would
 have to pass1 and as to the length of  
tunnelling and  amount of open cutting  
which would be required1 it is          
impossible to form  even an approximate 
estimate of the expense which the       
undertaking would  involve4 ,all that   
can be said at present is that the      
utilization of the  ,qattara ,depression
 offers a possible means of obtaining   
power on a large  scale for the drainage
 of the low-lying lands of the ,delta1  
with at the  same time a prospect of    
improving in some measure the           
agricultural  resources of the          
,mediterranean ,littoral2 much further  
investigation will  have to be          
accomplished before any judgment can be 

formed as to whether  such a project    
would be an economically sound one4     
,in formulating any scheme for improving
 the drainage of the ,delta1 it is  of  
course important to consider1 not only  
the manner in which the  drainage water 
could be ultimately disposed of1 but    
also the  modifications which would have
 to be made in the existing drains and  
irrigation canals--modifications which  
would need to be carried out  without   
serious interruption to existing        
agriculture4 ,a scheme which  otherwise 
appeared attractive might easily prove  
to be impracticable by  reason of the   
heavy expenses and inconveniences of the
 subsidiary works  which would be       
required to make it effective4          
,illustration3 ,,the ,,libyan ,,desert  
,showing ,surface-,relief1 ,contours of 
,static ,underground ,water-levels1     
,distribution of ,sand-dunes1 and       
,routes  of ,principal ,exploratory     
,expeditions in the ,west and ,south by 
,dr4 ,,john  ,,ball    ,,the            

,,geographical ,,journal ,,july #aibg   
#d4 ,the ,artesian ,water ,supplies4    
,the origin of the artesian water       
supplies of the ,egyptian oases of      
,baharia1 ,kharga1 ,dakhla1 and ,farafra
 7,siwa seems hitherto generally to     
have been left out of consideration7 has
 been a much-discussed question4  ,some 
geologists1 myself amongst them1 have   
always regarded the water as  being     
derived from rainfall in the western    
,sudan1 flowing underground in          
permeable beds towards the              
,mediterranean4 ,others have held the   
view that  the oasis waters are merely  
,nile water which has penetrated more or
 less  laterally into the adjoining     
deserts4 ,the arguments that have been  
urged  in support of the former view    
are1 firstly1 the high temperature of   
the  water in many of the oasis wells2  
and1 secondly1 that the levels of the   
springs and wells are often much higher 
than those of the ,nile in the  same    
latitudes4 ,to these arguments it has   

been justly replied that  neither of    
them is conclusive2 the high temperature
 of the outflowing  water merely        
testifies that it has descended to      
considerable depths at  some part of its
 underground path not very remote from  
the point of  outflow1 but really tells 
us nothing as to its place of origin2   
and the  high level of the springs in   
,baharia1 for instance1 as compared with
  that of the ,nile in the same         
latitude1 might be accounted for by the 
seepage from the ,nile taking place     
fairly high up in the river's course4   
,there the question remained until      
#aibe1 when ,i was able to visit and    
determine the positions and levels of a 
number of water-sources farther  in the 
interior than any of those on which the 
8,nile0 argument was  based4 ,amongst   
other level-determinations1 ,i          
ascertained that the ,sheb  well is #bbh
 metres above sea-level1 and that ,merga
 ,lake1 lying far to  the south-west 7in
 lat4 #ai #c1 long4 #bf #ah71 is at an  

altitude of no  less than #eji metres   
above the sea4 ,shortly before my tour  
in the ,sudan1  ,hassanein ,bey had     
confirmed ,rohlfs' level of #djj metres 
for the ,kufra  water-sources1 and ,i   
had found that of ,abu ,mungar          
7north-west of ,dakhla  ,oasis7 to be   
#aag metres4 ,at all these places the   
water-supplies are  derived from        
underground sources in the same         
rock--namely1 the ,nubian  sandstone1   
which covers such vast areas in the     
,sudan and ,egypt4    ,i had thus four  
well-determined natural water-levels at 
the corners of a  great quadrilateral   
whose sides averaged over #ejj          
kilometres in length1  and embraced more
 than #bj square degrees of the ,earth's
 surface4 ,now  just as in solid        
geometry the levels of any three points 
determine the  inclination of an oblique
 plane to the horizontal1 so on the     
,earth any  three levels will determine 
the inclination of a surface to the     
geoid  7of course assuming both geoid   

and surface to have the same curvature74
  ,and on making the calculation1 ,i    
found that ,i obtained practically the  
same degree and direction of inclination
 for the natural water-surface1         
whichever three of the four known points
 ,i utilized for the calculation4  ,in  
other words1 ,i found that if ,i took1  
say1 the levels of ,kufra1 ,abu         
,mungar1 and ,sheb1 and deduced from    
them the inclination of the water-      
surface to the horizontal1 ,i could     
calculate the level of ,merga pretty    
exactly4 ,extending the trial1 ,i found 
that ,i could do the same with a  fairly
 close approximation for the other wells
 in the ,sheb  neighbourhood1 and also  
for wells in the oases of ,dakhla and   
,kharga4 ,the  conclusion seemed        
irresistible that all the wells         
considered were fed  from a continuous  
sheet of underground water2 and it was  
evident that  this water did not come   
from the ,nile1 firstly because of the  
high level  of ,merga1 which is above   

that of the swamps of the ,bahr el      
,ghazal and  other western feeders of   
the ,white ,nile1 and secondly because  
of the  direction of the downward slope 
of the underground static water-surface1
  which is from the south-west1 instead 
of from the south as it would have  been
 had the water been derived from the    
,nile in the ,bahr el ,ghazal  region4  
,the true source of the water must be   
somewhere more or less  nearly on a line
 drawn south-west from ,dakhla1 for this
 is the direction  of upward slope of   
the underground static water-surface2   
and if such a  line be drawn on a map of
 ,africa1 it will be found to lead      
towards the  ,erdi and ,ennedi region1  
on the borders of the ,chad basin4 ,it  
is in the  highlands of ,eastern ,erdi  
and ,ennedi1 therefore1 that we must    
look for  the source of the artesian    
water of the ,egyptian oases4 ,what is  
known of  this region from the recent   
explorations of ,colonel ,tilho lends   
good  support to our conclusion4#ag ,it 

is a bare and rugged sandstone  country1
 where1 in spite of a rainfall which is 
by no means negligible1  permanent      
water-sources are scanty1 and where1 in 
consequence1 there  must be a           
considerable absorption of moisture by  
the rocks2 and it lies  at so high an   
altitude as to give sufficient 8head0   
for the absorbed  water to percolate    
through the porous sandstones and thus  
to reach  ,egypt4    ,being convinced   
that ,i had at last arrived at the true 
origin of the  artesian water1 ,i next  
began to entertain the idea of          
attempting to make  a map which would   
show the contours of the underground    
water-sheet1 and  from which1 in        
conjunction with the contour-map of the 
surface which ,i  had already prepared1 
,i might be able to predict the depth of
 boring  required to tap the underground
 water at any point in the desert4 ,but 
a  little consideration showed that this
 idea was an impracticable one1 by      
reason of our ignorance of the          

underground geological structure over   
the  greater part of the desert4 ,the   
underground water would naturally pass  
along permeable sandstone beds1 often   
confined between impermeable clays      
above and below4 ,and although the      
general structure of the ,libyan ,desert
  is doubtless one of simplicity as     
compared with that of other parts of    
,egypt1 yet we know1 from observations  
in the oases and in the ,owenat  region1
 that the beds are in some places folded
 and faulted1 and that in  others they  
have been uplifted and entirely removed 
by denudation1 with  the exposure of    
large areas of the underlying ancient   
crystalline rocks4  ,the only parts of  
the desert for which the boring-depths  
could safely be  predicted would be     
certain small areas within the oases1   
where wells  have been sunk in          
sufficient numbers to give us definite  
information as  to the local underground
 structure2 and underground-water maps  
of these  small areas1 though they might

 usefully systematize our knowledge     
concerning them1 would not be of any use
 for predictions at points  situated    
elsewhere in the deserts4    ,but while 
it was thus impracticable to prepare    
maps showing everywhere  the depth at   
which underground water actually exists1
 ,i conceived that  it might be quite   
possible to prepare maps showing static 
water-  levels2 that is1 the levels to  
which the water would anywhere rise     
hydrostatically when once it was tapped 
by borings4 ,for the slope of  the      
static water-surface between known      
points will be largely  independent of  
the underground structure of the        
intervening country4  ,apart from any   
physical changes which may still be     
going on in the  underground rocks      
themselves through geological           
agencies--changes which1  if taking     
place at all1 must be so slow as to be  
negligible except in  the course of     
centuries--the only factors which can   
affect the slope of  the static         

water-surface1 once it has been         
established1 are variations  either in  
the rate of supply of water to the beds1
 or in the rate at  which it is removed 
from them4 ,as regards variations in the
 rate of  supply1 it is obvious that    
variations in the annual rainfall of the
 ,erdi  and ,ennedi region must cause   
very considerable variations from year  
to  year in the amount of water received
 by the underground beds4 ,but the      
resistance of friction to the flow of   
water through the pores of the          
sandstones is so great1 that the annual 
oscillations of pressure must be        
rapidly damped out as the distance from 
the place of influx increases2          
consequently the levels of the water in 
the wells of the ,egyptian oases  7and  
even1 so far as is known1 that of the   
lake at ,merga7 show little or  no      
annual variation4 ,and with regard to   
variations in the rate of  removal of   
water from the beds 7by outflow to the  
,nile1 or to the sea1  or into lakes    

wherein it evaporates1 or by the        
exploitation of wells and  springs for  
irrigation purposes71 these changes1    
though possibly in some  cases they may 
be progressive1 and in restricted       
localities very  sensible1 can exercise 
but little influence from year to year  
on the  general distribution of         
water-pressure within the underground   
strata4 ,we  may therefore conclude that
 the gradient of the static             
water-surface  will everywhere have     
assumed practically a steady state4     
,unlike the  actual water bearing beds  
themselves1 which may be much folded1   
the  static water-surface will in       
general have simple gentle slopes       
everywhere in the open desert4 ,in the  
oases1 of course1 where numbers of      
wells yielding large outputs have been  
bored in proximity to each other1  the  
static water surface will be wrinkled2  
but over the vast bulk of the  desert   
the contours may be expected to be      
smooth curves4 ,the  diagrammatic       

section below will1 ,i think1 make clear
 this point about  the general          
non-dependence of the shape of the      
static water-surface on  the geological 
structure3    ,illustration3            
,diagrammatic section showing that the  
static water-level  is largely          
independent of the underground structure
    ,in the diagram1 ,,fekhg represents 
a water-conveying stratum1 folded       
throughout its course and faulted at    
,,hk1 but having a general downward     
slope from ,f to ,g4 ,a and ,b represent
 points at which the water just  rises  
to the ground-level1 either through     
natural fissures or in  artificial      
borings4 ,the straight line drawn       
through ,a and ,b represents  very      
approximately the static level at any   
point between ,a and ,b1 that  is1 the  
level to which the water would rise in  
bores carried down to the  water-bearing
 bed4 ,a boring at ,c1 for instance1    
would have to go down to  ,e to tap the 
water1 but once the bed was tapped the  

water would rise in  the bore as far as 
,d4 ,at the fault ,,hk1 the pressure of 
the water at ,k  will cause it to rise  
through the crushed rock at the         
fault-plane and  re-enter the porous    
stratum at ,h4 ,if there is a           
considerable outflow at  ,b1 and the    
fault-plane is a very narrow fissure1 we
 may expect some drop  in the line ,,ab 
over the fault1 by reason of the extra  
frictional  absorption of head at this  
place4 ,but unless the thickness and    
degree of  permeability of the          
fault-rock are markedly different from  
those of the  sandstone bed itself1 the 
drop of pressure will not greatly       
disturb the  general slope ,,ab4 ,in any
 case it is apparent that the level of  
the  static water-surface at any place  
between ,a and ,b is capable of being   
estimated with a far closer degree of   
approximation than is the level of  the 
water-sheet itself4 ,we may therefore   
justifiably assume a uniform  gradient  
for the static level between points at  

which that level is  known1 disregarding
 folds in the strata2 and though we     
cannot entirely  allow in detail for    
unknown faults and variations in        
permeability1 it  must be borne in mind 
that the total effect of all the unknown
 factors  between any two known points  
is already automatically allowed for in 
our  data4 ,it is only the variations   
from uniformity1 due to the unknown     
distribution of the faults and of the   
departures from the average             
permeability1 which can affect us2 and  
these variations and departures  are    
probably but small in most of the great 
unexplored areas of the  south-west of  
,egypt1 where the geological structure1 
from all we know of  it1 appears        
generally to be remarkably uniform4     
,the first requisite for the            
construction of a map showing the       
contours  of the static water-surface   
was1 of course1 a sufficiency of well-  
determined positions of points where the
 static water-level of the  artesian    

supply was fairly exactly known4 ,such  
points are the springs  and wells of the
 various oases1 the surfaces of lakes   
occupying  depressions and presumably   
fed by underground supplies1 and any    
places  on the ,nile where the river    
taps artesian beds4    ,in regard to the
 wells and springs1 it was obvious that 
only those known  to derive their       
supplies from artesian sources could be 
utilized as  giving points on the static
 water-surface4 ,this consideration cut 
out  from the discussion the springs of 
,owenat and ,arkenu1 which are known to 
be fed by local rainfall1 and also the  
small water-sources of ,kurkur1         
,dungul1 ,nakheil1 and ,ain ,amur1 which
 occur in situations where  percolation 
from occasional local rainfall seems to 
be the only possible  source of supply4 
,and for reasons which will appear      
presently1 none of  the wells and       
springs situated to the north of the    
,siwa-,qattara-,faiyum  chain of        
depressions could be considered as      

entering into the problem4  ,with these 
exceptions1 every water-source situated 
within the area of  the ,libyan ,desert 
covered by the map1 and whose level was 
known1 was  utilized2 but in the greater
 oases and in the ,wadi ,natrun the     
wells and  springs are so numerous and  
so close together that in these         
localities  it was necessary to select  
one or two wells as representatives of a
  group4 ,i had no hesitation in        
including the wells of ,siwa and the    
,wadi  ,natrun1 because the temperature 
of some of the wells and springs of     
,siwa1 and the quantity of the output of
 water at both places1 seem to me  to   
afford conclusive evidence of the       
artesian character of their  supply4#ah 
,the wells of the little oasis of       
,lageita1 to the east of the  ,nile near
 ,qena1 were included1 for although they
 are not in the ,libyan  ,desert1 they  
most probably derive their supplies from
 the same  underground flow which feeds 
the western oases4 ,i have included only

 one  well in which the water does not  
rise nearly to the ground-level4 ,that  
well is one which was bored by the      
,british ,army during the ,great ,war1  
at  a place called ,b#f1 some #dj       
kilometres to the east of ,baharia      
,oasis4 ,the  level of the ground at    
this point is #aab metres above         
sea-level1 and as  the water was        
stationary in the bore at #gh metres    
below the ground1 the  static level here
 is #cd metres above sea4#ai ,the well  
is said to have  yielded some #hjj      
gallons per hour without the water-level
 in the bore  being sensibly changed4   
,the level of the well at ,sarra has    
recently been determined by ,prince     
,kemal el ,din2 but ,i have not included
 it in my data1 because he informs  me  
that the water-level fluctuates by #bj  
metres or more in different  years1     
while the level of the artesian water of
 the ,egyptian oases and  ,merga is very
 nearly constant4 ,the inference ,i draw
 from the great  fluctuations in the    

water-level at the ,sarra well is that  
it is  dependent on percolation from a  
more or less local rainfall rather than 
on the same flow which feeds the        
,egyptian oases4      #e4 ,permanence of
 ,lakes4      ,in regard to lakes and   
salt-marshes1 the permanence of those   
occupying  the depressions of ,areg1    
,bahrein1 ,sittra1 and ,qattara can     
only1 ,i think1  be adequately explained
 by regarding them as fed1 at least in  
part1 by  underground supplies coming   
into them from the south4 ,the total    
area of  the lakes of ,bahrein1         
,nuemisa1 ,sittra1 and ,moghara is      
nearly #bj square  kilometres1 and that 
of the salt-marshes 7sabakha7 is not    
less than  #ejjj square kilometres4 ,the
 depressions are situated in a region   
which  is nearly rainless2 in ,siwa the 
mean annual rainfall is only about a    
quarter of an inch1 and that in the     
depressions farther south1 such as      
,bahrein and ,sittra1 is doubtless even 
smaller4 ,the mean daily  evaporation   

from the lake-surfaces cannot well be   
less than some #d mm41  which would mean
 a lowering of the lake-levels by       
evaporation of #a  metres each year     
unless there was some inflow to make up 
for the loss4  ,and though the rate of  
evaporation from the salt-marshes1 area 
for area1  is doubtless very much       
smaller than that of the lakes1 the     
#bej-;fold  greater extent of the       
marshes makes it certain that the total 
quantity  of water annually evaporated  
from them must far exceed that from the 
lakes4    ,it appears unlikely that the 
loss by evaporation in the lakes and    
marshes can be entirely made up from    
local rainfall and by seepages from  the
 northern slopes4 ,the rocks forming the
 surface of the great ,miocene  plateau1
 #bjj metres high1 which separates the  
depressions from the sea1  are chiefly  
limestones and clays2 the beds are      
nearly horizontal1 but  such slight dips
 as exist are believed to be towards the
 sea4 ,the  average annual rainfall on  

the coastal portion of the plateau is   
about #f  inches2 but it falls off      
rapidly inland1 till it is only about a 
quarter  of an inch near ,siwa4 ,the    
heaviest rainfall on the plateau thus   
occurs  along a strip parallel to the   
coast1 where it is largely drained off  
towards the sea by the gullies which    
indent the plateau-edge4 ,of that  which
 falls on the plateau-surface farther   
inland comparatively little  is         
absorbed1 owing to the generally        
non-porous nature of the uppermost      
rocks2 after a heavy shower1 water lies 
on the surface in shallow pools  for a  
few days and is soon evaporated4 ,so    
impervious to water is the  limestone in
 this region1 that the ,romans excavated
 chambers in it to  form reservoirs1 of 
which many hundreds still exist4 ,nor   
can we think  that much surface         
drainage-water from the country to the  
south ever  finds its way into the      
depressions2 for there is an almost     
complete  absence of drainage-lines     

entering them4 ,at the feet of the      
northern  scarps of the ,qattara        
depression1 and along the north-eastern 
shores of  the lakes in the ,wadi       
,natrun1 there are1 indeed1 small       
springs which  show that some of the    
rain falling on the plateau does        
actually  penetrate the rocks and escape
 by seepage into the depressions4 ,but  
the  amount of this seepage appears to  
be insignificant compared with the      
volume of water which must annually     
disappear from the lakes and marshes  by
 evaporation4 ,a further consideration  
bearing on this point is that  whatever 
may have been the agency by which the   
depression of ,siwa was  formed1 that   
same agency almost certainly operated to
 produce the other  depressions of the  
northern chain2 and it seems most       
unlikely that a  connection should have 
been opened up with the underground     
water-bearing  beds in ,siwa1 and not   
also in the larger and much deeper      
depression of  ,qattara4    ,it would be

 a difficult matter to estimate the     
relative proportion of  the water       
entering the depressions by underground 
flow from the south1  to that           
contributed by local rainfall and       
seepage from the northern  slopes4 ,but 
that is not necessary for our immediate 
purpose4 ,it is  sufficient to show that
 there must be some influx into the     
depressions  from the same source as    
that which supplies the wells of the    
greater  oases1 to establish the        
existence of that underground           
water-connection  which is all that we  
need to justify us in regarding the     
levels of the  lakes and salt-marshes as
 furnishing us with points on the static
 water-  surface2 and from the          
considerations mentioned above it seems 
to me  certain that some influx of      
underground water really does take      
place4    ,i have also thought it       
justifiable to include the ,birket el   
,qarun in my  collection of static      
water-level data1 because although that 

lake was  probably first formed by an   
overflow of the ,nile into the ,faiyum1 
and is  even now being fed by ,nile     
water through the ,faiyum drains at the 
rate  of some #cej million tons a year1 
there is a certain amount of evidence   
suggesting that it has some underground 
water-connection with the  ,qattara     
depression4 ,that evidence1 to which    
attention was first drawn by  ,professor
 ,schweinfurth1#bj consists in the      
relatively low salinity 7#ac  per cent47
 of the lake1 notwithstanding the long  
period through which it  has been       
subject to evaporation and the fact of  
its having shrunk to  dimensions very   
much smaller than it possessed in       
ancient times4 ,unless  there has been a
 large underground efflux of salt water 
from the lake1  it appears impossible to
 account for its present degree of      
freshness4 ,in  ,professor              
,schweinfurth's day1 of course1 the     
existence of the ,qattara  depression   
was unknown1 and it was puzzling to     

suggest where the salt  water had gone  
to4#ba ,an underground leakage from the 
,birket el ,qarun  into the ,qattara    
depression is quite conceivable1 for    
although the two  places are separated  
by some #bjj kilometres1 there is a very
  considerable fall between them4 ,thus 
the salt in the marshes of the  ,qattara
 depression may possibly have come in   
part from the ,birket el  ,qarun4 ,the  
present rate of discharge of the ,faiyum
 drains into the lake  is1 however1 just
 sufficient to make up for an average   
daily evaporation  from the lake-surface
 of a little over #d mm41 which is about
 the rate we  might expect2 and although
 the level of the lake-surface has      
fallen some  #e metres since            
observations of it were first made in   
#ahhf1 it is now  nearly stationary2    
hence it does not appear likely that    
there is much  underground leakage at   
present4 ,if the former leakage from the
 lake took  place by lateral flow into  
porous strata near its surface1 of      

course the  leakage may have been       
arrested by the lowering of the         
lake-level  uncovering the porous beds  
into which it took place2 but ,i think a
 more  likely explanation is that the   
leakage occurred at or near the bed of  
the lake1 and has gradually been reduced
 by the continued deposition of  ,nile  
mud on the lake-bottom1 and by the      
diminution of head due to the  fall in  
the water-level4    ,in regard to the   
tapping of the artesian waters by the   
,nile1 there is  only one locality in   
which this is known to take place2 but  
the quantity  of underground water which
 is there withdrawn by the river is     
probably  very considerable4 ,when ,i   
was surveying the ,nile ,valley between 
,aswan  and ,korosko in ,december #ahih1
 ,i observed that in the vicinity of the
  temple of ,dakka 7about #aje          
kilometres south of ,aswan7 the lands on
 the  west bank of the river were being 
irrigated with warm water1 drawn by     
8sakias0 7water-raising machines7 from  

pits sunk in the alluvial flat  which   
extends between the river and the edge  
of the sandstone desert4  ,the length of
 the tract over which the warm water was
 being withdrawn  for irrigation was    
found to be about #af kilometres1       
stretching from #b  kilometres north of 
,dakka temple southwards to the temple  
of ,maharraga2  and the width of the    
alluvial tract at ,dakka1 where it is   
widest1 was  about #acjj metres4 ,some  
of the water-pits were more than a      
kilometre  from the river4 ,levelling   
from the ,nile 7the surface of which was
 then  about #ii metres above sea7      
across the cultivation to one of the    
sakia-  pits #gej metres west of the    
river1 ,i found the level of the ground 
at  the sakia-pit to be #gi metres above
 that of the ,nile1 and the water-      
surface in the pit to be #hd metres     
below the ground-level2 there was  #ab  
metres depth of water in the pit4 ,the  
temperature of the water in  the pit ,i 
found to be #hc ,f41 while that of the  

,nile was #fj ,f4 and that  of the air  
was #fg ,f4 ,the headman of ,dakka told 
me that the exploitation  of this warm  
underground water had begun about #ahhg2
 they dig out the  sandy mud1 and then  
see the water oozing rapidly into the   
pit out of the  sandstone below4 ,on    
crossing to the east bank of the river1 
,i found that  there also the warm water
 was being similarly raised for         
irrigation1  though to a smaller extent1
 because on that side the sandstone     
desert  approaches more closely to the  
river and there is much less cultivable 
land4 ,the exploitation of the water on 
the east side of the ,nile  extended    
only over a distance of about #e        
kilometres along the bank1 with  a      
maximum width of alluvial plain of #fjj 
metres1 just at the place where  the    
great ,wadi ,alagi debouches into the   
,nile ,valley4 ,as the sandstone  bed   
from which the warm water issues is less
 than #b metres below the  level of the 
water-surface of the ,nile1 and the     

water occurs on both  sides of the      
river1 it is certain that the           
water-bearing bed is cut  through by the
 ,nile channel itself2 the seepage into 
the river along the  stretch of #af     
kilometres must therefore be very       
considerable4 ,it seems  evident that   
the water is not derived from the bed of
 the ,wadi ,alagi1  great               
drainage-channel though that wadi is2   
for we could not then  account for the  
temperature of the water1 nor for its   
appearing to a  larger extent on the    
west bank than on the east1 with the    
river in  between4 ,moreover1 the water 
appeared to be much more free from salts
  than we should expect it to be if it  
were merely drainage from the ,wadi     
,alagi4 ,it strongly resembles1 in fact1
 both in temperature and  character1 the
 artesian water of the greater oases1   
and there can hardly  be the smallest   
doubt that at ,dakka the ,nile is not   
only continually  abstracting artesian  
water from the same underground         

water-sheet that  feeds the oases1 but  
is abstracting it in far larger         
quantities than  those yielded by all   
the oasis wells and springs put         
together4#bb ,it is  certainly          
remarkable that the place where         
considerable supplies of warm           
underground water enter the ,nile should
 coincide with the embouchure of  what  
is perhaps the greatest drainage channel
 of the ,eastern ,desert of  ,egypt2 but
 ,i think it is likely that the         
explanation of the coincidence  may be a
 tectonic one2 the water-bearing beds   
may have been brought up  by a local    
fold in the strata1 and the same fold   
may in some way have  conditioned the   
formation of the primitive drainage-line
 which was  ultimately to become the    
,wadi ,alagi4    ,having now indicated  
briefly the grounds for their           
acceptance1 ,i give  below a table      
showing the various points which ,i have
 adopted as  furnishing data for        
constructing the contours of the static 

water-  surface underlying the ,libyan  
,desert1 together with the altitudes of 
the  points above or below sea1 and the 
sources of these level-data4 ,the       
levels are doubtless in some cases      
slightly inaccurate2 but a few metres   
of error are immaterial to the object in
 view1 and it is believed that  even    
those levels which rest on barometric   
determinations are  sufficiently        
accurate for our purpose4               
,,list ,,of ,,adopted ,,points ,,on     
,,the ,,static ,,water-,,surface        
,place4               ,level            
,determined by4                         
7metres74      ,wadi ,natrun1 surface of
          #bc    ,ball1 ,trigonometric  
lakes                                   
levelling1 #aiad4      ,birket el       
,qarun1 surface of      #de    ,survey  
of ,egypt1 #aibf4    lake               
,based on spirit levelling              
from ,alexandria4      ,moghara1 surface
 of lake         #bc    ,walpole1       
,trigonometric                          

levelling1 #aibd4      ,qattara         
,depression1 various    #hjbc           
points on salt-marsh1 the    lowest     
being      ,sittra1 surface of lake     
#af                  ,areg1 surface of  
lake            #be                     
,siwa                             #ag   
,jaghbub                          #cb   
,hassanein1 ,barometric                 
observations1 #aibc4      ,jalo         
#fa                  ,bir ,butaffal     
#ih                  ,el ,harrash       
#caj                  ,awadel 7,kufra   
,oasis7            #dcd                 
,ezeila 7,kufra ,oasis7            #chi 
,bawitti 7,baharia ,oasis7         #abi 
,ball1 #aiag1 and ,walpole1             
#aibd4 ,trigonometric                   
levelling4      ,el ,hez 7,baharia      
,oasis7          #acd                   
,b#f ,well 7water surface in7       #cd 
,walpole1 ,trigonometric                
levelling1 #aibd1 and                   
military records of depth1              
#aiaf4      ,lageita 7,eastern ,desert7 

#aba    ,murray1 ,trigonometric         
levelling1 #aiba4      ,farafra         
#ij    ,ball1 ,barometric               
observations1 #aibd4      ,abu ,mungar  
#aag                  ,mut 7,dakhla     
,oasis7              #aai               
,kharga 7average of numerous      #gj   
,beadnell1 ,spirit levelling1    wells7 
#aiji4      ,ain ,ismail 7,kharga       
,oasis7        #fg    ,ball1 ,barometric
                                        
observations1 #aibe4      ,bir ,murr    
#aef                  ,bir ,abu ,hussein
                 #ahb                   
,bir ,kassaba                     #agf  
,sheb ,well                       #bbh  
,safsaf                          #bcj   
,bir ,terfawi                     #bdd  
,merga1 surface of lake          #eji   
,dakka1 water-surface in          #ii   
,ball1 ,spirit levelling from    wells  
the ,nile1 #ahih4    ,to prepare a map  
showing the contours of the static      
water-surface1 ,i  took a graticuled    
sheet and plotted the above-scheduled   

points on it in  their ascertained      
geographical positions1 affixing the    
adopted level to  each4 ,to get points  
on the various contours at vertical     
intervals of #ajj  metres1 ,i joined    
each pair of points on the map by a     
pencil line1 and  then1 by interpolation
 from the terminal levels1 found the    
points on  this line where the various  
contours crossed it1 on the assumption  
of a  uniform gradient between the      
terminal points4 ,many of the lines thus
  drawn of course crossed each other1 so
 that interpolation of the static  level
 at the point of their intersection gave
 two values for the same  place4 ,but   
their agreement was wonderfully close1  
considering the  fewness and the        
scattered nature of the datum-points1   
and this went a  long way to encourage  
me in the belief that the hypothesis on 
which ,i  had been working1 namely1 that
 of an underground water-connection     
between all the points included in my   
list1 was correct4 ,i found that  the   

contours of the static water-surface    
could be approximately  represented by a
 series of smooth curves1 as shown 7on a
 reduced scale7  in the outline map     
below4    ,apart from the general       
smoothness of the curves1 especially in 
the  south-west1 where it may in part be
 due to the scantiness of control-      
points1 the most striking thing on this 
outline map is the north-  eastward     
projection of the #ajj-metre static     
contour1 where it runs out  so as to    
include ,baharia ,oasis4 ,the reasons   
for this projection are  obviously the  
efflux of water1 on the one hand        
north-westwards into the  great ,qattara
 depression1 and on the other hand into 
the ,nile at ,dakka4  ,the indentation  
of the #djj-metre contour near ,kufra is
 likewise  explained by the withdrawal  
of water from the wells of that oasis4  
,the  general parallelism of the curves 
in the south-western part of the map1   
showing a gradual rise in a             
south-westerly direction towards the    

,erdi  and ,ennedi country 7which1 as ,i
 have already stated1 is the most       
probable source of the underground      
water7 is strikingly apparent4 ,i have  
not been able to extend the contours far
 to the east and west of ,merga1  for   
lack of control-points4 ,it is much to  
be hoped that some future  traveller    
will determine the water-levels at      
,selima and ,lagia1 which  would enable 
the static contours to be extended into 
the region between  ,merga and ,dongola2
 provided1 of course1 that an           
examination of the  water-sources at    
these places proves their supplies to be
 artesian4    ,the most effective way of
 testing any working hypothesis in      
natural  science being the prediction of
 hitherto unobserved facts1 ,i venture  
to  forecast that if1 as is most likely1
 the water-sources of ,selima and       
,lagia are artesian1 their levels when  
eventually determined will not be  found
 to differ very much from #bgj and #cij 
metres above sea  respectively4 ,these  

are the approximate levels deduced by   
prolonging the  static water-contours of
 my maps into the localities of these   
wells1  assuming the contours to        
continue as smooth curves4              
,illustration3 ,outline map of the      
,libyan ,desert1 showing the points     
where the static water-levels are known1
 and the deduced contours of the        
underground static water-surface1 on the
 hypothesis of a continuous  hydraulic  
connection between the points           
,another interesting prognostication    
which ,i think may fairly be deduced    
from the map is that if ever the well at
 ,sarra is considerably deepened1  a    
much more abundant water-supply will    
probably be obtainable4 ,the            
ground-level at ,sarra1 according to    
observations made by ,prince ,kemal el  
,din1 is #dfa metres above sea1 and the 
water-level in the well varies in       
different years from about #cij to about
 #daj metres above sea4 ,but an         
examination of the static contours of   

the map shows that the static  level of 
the true artesian water in the          
neighbourhood of the well is  probably  
somewhere about #ejj metres above sea1  
though an exact  estimation of the      
static level at that spot is not        
possible because of  the lack of data   
farther west4 ,as already remarked on p4
 #aaj1 ,i think  the present supply at  
,sarra is derived from more or less     
local rainfall1  conveyed by            
higher-lying permeable strata than those
 which convey the  main artesian        
supplies of ,kufra and the ,egyptian    
oases2 by deepening the  well           
considerably1 lower-lying beds might be 
reached so as to tap the  main supply1  
and the water might even be expected to 
overflow at the  surface4               
,interesting as are the static          
water-level contours in themselves1 they
  become vastly more so when superposed 
on the ground-contours1 as is done  in  
the larger map 7,g4,j41 ,july1 following
 p4 #if74 ,from the two sets of         

contours on that map we can estimate at 
any point the approximate depth  of the 
static water-level below the ground2 and
 this information affords  new light on 
some of the most interesting1 but       
hitherto the most  difficult1 of the    
problems connected with the ,libyan     
,desert4    ,illustration3 ,pottery     
,hill1 possible site of 8,zerzura10 from
 the  south-west    ,illustration3 ,bir 
,kassaba1 a watering-place on the ,darb 
el ,arba'in    ,illustration3 ,the      
waterless stretch of the ,darb el       
,arba'in between ,bir  ,murr and ,kharga
    ,illustration3 ,bir ,sheb1 a well on
 the ,darb el ,ar ba'in      #f4 ,can   
the ,present ,water-supplies of the     
,mediterranean ,littoral be             
supplemented by ,artesian ,borings8     
,the present water-supplies of the      
,egyptian portion of the ,mediterranean 
littoral1 derived mainly from shallow   
wells dependent on the local  rainfall1 
are neither very abundant nor of very   
good quality4 ,at one or  two of the    

most important settlements along the    
coast1 such as ,matruh  and ,sollum1    
attempts have been made to improve the  
supplies by sinking  wells to a         
considerable depth in situations where  
it appeared likely  that the drainage   
from the inland plateau would be        
specially abundant4  ,but these have met
 with little success2 the yield has been
 found to be  very moderate in quantity1
 and of poor quality owing to dissolved 
salts4  ,the question has often been    
raised as to whether very deep borings1 
carried down right through the ,tertiary
 strata and into the ,nubian  sandstone1
 might result in the procuring of an    
artesian supply of the  same excellent  
water as occurs in the oases4 ,hitherto 
it has not been  possible to give a     
definite answer to this question1 and   
geologists have  been reluctant to      
recommend deep borings1 which would     
entail great  expense1 without feeling  
some assurance that they would be       
successful4  ,the depth to the ,nubian  

sandstone is unknown1 but is certainly  
great2  and if borings were carried down
 into the sandstone1 it was not known   
whether the water would rise to anything
 like the ground-level4 ,from our  new  
map1 however1 we obtain a very decisive 
verdict on the matter4 ,the  ,nubian    
sandstone1 even if reached1 would not be
 found to be charged with  artesian     
water under anything like the pressure  
that it is in the oases2  leakage into  
the ,qattara and other depressions will 
have depleted the  beds of much of the  
water coming from the south-west1 and   
will have  lowered the static head to   
such an extent1 that the water left in  
the  sandstone will have too little     
pressure to rise far into the bores4    
,any  idea of sinking deep artesian     
wells along the coast to tap the ,nubian
  sandstone can consequently be         
definitely abandoned4 ,we are driven to 
the  conclusion that in any attempt to  
improve the local water-supplies of  the
 littoral settlements1 we can count only

 on local rainfall for our  primary     
source1 and we must do our best to      
collect the run-off before it  has had  
an opportunity to absorb much salt4 ,the
 ,romans evidently  understood this when
 they excavated the large rock-cisterns 
on the  plateau1 of which there are     
hundreds4 ,we cannot do better than     
imitate  their example1 and arrange for 
the collection and storage of a         
sufficient volume of rainwater as it    
runs from the rocky surface of the      
plateau4 ,we may do this by restoring to
 use the old reservoirs2 or we  might   
possibly achieve our end by damming some
 of the rocky gullies  which bring down 
the run-off from the plateau to the     
plain4 ,now that the  artesian idea is  
shown to be out of the question1 there  
is justification  for a thorough        
investigation as to the best method of  
collecting and  conserving the local    
rainfall4      #g4 ,are the ,artesian   
,water ,supplies of the ,oases          
diminishing8      ,the native           

cultivators in certain parts of ,kharga 
and ,dakhla have for  some years past   
found that their wells no longer        
discharge at so high a  level as        
formerly1 and in consequence some of    
their land has gone out of  cultivation4
 ,from this fact1 and from the evidence 
of the former greater  prosperity of the
 oases which is afforded by the various 
ruins of  temples1 forts1 and villages1 
by the large areas of formerly          
cultivated  lands1 and by numerous      
sanded-up wells1 it has sometimes been  
inferred  that the total yield of the   
oasis-wells is now but a fraction of    
what it  formerly was4 ,but1 as ,mr4    
,beadnell has pointed out1#bd the       
remains of  the past which exist in the 
oases belong to successive generations1 
so  that we cannot fairly draw such a   
conclusion from them2 and the  reduction
 or cessation of the discharge of       
certain wells does not  necessarily     
imply any falling-off in the total      
water-output of the  oases4 ,mr4        

,beadnell's experiments on flowing wells
 in ,kharga have  clearly shown how the 
opening of a new well at a slightly     
lower level  will affect the discharge  
of an old well1 even one at a distance  
of a  kilometre or more1 by lowering the
 static head in its vicinity4#be ,and   
since a large number of wells have been 
bored in recent years both in  ,kharga  
and ,dakhla1 it is most likely that the 
discharge from these wells  has caused a
 falling-off in the yield of older ones 
situated at slightly  higher levels4 ,in
 this connection it will be well to note
 that it is not  the mere existence of a
 new well that affects the static head1 
but the  discharge from it4 ,if the new 
well is securely closed so as to        
discharge nothing1 it has then no effect
 on the static head and  therefore none 
on the neighbouring wells4 ,but for this
 to hold1 it is  important that the well
 which is closed should be closed       
throughout its  entire depth2 it is not 
sufficient merely to close its mouth so 

that it  does not discharge any water on
 to the ground1 for there may still be  
rapid leakage somewhere in the bore     
7unless effectively cased7 into  porous 
unsaturated underground strata4 ,owing  
to the rapid rate at which  iron pipes  
are corroded in the wells of the oases1 
leakage of this kind  is more likely to 
happen with an abandoned modern well    
cased with iron  piping and plugged near
 the top1 than with old wells which were
 filled  up with clay and sand4 ,these  
factors1 the mutual interference of     
wells  and the importance of preventing 
underground leakage1 especially from    
abandoned wells1 being now thoroughly   
understood1 steps are being taken       
towards ensuring that future sites for  
new wells shall be judiciously          
selected1 and that leakage and waste    
from abandoned wells shall be as  far as
 possible arrested4    ,the method of   
carrying out measurements of            
well-discharges in the oases  is so     
inaccurate1 and the records of the past 

output so defective1 that  it is not    
possible to gather from them whether the
 total yield of  artesian water is at   
present diminishing or not4 ,mr4        
,beadnell considers  it likely1 however1
 that the general average water-pressure
 in the oases  has been very much       
reduced within the historical period1   
owing to the  long-continued            
exploitation of the artesian            
supplies4#bf ,the general  study of the 
,libyan ,desert which ,i have made in   
the last few years  suggests that a     
gradual reduction in the static         
water-pressure in the  oases may        
possibly have been brought about by     
other agencies than the  exploitation of
 the water in the oases themselves4     
,the first and most important of these  
other agencies is the withdrawal  of    
artesian water by the ,nile in the      
neighbourhood of ,dakka4 ,as  mentioned 
on p4 #aac1 it is practically certain   
that sandstone beds  carrying artesian  
water are cut through by the ,nile along

 a distance of  several kilometres in   
that locality1 and the influx of        
artesian water  into the ,nile may far  
transcend in quantity that removed by   
the wells  and springs of the oases4    
,the ,nile has probably deepened its    
channel in  this region by a few metres 
within historical times1 and thus cut   
through a greater section of the        
water-bearing beds4 ,an increase in the 
sectional area of the beds cut through  
would naturally mean an increase  in the
 quantity of artesian water passing into
 the ,nile1 and hence a  lowering of the
 static water-surface extending perhaps 
to the oases4    ,the second possible   
other cause operating to diminish the   
static head of  the artesian water of   
the oases is the progressive desiccation
 of a lake  which may once have occupied
 a part of the ,qattara depression4 ,as 
mentioned on p4 #aaj1 the floor of this 
great depression1 large areas of  which 
are #hj metres and more below sea-level1
 is partly covered by a  salt-marsh1    

which is so soft and watery that it can 
only be crossed at a  few places4 ,the  
hundreds of great water-cisterns cut in 
the limestones  of the plateau to the   
north of the depression--cisterns most  
of which are  now dry--as well as other 
ruins along the coast indicative of a   
considerable former population1 seem to 
show that the rainfall in the  littoral 
region has within the historical period 
been greater than it is  at the present 
day4 ,when the rainfall in the coastal  
region was greater1  there must have    
been more drainage into the ,qattara    
depression1 and what  is now salt-marsh 
was thus possibly once a lake of some   
depth4 ,assuming1  as ,i think is       
likely1 that an underground             
water-connection exists  between the    
marsh occupying the bottom of the       
depression and the  artesian water of   
the oases1 it is obvious that any       
progressive lowering  of the lake-level 
consequent on the change of climate must
 have lowered  the static water-surface 

in the country extending southwards     
towards the  oases4 ,in the oases       
themselves the lowering of the static   
surface would  of course be much less   
than at the lake2 but it is quite       
conceivable  that even in the oases the 
lowering may have amounted to the few   
metres  which would cause some of the   
older and higher-lying wells to cease to
  flow4    ,as both the deepening of the
 ,nile channel in ,lower ,nubia and the 
desiccation of the ,qattara depression  
are probably still slowly  progressive1 
it is possible that these causes may to 
some extent account  for any slow       
lowering of the static water-surface in 
the oases which may  be still going on4 
#h4 8,lost0 ,oases--8,zerzura40      ,of
 all the questions asked by intending   
travellers in the ,libyan ,desert1  none
 is more frequent than that as to the   
most likely whereabouts of  undiscovered
 oases1 and especially as to the        
possibility of finding the  mysterious  
8,zerzura1 or ,oasis of the ,blacks40   

,hitherto the only aid  which ,i have   
been able to render to such inquirers   
has been to acquaint  them with the     
various statements which have been made 
by ,arabs at  different times as to the 
situation of ,zerzura1 with the routes  
which  have been followed by others     
7including myself7 who have sought in   
vain  for it1 and with the indications  
of old tracks which have been           
encountered by these previous           
travellers4 ,so contradictory have been 
the  various ,arab statements1 and so   
numerous the vain attempts to find the  
place1 that ,i have at times felt almost
 convinced that 8,zerzura0 is a  myth4  
,but ,owenat and ,merga were little more
 than traditions until a year  or two   
ago1 and ,i think there is a sufficient 
possibility of the  existence of        
undiscovered springs or oases to        
encourage a further look-  out being    
kept for them1 more especially as a     
consideration of the  general           
surface-contours and static             

water-contours which are now  available 
may furnish a new aid in the matter by  
narrowing down the  field of search4    
,as regards ,arab traditions concerning 
,zerzura1 the earliest account of  them 
which ,i have been able to trace is that
 of ,sir ,gardner ,wilkinson in  his    
#8,topography of ,thebes and ,general   
,view of ,egypt1' published in #ahce1   
p4 #cei4 ,wilkinson's book is now rather
 scarce1 and his statement  concerning  
,zerzura is so short that ,i quote it in
 full3    8,about five or six days west 
of the road from el ,hez to ,farafra is 
another ,oasis1 called ,wadee ,zerzoora1
 about the size of the ,oasis ,parva1   
abounding in palms1 with springs1 and   
some ruins of uncertain date4 ,it  was  
discovered about nine years ago 7i4e4   
about #ahbf7 by an ,arab in  search of a
 stray camel1 and from the footsteps of 
men and sheep he  there met with1 they  
consider it inhabited4 ,gerbabo1 another
 ,wah1 lies  six days beyond this to the
 west1 and twelve days from ,augela2 and

  ,tazerbo1 which is still farther to   
the west1 forms part of the same        
,oasis2 and they suppose that ,wadee    
,zerzoora also communicates with it4    
,the inhabitants are blacks1 and many of
 them have been carried off at          
different times by the ,moghrebins for  
slaves2 though the 8,vallies of the     
,blacks10 a series of similar ,oases1   
lie still farther to the west40    ,in  
footnotes he adds3    8,it is supposed  
that the blacks1 who invaded ,farafreh  
some years ago1  and kidnapped a great  
number of the inhabitants1 were from    
this ,oasis4    8,by another account    
,zerzoora is only two or three days due 
west from  ,dakhleh1 beyond which is    
another wadee2 then a second abounding  
in  cattle2 then ,gebabo and ,tazerbo2  
and beyond these is ,wadee ,rebeeana2   
,gebabo is inhabited by two tribes of   
blacks1 the ,simertayn and  ,ergezayn40 
,particular interest attaches to        
,wilkinson's account of the tradition1  
not only because of its being the       

earliest1 and therefore less likely to  
be coloured by imagination than later   
versions1 but also because of the       
remarkable fact that although some of   
the other places named in the  above    
extract were unknown to ,european       
geographers at the time1 they  have all 
since been discovered2 8,gebabo0 and    
8,tazerbo0 by ,rohlfs1 and  8,rebeeana0 
by ,mrs4 ,forbes and ,hassanein ,bey4   
,the weak point in the account is the   
loose ,arab way of stating  directions4 
,gebabo 7,kufra7 is not west of the     
,baharia-,farafra road1  but south-west4
 ,if we amend the bearing in the first  
account  accordingly1 and take ,zerzura 
at about midway between the ,baharia-   
,farafra road and ,kufra1 it must lie   
near the intersection of the  parallel  
of #bf with the meridian of #bf1 or some
 #bjj kilometres east of  the ,mehemsa  
,hattia1 and some #aej kilometres       
north-west of ,rohlfs'  8,regenfeld0    
camp4 ,in the second account given by   
,wilkinson1 the words  8due west0       

suggest that the bearing is more        
certain4 ,two or three days  7say #abj  
kilometres7 due west of ,dakhla would   
put ,zerzura in about  latitude #be1    
longitude #bg1 or about #cj kilometres  
north of ,rohlfs'  8,regenfeld40 ,there 
is thus a difference of more than #ajj  
kilometres  between the two positions   
indicated by the accounts given to      
,wilkinson4    ,rohlfs evidently knew of
 the traditions regarding ,zerzura      
before making  his attempt to reach     
,kufra from ,dakhla in #ahgd2 and since 
such an  intermediate oasis1 if it      
really existed1 would be an immense aid 
to him  in attaining his objective1 he  
made careful inquiries concerning it    
before leaving ,dakhla4 ,but he found   
that though every one in ,dakhla knew   
the names of ,zerzura and ,kufra1 no one
 could tell him where ,zerzura was1  nor
 how far it lay from ,dakhla4#bg        
,evidently ,rohlfs placed little faith  
in its existence1 for during his journey
 he gave the name 8,zerzura0 to a       

locality1 about #abj kilometres         
west-south-west of ,dakhla1 where he    
found  nothing but very sparsely        
scattered vegetation4#bh ,ascherson1 who
 was  with ,rohlfs in ,dakhla1 was      
however informed by ,hassan ,effendi1   
one of  the principal inhabitants of    
,mut1 that about a hundred years before 
7i4e4 about #aggj7 there had been       
frequent raids on ,dakhla by ,arabs     
from the south-west2 and that in order  
to stop these raids the ,mameluke       
,government of the time installed a     
military colony1 called the ,surbaghi1  
in the village of ,qalamun4 ,these      
,surbaghi went out and destroyed all the
  wells for seven or eight days'        
distance along the road by which the    
raiders had come4 ,this road1 which up  
to that time had served as a trade      
route from ,darfur1 before the road     
through ,kharga was opened1 was in      
consequence forsaken4 ,the road was said
 still to exist1 and to lead into  the  
desert from ,mut4 ,at a day-and-a-half's

 journey from ,mut there were  said to  
be two 8pillars10 half an hour's        
distance apart1 which ,hassan           
,effendi's guard likened to minarets4   
,in the neighbourhood there were  said  
to be large stone-quarries1 and about   
thirty years previously an  iron        
instrument had been found2 the          
instrument was still in ,hassan         
,effendi's possession1 and some         
wonderful stories had grown up as to the
  manner of its use4#bi    ,ascherson   
himself believed this information of    
,hassan ,effendi's to be  substantially 
correct1 but he thought the 8pillars0   
might be merely  pinnacle-shaped natural
 rocks4 ,i am likewise inclined to      
believe it  trustworthy1 but ,i think   
the 8wells0 may have been merely water- 
dumps--that is1 collections of jars of  
water4 ,my reason for this view is      
twofold4 ,in the first place1 the       
ground-levels in that part of the       
desert are so far above the static      
water-level1 that if wells were bored   

they would have to be very deep1 and the
 water would not rise anywhere  near the
 surface 7there can1 of course1 be here 
no question of local  rainfall as a     
source for the water in the 8wells072   
and in the second  place1 it seems very 
probable that the accumulation of large 
broken  earthenware jars which ,i       
discovered in #aiaf at the place ,i     
named  8,pottery ,hill0 7latitude #bd   
#bf #bg1 longitude #bg #ch #ed7 is one  
of  the dumps in question4#cj    ,the   
importance of the above interpretation  
of ,hassan ,effendi's story1 if         
accepted1 as ,i think it must be1 lies  
in the proof which it furnishes  that   
there cannot possibly be an undiscovered
 oasis anywhere near a  point seven or  
eight days from ,dakhla in the direction
 of ,kufra4 ,a  consideration of the    
static water-levels and the contours of 
the ground  would lead us to this       
conclusion if the views ,i have advanced
 on the  underground-water question are 
correct2 but the fact that the raiders  

would never have made such a large      
water-dump if water could have been     
readily got from a well in the vicinity 
makes the conclusion almost  certain    
independently of my hypothesis1 and thus
 incidentally tends to  support the     
latter4 ,is it possible that 8,zerzura10
 which ,i am told  signifies in ,arabic 
a starling 7but is commonly applied to  
any small  bird71 is here a corruption  
of some other name derived from 8zeer10 
a  water-jar1 and that instead of 8the  
oasis of the blacks10 ,zerzura was      
really 8the water-dept of the blacks08  
,schweinfurth has recorded#ca a story   
which was told him in ,kharga  ,oasis1  
that in #ahgb some ,arabs of a ,darfur  
caravan1 who had missed the  road1 found
 a small oasis about #a days' journey to
 the west of ,beris4  ,the oasis was    
said to contain pools full of wild      
geese1 date-palms1 and  a temple4       
,people who went out of ,beris to find  
the place returned  unsuccessful4 ,i am1
 however1 rather inclined to think that 

the story has  some basis of fact1      
because in #ahih ,i myself found springs
 and traces of  ancient conduits in the 
dunes north-west of ,beris1 and there   
may be  other water-sources beyond the  
point which ,i reached4#cb    ,a writer 
in the ninth edition of ,murray's       
#8,guide to ,egypt1' published in       
#ahif1 gives the following different    
statements of ,arabs as to the  position
 of ,zerzura3    7#a7 ,some days south  
of the ,dakhla ,oasis4    7#b7 ,five    
days west of ,farafra ,oasis4    7#c7   
,three days west of ,dakhla ,oasis4     
7#d7 ,two or three days west of ,selima 
,oasis4    ,the first of these          
statements would correspond sufficiently
 well with  ,bir ,terfawi1 which is     
about #bhj kilometres due south of      
,dakhla ,oasis2  the second would place 
,zerzura about in latitude #bg1         
longitude #bf2 the  third corresponds   
with the second account given to        
,wilkinson2 while the  fourth would     
place it far to the south-west1 in      

latitude #ba1 longitude  #bh1 or rather 
less than halfway between ,bir ,terfawi 
and ,merga4    ,mr4 ,harding ,king1 who 
in his journeys in the ,libyan ,desert  
in #aiji and  #aiaa devoted much        
attention to the collecting of native   
information  regarding its geography1   
thinks that 8,zerzura0 may possibly be  
only a  generic name applied to any     
mythical or undiscovered oasis4#cc ,he  
heard  the name applied to the following
 localities3    7#a7 ,rohlfs'           
8,sersura40    7#b7 ,the 8,egyptian     
,oasis10 said to have been seen by an   
,arab from the top  of a high black hill
 lying in the dune-belt ten long days by
 ordinary  caravan from ,kharga4        
,another ,arab is said to have seen what
 is possibly  the same place eight days 
somewhere to the south of ,dakhla4 ,both
 these  accounts agree that the place is
 a large oasis lying at the foot of a   
scarp and containing olive trees4       
7#c7 ,a stone temple eighteen hours'    
journey west of ,gedida in ,dakhla      

,oasis4    ,the information given to    
,mr4 ,harding ,king as to the position  
of the  8,egyptian ,oasis0 would place  
it about in latitude #bc1 longitude #bh1
  or only some #ej kilometres north-west
 of ,bir ,terfawi2 in fact1  considering
 the vagueness of the information1 it   
might correspond fairly  well with      
,terfawi itself1 except that there are  
no olive trees at  ,terfawi1 nor is that
 place overlooked by any escarpment or  
hill4 ,the  8high black hill in the     
dune-belt0 may just possibly be one of  
those ,i  mapped near the farthest point
 ,i reached with ,moore in #aiaf1 in    
about  latitude #bd1 longitude #bf1     
though this would imply a direction     
south-  west of ,dakhla1 not south4 ,it 
is not likely to be ,gebel ,kamil1 as   
that  mountain lies much nearer to      
,merga than to ,dakhla4    ,the 8stone  
temple10 according to the information   
given to ,mr4 ,harding  ,king1 would be 
about #hj kilometres west of ,dakhla    
,oasis1 in about  latitude #be1         

longitude #bh1 or not very far from the 
second of the  positions indicated by   
,wilkinson for ,zerzura4 ,but ,i think  
it is likely  that the statement really 
refers to the 8,deir el ,hagar10 a      
well-known  temple ruin much nearer to  
,dakhla4    ,so much for the various    
statements as to whereabouts ,zerzura   
may be4  ,let us now inquire where it is
 not4 ,on the map ,i have indicated the 
principal routes followed by explorers  
of the southern and western parts  of   
the ,libyan ,desert during the last     
fifty years4 ,we may be tolerably       
certain that ,zerzura is not on1 or very
 close to1 any of these routes2  for    
although a depression within a kilometre
 or so of one's track may  easily be    
passed without notice1 the existence of 
a large oasis1 such as  most of the     
traditions make ,zerzura out to be1     
would almost certainly be  betrayed to  
an explorer by animal-tracks leading to 
it from considerable  distances1 except 
possibly in places where the ground was 

very sandy4    ,illustration3 ,pottery  
,hill from the south3 at foot1 petrol   
and water  supplies of ,prince ,kemal el
 ,din's ,expedition of #aibc            
,illustration3 ,jars at northern foot of
 ,pottery ,hill found by ,prince  ,kemal
 el ,din in #aibc    ,illustration3     
,jars1 worn away by sand-laden winds1   
found by ,dr4 ,ball  in #aiag at        
southern foot of ,pottery ,hill         
,there is another method now available  
to us by which we may narrow down  the  
search for ,zerzura or other 8lost0     
oases2 and that is1 by a  consideration 
of the general contours of the country  
and those of the  static water-surface4 
,every oasis in the ,libyan ,desert must
 owe its  existence to one or other of  
two conditions3 either it must depend on
  springs fed by local rainfall1 in     
which case1 like the oases of ,owenat   
and ,arkenu1 it probably lies near to   
mountains of considerable height2  or   
else it must depend on underground      
supplies1 and must therefore lie  in a  

depression wherein the ground-level and 
static water-level are  practically     
coincident1 as in the cases of ,kharga1 
,dakhla1 ,farafra1  ,baharia1 and ,siwa4
 ,it is highly doubtful whether any     
mountain masses at  all approaching the 
altitude of ,arkenu and ,owenat can     
remain  undiscovered in any of the      
various areas in which ,zerzura has been
  traditionally placed4 ,zerzura is     
immensely more likely to be in a        
depression1 and indeed ,wilkinson's name
 ,wadi ,zerzura almost  conclusively    
points to that view4 ,the depression is 
more likely to be  shallow than very    
deep1 for it presumably lies in the     
sandstone country  of the south-west1   
and all the known depressions of great  
depth are  confined to the limestone    
country of the north-east4 ,it is quite 
easy to  trace out on our new map the   
areas wherein the static water-surface  
would be reached by a depression of say 
#ej or #ajj metres below the  general   
ground-level as indicated by the        

contours4 ,we must1 however1  remember  
that our ground-contours are liable to  
be considerably in error  in areas where
 observations have been few--that is1 in
 precisely those  areas where the       
depression1 if it exists1 is most likely
 to be found4 ,so  we must allow a good 
margin for our depth1 and ,i have chosen
 #ajj metres  on this account4 ,on the  
map ,i have drawn the 8locus0 of points 
in the  southern part of the ,libyan    
,desert where the static water-surface  
is #ajj  metres lower than the general  
ground-surface#cd2 and ,i have edged    
with  red the only areas in the west and
 south in which the two surfaces are    
within #ajj metres of each other--that  
is to say1 the areas within which       
comparatively shallow depressions with  
underground springs must lie1  if our   
contours of the two surfaces are drawn  
with even approximate  correctness4 ,it 
will be seen from the map that this     
restricts the search  very considerably4
 ,in fact1 if ,zerzura is within the    

frontiers of ,egypt1  it lies in all    
probability either to the west of       
longitude #bf #bj and  north of latitude
 #bf1 or to the east of longitude #bg   
and south of  latitude #bc #cj4 ,we may 
dismiss from our field of search all the
 broad  tract of rising ground which    
extends from near the ,dakhla escarpment
  south-westwards towards ,owenat2 for  
unless ,zerzura is in a depression of   
great depth1 it cannot possibly lie     
within this tract4 ,this  consideration 
shows that most of the previous rough   
estimations of the  possible position of
 ,zerzura must have been erroneous2 and 
indeed it is  remarkable how few of the 
various explorers' tracks traverse the  
only  two areas within which ,zerzura1  
if it exists1 almost certainly lies4    
,the  northern area has only been       
crossed by the ,rohlfs expedition of    
#ahgd1  and that near its eastern edge2 
while the western part of the southern  
area has only been crossed by ,prince   
,kemal el ,din's expedition of #aibe4   

,of all the ,arab traditions1 only those
 which would place ,zerzura far to  the 
west of ,farafra1 or far to the         
south-south-west of ,dakhla1 can now    
have any high degree of credibility4 ,it
 can hardly1 ,i think1 be doubted  that 
the various traditions refer to more    
than one place2 and in view of  the     
almost totally unexplored state of the  
only two areas in which our  new        
contour-maps indicate the possibility of
 unknown oases existing1 it  is quite   
conceivable that at least one oasis may 
lie within each of  them4 ,in the       
northern area1 ,siwa would probably make
 the best starting-  point from which to
 conduct a search1 as it is easily      
reached by motor-  car from ,alexandria 
or ,cairo1 and exploratory journeys     
southwards from  ,siwa would mostly lie 
along the direction of the dune axes4   
,in the  southern area1 ,terfawi or     
,sheb would form the best base for      
exploration2  at each of these places   
there is a good water-supply4 ,i am     

inclined to  think that the southern    
area is more likely to yield results    
than the  northern one4 ,water was found
 to exist at a point some #ae kilometres
  west of ,terfawi1 and though no other 
source was observed on the way to       
,owenat1 it was impossible to see very  
far on either side of the track1  so    
that such a source might have been      
passed within a few miles without       
notice4 ,terfawi itself is very         
difficult to find1 being inconspicuous  
even when one is fairly close to it2 and
 as it is in a sandy area1  tracks      
leading to it are soon obliterated4     
,another factor which favours  this     
southern area is that1 the country being
 all ,nubian sandstone1 the  depth from 
the surface to the actual water-bearing 
beds 7as  distinguished from the depth  
to the static water-surface7 is certain 
to  be much less than in the northern   
area1 where ,cretaceous strata may      
overlie the sandstone2 hence there is   
more likelihood of the existence  of    

natural springs in the south than in the
 north4      #i4 ,can ,travel in the    
,great ,tracts of the ,libyan ,desert   
which are now  ,waterless be facilitated
 by the ,sinking of ,new ,wells8        
,it has sometimes been asked whether    
tracts which it is now difficult or     
impossible to cross by camel1 owing to  
the non-existence of wells or  natural  
springs within them1 might possibly be  
opened up to transport by  the sinking  
of new wells along a proposed route1 as 
has in fact been  done by the ,senussi  
in the case of the well at ,sarra1      
between ,wanianga  and ,kufra4 ,hitherto
 there have been no data from which to  
form an  opinion on this question2 but a
 study of the new map will enable at    
least a qualified answer to be given4   
,to be a practicable proposition1 a new 
well must fulfil two conditions3  the   
first1 that the boring must not be      
required to descend to a very  great    
depth2 and the second1 that the water   
when struck must rise in the  bore to   

within a reasonable distance1 say #bj to
 #cj metres1 of the  ground-level at the
 place4 ,the first of these conditions  
will be  satisfied if the geological    
horizon of the water-bearing bed is     
comparatively near the surface2 the     
second1 if the level of the static      
water-surface in the locality is within 
#bj or #cj metres of the ground-  level4
    ,as regards the first of these      
conditions1 we know that the            
water-bearing  beds underlying the      
,libyan ,desert are situated within the 
geological  formation called the ,nubian
 sandstone4 ,we may therefore eliminate 
from  our consideration all tracts in   
which this formation is overlain by any 
great thickness of younger rocks1 for   
all these rocks will have to be  passed 
through in order to tap the             
water-bearing strata4    ,concerning the
 second condition1 our map at once      
informs us that the  areas in which the 
static water-surface is within #bj or   
#cj metres' depth  below the            

ground-level are decidedly limited4     
,even if we suppose that  there may be  
unknown depressions extending to a depth
 of #gj metres below  the general level 
of the country indicated by the         
contour-lines1 we see  that the         
localities in which the second condition
 would be fulfilled are  confined to the
 tracts edged with red on the map4      
,outside these tracts1  not only have we
 no chance of discovering               
oasis-depressions1 but we also  have no 
prospect of being able to bore wells in 
which water would rise  to within a     
reasonable distance of the ground-level4
 ,thus the broad  tract of rising ground
 which extends south-westwards from     
,dakhla to  ,owenat must always remain a
 waterless waste4    ,in the ,egyptian  
portion of the ,libyan ,desert there    
are1 as will be seen  from the map1 only
 two areas in the west and south in     
which new wells  might successfully be  
bored3 one extending for some #cjj      
kilometres or so  to the south of ,siwa 

,oasis in the neighbourhood of the      
western frontier1  the other extending  
for some #djj kilometres westward from  
the ,nile in  the neighbourhood of the  
southern boundary4 ,fortunately1        
however1 these  areas are so situated   
that wells sunk within them might be of 
considerable use in opening up the      
outermost parts of ,egypt to            
exploration4 ,a well near the western   
frontier about on the parallel of  #bf1 
for instance1 might make it just        
possible for cars or camels to  reach   
,owenat directly from ,siwa1 since it   
would divide the present  waterless     
stretch of #hcj kilometres into two     
stretches of about half  that length2   
while one or two wells near the southern
 frontier between  the meridians of #bg 
and #bh would render ,owenat fairly     
accessible to  camels coming from the   
,nile vi ,terfawi or ,sheb1 and might be
 of great  use to explorers or          
geologists desirous of making a detailed
  investigation of the ,owenat and      

,arkenu region4 ,from the little ,i saw 
of  ,gebel ,owenat during my visit to it
 in #aibe1 its geology must be of       
extreme interest4 ,the south-western    
part of the mountain appears to be      
entirely composed of granite and other  
crystalline rocks1 while the  eastern   
part presents huge cliffs of sandstone1 
with crystalline rocks  showing only at 
the foot2 there is evidently a great    
fault traversing  the mountain mass1    
with a downthrow to the east2 and the   
thickness of  ,nubian sandstone exposed 
on the eastern precipices is greater    
than that  at any other place ,i have   
seen4#ce ,gebel ,kissu probably         
resembles the  south-western part of    
,owenat in being entirely composed of   
crystalline  rocks4#cf ,east of ,gebel  
,owenat there are many igneous hills1   
some of  which exhibit bands of a dark  
brown colour4 ,these bands1 though      
probably  mostly igneous dykes1 may     
possibly in some cases be the gozzany   
outcrops  of veins containing metallic  

minerals2 ,i had no opportunity of      
examining  them at close quarters1 but  
,i saw enough to make me long for       
facilities  to undertake such an        
examination4    ,it may be remarked that
 a well in the northern area would      
probably have  to be very deep1 owing to
 the comparatively high geological      
horizon of  the surface rocks there2 but
 in the southern area1 where the ,nubian
  sandstone forms the surface rock1 no  
great depth of boring would be  likely  
to be required in order to tap the      
water-bearing beds4    ,apart from the  
question of new wells in the more remote
 parts of the  ,libyan ,desert1 a study 
of the map gives us some hints which may
 be of  value should it ever be desired 
to sink wells in places nearer to the   
oases and to the well-known tracks4     
,there appears1 for instance1 to be  no 
reason why wells should not be          
successfully bored at intervals along   
the ,darb el ,arbain between the south  
end of ,kharga and ,lagia1 or on the    

south side of the ,qattara and other    
depressions of the northern part of  the
 desert4 ,in the southern area1 the best
 sites to select for wells  will be     
depressions wherein the ground-level    
approximates most closely  to the static
 water-level2 and readings of an aneroid
 barometer1  compared with corresponding
 readings at a place of known altitude1 
such  as ,sheb or ,terfawi1 would enable
 the most favourable sites to be        
determined4 ,observations of the        
geological structure will also be of    
importance2 for anticlinal folds1 by    
bringing the water-bearing strata       
nearer to the surface1 would diminish   
the depth to which borings would  have  
to be carried to tap the beds2 while    
faulting might likewise  introduce      
favourable conditions by producing      
cracks and fissures along  which the    
water could rise4 ,it may be remarked   
that tamarisk-bushes are  generally a   
sign that water exists at no great      
depth4 ,in regard to wells  in or near  

the northern depressions1 it is obvious 
that sites on the  south side of the    
lakes and salt-marshes should be        
selected2 for not  only is the artesian 
static level higher in the south1 but   
the water is  less likely to be         
contaminated by salts derived from the  
lake and  marshes4      #aj4 ,the       
8,tortoise ,marshes0 of ,ptolemy4       
,the passage in ,ptolemy's              
#8,geographia' 7lib4 ,,iv4 cap4 #f1     
sect4 #d7 in  which the position of the 
8,tortoise ,marshes0 is given may be    
translated  as follows#cg3      ,there  
are two great rivers running into the   
,mediterranean2 one of them    is the   
,gir1 joining ,mount ,usargala with the 
,garamantic narrows1 from    which1     
changing its course1 the river is       
located in long4 #db1 lat4    #af1 and  
makes the ,tortoise ,marshes            
7,chelonitides ,paludes71 whose         
position is long4 #di1 lat4 #bj4    ,the
 information on which ,ptolemy based    
this statement1 at least as  regards the

 river ,gir1 must have been very        
fragmentary1 if not1  indeed1 grossly   
erroneous2 for there is no river flowing
 to the  ,mediterranean anywhere near   
the positions he gives4 ,but there can  
be  little doubt that his names ,gir and
 ,chelonitides ,paludes refer to  real  
places1 and there has been much         
speculation among geographers as to     
their identification4    ,thus1 for     
instance1 ,knoetel#ch suggested that the
 ,gir may have been  the ,wadi ,djedi1  
to the south of ,biskra1 and the        
,tortoise ,marshes the  modern ,lake    
,melghir 7lat4 #cd1 long4 #f7ci ,dr4    
,william ,smith#dj  thought that the    
,gir was really a branch of the ,niger1 
and the marshes  the modern ,lake       
,fittri 7lat4 #ac1 long4 #ah74 ,on the  
map of ,africa on  the #b-million scale 
published by the ,geographical ,service 
of the ,french  ,army in #ahii the      
,tortoise ,marshes are depicted as lying
 in about  latitude #ai #bj1 longitude  
#bg1 with a note stating that this      

delineation is taken from an earlier map
 of the ,nile ,basin by ,miani1 who     
regarded the marshes as being connected 
with the 8dry river0 which was  then    
supposed to run northwards through      
,dakhla ,oasis4 ,colonel ,tilho has     
lately suggested#da the lowlands to the 
north-east of ,lake ,chad 7lat4  #ah1   
long4 #ag7 as a possible site for the   
marshes2 while still more  recently ,mr4
 ,harding ,king#db has thought that they
 might perhaps be  identified with the  
salt lake of ,merga 7lat4 #ai #c1 long4 
#bf #ai74    ,of the various localities 
which have been suggested as possible   
sites  for the ,tortoise ,marshes1 the  
only one which ,i have visited is       
,merga4 ,i  found the salt lake at that 
place to be very small1 covering only   
some  #aj acres2 it lies at an altitude 
of #eji metres above sea-level1 and     
though it is situated in a rather wide  
shallow depression1 ,i saw no  traces of
 any extensive salt-marshes around the  
lake1 while the  configuration of the   

surrounding country appeared to me to be
 such that  the depression cannot       
possibly have formed part of a          
continuous  drainage-channel4    ,i do  
not know whether it has hitherto been   
suggested that ,kufra ,oasis  may be the
 site of the ,tortoise ,marshes2 but on 
correcting ,ptolemy's  figures for the  
errors in his adopted position for      
,alexandria and in the  length which he 
assumed for a degree of latitude1 ,i    
find ,kufra is in  very much closer     
agreement with them than any of the     
places named above4  ,in ,ptolemy's day1
 even the latitudes of but few places   
had been  astronomically observed       
7,alexandria1 where he himself resided1 
was  supposed by ,ptolemy to be in      
latitude #ca1 instead of its true #cb   
#ab71  and as the only method at that   
time known for astronomically           
determining  differences of longitude   
was by the observation of eclipses1 the 
number  of observed longitudes was      
smaller still4 ,the process by which    

,ptolemy  deduced his position for the  
,tortoise ,marshes and other places in  
the  interior of ,libya was most        
probably that of first estimating their 
distances south and west of ,alexandria 
from travellers' itineraries1  then     
converting these distances into degrees 
of latitude and longitude1  and finally 
subtracting the differences thus found  
from the latitude and  longitude of     
,alexandria4 ,but ,ptolemy made the     
great mistake of assuming  the length of
 a degree of latitude 7or of equatorial 
longitude7 to be  #ejj stades1 instead  
of the #gjj stades which it really is4  
,thus all his  dead-reckonings resulted 
in differences of latitude and longitude
 which  were too great in the proportion
 of seven to five4 ,if we correct       
,ptolemy's position for ,alexandria1 and
 his dead-reckoning for the  erroneous  
assumption which he made regarding the  
size of the ,earth1 as  follows3        
,latitude4     ,longitude4              
,ptolemy's position for ,alexandria     

#ca           #fj #cj      ,ptolemy's   
position for the ,tortoise    ,marshes  
#bj           #di                       
-------       -------    ,ptolemy's     
difference of lat4 and long4        #aa 
#aa #cj      ,these differences reduced 
in the    proportion of #e to #g become1
 in true    degrees and minutes         
#g #eb        #h #ab      ,the true     
position of ,alexandria is              
#cb #ab       #bi #ec                   
-------       -------    ,whence the    
corrected position for the    marshes in
 our modern system becomes          #bd 
#bj       #ba #da    we get lat4 #bd #bj
 and long4 #ba #da for the ,tortoise    
,marshes4  ,comparing this position with
 that of ,kufra1 we find that the       
latitude  agrees very closely with the  
#bd #ad which ,hassanein observed at    
,taj1  the principal village of that    
oasis2 while the longitude1 though more 
than a degree and a half west of that of
 the principal village1 is  almost      
exactly correct for ,taiserbo1 the      

north-western oasis of the  ,kufra      
group4    ,besides this remarkably close
 agreement as regards position1 ,kufra  
presents several natural features which 
would tend to support the view  that it 
may be the locality which ,ptolemy meant
 by the 8,tortoise  ,marshes40 ,not only
 is ,kufra an extensive tract of        
relatively low-lying  ground with       
numerous lakes and salt-marshes of very 
considerable size1  but it has          
distinctly the form of a valley4        
,hassanein ,bey repeatedly  refers to it
 as a valley in his description#dc2     
,mrs4 ,forbes also speaks  of the 8,wadi
 of ,kufra10 and mentions that as a     
result of a ride westward  from ,taj the
 8wadi0 was found to have no definite   
ending to the  west4#dd ,what more      
natural1 therefore1 than that some      
ancient traveller  should have imagined 
that ,kufra was a series of marshes     
formed by a  river coming from the      
south-west8 ,and is it not possible that
 ,ptolemy1  in endeavouring to piece    

together the scraps of information he   
could  get1 may have mistakenly inferred
 that this river ultimately reached the 
,mediterranean1 and also have confused  
the account of it with those of  other  
streams further south1 which may have   
been branches of the ,niger8      #aa4  
,the ,sand-,dunes4      ,the sand-dunes 
of the ,libyan ,desert have been the    
subject of careful  studies by ,mr4     
,beadnell and ,mr4 ,harding ,king1 and  
practically all that  was known         
concerning them up to the outbreak of   
the ,great ,war is  contained in the    
excellent papers by them which were read
 and discussed  at meetings of the      
,royal ,geographical ,society in #aiaj1 
#aiaf1 and  #aiah4de    ,with the       
commencement of the ,senussi campaign in
 ,egypt in #aiae1 the  sand-dunes sprang
 into new and unexpected importance1    
from the fact that  they formed one of  
the principal hindrances to the free    
movement of  troops1 and more especially
 of military motor transport1 across the

  desert4 ,every line of dunes of any   
considerable extent had now to be       
carefully mapped and examined for       
possible car-passages through it2 the   
result was to add greatly to our        
knowledge of the distribution and       
extent of these remarkable features of  
the ,libyan ,desert1 especially in  the 
northern parts1 where many long lines of
 dunes were found of which  the         
existence was previously unsuspected by 
geographers1 though they are  familiar  
landmarks to the ,bedouin of the region1
 and all except the  smallest bear      
,arabic names4 ,after the cessation of  
hostilities1 interest  in the           
distribution of dunes was maintained1   
because of the increasing  use of       
motor-cars in place of camels for       
transport across the desert2  and this  
circumstance has recently led to light  
being thrown on the  distribution of the
 dunes in those southern regions which  
lay outside  the field of operations    
during the war4    ,it is rather curious

 to note that although the sand-dunes   
form the  greatest obstacle to          
motor-cars in the desert1 yet it is     
chiefly by  means of motor-cars that the
 true extent and distribution of the    
sand-  dunes has been ascertained4      
,dunes are the most difficult of all    
desert  features to map properly by     
ordinary reconnaissance methods with    
camel  transport4 ,their smooth outlines
 provide no points on which             
intersections can be made1 and no survey
 marks put on them will remain  in place
 for more than a few hours1 or at most a
 few days2 they occur  mostly in nearly 
level country1 where it is impossible to
 find a station  whence they can be     
overlooked2 the absence of shadows on   
them renders it  impossible to say      
whether one is looking at a single line 
of dunes1 or  at several lines1 miles   
apart1 one behind the other in echelon4 
,the only  sure way of mapping dunes is 
to traverse their sides along their     
entire  length1 and this is             

impracticable with camels owing to the  
enormous  distances which would have to 
be covered without water4 ,but with     
motor-  cars one can run alongside them 
at #dj kilometres an hour instead of the
  camel's #d1 and their distribution can
 thus be rapidly and easily             
ascertained4    ,illustration3 ,prince  
,kemal el ,din's expedition of #aibe    
leaving ,bir  ,terfawi for the waterless
 journey of #bej miles to ,owenat       
,illustration3 ,the well at ,bir        
,terfawi in the palm clump              
,illustration3 ,jebel ,owenat from the  
south3 the triple peak 7#efce feet7  in 
centre    ,illustration3 ,the lake at   
,merga located by ,prince ,kemal el     
,din's  expedition of #aibe    ,on the  
map ,i have shown the distribution of   
sand-dunes as far as it is  known at the
 present day4 ,a comparison of this     
latest map with that  given by ,mr4     
,beadnell in his paper of #aiaj will    
show how large is the  number of dunes  
discovered and mapped in more recent    

years2 and it will  be noticed how      
pronounced is the constancy of the      
general direction of  all the lines in  
the ,egyptian portion of the ,libyan    
,desert4 ,though no  new lines of dunes 
comparable in extent with the great ,abu
 ,moharik belt  have been added to the  
map1 some of the newly discovered lines 
are of  very considerable length1 and   
they show an even more remarkable ratio 
of  length to breadth than the ,abu     
,moharik belt2 the ,ramak dunes1 for    
instance1 extend from near ,moghara     
south-south-eastwards in a straight     
line for more than #ajj kilometres1 with
 only a single small break1 and  their  
width nowhere exceeds #a kilometre4     
,moreover1 the linear  arrangement in a 
direction from about #bj west of north  
to about #bj  east of south is even more
 pronounced in the newly discovered     
northern  dunes than it is in those     
previously known farther south4 ,in the 
8great  sand sea0 of ,rohlfs1 to the    
west of ,dakhla and ,farafra1 the same  

directional arrangement of the          
individual lines of dunes is very       
noticeable1 at least in the part near   
8,regenfeld0 where ,i have  penetrated  
it2 and ,i found the same general       
direction to hold for most  of the lines
 of dunes which ,i crossed on the way   
from ,terfawi to ,owenat4  ,during the  
war ,i received a number of reports of  
dunes extending nearly  east and west1  
often in curved lines2 but              
investigations on the spot  showed      
practically all these reports to be     
erroneous1 the commonest  mistake having
 been that of sighting different lines  
of dunes from  different places under   
the impression that they were a single  
one4    ,the general                    
south-south-easterly direction which is 
so marked a feature  of the lines of    
dunes in the ,egyptian portion of the   
,libyan ,desert is  not1 however1       
preserved in the extreme south-west of  
the country4 ,the  line of dunes which  
crosses the ,egypt-,sudan frontier in   

longitude #be  #dj has a direction of   
about #cj west of south1 and the dunes  
which  extend from near ,gebel ,arkenu  
to the west of ,gebel ,owenat run about 
#ch  west of south4 ,from a point about 
#hj kilometres to the south-west of     
,gebel ,owenat1 the dune-lines make a   
still further distinct bend to the      
west1 changing their direction by some  
#bj to about #eh west of south1  and    
this latter direction is maintained by  
the dunes in the  neighbourhood of      
,sarra ,well4#df ,according to the maps 
of ,rohlfs and  ,mrs4 ,forbes1 the dunes
 in the sandy tract to the north-west of
 ,kufra  follow approximately the same  
bearing as those near ,sarra4 ,the      
suggestion has been made that this      
swinging round of the direction of  the 
dunes in the south-western part of the  
,libyan ,desert may be due to a         
deflection of the prevailing wind by the
 mountain-masses4 ,it is almost         
certainly caused by differences in the  
prevailing winds--in fact1 the          

dune-lines probably afford a very exact 
index to the general wind-  direction in
 the areas where they occur--but ,i am  
inclined to think that  the regional    
distribution of atmospheric pressure1   
rather than local  deflection by        
mountain masses1 is the cause of the    
differences of wind-  direction4 ,the   
dunes1 especially those near ,sarra and 
,kufra1 extend into  localities which   
seem to me to be too distant from the   
mountains for the  influence of the     
latter on the prevailing winds to afford
 a satisfactory  explanation4#dg    ,in 
certain areas1 especially in the south1 
as for instance on the ,arbain  road    
from ,kharga to ,sheb1 around ,pottery  
,hill1 and in the region between        
,owenat and ,erdi1 there are            
sand-covered tracts which can hardly be 
mapped as dunes1 because there are no   
very marked crests4 ,these tracts  are  
easily crossed by camels1 but give much 
trouble with cars1 and would  probably  
be classed as dunes by car-drivers2 but 

they are really only  vast undulating   
fields of drifted sand4 ,on the old     
,darb el ,arbain slave  road between    
,kharga and ,sheb1 one travels for more 
than #ajj miles over  drifts of this    
kind4 ,no footprint of camel marks the  
track1 footprints  being obliterated in 
an hour or two4 ,but one is never in    
doubt about the  way1 for it is         
indicated by the skeletons of countless 
camels which have  perished on the weary
 march4    ,as regards the relation     
between dunes and the relief of the     
ground1  there is a gradual rise in the 
general level of the country from north 
to south of about #a in #ajjj1 so that  
the southern ends of most of the        
,egyptian lines of dunes lie at higher  
altitudes than the northern ends2  but  
,i am fairly certain that this slight   
general inclination has nothing  to do  
with dune-formation4 ,the straightest   
and cleanest-cut lines of  dunes are    
found in the flattest and most open     
parts of the desert1 over  which the    

wind can sweep without obstruction4     
,when a line of dunes  encounters in its
 southward progression a sudden fall in 
the ground-  level1 as for instance at  
the north end of ,kharga ,oasis and to  
the east  of ,pottery ,hill1 it usually 
breaks up2 sometimes1 as in ,kharga1 to 
resume its course as dunes in more open 
formation1 and at other times1  as near 
,pottery ,hill1 to spread out into a    
rolling plain of drifted  sand4 ,it is  
not uncommon for the south end of a line
 of dunes to split  up1 even on level   
ground1 and the same can be seen1 though
 less often1  at the northern ends2 but 
this is probably merely because the     
dunes are  lower near the ends of the   
lines1 and the width of the individual  
dunes  is consequently less4    ,the    
great lines of dunes are probably       
extending southwards at a very  slow    
rate1 under the action of the prevailing
 wind4 ,in this connection  it is       
interesting to note that ,arabs always  
speak of the south end of a  line of    

dunes as its head1 and of the north end 
as its tail2 just the  opposite of what 
one would instinctively call them from  
merely looking  at the map1 but correct 
if the dunes are known to have a        
southward  progression4 ,mr4 ,beadnell  
found the average rate of progression of
  isolated small dunes in ,kharga to be 
#ae metres per annum2 but he remarks    
that large dunes move more slowly than  
small ones1 owing to the greater  mass  
of material to be transported4 ,it is   
interesting to make a rough  guess at   
the antiquity of the dunes from the     
length of certain of the  longer lines  
and an estimated rate of progression4   
,the ,abu ,moharik belt1  for instance1 
has a total length of about #cej        
kilometres2 hence1 if its  tail has     
remained stationary and its head has    
advanced southwards at an  average rate 
of #aj metres a year1 some #ce1jjj years
 must have been  occupied in its        
formation4    ,as regards the height of 
the dunes1 the only one ,i have         

carefully  measured is that close west  
of ,rohlfs' camp at ,regenfeld1 which ,i
 found  to be exactly #cj metres4 ,some 
of the dunes in the ,abu ,moharik and   
,ramak  belts are considerably higher2  
but ,i doubt if any of the ,libyan dunes
  rise much over #ej metres above       
ground-level1 except in the 8great sand 
sea0 which commences some #ad kilometres
 to the north-west of ,regenfeld1  where
 ,jordan estimated them to attain #ajj  
metres or more4#dh ,the top of  a high  
dune to the south of ,melfa ,oasis was  
found by triangulation to be  #agb      
metres above sea2 the level of the      
ground at its foot is unknown1  but is  
probably not very much above the        
sea-level1 so that ,jordan's  estimate  
of the height of some of the dunes in   
the 8sand sea0 is  probably by no means 
an exaggerated one4    ,much has been   
written about eddies in connection with 
dune-formation4  ,the only observations 
,i have made in this connection have    
been when  endeavouring to place        

temporary marks on dunes to form        
survey-points2  and the observations    
seem to show that if eddies are         
artificially  created at the top of a   
dune1 a rapid lowering of the dune-crest
  results4 ,at first ,i used to thrust a
 walking-stick or ranging-rod some #b   
or #c feet into the dune-crest4 ,the    
stick or rod1 though quite firmly  fixed
 at first1 was always found after a few 
hours lying halfway down  the           
dune-slope4 ,the same thing happened    
with tripods firmly pressed down  into  
the crest4 ,when ,i was carrying out a  
little triangulation to  determine the  
position of ,rohlfs' cairn at ,regenfeld
 in #aibd1 ,i had  occasion to place a  
mark on a high dune1 and ,i used an     
empty #d-;gallon  petrol tin filled with
 sand1 bedding it well into the dune2   
but the next  day it had disappeared    
from the crest1 and was found1 as the   
other  things had been1 halfway down the
 slope4 ,these observations remind me of
  ,mr4 ,barclay's description of the    

method of dealing with sand-            
accumulations in the ,peruvian          
,desert1#di where1 as soon as dunes     
appear  and threaten to obstruct a      
railway1 the local inhabitants turn out 
and  scatter pebbles and stones on the  
dunes1 and very soon the dunes are      
gone1 having been carried away owing to 
eddies produced by the wind  around the 
stones4 ,this device for removing       
incipient dunes might1 ,i  think1 be    
tried along the ,kharga ,railway1 where 
the screens put up at  ,mr4 ,harding    
,king's suggestion have not been        
entirely successful in  preventing the  
encroachment of sand on the line4 ,i am 
the more disposed  to think an          
experiment of this kind might succeed1  
because ,i have  noticed that at the gap
 in the ,ramak dunes 7discovered by     
,col4 ,partridge  and known during the  
war as 8,partridge ,gap07 there are     
great lumps of  silicified wood1 which  
may have led to the gap being formed4   
,there are two other physical           

characteristics of dunes which ,i do not
  remember having seen mentioned4 ,one  
of these is their low thermal           
conductivity4 ,on a hot day1 one has    
only to thrust one's hand a few  inches 
into a dune to encounter cool sand1     
while on a bitterly cold day  one can   
warm one's hands by the same action2    
thus while the diurnal  variation of    
temperature of the surface of a dune is 
frequently very  great1 it is almost    
insensible at quite a shallow depth in  
the interior4  ,it follows that diurnal 
expansion and contraction of the grains 
composing the dune must be confined to  
the superficial layers1 and the         
movements thereby caused may materially 
assist in consolidating the  dune1 by   
causing a 8packing0 of the grains4 ,the 
other characteristic ,i  have noticed is
 that the surfaces of the dunes always  
appear to be  harder underfoot in the   
cool of the early morning than in the   
heat of  the day4 ,this may1 of course1 
be an illusion owing to one's being less

  sensitive to fatigue in the early     
morning1 when one's body has been       
refreshed by sleep1 and when the        
air-temperature is comfortable2 but ,i  
have often fancied there is more in it  
than that1 and it may easily be  that   
the 8packing0 which has taken place     
owing to the considerable fall  of      
temperature in the night1 to say nothing
 of the action of dew1 may  have caused 
a real compacting of the surface layers4
    ,in his paper of #aiaj1 ,mr4        
,beadnell considered that the sand      
composing  the dunes must be derived    
from arenaceous formations to the north1
 and  he made special mention of the    
need for a careful survey of the region 
in which the dunes originate4 ,a        
reference to the map will show how      
correct was ,mr4 ,beadnell's surmise1 at
 least in the case of the ,egyptian     
dunes which he had studied4 ,the dunes  
originate in the great depressions      
which stretch from ,siwa to the ,wadi   
,natrun1 where1 as ,mr4 ,beadnell       

inferred1 the supply of arenaceous      
material from the loosely compacted     
,miocene and ,oligocene beds is almost  
inexhaustible4 ,we have here one of  the
 clearest possible examples of the      
powerful action of the wind as an       
excavating and transporting agent4 ,the 
,qattara depression has been  excavated1
 largely by the wind1 to a depth of over
 #acj metres below sea-  level1 and the 
excavated material has been carried     
southwards1 some of  it for nearly #ajjj
 kilometres in distance and more than   
#ejj metres in  height1 to form the     
dunes4 ,we see not only the excavated   
hollow1 but  also the transported and   
piled-up arenaceous material removed    
from it2  and the total quantity of rock
 thus removed and re-deposited must     
amount  to hundreds of cubic            
kilometres4#ej    ,it is noticeable1    
however1 that to the north of the 8great
 sand sea0 of  ,rohlfs1 which extends   
for an unknown distance westward1 the   
known  depressions are much shallower2  

and yet the total quantity of sand in   
this region is probably greater than    
that of all the more easterly dunes  put
 together4 ,the country between ,jarabub
 and ,jalo is however almost            
unexplored1 though it is known to be    
very sandy and to be the theatre of     
violent sandstorms4 ,whether similar    
deep depressions to that of ,qattara    
have been excavated along1 or to the    
north of1 the ,jarabub-,jalo road1 or   
whether the area of loosely compacted   
arenaceous rocks exposed there is  so   
enormous as to have yielded such a      
quantity of sand without any very  deep 
depressions being formed1 is a point    
that can only be cleared up by  further 
exploration in ,cyrenaica4    ,we now   
come to the most puzzling of all the    
questions connected with the            
sand-dunes1 namely1 why do they persist 
as sharply defined long narrow  lines in
 certain places1 while the ground       
elsewhere is almost absolutely  free    
from sand8 ,as ,mr4 ,harding ,king puts 

it1 the dunes appear to have a  curious 
power of collecting all the sand in the 
neighbourhood4#ea ,the  sheltering      
effect of ripples in the dunes1 and a   
8shepherding0 effect of  winds a point  
or two off the normal1 have been        
suggested as possibly  affording some   
explanation of this apparent            
collecting-power1#eb but  neither of    
these suggestions appears to be         
adequate4 ,i think a more  direct       
explanation is possible2 namely1 that   
the dunes really have the  power of     
attracting sand from the air1 and that  
this power is due to the  well-known law
 of attraction between a conducting     
surface at zero  potential and an       
electrically charged body4 ,that        
air-borne sand-grains  in the           
neighbourhood of a dune may carry       
electric charges was shown by  ,mr4     
,harding ,king's experiments1 recorded  
in his paper of #aiaf1 and ,i  have     
since found sand-grains to carry        
electric charges of high voltage  during

 sandstorms in ,cairo4 ,as to how the   
grains become charged with  electricity1
 it can hardly be due to friction       
against each other1 for  the sand is    
remarkably uniform in composition1      
consisting generally of  rounded grains 
of almost pure silica coated with a thin
 translucent film  of ferric oxide1#ec  
and for the production of frictional    
electricity it  is generally regarded as
 necessary that the two bodies which are
 rubbed  together should be of          
dissimilar materials2#ed nor is it      
likely that  they are electrified by    
friction with the air1 for they travel  
with it4  ,but if the particles are     
carried into an upper air-stratum1 they 
will  gradually acquire its potential by
 conduction2 and the ordinary  potential
 gradient in the air in ,egypt is over  
#ajj volts per metre of  height4#ee     
,hence a sand-particle carried along for
 some time in the air  at a height of   
only #bj metres above the ground may    
become charged to #g  electro-static    

units of potential1 or #bajj volts2 and 
on approaching a  dune rising to about  
that height it will be attracted to the 
dune1 which  being in connection with   
the earth is at zero potential4 ,the    
attraction  will be very small unless   
the sand-grain approaches very closely  
to the  surface of the dune2 from some  
calculations ,i have made1 a spherical  
grain of silica half a millimetre in    
diameter charged to a potential of      
#bajj volts will not be attracted with a
 force equal to half its own  weight    
until it approaches within a centimetre 
of the conducting  surface1 and the     
grain will have to approach within #g   
millimetres of the  surface before the  
attraction is equal to the weight of the
 grain4 ,but  the important thing to    
note is that the attraction is          
independent both  of the sign of the    
charge and of the direction of the wind 
which carries  the particle4 ,another   
way of looking at the matter is to      
consider the  probable distribution of  

the equipotential surfaces in the air   
about a  dune1 as in the diagram below1 
which represents a section taken        
perpendicular to the direction of the   
wind and to the axis of the line  of    
dunes3    ,illustration3 ,diagram       
showing suggested distribution of       
equipotential  surfaces and directions  
of lines of force in the neighbourhood  
of a  sand-dune    ,the equipotential   
surfaces1 shown by dotted lines1 will be
 squeezed  together over the dune1 and  
the electric forces1 shown by full lines
 and  arrows1 being everywhere normal to
 those surfaces1 will converge to the   
dune4 ,thus the dune will attract any   
particles carried by the wind and       
charged by conduction to the potential  
of the air conveying them4 ,if the  wind
 changes its direction1 the attraction  
will still persist unaltered4  ,another 
point worth mention is that a sand-dune 
may be far more  effective in its       
attraction of sand than a rocky ridge of
 the same size  and shape would be2 for 

when the electrified grains approach the
 surface  of the dune1 uncharged grains 
can rise from the dune to meet them2    
possibly some of the dancing of         
sand-grains which is frequently         
observable along the crest of a dune    
during a wind may be due to this        
cause4#ef ,during violent sandstorms1   
particles of sand may be whirled  aloft 
and kept suspended at high altitudes for
 a period long enough for  them to      
acquire very high potentials1 and a     
sudden cessation of the  storm may cause
 them to fall so rapidly that much of   
the charge may be  retained2 in which   
case1 of course1 electrical attraction  
may cause a  very considerable deviation
 from the purely gravitational paths of 
the  falling particles1 the deviation   
being always towards the dune4 ,since   
the closeness of the equipotential      
surfaces and the mobility of the        
sand-grains composing the dune are      
greatest along the dune-crest1 the      
maximum rate of deposition will be at   

the top of the dune1 which is also  the 
place where the wind exerts its greatest
 action in conveying the  sand of the   
dunes southward4 ,that the long axes of 
the lines of dunes do  really correspond
 with the direction of the prevailing   
wind is certain1  both from ,mr4        
,beadnell's observations of             
wind-direction#eg and from the  fact    
that the scoring of the limestones in   
the ,libyan ,desert by wind-  borne sand
 coincides in direction with the lines  
of dunes4#eh ,thus ,i  suggest that     
while the extension of the lines of     
dunes southwards is  purely the result  
of the prevailing north-north-west wind1
 their clean-  cut character and narrow 
width is the consequence of lateral     
attraction  by the dunes themselves on  
the flying electrified particles of     
sand4    ,if the hypothesis ,i have     
ventured to put forward is regarded as  
likely  to furnish the true explanation 
for the formation of the lines of dunes1
  ,i hope that someone possessing the   

necessary skill in electrostatic        
measurement will put it to a crucial    
test1 by carrying out observations  on  
and near the dunes themselves4 ,if a    
number of flying sand-grains  could be  
caught from different levels in an      
insulated metallic receiver  connected  
to an electrometer1 the readings of the 
electrometer would  enable the          
potentials to which the grains were     
charged at different  levels to be      
calculated1 provided the electrostatic  
capacity of the  receiving system and   
the number and diameter of the grains   
giving up  their charge were measured4  
,allowance would1 of course1 have to be 
made  for any electrification of the    
receiver by the air1 or by uncaught     
sand-  grains1 as well as for losses by 
imperfect insulation of the collecting  
system4 ,in a preliminary experiment of 
this kind which ,i made in ,cairo       
during a sandstorm1 leakage from the    
electrometer was found to be so  great  
as to vitiate any attempts at accurate  

measurement2 but ,i think  this         
particular difficulty could be overcome 
with a specially designed  apparatus1 or
 that at least the leakage could be     
measured and allowed  for4 ,the taking  
of observations of any kind in dune     
areas during windy  weather is a most   
difficult and trying operation1 and     
commonly means1 in  addition1 a sojourn 
of some weeks in isolated and otherwise 
uninteresting areas4 ,but the advent of 
the motor-car has so greatly            
facilitated communication in the deserts
 that difficulties of access are  now   
not so great as they used to be2 the    
south end of the #ce-kilometre  line of 
the ,kattania ,dunes1 for instance1     
about #ij kilometres west-  south-west  
of ,cairo1 which would form an excellent
 site for detailed  observations1 can   
now be reached by a four or five hours' 
car journey  from ,cairo instead of the 
several days' journey by camel which was
  formerly necessary4      #ab4 ,the    
,distribution of ,stone ,implements4    

,i have not made any special study of   
stone implements1 nor have ,i been  able
 to pay any considerable attention to   
their collection during my  journeys1   
having usually found my time very fully 
taken up with other  matters4 ,i have1  
however1 been much struck by the wide   
distribution of  stone implements in the
 desert4 ,i have found them1 for        
instance1 not  only in ,siwa ,oasis and 
near the wells of ,abu ,mungar and      
,sheb1 but also  on the plateau between 
,baharia and ,farafra1 on the open      
desert between  ,terfawi and ,owenat1   
and to the south-west of ,owenat near   
the ,anglo-  ,french boundary4 ,this    
wide range of occurrence1 coupled with  
the finds  of ,schweinfurth and others  
on the plateaux nearer the ,nile1       
inclines me  to think that there is     
scarcely any part of the ,libyan ,desert
 in which  stone implements might not be
 found by an expedition which would make
  the collection and study of them one  
of its main objects4 ,the likeliest     

places in which to search 7besides the  
neighbourhood of old wells and  springs7
 would appear to be the shores of the   
various lakes and around  the feet of   
hills affording shelter from wind and   
sun2 for it is in such  localities that 
,i have most usually come across        
implements and pottery4                 
,grinding-stones1 often with a sort of  
stone rolling-pin1 unpolished  celts1   
knives1 and arrow-heads are the         
principal forms of implement ,i  have   
met with4 ,many of the grinding-stones  
must have been carried for a            
considerable distance1 for they are made
 out of rocks which do not  naturally   
occur in the localities in which they   
are found4    ,whether this wide        
distribution of stone implements would  
justify the  view of ,blanckhenhorn#ei  
that primitive man lived on the desert  
plateaux rather than in the ,nile       
,valley must1 ,i think1 be settled by   
the  further collection of specimens and
 by a careful comparison of the forms   

to be found in the two situations4 ,in  
this connection ,i may remark that  the 
grinding-stones ,i have seen in the     
desert seemed to me to be very  similar 
to those used by the ,nubians of the    
,nile ,valley to-day for  grinding corn4
                                        
,,appendix            ,,some ,,recently 
,,determined ,,positions ,,in ,,the     
,,libyan ,,desert      ,in view of their
 possible utility in connection with    
future exploratory  surveys1 ,i give    
below a list of some of the more        
important of the  positions which ,i    
have recently determined by astronomical
 observation  in the southern part of   
the ,libyan ,desert1 with brief         
descriptive notes  on the places to     
which they refer4 ,the observations were
 made whilst  accompanying ,h4,r4,h4    
,prince ,kemal el ,din ,hussein on his  
exploratory  motor-car expeditions of   
#aibc1 #aibd1 and #aibe4 ,the longitudes
 of ,qasr  ,farafra1 ,abu ,mungar1      
,pottery ,hill1 and ,regenfeld depend on

 the transport  of a box-chronometer2   
the others on wireless time-signals from
 ,europe4  ,the positions of peaks were 
found by triangulation from the actual  
observation-spots4 ,the altitudes of    
camps are from careful barometric       
determinations2 those of the peaks      
depend on trigonometric levelling  from 
the camps4                              
,altitude                ,place4        
,lat4 ,n4  ,long4 ,e4  above sea4       
,metres4                                
,merga1 ,camp #fjj metres ,s4,w4 of west
  #ai  #b #bi   #bf #ah #cb      #ebf   
corner of salt lake4 7,lake surface     
is #ag metres below level of camp47     
,bir ,terfawi1 ,camp close to well and  
#bb #ee #ab   #bh #eb #ea      #bdd     
palms      ,gebel ,kissu1 ,summit       
#ba #cd #ei   #be  #h #bf     #agbf     
,gebel ,owenat1 highest point           
#ba #ed #cd   #be  #j #dg     #aijg     
remarkable triple peak       #ba #ec #ea
   #be  #a #ci     #agah                
,s4,w4 peak                    #ba #di  

#ce   #bd #ec #eb     #adej      ,chunk 
,hill1 ,summit                   #ba #eb
 #df   #be #ac #ef      #ihe            
,owenat1 ,camp #fjj metres ,s4,e4 of    
#ba #dh #ce   #bd #ea #de      #efh     
western spring1 on plain at foot of     
mountain      ,owenat1 ,camp at mouth of
 gully1      #ba #ec  #h   #be  #g #eh  
#fbf    about #hjj metres ,s4,s4,e4 of  
eastern    springs      ,gebel ,kamil1  
,summit 7#afj metres      #bb #af #ca   
#bf #ch #aa      #hjj    above plain7   
,regenfeld1 ,rohlfs' cairn of #ahgd1    
#be #aj #di   #bg #bd #bb      #dgj     
rediscovered #aibd      ,pottery ,hill1 
,summit 7#ci metres      #bd #bf #bg    
#bg #ch #ed      #ejf    above plain7   
,sheb1 ,camp close to well1 #bdj        
#bb #ai #dh   #bi #de #df      #bbh     
metres ,n4,n4,e4 of fort      ,mut1     
,government ,rest-house           #be   
#bh #cg   #bh #eh #bd      #aai         
,abu ,mungar1 ,camp at small ruin1 #djj 
#bf #cj #bb   #bg #ce #bi      #aag     
metres ,e4,s4,e4 of well      ,qasr     

,farafra1 ,camp ,e4 of village1    #bg  
#c #bf   #bg #eg #eb       #ij    #bjj  
metres ,s4,w4 of ,tomb of ,sheikh       
,dakhil    ,merga4--,to geographers the 
most important of the new determinations
  will undoubtedly be that of the       
uninhabited oasis of ,merga1 which had  
not previously been visited by a        
,european1 and of which the situation   
could hitherto only be guessed at from  
,arab statements4 ,merga lies in a      
shallow depression about #ej metres     
deep1 broken by sandstone hills and     
sand-dunes1 and extending for some #bj  
kilometres north-east and south-  west4 
,the salt-lake1 near the centre of the  
depression1 measures about  #cjj metres 
by #aej4 ,it is surrounded by tall      
rushes and sandhills except  at its     
south-western end4 ,there are numerous  
date-palms1 both near the  lake and at  
considerable distances from it1 as well 
as acacia trees and  tamarisk bushes4   
,the neighbourhood of the lake swarms   
with mosquitoes4  ,good and plentiful   

water was got by shallow digging about  
#a kilometre  south-south-east of the   
observation-spot1 and could probably be 
obtained  by digging almost anywhere in 
the depression4 ,it is possible that the
  names ,bidi and ,tura el ,bedai1 shown
 with a question mark on some ,sudan    
maps1 may refer to different spots      
within the same depression4 ,owing to   
the plentifully scattered vegetation1   
the place cannot easily be missed1      
either by travellers passing within     
several miles of the lake1 or by        
aircraft2 but the landing of aeroplanes 
in the neighbourhood of the lake  might 
be difficult owing to the extensive     
sand-drifts4    ,bir                    
,terfawi4--,scarcely less important than
 the accurate fixation of  ,merga is    
that of ,bir ,terfawi1 the farthest     
south-west of all the  ,egyptian        
artesian water-sources hitherto known4  
,it will be remarked that  this latest  
determination places the well some #bb  
south and #ae east of  the position     

which ,i had provisionally assigned to  
it from the rough  data furnished by    
,lieut4 ,moore's traverse of #aiaf4fj ,a
 knowledge of  the true position of     
,terfawi is specially desirable for a   
traveller who  wishes to reach it1 owing
 to the absence of any conspicuous      
landmark  near it and to the sandy      
nature of the surrounding country1 which
 causes  tracks to be soon obliterated4 
,there are numerous sandhills covered   
with  tamarisk bushes around ,terfawi1  
and a little grazing for camels4        
,besides  the well at which observations
 were taken1 water was found by digging 
in  the sand at the foot of some        
tamarisk mounds about #ac kilometres    
farther  west1 and it is probable that  
good and plentiful supplies could be    
obtained at shallow depths near any of  
the other mounds4 ,the palmtrees  at    
,terfawi are few and small1 and are less
 conspicuous than the  tamarisk-bushes4 
,these latter should enable the place to
 be easily found  by aircraft2 but      

landing would require some caution owing
 to the  prevalence of drifted sand4    
,gebels ,kissu and ,owenat4--,the peaks 
of these mountains 7especially that  of 
,kissu1 because of its isolated         
character and sharply marked summit7    
will form useful points for the         
connection of future surveys1 being     
visible from very long distances4       
,chunk ,hill is a prominent isolated    
hill1 nearly conical and of dark        
colour1 which forms a good landmark in  
the broken country to the east of       
,gebel ,owenat4 ,it rises some #cce     
metres above the ground at its foot4    
,the ,springs of ,owenat4--,of the two  
water-sources of ,owenat whose          
positions are given1 the western one is 
the better1 and is moreover very  easy  
of access1 being practically on the     
level of the plain which  extends       
southwards from the mountain mass1 and  
easily discoverable by  the numerous    
animal-tracks converging to it2 it is a 
pool among great  boulders1 obviously   

fed by percolation through cracks and   
fissures in  the granite mountain which 
towers above it4 ,the eastern           
water-source is  less easy of access2 it
 lies about #a kilometre up a stony     
gully1 and  consists of a series of     
pools in the rocky floor of the gully1  
fed by  trickling springs at the level  
where the granite is overlain by        
sandstone4 ,the plain to the south of   
the western spring would form an        
excellent landing-ground for aircraft4  
,whilst in the neighbourhood of ,owenat1
 ,i had hoped to re-determine the       
longitude of ,hassanein ,bey's camp of  
#aibc with the aid of wireless time-    
signals1 or at least by                 
triangulation-connection to one of my   
observation-points1 because a really    
accurate fixation of the longitude  of a
 point about midway along his route from
 ,jarabub to ,furawia would  possibly   
furnish the means of slightly correcting
 the longitudes  assigned to            
,hassanein's camps at ,kufra and ,erdi4 

,i was unfortunately  prevented from    
carrying out the desired connection2 but
 from a hurried  car-traverse which ,i  
made1 skirting the western side of the  
mountain  mass1 in the course of which  
,i must have passed pretty close to the 
site  of ,hassanein's ,owenat camp1 ,i  
think that camp really lies about in    
longitude #bd #di1 or some #e miles to  
the west of where ,i had previously     
calculated it to be from ,hassanein's   
traverse data2#fa and that in           
consequence the longitudes assigned to  
,kufra and ,erdi from the same data  may
 be some #b or #c miles too great4      
,gebel ,kamil is a sharply pointed hill 
of dark sandstone1 forming a  useful    
landmark between ,terfawi and ,owenat4  
,it was visible from the east  for more 
than #dj1 or from the west for about    
#bj1 kilometres4 ,the name  was given to
 it by ,prince ,kemal el ,din in honour 
of his father1 ,hussein  ,kamil1 the    
late ,sultan of ,egypt4    ,regenfeld1  
it will be remarked1 was found to be    

very nearly in the  position assigned to
 it by ,jordan in #ahgf1fb and my       
estimation of the  level of the place is
 only #bj metres higher than ,jordan's4 
,the  neighbouring dune ,i found to be  
#cj metres high1 agreeing exactly with  
,jordan's measurement of fifty years    
previously2 and as far as ,i could      
judge1 the situation of the dune        
relative to the cairn seems to have     
remained unchanged through this long    
interval1 showing that there has  been  
at any rate no great lateral            
displacement of the dunes4 ,the iron    
tanks left by ,rohlfs were quite intact1
 in spite of their half-century  of     
exposure2 they had become covered with a
 hard dark brown film1  apparently of   
magnetic oxide of iron1 not rusted in   
the ordinary way1 a  fact which speaks  
strongly for the dryness of the region4 
,empty wine-  bottles left by the       
,rohlfs expedition were frosted by the  
sand-blast  wherever they were exposed2 
but surprisingly little of the glass had

  been removed in this way4    ,pottery 
,hill is the northern one of a pair of  
nearly conical dark  sandstone hills    
about #dj metres high1 which are        
conspicuous from some  distance owing to
 their situation on a nearly level      
sand-plain4 ,i gave  it its name from   
the numerous jars which ,i discovered at
 its foot in  #aiag4    ,sheb ,well is a
 pool of fairly good water in a shallow 
excavation at  the foot of a clump of   
dom palms1 half surrounded by sand-dunes
 and  tamarisk mounds1 #bdj metres      
north-north-west of a fort2 the latter  
occupies a fairly conspicuous position  
on a sandstone hill about #be  metres   
high4 ,another well1 situated at the    
foot of a clump of dom palms  about #aa 
kilometres farther north1 is called ,bir
 ,terfau2 this should  not1 of course1  
be confused with the ,bir ,terfawi      
already mentioned4    ,to the north of  
,sheb1 on the ,arbain road1 are three   
other water-sources  which ,i visited in
 #aibe and of which ,i determined the   

approximate  positions by a carefully   
controlled car-traverse3 ,bir ,kassaba1 
in lat4  #bb #da1 long4 #bi #ee2 ,bir   
,abu ,hussein1 in lat4 #bb #ec1 long4   
#bi #ee2  and ,bir ,murr1 in lat4 #bc   
#bb1 long4 #cj #e4 ,bir ,kassaba is a   
pool of  good water at the foot of a    
clump of palms2 ,bir ,abu ,hussein1     
which  likewise yields good water1 is a 
small excavation in sand near a hill of 
pink coarse-grained granite1 and usually
 requires to be dug out afresh  by each 
traveller2 ,bir ,murr1 on a little plain
 surrounded by hills1  consists of      
several holes1 with fairly good water1  
excavated in the sand  at the south side
 of the outcrop of a steeply inclined   
bed of speckled  calcareous sandstone4  
,i have not myself traversed the desert 
to the east of ,sheb1 but  according to 
an intelligent ,arab who has recently   
made the journey from  ,sheb to ,dungul1
 there are only two spots between these 
places at which  water is obtainable2   
they are ,bir ,abu ,seifa1 a small well 

of good water  about #ej kilometres from
 ,sheb1 and ,bir ,haleifa1 about #ae    
kilometres  farther on1 where there is a
 fort and numerous wells4 ,this latter  
place  must1 ,i think1 be the same as   
the ,bir ,nakhlai1 of which the position
  found astronomically by ,colonel      
,talbot in #ahic was lat4 #bb #bi #a1   
long4 #cj #ai #cf4    ,the ,rest-house  
at ,mut1 in ,dakhla ,oasis1 is a low    
whitewashed building  of three rooms1   
situated on open ground a little to the 
south of the  village4 ,it is           
conspicuous by reason of its isolation  
from other  buildings1 and forms a      
convenient starting-point for car       
journeys to the  south-west of ,dakhla1 
as well as for journeys to ,kharga by   
the southern  track which was mostly    
followed by cars during the war4    ,abu
 ,mungar proved to be very close to the 
position given by ,mr4  ,harding ,king's
 observations of #aiab4fc ,to the       
south-east of ,abu  ,mungar1 about      
halfway to ,dakhla1 are two remarkable  

hills forming  outliers of the plateau4 
,these hills1 which are good landmarks1 
were  first discovered by ,mr4 ,harding 
,king1 and as they appear to possess no 
native name1 ,i have called them        
8,king's ,hills0 on the map4 ,the       
farther  one of the two from the plateau
 lies in lat4 #be #eh1 long4 #bh #aa1   
from compass-bearings which ,i took to  
it on a careful car-traverse in  #aibd4 
,the other is about #b kilometres       
farther north4    ,qasr ,farafra4--,the 
position of the village of ,qasr        
,farafra which ,i gave  in my paper of  
#aiaifd is proved to be very nearly     
correct by the  latest observations4    
,the main advantage of the new          
determination is that  it is referred to
 an easily identifiable landmark1 the   
tomb of ,sheikh  ,dakhil1 instead of to 
the ill-defined centre of the village4  
,levels in or near ,baharia ,oasis4--,i 
think it may be well to record here     
that owing to an unfortunate mistake    
about the datum to which the level  of  

the old military railway-terminus at    
,b#f was referred1 all the  altitudes   
given on pp4 #aj and #aa of my          
above-mentioned ,survey ,department     
,paper of #aiai require a correction of 
#ai metres to be added4 ,at the time    
when ,i triangulated ,baharia in #aiag1 
,i was informed that the level found  by
 the military authorities for the       
terminus was measured from the sea-     
level datum1 and ,i employed the value  
given for it as my fundamental  level4  
,but ,i have since ascertained that an  
arbitrary datum was employed  by the    
military engineers2 and trigonometric   
levelling from the ,nile  ,valley has   
shown that this arbitrary datum was     
about #ai metres above  sea-level4      
,,footnotes3      ,footnote #a3 ,the use
 of motor cars for reconnaissances in   
the ,libyan  ,desert1 initiated by the  
,british ,army during the ,great ,war1  
has been  considerably developed in the 
last few years by ,prince ,kemal el ,din
  ,hussein 7son of the late ,sultan of  

,egypt71 who has made several long      
exploratory journeys with a fleet of    
cars of the caterpillar type1  specially
 constructed so as to be capable of     
carrying considerable loads  over sandy 
tracts which were impassable to the     
,army patrols4 ,the  expeditions        
organized and led by ,his ,royal        
,highness have resulted in  important   
additions to geographical knowledge     
concerning the ,libyan  ,desert1        
especially the southern and western     
regions1 which have hitherto  been      
practically inaccessible4 ,i had the    
pleasure of accompanying the  ,prince on
 three of his journeys1 and am much     
indebted to him for thus  affording me  
the opportunity of making many          
observations which would  otherwise have
 been impossible to me4 ,i have further 
to thank him for  kind permission to    
illustrate this paper by reproductions  
from a  selection of the excellent      
photographs taken by him during our     
travels4    ,footnote #b3 ,kindly       

communicated by ,mr4 ,a4 ,r4 ,boyce1    
,director of ,sudan  ,surveys4          
,footnote #c3 ,printed by the ,french   
,army ,staff1 #aibf4    ,footnote #d3   
,by way of comparison1 it may be        
remarked that the area 7at  the         
sea-level contour7 of the ,qattara      
depression is about four times  that of 
the ,dead ,sea and ,jordan ,valley      
depression2 but the latter  7reckoning  
to the lowest point of the bed of the   
,dead ,sea7 is about six  times the     
deeper of the two4    ,footnote #e3 ,a  
similar ambiguity of meaning very       
commonly attaches to  ,arabic           
geographical terms4 ,thus beled may mean
 either a village or an  entire country2
 gebel1 either a mountain or a desert2  
gezira1 either  an island or a part of  
the ,nile bank which is alternately     
covered and  uncovered by the rise and  
fall of the river2 bir1 which properly  
signifies a well1 is often used to      
denote a spring or a water-cistern2     
wadi1 though its proper meaning is a    

valley1 is also sometimes  employed for 
a closed-in depression1 as in the case  
of the ,wadi ,natrun4    ,footnote #f3  
#8,nouveaux ,mmoires des ,missions de la
 ,compagnie de ,jesus  dans le ,levant1'
 ,tome ii4 7,paris1 #agag71 p4 #gd4     
,this little book  contains a map of    
,egypt1 prepared by ,father ,sicard at  
,cairo in #agae1 on  which the 8,mer    
sans eau0 is shown with 8bateaux        
petrifiez0 depicted  alongside it4      
,footnote #g3 ,see 8,particulars        
concerning the ,valley of the ,natron   
,lakes1  and that of the ,old ,bed of   
the ,river0 7with map7 by ,andreossi1   
,general  of ,artillery1 in #8,memoirs  
,relative to ,egypt1 ,written in ,that  
,country  during the ,campaigns of      
,general ,bonaparte in the ,years #agih 
and #agii1 by  the ,learned and         
,scientific ,men who ,accompanied the   
,french ,expedition'  7,london1 #ahjj71 
p4 #bgj4    ,footnote #h3 ,see ,rohlfs' 
#8,drei ,monate in der libyschen ,wste' 
7,cassel1  #ahge71 p4 #ccg2 and         

,jordan's #8,physische ,geographie und  
,meteorologie der  libyschen ,wste'     
7,cassel1 #ahgf71 p4 #bad4    ,footnote 
#i3 #8,zeitschrift der ,gesellschaft fr 
,erdkunde zu ,berlin1'  #aijb1 ,tafel   
,,iii4    ,footnote #aj3 #8,topography  
and ,geology of the ,fayum ,province of 
,egypt'  7,cairo1 #aije71 p4 #fg4       
,footnote #aa3 ,since the above was     
written1 the ,professor of ,geography at
  the new ,university of ,cairo1 ,m4    
,lorin1 has suggested that at a former  
geological epoch the ,nile flowed       
through ,siwa ,oasis and thence westward
  so as to make ,cyrenaica an island4   
7,see #8,l',egypte1' published by the   
,institut ,franais d',archologie        
,orientale1 ,cairo1 in ,december #aibf1 
p4  #aec47 ,m4 ,lorin does not give any 
grounds for this suggestion1 and ,i know
  of no evidence that would justify its 
acceptance4 ,as will be gathered  from  
my remarks elsewhere in this paper1 it  
seems to me far more likely  that ,siwa 
and the other northern depressions were 

in recent geological  times regions of  
central drainage1 than that they were   
local deepenings  of a single channel2  
and in regard to earlier geological     
periods we  possess too little          
information to form any conclusions as  
to drainage-  lines4    ,footnote #ab3  
,see ,sir ,hanbury ,brown's #8,the      
,fayum and ,lake ,moeris'  7,london1    
#ahib71 pp4 #dj-dh and #ajf-aaj2 ,sir   
,w4 ,willcocks' #8,perennial            
,irrigation and ,flood ,protection for  
,egypt' 7,cairo1 #ahid71 also the same  
author's #8,egyptian ,irrigation1' third
 edition 7,london1 #aiac72 ,sir ,w4 ,e4 
,garstin's #8,report on the ,basin of   
the ,upper ,nile' 7,cairo1 #aijd71      
,appendix ,i4 pp4 #f-i2 and ,beadnell's 
#8,topography and ,geology of the ,fayum
  ,province of ,egypt' 7,cairo1 #aije71 
pp4 #af-bd4    ,footnote #ac3 #8,report 
on the ,administration of the           
,irrigation ,department  for #ahie'     
7,cairo1 #ahif71 pp4 #be-bh4            
,footnote #ad3 #8,report on the         

,administration of the ,irrigation      
,department  for #ahif' 7,cairo1 #ahig71
 p4 #abi4    ,footnote #ae3 ,it may be  
remarked that even if a channel were to 
be cut  from ,lake ,mariut to the ,wadi 
,natrun it would still be necessary to  
continue pumping on a large scale from  
,lake ,mariut to maintain the           
present-day drainage4 ,according to     
returns communicated to me by the       
,irrigation ,service1 the quantity of   
water removed from ,lake ,mariut by     
pumping during the last nine years has  
averaged nearly #fej million cubic      
metres a year2 and even on the most     
optimistic estimate of evaporation  and 
seepage the ,wadi ,natrun could not be  
expected to dispose of half  this       
quantity after the lapse of the few     
years which would be occupied  in       
filling it to a permanent level4        
,footnote #af3 ,the average discharge of
 the ,nile past ,cairo in a year is  #fg
 cubic kilometres4 ,the capacity of the 
,qattara depression at the sea-  level  

contour is roughly about #ijj cubic     
kilometres4    ,footnote #ag3 ,geogr4   
,journ41 #ef 7#aibj71 pp4 #ig-ii and    
#afa-afc4    ,footnote #ah3 ,lucas      
7#8,natural ,soda ,deposits in ,egypt'  
7,cairo1 #aiab71 p4  #ae7 regarded the  
water of the ,wadi ,natrun as being due 
to infiltration  from the ,nile1 mainly 
on the ground that he supposed the water
 visibly  entering the wadi 7as small   
streams and trickles7 to do so on the   
north-  eastern side4 ,but this1 ,i     
think1 is a mistake1 as it neglects     
consideration of the large springs of   
warm fresh water which bubble up  in and
 near the salt-lakes themselves1 and    
also the large wells of the  monasteries
 which lie south-west of the lakes4     
,footnote #ai3 ,a far better site for   
this well would have been in the        
depression some #bj kilometres to the   
north-west1 the ground-level at the     
lowest point of which is only #fa metres
 above sea2 but at the time when  the   
site of the well was chosen the         

existence of this depression was        
unknown4    ,footnote #bj3 ,see         
,appendix ,,iii4 in the second volume of
 ,willcocks'  #8,egyptian ,irrigation1' 
#aiac1 p4 #hec4    ,footnote #ba3       
,schweinfurth 7op4 cit41 p4 #hee7 even  
thought it might  have percolated to    
,siwa1 in spite of the great distance   
7#dhj kilometres7  and the adverse      
direction of the difference of level    
between the two  places4    ,footnote   
#bb3 ,mr4 ,beadnell 7#8,an ,egyptian    
,oasis' 7,london1 #aiji71 p4 #aci7      
estimates the total discharge of the    
,kharga wells at #ec1jjj cubic metres   
per diem4 ,we should not1 ,i think1 err 
greatly in estimating the total  output 
of all the ,egyptian oasis wells and    
springs at about five times  this1 or   
#bej1jjj cubic metres per diem4 ,as the 
average daily discharge  of the ,nile in
 ,egypt is about #ahj million tons1 a   
local influx into it  several times as  
great as the total discharge of the     
oasis wells would  represent but an     

insignificant addition to the discharge 
of the ,nile4 ,i  think1 however1 that  
the influx of the warm water might      
possibly be  detected by careful        
thermometric measurements made in the   
river near its  banks at the time of low
 ,nile4    ,footnote #bc3 ,this was the 
lowest level recorded at the time when  
,i drew  the static contours on the map4
 ,the further exploration of the        
depression by ,mr4 ,walpole in the      
present year has shown that at one      
place the ground-level descends to  #acd
 metres2 the situation of this  local   
deepening is1 however1 such that the    
drawing of the static  contours would   
not have been affected by its inclusion 
in the list of  adopted data4           
,footnote #bd3 #8,an ,egyptian ,oasis'  
7,london1 #aiji71 p4 #aef4    ,footnote 
#be3 8,the ,mutual ,interference of     
,artesian ,wells10 ,geol4 ,mag4         
7,london1 #aiji71 pp4 #bc-bf2 also #8,an
 ,egyptian ,oasis1' chap4 x4            
,footnote #bf3 #8,an ,egyptian ,oasis1' 

p4 #adj4    ,footnote #bg3 #8,drei      
,monate in der libyschen ,wste'         
7,cassel1 #ahge71 p4  #aae4    ,footnote
 #bh3 ,see ,jordan's #8,physische       
,geographie und ,meteorologie der       
libyschen ,wste' 7,cassel1 #ahge71 p4   
#bjd4 ,jordan states that there were  on
 an average not more than two to four   
plants per acre in this  locality4      
,footnote #bi3 ,see ,rohlfs' #8,drei    
,monate in der libyschen ,wste' 7chapter
  ix4 of which was written by           
,ascherson71 p4 #bej4    ,footnote #cj3 
,in my paper on #8,recent               
,determinations of ,geographical        
,positions in the ,libyan ,desert1'     
published in ,cairo in #aiai1 ,i gave   
7p4  #ad7 the approximate position of   
the hill as lat4 #bd #bh1 long4 #bg #de4
  ,the position given above is from a   
more accurate determination which ,i    
made on revisiting the place with       
,prince ,kemal el ,din in #aibc4 ,on    
this  latter occasion the excavations   
made by the ,prince in the sand around  

the foot of the hill revealed the       
existence of hundreds of additional     
jars1 many of them intact1 set in       
regular order in the sand and  obviously
 forming a water-dump4 ,the majority of 
the jars bore clearly  incised markings1
 which ,prince ,kemal el ,din was able  
later to identify  positively as being  
tribal marks of the ,tebus1 the marks   
being in fact  exactly the same as those
 used by the ,tebu tribes of the present
 day4    ,footnote #ca3 ,see ,jordan's  
#8,physische ,geographie und            
,meteorologie der  libyschen ,wste'     
7,cassel1 #ahgf71 p4 #bae4    ,footnote 
#cb3 #8,kharga ,oasis' 7,cairo1 #aijj71 
p4 #eg4    ,footnote #cc3 ,geogr4       
,journ41 #db 7#aiac71 p4 #bhc2 also     
#8,mysteries of the  ,libyan ,desert'   
7,london1 #aibe71 p4 #cjd4    ,footnote 
#cd3 ,this 8locus0 is of course given by
 joining up the points  of intersection 
of the #ajj-metre water-contour with the
 #bjj-metre  ground-contour1 the        
#bjj-metre water-contour with the       

#cjj-metre ground-  contour1 and so on4 
,footnote #ce3 ,it is possible that the 
8,nubian ,sandstone0 in ,south-         
,western ,egypt may represent more than 
one geological system1 as has been      
found to be the case in ,sinai4 ,col4   
,tilho 7,geogr4 ,journ41 #ef 7#aibj71   
p4 #bei7 records that the sandstone at  
,ennedi proved to be of ,upper          
,silurian age by the fossils found in   
it4    ,footnote #cf3 ,though we passed 
within #aj kilometres to the east of    
,kissu  on the return journey from      
,merga to ,owenat in #aibe1 ,i could not
 observe  the structure of the mountain 
very clearly1 owing to haze4 ,but it    
appeared to me to be a huge granitic    
intrusion rising through the gneiss     
which covers a large area hereabouts4   
,the sandstone over which we had  been  
travelling since leaving ,merga gave    
place to gneiss about #dj  kilometres   
before we came abreast of ,kissu1 and   
gneiss continued to be  the country rock
 until we came within #cj kilometres of 

,gebel ,owenat1  when sandstone         
reappeared1 at first capping low hills  
and then forming  the plain4            
,footnote #cg3 ,there exists no         
published ,english translation of       
,ptolemy's  #8,geographia4' ,mller's    
edition 7,paris1 #ahhc-aija7 gives      
,greek and ,latin  texts1 with a ,latin 
commentary4    ,footnote #ch3 ,quoted in
 ,mller's edition of ,ptolemy's         
,geography1 p4  #gci4    ,footnote #ci3 
,for the latest delineation of this     
region1 see the  hypsometric map in the 
#8,atlas de l',algrie et de ,tunisie1'  
published by  the ,cartographic ,service
 of the ,algerian ,government1 ,paris1  
#aibd1  ,fascicule ,,ii4    ,footnote   
#dj3 #8,manual of ,ancient ,geography'  
7,london1 #ahia71 p4 #caa4    ,footnote 
#da3 ,geogr4 ,journ41 #ef 7#aibj71 p4   
#id4    ,footnote #db3 #8,mysteries of  
the ,libyan ,desert' 7,london1 #aibe71  
p4 #cjc4    ,footnote #dc3 ,geogr4      
,journ41 #dc 7#aibd71 p4 #bhh4          
,footnote #dd3 #8,the ,secret of the    

,sahara--,kufara' 7,london1 #aiba71 p4  
#bce4    ,footnote #de3 ,beadnell1 8,the
 ,sand-dunes of the ,libyan ,desert10   
,geogr4  ,journ4 #be 7#aiaj71 pp4       
#cgi-cie2 ,harding ,king1 8,the ,nature 
and ,formation  of ,sand ,ripples and   
,dunes10 ,geogr4 ,journ41 #dg 7#aiaf71  
pp4 #ahi-bji2  ,harding ,king1 8,study  
of a ,dune ,belt10 ,geogr4 ,journ41 #ea 
7#aiah71 pp4  #af-cc1 and ,discussion1  
pp4 #bej-beh4    ,footnote #df3 ,for    
particulars of the distribution and     
directions of the  dune-lines near      
,gebel ,owenat1 and between that        
mountain and ,sarra1 ,i am  indebted to 
,prince ,kemal el ,din ,hussein1 who    
devoted special attention  to observing 
them on his expedition to ,sarra in     
#aibf4    ,footnote #dg3 ,it may be     
remarked that in the desert of ,northern
 ,sinai  the dune-lines follow curved   
directions1 instead of maintaining a    
single  direction as in the ,egyptian   
,libyan ,desert1 and this curvature of  
the  ,sinai dune-lines has generally    

been thought to be caused by the        
deflecting influence of the mountain    
masses of ,moghara1 ,yelleg1 and        
,hellal on the wind2 but here also there
 may be regional influences at  work4   
,footnote #dh3 ,see ,jordan's notes on  
pp4 #bjd and #bjh of his 8,physische    
,geographie und ,meteorologie der       
libyschen ,wste10 ,cassel1 #ahgf4       
,footnote #di3 ,geogr4 ,journ41 #di     
7#aiag71 p4 #ee4    ,footnote #ej3 ,the 
steep ,miocene escarpment1 some #bjj    
metres high1 which  bounds the ,qattara 
depression on the north1 probably       
produces a great  eddy in the wind      
sweeping southwards over it1 causing a  
whirl round a  horizontal axis south of 
the scarp2 this may be very influential 
both in  excavation and in lifting the  
sand to great heights4 ,as a large      
portion  of the floor of the depression 
at the foot of the escarpment is formed 
of a salty sludge 7sabakha71 it is      
likely that a considerable quantity  of 
finely divided salt crystals are carried

 up with the sand in summer1  and this  
may conceivably act to some extent as a 
binding material in the  dunes4         
,footnote #ea3 ,geogr4 ,journ41 #dg     
7#aiaf71 p4 #bji4    ,footnote #eb3     
,geogr4 ,journ41 #ea 7#aiah71 p4 #beb4  
,footnote #ec3 ,many years ago ,i       
discovered that this film can be removed
  by treating the sand with warm        
hydrochloric acid1 leaving the grains of
  snowy whiteness 7see my #8,description
 of the ,first or ,aswan ,cataract'     
7,cairo1 #aijg71 p4 #eg74 ,but ,i think 
traces of iron in the ferrous state     
must exist even within the white        
siliceous body of the grains1 and be    
continually passing into the ferric     
state at the exposed surface2 for       
otherwise it is difficult to account for
 the persistence of the yellow  colour  
in spite of the mutual rubbing of the   
grains during their  transport by wind4 
,the film may possibly have an influence
 on the  electrical behaviour of the    
grains1 by reason of its possessing a   

higher  conductivity than the silica of 
the interior4    ,footnote #ed3         
,professor ,p4 ,e4 ,shaw has quite      
recently 7,nature1 vol4  #aah 7#aibf71  
p4 #fei7 suggested from laboratory      
experiments that the  mutual impact of  
particles of identical nature in        
sandstorms may  result in               
electrification of the particles and of 
the air with charges  of opposite signs4
 ,i think most travellers in the desert 
have1 like  myself1 formed the          
impression that electrification of the  
air is more  pronounced during          
sandstorms 7khamsins7 than at other     
times4 ,but it is  curious that         
observations made with the electrograph 
at ,helwan  ,observatory do not seem    
altogether to bear this out4 ,dr4 ,hurst
 finds  that khamsins are usually       
accompanied by low values of potential  
gradient in their early stages1 with    
great disturbances both positive  and   
negative for some hours before and after
 the break of the khamsin               

7#8,observations on ,atmospheric        
,electricity at ,helwan ,observatory1'  
,survey  ,dept4 ,paper ,no4 #aj 7,cairo1
 #aiji71 pp4 #eb-fb74    ,footnote #ee3 
,hurst1 op4 cit41 p4 #bh4    ,footnote  
#ef3 ,mr4 ,harding ,king records in his 
paper of #aiae that he  found           
sand-grains blown off the dunes to be   
electrified2 can these have  been grains
 which became charged by jumping up from
 the dune to meet  others and thus      
sharing their charge8    ,footnote #eg3 
,geogr4 ,journ41 #ce 7#aiaj71 p4 #che4  
,footnote #eh3 ,the hot and disagreeable
 south and south-west winds which  blow 
during the 8khamsins0 of the spring are 
much less constant in their  direction2 
and though they produce thick           
sandstorms1 they have always  seemed to 
me to occasion rather a general         
scattering of the sand over  the surface
 of the desert than to form deposits    
having very definite  arrangement2      
moreover1 they blow on relatively few   
days of the year4 ,the  far more        

prevalent cool strong north-north-west  
winds1 on the other  hand1 often        
scarcely vary a point in direction for  
days together1 and  their coincidence   
with the direction of the dune-lines is 
very  pronounced4    ,footnote #ei3     
,zeitschrift der ,gesellschaft fr       
,erdkunde zu ,berlin1  #aijb1 p4 #gfj4  
,footnote #fj3 #8,recent ,determinations
 of ,geographical ,positions in the     
,libyan ,desert1' ,survey ,department   
,paper ,no4 #cd1 #aiai4 p4 #ad4         
,footnote #fa3 ,geogr4 ,journ41 #dd     
7#aibd71 p4 #cgg4    ,footnote #fb3     
,jordan's final position was lat4 #be   
#aa #g1 long4 #bg #be  #j4 ,the         
longitude given on the document found in
 the bottle at the cairn  7#ad #db ,e4  
of ,berlin1 or #bh #c #db ,e4 of        
,greenwich7 was a preliminary  value    
resulting from ,jordan's observation of 
a lunar distance1 and was  wrong by some
 #dj miles4    ,footnote #fc3 ,mr4      
,harding ,king's observations gave the  
latitude as #bf  #cj #df1 and the       

longitude as #bg #cf 7see his map in    
,geogr4 ,journ41  #db 7#aiac71 p4 #eaf74
    ,footnote #fd3 #8,recent            
,determinations of ,positions in the    
,libyan ,desert1'  ,survey ,department  
,paper ,no4 #cd 7,cairo1 #aiai71 p4 #ab4