APPENDIX I

THE RECEPTION OF THE EXPLORER AT EL FASHERThe governor of the Darfur Province and his staff welcome the explorer to the capital of the provinceWe stopped at Um Buru for two days. Abdel Rahman Jeddu,wakilof Mohammedin, the head of the Zaghawa tribe, visited me and brought sheep and chicken asdiafa. On the second day we were given an official welcome, thewakilcoming with a retinue of retainers on horseback beating drums. Mohammedin’s family, in the absence of the master of the household, sent a lunch ofasida, vegetables,merissa, and pastry.The next stage of our journey was a five days’ trek to Kuttum, 129 kilometers to the southward. The weather was generally good, though hot, with an occasional shower. We traveled as usual in the early morning and late afternoon. There was a beaten track with fairly good going, through hilly country covered with dry grass and small trees. At intervals there were patches which had been burnt in preparation for being cultivated.On the third day my messenger to El Fasher arrived, with two companions, but it was a disappointing meeting. It had taken him five days instead of four to reach his destination, and he had not brought the answer to my letter back with him. It was waiting for me, he said, in the possession of a soldier at Mutarrig Well, twelve hours’ journey from where we were. The soldier also had provisions for us, but they did us little immediate good at that distance.There was little for dinner when we camped that night. After dinner I sent our guide off post-haste with orders to ride all night and until he reached Mutarrig. There he was to tell the soldier to come to us as fast as he could.We started before four the next morning, and in an hour the men came rushing to me with the news that there was a soldier ahead on a camel. In a few minutes I had a letter from Charles Dupuis, acting Governor of Darfur, in the absence of Saville Pasha who had resigned from the service, and a small supply of rice, flour, tea, and sugar. I was especially pleased to be handed a supply of cigarettes.I had not smoked since soon after leaving Erdi. At Ouenat I had suddenly realized that there were only a few cigarettes left. I then laid down a strict rule for myself: one cigarette a day after dinner. It was hard work waiting all day for that brief smoke, but it was worth it when the moment came. I would get into a sheltered corner, light the precious cigarette, and shield it carefully from any breath of wind that might make it burn ever so slightly faster. When the few cigarettes were gone, there was nothing left but memories and expectation. Now at last the expectation was gratified with a vengeance, for I smoked until my throat was sore.Bukara, with a handful of the newly arrivedcigarettes, put on his long-tasseled redtarboosh, got on the guide’s horse, and did a littlefantasiaof joy. But it was when we camped at the government rest-house at Marahig that general rejoicing broke loose with singing and dancing. The corporal, looking on while the men set the sugar-loaf on the ground and executed a wild dance about it, thought us all a little mad.“Why all this rejoicing?” he demanded.“Because for a month we have had no sugar, and now our tea is sweetened again,” said Abdullahi.Until one has tried going without any sugar whatever, one does not realize how keenly it will be missed.The corporal shook his head and smiled. “I must return at once to Kuttum and bring you more provisions,” he said. “We never realized that you were so short of food.” Before he left he was kind enough to go to a camp near-by and bring us a sheep and butter, which were to be paid for by themoawinof Kuttum, since the seller refused to accept Egyptian paper money. The corporal then left with letters from me for Mr. Dupuis and themoawin, the deputy Governor of Kuttum.The provisions which he had brought us were good as far as they went, but we should very soon be in need of more. I decided to push on at once. We made our midday halt at the government rest-houseat Marahig Well and our stop for the night only a few kilometers farther on. The camels were in very bad condition. The backs and sides of some of them were sore and bleeding, and two camels refused to move until their loads were taken off. It rained for an hour that evening, but it could not dampen our spirits. The men sang and danced around a big fire. The humidity and the smell of the wet grass reminded me of my walks in English country.We made an early start the next morning in order to reach Mutarrig Well for the midday halt. We lunched at the rest-house near the well and received a visit from thesheikhof Mutarrig, who brought a few chickens asdiafa. He wanted us to stop the night so that he could entertain us properly the next day, but I felt the necessity of going on as fast as possible.The camels were getting steadily worse. We had to leave one of them with thesheikhof the village on the understanding that if it recovered he was to get a quarter of the price it brought when sold, while if it died he was not to be held responsible.An hour and a half after starting the next day another soldier on horseback appeared. He brought a letter from themoawinof Kuttum and a small quantity of rice and sugar. They are gratefully received, for once more we were on short rationsand without sugar for our tea. I gave him a letter to take back to Kuttum. A little later we camped in the small valley of Boa. In the afternoon, soon after we had started again, it came on to rain with a strong southeast wind, and I thought it might be wise to camp until the storm was over. But through my glasses I made out ahead of us the row of straw huts of the Markas—the government house—of Kuttum, and spurred on by the sight we drove the camels faster.Soon a group of horsemen were seen approaching us, and my Bedouins impulsively raised a cheer. When I recognized the uniform of Sudanese troops, it was the most cheering sight that I had seen for many weeks. Riad Abu Akla Effendi and Nasr El Din Shaddad Effendi, the twomoawinsof Kuttum, approached with a detachment of ten soldiers, thekadi, the head clerk, and other officials and notables of Kuttum. I shook hands warmly with them all, and under their escort the caravan moved on through the village. As we approached, the Markas women clothed in white and beating drums greeted us with singing and “lu-lias.” We settled ourselves in and about the rest-house, and the women came again to offer greetings. In a long line they sang and danced, much to the delight of my Bedouins, who asked permission to empty gunpowder in acknowledgment ofthe courtesy. I could not refuse my consent, and one by one, beginning with Bukara, the men performed the ceremony of singeing the girls’ slippers. The Sudanese women were not so accustomed to the Bedouin manner of paying homage as the girls of the northern desert, and flinched a little as the powder flashed at their feet. But they accepted it all in good part, the whole line swaying and dancing to the rhythm of the drums while one by one my men singled them out for the “slipper-singeing honor.” It was a wonderful reception, and the pleasure of it dispersed like magic the fatigue and lassitude of the journey.More hospitality was to come. Four sheep, butter, and fresh vegetables, to say nothing of sugar, were brought to us asdiafafrom themoawinsand officials, and we spent a pleasant evening feasting.Our arrival at Kuttum at this particular moment had seemed to the inhabitants there an especially auspicious one, for we came with the first rain of the season.We stopped there for two days, entertained generously by themoawinsin the absence of the inspector, Mr. Arkell, who was at El Fasher.One afternoon we attended a soccer match between two teams of soldiers. It was played with energy if not with finesse. At times a player, strivingto give the ball an especially vigorous kick, would miss it and send his Sudanese slipper shooting high into the air. Thecamaraderiebetween officers and men, playing this not exactly gentle game together, was interesting to see.Dinner that night with Riad Effendi and Nasr El Din Effendi, themoawins, was the first meal I had eaten in a house since leaving Kufra. My hosts gave me Egyptian newspapers to read, the first I had seen in nearly six months.We left Kuttum at six o’clock on the morning of June 17, cheered by the generous hospitality we had enjoyed and the friendly send-off our friends gave us. The two days’ journey to El Fasher was a joy-ride. We all felt the thrill and exhilaration of getting in touch with the world again.But as I went to bed on the eighteenth I realized with a stab of regret that this was my last day in the real desert. I thought how I should miss my men and my camels, the desolateness and the beauty, the solitude and the companionship; in two words, the desert and its life. I thanked God for His guidance across this vast expanse of pathless sand and found myself adding a prayer, half wistfully, that I might come back to it again.I had given orders for an early start the next morning. In their eagerness my men somewhat exaggeratedmy idea of “early,” but I was excited myself and did not mind getting under way at half-past two.Three hours’ march from El Fasher we camped to make preparations for entering the place. We all shaved and put on our best clothes. Mr. Dupuis had sent a supply of white cloth to Kuttum for us, and my men were able to appear once more in decent raiment. They crowded around my remnant of a mirror to see how they looked. Rifles were cleaned, and the luggage, which was in a very shabby state, was tidied as much as possible. I wished that I might be able to do something for the camels as well, which were thin and dejected-looking. But rest and attention to their sore backs were what they needed, and we had no time or facilities for giving them that. Nevertheless they too seemed to be infected with the spirit of eagerness felt by all of us and walked forward briskly. Abdullahi and Zerwali got into their silks, and the caravan moved gaily toward its destination.As we reached the outskirts of El Fasher, cheers of rejoicing rose throughout the caravan. A cavalcade of men in khaki was coming toward us. I put spurs to Baraka, and he responded willingly. He saw the horses before us, pricked his ears forward, and dashed toward them.EL FASHERThe capital of Darfur ProvinceMr. Dupuis came forward on his horse to meet me, and we shook hands warmly. The greetings were repeated by the English and Egyptian officers of his staff, and we went on to his house, a part of which he generously made over to me and the men of my caravan. The weary camels were promptly taken in hand by Bimbashi Andas, who gave them food, water, and the medical treatment for their wounds they so much needed.The officer in charge of the wireless station kindly got me the exact Greenwich time from Paris by radio. I was pleased to discover that my chronometer had lost only twenty-three minutes and twenty-three seconds in eight months.For ten days I was the guest of Mr. Dupuis and was lavishly entertained by the officers and officials of the garrison, both English and my own compatriots, and the notables of the town. Hospitality was showered upon me, and every kind of assistance that could possibly be needed was eagerly rendered. This was civilization again. I enjoyed once more the luxuries of life, especially vegetables and fruits. It is only when one has gone through the austere régime of the desert that one looks upon these things as luxuries and not necessities. There was in particular a brand of prunes, the pride of Major Smith, and of peculiar lusciousness. He called them “IfWinter Comes,” and I have never tasted their like anywhere.At last the day came when I must take leave of my companions of the trek from Kufra. When Bukara and his brother and Hamid and Senussi Bu Jaber came to my room to say good-by, it was a moment full of real emotion and crowded with memories. These rugged men of the desert burst into tears, and I found my own eyes wet. We had been through thick and thin together and came out fast friends. I could never wish for better companions on a journey into desolate regions, more able, more manly, or more loyal.We read the “Fat-ha,” the sound of the familiar sacred phrases punctuated by Bukara’s sobbing. I exchanged a final handclasp with each of them, and we parted, to meet one day, I hope, in that desert that I love as much as they.One more camel-trek before me eastward to El Obeid. There I took train for Khartum and thence home to Cairo, where I arrived on August 1, 1923.I had been away from home seven months and twenty-three days, having trekked twenty-two hundred miles across the desert by caravan.I had determined finally the position of the Zieghen Wells and of Kufra on the map of Africa, in the placing of which there had been hitherto errorsof one hundred and of forty-five kilometers respectively.I had also had the great good fortune to put the “lost” oases of Arkenu and Ouenat definitely on the map of the Libyan Desert.To A. M. H.I crave no statue in a public street,Nor page of history to give my name:A desert flower on my winding sheetIs all I ask to mark the way I came.There were no jewels buried in the sand,The treasure that I sought was little worth:I went—but oh, how few will understand—To tread an unworn carpet of the earth.Wide spaces called me, and the way was free;Feet falter not upon a road unknown:How languish, one who, looking back, can see—A thousand miles—no footsteps but his own?Not half a hundred voyagings for goldCould make me rich as many times I’ve beenWhen, weary-eyed, I’ve watched the dawn unfoldAnd spread soft radiances o’er a desert scene.Thoughts were my treasure; where may thoughts be sold?My world was empty, but my world was clean.G. F.Foley.El Fasher,June 30, 1923.APPENDIX INote on the Cartographical Results of Hassanein Bey’s JourneyJohn Ball, O.B.E.,D.Sc., Director of Desert Surveys, Egypt1. IntroductionTHE cartographical data brought back by Hassanein Bey consist of:(1) Note-books containing the records of astronomical observations for the determination of time, latitude, and compass-variation at nineteen principal camps, with records of watch-comparisons.(2) A journal giving a continuous record of observed compass-bearings and estimated distances from Siwa Oasis to Lameina Wells, near El Fasher, a distance of about 2430 kilometers.The journal also contains a considerable number of observed compass-bearings to conspicuous features on either side of the route, with a few rough trigonometrical estimations of the altitudes of mountains passed, a large number of readings of an aneroid barometer and sling thermometer for the estimation of altitudes along the route, daily observations of maximum and minimum temperatures, observations on the character of the country passed through, and notes on the meteorological conditions.These observational data have been reduced in the Desert Survey Office, Cairo, and utilized in the preparation of the map on a scale of 1:2,000,000 which accompanies Hassanein Bey’s account of his travels. The objects of the present note are, first, to give an account of the critical examination to which the records were subjected in the course of the reduction of the observations, so as to enable an estimate to be formed of the degree of precision which may be fairly assigned to the geographical positions, altitudes, and other results used in the construction of the map; and, secondly, to indicate the additions to existing geographical knowledge concerning a little-known region of northeast Africa which have accrued from the expedition.2. Astronomical Determination of Local TimeTheodolite observations of altitudes of the sun or of stars were made at all the principal camps for determining the error on local mean time of the half-chronometer watch which was used in the latitude observations. In all, thirty-four complete time determinations were made at seventeen camps. The observations were made with a three-inch Troughton & Simms theodolite, the vertical circle of which could be read by two verniers to 1′, and which was provided with a sensitive level on the microscope arm. The theodolite was invariably set up in the magnetic meridian by its trough compass, and the method used was to note the times of passage of the sun’s limb or of the star over each of the three horizontal wires of the stadia-graticule, reading the level and circle at each pointing, face-right and face-left. In the case of stars, the magnetic bearing of the star was also noted from the horizontal circle, and a note made of the color and brightness of the star, for the identification of the stars subsequently in the office, and thus to free theobserver from the necessity of knowing the stars’ names. The barometer and thermometer were carefully read at each observation for calculating the refraction.No difficulty was experienced in subsequently identifying the stars. In only a single case was it found necessary to reject an observation, and this because the observer had accidentally sighted different stars on the two faces of the instrument. On many days two or more observations were taken at the same place, and comparisons of the results at these places indicated that the observations are remarkably accurate for so small an instrument. In seven cases where the sun has been observed shortly before sunset and a star soon after sunset, for example, the maximum difference between the results given by the two observations is only seven seconds, while the average is under four seconds. It is thus apparent that the precision of the time observations is amply sufficient to insure that no sensible error in the latitudes can be due to errors of the adopted local times.As the only use made of the time observations in the preparation of the map has been in the determination of latitude, it would serve no useful purpose to give a list of the watch errors. But it may interest future geographers, undertaking long desert journeys, to note some of Hassanein Bey’s experiences in the transport of watches, and the hazard of relying on constancy of rate for long periods with even the best watch.Of the six watches carried, only a single one remained in going order throughout the journey. The timekeeper which thus successfully resisted the vicissitudes of the seven months of desert travel was fortunately the one with which Hassanein Bey took all his observations, and was carried in his pocket during the entire journey; it was a large-sized half-chronometer “explorer’s” watch of English manufacture,with a dust-proof cap to the winding mechanism. It had been awarded an “especially good” certificate at the National Physical Laboratory of England, and was consequently the most expensive of all the six watches taken on the journey. Even this watch failed to maintain a sufficiently constant rate to be of any service in the determination of longitudes, though it amply sufficed for the latitudes, even in two cases when reliance had to be placed on the constancy of its rate for one or two days owing to latitude alone being observed without corresponding observations for local time. Thus, for instance, the following were the average rates of the principal watch deduced from local time observations at places of previously known latitudes:Rate of Principal WatchSollum to SiwaDec. 29-Jan. 1315dayslosing5.8secs.Siwa to JaghbubJan. 13-Jan. 207““0.1“Jaghbub to FurawiaFeb. 14-June 5111““7.7“Furawia to Um BuruJune 5-June 83““6.6“Um Buru to El FasherJune 8-June 2618““9.4“El Fasher to El ObeidJune 30-July 1515““9.4“The above table fails, however, to bring out fully the actual variations of the watch. So long as the other five watches remained in order, Hassanein Bey made frequent comparisons with his principal watch, and between March 21 and 23 there is strong evidence that the principal watch made an abnormal gain of about fifty seconds. A similar abnormal gain of twenty-nine seconds by the principal watch is evidenced in the twenty-four hours between comparisons of March 24 and 25. Both these abnormalities occurred between Jalo and El Harrash, at an early stage of the journey, while all the watches appeared to be behaving tolerably well, and it is quite possible that other abnormalitiesoccurred at later stages, when, owing to some or all of the other watches having stopped or broken down, no satisfactory control by comparison was possible.Of the other five watches carried, one was an English half-chronometer, similar to the principal watch but of smaller size; three were high-class Swiss lever (“Peerless”) watches with very tight-fitting cases; and the fifth was a small Swiss lever-watch with luminous dial, carried on the wrist for noting the times of marching. The small half-chronometer stopped on April 3, after going for over four months; and though it was restarted, its rate changed considerably after the stoppage. The three “Peerless” watches, though they failed to continue going to the end of the journey, showed by no means a bad record. One was found stopping and unreliable on May 6, after going for over five months; the two others continued to go for over a month longer; and so far as can be judged from the comparisons made on the route, their variations of rate were about of the same order as those of the half-chronometers. The wrist-watch, from the manner in which it was carried, was of course liable to much greater variations of rate, and was occasionally reset by the principal watch; but it kept going till nearly the end of the journey.As regards dust-resisting power, which must always be one of the principal aims in selection of watches for desert exploration, there appears to be nothing to choose between good English half-chronometers and the highest class of Swiss watches, the cases of the latter being remarkably close-fitting. The most probable cause either of stoppage or of abnormal changes of rate appears to be the sudden shocks which may arise either to a watch carried on the person when jumping on or off a camel, or to one carried in the baggage by sudden movements of the camel.The most likely explanation of the abnormal gains of the principal watch for short periods on the two occasions above noted would seem to be that, owing to a jerk in mounting or dismounting, two contiguous coils of the hair-spring may have been made to touch each other for a short time, with consequent temporary shortening of the period of vibration of the balance-wheel. It is noteworthy that the watch which remained going throughout the journey was the largest of all those taken, and its greater resisting-power may have been to some extent due to its size, permitting of greater strength in its component parts.3. Astronomical Determinations of LatitudeObservations for latitude by altitudes of the pole-star were carried out on thirty-five nights at nineteen principal camps, using the same three-inch theodolite as was employed for the time-observations. Three readings of altitude were made on each face, using each of the three horizontal stadia-wires in turn, the corresponding times being noted on a half-chronometer watch whose error on local time was accurately known from sun or star-observations carried out just before the latitude-observation. Particular care was taken with the level-adjustment, and the air-pressure and temperature at the time of the observation were recorded.The following table gives the results of the observations:Astronomical Latitudes°′″Sollum4nightsLat.31359N.Siwa1““291241“Jaghbub5““294426“Camp near Jalo1““291156“Jalo (El Erg)1““29233“Buttafal1““285426“El Harrash1““252629“Taj6““241347“Arkenu2““221232“Ouenat1““215229“Erdi1““183539“Agah1““175238“Enebah1““172124“Bao1““162824“Furawia2““152151“Um Buru2““15357“Kuttum1““141215“El Fasher2““13383“El Obeid1““131051“Of six of the above places (Sollum, Siwa, Jaghbub, Kuttum, El Fasher, and El Obeid) the latitudes are accurately known from the Egyptian and Sudan official surveys, and the agreement in these cases is very satisfactory, though a very close comparison is not generally possible owing to uncertainty as to Hassanein Bey’s precise observation-spot. At Jaghbub, Hassanein Bey records that his observation-spot was 200 meters S.S.W. of the dome of the mosque. Applying the corresponding difference of latitude (− 6″) to my own determination of the latitude of the dome in 1917 (29° 44′ 41″) we obtain 29° 44′ 35″, showing a difference of only 9″ from Hassanein Bey’s observed latitude.A further test of the degree of precision of the latitude-observations can be made by comparison of the latitudes found for the same camp by observations taken on different nights. The following gives the average deviation of a single observed latitude from the mean at all the camps where two or more observations for latitude were made:″Sollum4nightsAv. dev.8Jaghbub5““40Taj6““12Arkenu2““6Furawia2““8Um Buru2““23El Fasher2““6It thus appears unlikely that any observed latitude can be as much as 1′ in error, and consequently in the preparation of the map, Hassanein Bey’s observed latitudes have been accepted as fundamental data for all the places for which no previous determinations are known to exist, viz., El Harrash, Taj, Arkenu, Ouenat, Erdi, Agah, Enebah, and Bao. His latitudes for Jalo (El Erg), Bir Buttafal, and Furawia have also been adopted for the map, the first because it is possibly better than that of Rohlfs, with whose mapped position it is however in very close agreement; the second because while differing by about 2′ from Rohlfs’s value (28° 36′ 22″) it is doubtless more exact, because it checks admirably well with Hassanein Bey’s dead reckoning; and the third because, although the position of Furawia is shown on the Sudan maps, it is outside the present limits of the Sudan triangulation and is possibly liable to some slight error.[1]4. Observations of Compass-VariationsFor finding the pole-star easily when the sky was not very dark or was partially obscured by clouds, and also for obtaining the approximate bearings of time-stars for their subsequent identification, the theodolite was invariably set up in the magnetic meridian by its trough-compass, and the magnetic bearing of the pole-star was read on the horizontal circle after each latitude-observation and the time noted. In this way approximate compass-variation was determined at each camp, with the following results:Variation of the Compass°′SollumDec., 19223obs.234W.SiwaJan., 19231“242“JaghbubFeb., 19235“225“Near JaloMarch, 19231“412“Jalo (El Erg)““1“45“Buttafal““1“—El Harrash““1“348“TajApril, 19236“332“Arkenu““2“325“Ouenat““1“332“ErdiMay, 19231“357“Agah““1“40“Enebah““1“421“Bao““1“459“FurawiaJune, 19232“432“Um Buru““2“325“Kuttum““1“426“El Fasher““2“251“The method of estimating the compass-variation with the theodolite is, of course, only rough; but the values found are probably correct at most places within half a degree, and they serve to show that there is no likelihood of any serious errors of dead-reckoning owing to local irregularities of the compass-variation. They have accordingly been utilized in reduction of the compass-bearings of the traverse to true bearings over the major portion of the route, where no previous determinations exist, and where in consequence the distribution of the isogonic lines is not known with any exactitude.5. LongitudesThe probability of some watches breaking in the course of seven months’ travel had been foreseen, and from the outset it appeared improbable that any use could be made of the watches in the direct determination of longitude of so long and difficult a journey. We had decided accordingly to depend ultimately on dead-reckoning for longitude, making every effort to obtain an unbroken chain of compass-bearings and estimated distances between Jaghbub and some known place in the Sudan, the bearings to be taken with a good compass with all possible precision, at very frequent intervals, and the estimates of distance to be carefully made each day from the marching time of the baggage-camels, assuming a normal rate of 4 km. per hour over average desert, and making allowance for the variations in speed over ground of varying character. The journey being predominantly north to south, the estimates of distance could mostly be well controlled by the latitudes, while errors of bearing would not be cumulative, and would tend to cancel out over any considerable stretch of route. The primary reason for taking six watches was therefore not to determine longitude,for which at best they could afford only somewhat uncertain values, but to make sure of at least one watch being available throughout the journey for latitude-observations, without which no proper control of the all-important distances could be obtained.The doubts about the possibility of safely transporting the watches proved justified, for all but one broke down before the end of the journey. But fortunately on the one hand the watch which survived sufficed amply for the determination of latitude (though its rate was insufficiently constant for it to be used uncontrolled in finding longitudes), and on the other hand the program of a continuous chain of very careful bearings and estimation of distances was scrupulously adhered to from the departure of the caravan from Jaghbub, the last known place in Egypt, to Furawia, the first known place in the Sudan—a journey of 2430 kilometers—and from this chain of bearings and estimated distances, combined with the observed latitudes, it was possible to estimate the longitudes of all places on the route with a fairly high probability of accuracy.For the estimation of the longitude of Jalo (El Erg) a slightly different procedure was followed from that adopted for the other principal camps on the route. It will be noticed from the map that the general direction of the march from Jaghbub to Jalo was predominantly from east to west, instead of from north to south as in the rest of the journey. Consequently the observed latitudes do not afford so good a means of correcting the estimated distances in this stretch as elsewhere. But fortunately the observed latitude at Jalo does enable us to correct the previous estimation by Hassanein Bey (in 1920) of the distance of that place from Jedabia, and this combined with the then observed bearings would lead to one value for the longitudefor Jalo, while if we can assume the accuracy of the estimated distances from Jaghbub to Jalo, we may use the observed latitude of the latter place to correct the bearings and thus arrive at another value for its longitude.From careful consideration of all the available data, the two methods appear likely to be about equal in degree of approximation. The position at present accepted for Jedabia (Lat. 30° 48′ 10″ N., Long. 20° 13′ 30″ E.) is open to a little uncertainty,[2]and the bearings taken by Hassanein Bey on his former expedition are probably a little less accurate than those of the present one. On the other hand, the estimations of the distances from Jaghbub to Jalo, as gaged by the latitude-control of the other portions of the route of the present expedition, are remarkably close to the truth, while a uniform correction to his bearings of less than half a degree would swing his dead-reckoning position for Jalo on to its observed parallel of latitude.For the longitude of Jalo on the map I have therefore taken the mean of the two longitudes found (1) by assuming Hassanein Bey’s bearings correct from Jedabia and correcting his distances by the latitudes, and (2) by assuming his distances from Jaghbub correct and using the observed latitudes to correct his bearings. The results are:°′″(1) From Jedabia, long. of Jalo (El Erg)212948(2) From Jaghbub“““212619Adopted mean21283It may be remarked in passing that the result placesJalo almost precisely where it is shown on Rohlfs’s map of 1880.As regards the longitudes adopted for the other principal camps along the route, the procedure has been as follows. The route was divided into the following nine sections between principal camps where latitudes had been observed: Jalo, El Harrash, Taj, Arkenu, Ouenat, Erdi, Agah, Enebah, Bao, Furawia; and the compass-traverse for each section was plotted on a scale of 1:500,000 from the recorded bearings and estimated distances. A true meridian was then drawn on each section from the mean of the observed compass-variations at its two ends, and the total difference of latitude of each section was scaled off and compared with the difference of latitude given by the latitude-observations. This comparison gave, of course, the average error of estimation of distance along each section, assuming the bearings correct. The results of the comparison for the various sections are tabulated below:Correction to Estimated DistancesSection of traversePlotted difference of latitudeTrue difference from latitude-observationsTrue-plotted diff. lat.Correction to estimated distanceskm.km.km.%Jalo-El Harrash375.0399.0+ 24.0+ 6.4El Harrash-Taj131.5134.2+2.7+ 2.1Taj-Arkenu217.7223.7+6.0+ 2.8Arkenu-Ouenat36.037.0+1.0+ 2.8Ouenat-Erdi369.0363.2−5.8− 1.6Erdi-Agah75.679.2+3.6+ 4.8Agah-Enebah57.057.5+0.5+ 0.9Enebah-Bao99.097.7−1.3− 1.3Mean error of estimation of distances, per cent2.6The average error of distance-estimation in each sectionof the route having been thus found, the next step was to scale off the various departures from the plotted traverses, correcting for the errors of distance-estimation, and then to convert the departures into differences of longitude. When this was done, the resulting total difference of longitude between Jalo and Furawia was 2° 25′ 55″. But assuming the true longitude of Jalo to be that found above, and the true longitude of Furawia to be as shown on sheet 53 D of the 1:250,000 Sudan survey map of 1921,[3]we have:°′″Longitude of Jalo21283Longitude of Furawia233810Difference2107So that the difference of longitude found by the dead-reckoning requires correction by 15′ 48″. This correction, which implies an average error in the observed compass-bearings of less than a degree, and a negligible correction to the adjusted distances, was distributed along the entire traverse in proportion to the difference of latitude between the principal camps, leading to the finally adopted longitudes shown in the following table:Concluded LongitudesDead-reckoning corrected by the latitudesFurther correctionConcluded longitude°′″′″°′″Jalo——21283 E.El Harrash22155 E.410221055 “Taj23295 “534232341 “Arkenu245210 “755244415 “Ouenat25234 “818245416 “Erdi232234 “125231029 “Agah232849 “1254231555 “Enebah232558 “1330231428 “Bao231618 “143123147 “Furawia235358 “1548233810 “In attempting to estimate the probable degree of accuracy of the concluded longitudes, we are faced with the difficulty that while we may be certain that theaverageerror of the compass-bearings was less than 1°, which average error has been allowed for in the adjustment, we have no proof that in some of the individual sections the errors may not have been considerably greater. But in view of the great number of the observed compass-bearings (339) which make up the directional data of the 1754 kilometers of traverse from Jalo to Furawia (an average of thirty-eight observed bearings for each of the nine sections), and bearing in mind also the remarkable accuracy of the estimations of distance as evidenced by the latitude-observations, it would seem unlikely that any of the above-adopted longitudes for the principal camps can be in error by more than three or four miles. This implies a degree of accuracy which it would have been difficult to insure by transport of even a considerable number of chronometers over a land journey lasting more than three months. It may, I think, be concluded that no better values for the longitudes can be obtained without the aid of wireless time-signals.6. Altitudes above Sea-levelFor the barometric estimations of altitudes above sea-level, a two-inch aneroid by Steward was used. This instrument, which was one of two specially made for the expedition,was very carefully compensated for temperature, and provided with a fairly open pressure-scale, a millimeter of pressure being represented by very nearly a millimeter of actual scale-length, so that estimations to half-millimeters of pressure could be readily made.The aneroid was read morning and evening at each camp, and at numerous other points on the route, the air-temperatures being as a rule recorded at the same time, as given by sling-thermometer. The aneroid behaved very satisfactorily throughout the journey. There had unfortunately been no opportunity of testing the instrument before Hassanein Bey’s departure, but it was in perfect order on his return, and was then tested in the laboratory of the Physical Department at Cairo, when it was found to require the following corrections (at about 25° C.):Pressure, mm.760750740730720710700690680670660650Correction, mm.− 2.3− 2.3− 2.3− 2.1− 1.4− 1.1− 0.1+ 0.6+ 1.7+ 2.0+ 2.8+ 2.9That the above corrections had remained sensibly constant throughout the journey is rendered extremely probable by the close agreement noted further on (p. 329) between the levels found for Jalo directly from the aneroid readings (corrected, of course, on the assumption of constancy of the table) and those found indirectly from readings of the mercurial barometer in the meteorological station at Siwa.The first step in the calculation of the barometric levels was to collect the whole of the readings of the barometer and sling-thermometer at each of the nine principal camps, where a halt of at least several days had been made, and a considerable number of readings taken. The means of all the recorded pressures and air-temperatures were taken for each of these principal camps, and the pressure corrected for instrumental error from the table above given. The readingsbeing taken at various times of the day, the diurnal variation of pressure could safely be neglected, as it would most probably disappear on taking the mean of the readings. To allow for the annual variation, the mean pressures were next reduced to the mean of the year by applying a correction based on the mean of the normal annual variations at Siwa and El Obeid, as found from the recent volume of “Climatological Normals” issued by the Physical Department of Egypt and shown in the following table:Corrections to Reduce Monthly Mean Pressures to Annual MeansJan.Feb.MarchAprilMayJuneJulymm.mm.mm.mm.mm.mm.mm.Siwa− 3.4− 2.0− 1.9+ 0.9+ 0.9+ 2.7+ 3.5El Obeid− 1.2+ 0.7+ 0.3+ 1.2+ 1.0+ 0.60.0Mean− 2.3− 1.4− 0.8+ 1.0+ 1.0+ 1.6+ 1.8A further correction to allow for the distribution of the sea-level isobars over the region traversed was desirable, but no sufficient data exist for estimating its amount; the distribution is, however, probably nearly linear, and such a distribution was approximately allowed for by assuming the previously accepted levels at Siwa (− 17 m.) and El Fasher (793 m.) to be correct and distributing any residual difference found by the otherwise corrected barometer readings between these two places uniformly among the different sections.The difference of height corresponding to each difference of mean corrected barometer-readings was calculated by the tables ofBarometrische Höhenstufenin Jordan’s “Mathematische und Geodätische Hülfstafeln,” for the air-temperature corresponding to the mean of the thermometer-readings at the two ends of the line.The adopted levels of thirteen principal camps as found in the above manner are tabulated below. It is interesting to note that the residual difference of height which had to be distributed between Siwa and El Fasher, and which is presumably mainly due to systematic pressure-gradient, was sixty-three meters, corresponding to a normal fall of sea-level pressure between the two places of about 5 mm., and this is from other considerations probably very near the truth; also that the resulting adjustment which had to be made in the levels in any single main section of the route did not exceed five meters.Concluded Altitudes above SeaNumber of observationsMean pressure (corrected)Mean temperatureDiff. of height from Jordan’s tablesDiff. of height (adjusted)Altitude above sea-levelmm.° C.metersmetersmetersSiwa4762.612——− 17Jaghbub50757.715+ 54+ 49+ 32Jalo18754.717+ 34+ 2961El Harrash6732.823+ 254+ 249310Taj31718.519+ 170+ 165475Arkenu12708.031+ 128+ 123598Ouenat14706.331+ 21+ 18616Erdi7683.331+ 295+ 290906Agah3695.234− 157− 162744Bao5677.733+ 230+ 225969Furawia11685.831− 107− 112857Um Buru8679.530+ 83+ 78935Kuttum5660.224+ 254+ 2491184El Fasher5689.731− 386− 391793After thus determining the levels for the principal camps, those of intermediate camps and other places were computed in a similar manner, adjusting each section to the adopted levels at its terminal points. The maximum adjustment which it was found necessary to apply to thedifference of height given by the barometer between points a day’s journey apart was five meters, and the average three meters.An exception was made in the stretch between Jaghbub and Jalo, where no intermediate levels were adopted for the map, owing to the extremely unstable state of the atmosphere during the journey between these two places; sand-storms of great violence occurred on several days of marching, with such rapid fluctuations of air-pressure that no heights could safely be deduced from the barometer-readings.As regards the degree of reliability of the deduced levels, some little uncertainty exists in the levels adopted for the terminal points Siwa and El Fasher, while the temperature-compensation of the aneroid has not been tested and may not be quite perfect. Taking everything into account, it may be estimated that the levels of the principal camps are probably correct to within about twenty meters, while those of the intermediate camps and other points, for which only one or two readings of the barometer are available, may possibly be in error by twice that amount.7. Summary of Principal Geographical Positions and LevelsLatitude N.Longitude E.Meters above seaRemarks°′″°′″Jaghbub (mosque)29444124311132Position from previous determination by Dr. Ball.Jalo (El Erg)292332128361Bir Buttafal28542621451598El Harrash Well (Zieghen)252629221055310Taj (Kufra)241347232341475Boema (Kufra. Rohlfs’s camp)24138232440400Short compass traverse from TajArkenu221232244415598Ouenat215229245416616Erdi (camp 8 km. north of well)183539231029906Agah175238231555744Enebah1721242314281100Bao16282423147969Furawia152151233810857Longitude from Sudan map

THE RECEPTION OF THE EXPLORER AT EL FASHERThe governor of the Darfur Province and his staff welcome the explorer to the capital of the province

THE RECEPTION OF THE EXPLORER AT EL FASHER

The governor of the Darfur Province and his staff welcome the explorer to the capital of the province

We stopped at Um Buru for two days. Abdel Rahman Jeddu,wakilof Mohammedin, the head of the Zaghawa tribe, visited me and brought sheep and chicken asdiafa. On the second day we were given an official welcome, thewakilcoming with a retinue of retainers on horseback beating drums. Mohammedin’s family, in the absence of the master of the household, sent a lunch ofasida, vegetables,merissa, and pastry.

The next stage of our journey was a five days’ trek to Kuttum, 129 kilometers to the southward. The weather was generally good, though hot, with an occasional shower. We traveled as usual in the early morning and late afternoon. There was a beaten track with fairly good going, through hilly country covered with dry grass and small trees. At intervals there were patches which had been burnt in preparation for being cultivated.

On the third day my messenger to El Fasher arrived, with two companions, but it was a disappointing meeting. It had taken him five days instead of four to reach his destination, and he had not brought the answer to my letter back with him. It was waiting for me, he said, in the possession of a soldier at Mutarrig Well, twelve hours’ journey from where we were. The soldier also had provisions for us, but they did us little immediate good at that distance.

There was little for dinner when we camped that night. After dinner I sent our guide off post-haste with orders to ride all night and until he reached Mutarrig. There he was to tell the soldier to come to us as fast as he could.

We started before four the next morning, and in an hour the men came rushing to me with the news that there was a soldier ahead on a camel. In a few minutes I had a letter from Charles Dupuis, acting Governor of Darfur, in the absence of Saville Pasha who had resigned from the service, and a small supply of rice, flour, tea, and sugar. I was especially pleased to be handed a supply of cigarettes.

I had not smoked since soon after leaving Erdi. At Ouenat I had suddenly realized that there were only a few cigarettes left. I then laid down a strict rule for myself: one cigarette a day after dinner. It was hard work waiting all day for that brief smoke, but it was worth it when the moment came. I would get into a sheltered corner, light the precious cigarette, and shield it carefully from any breath of wind that might make it burn ever so slightly faster. When the few cigarettes were gone, there was nothing left but memories and expectation. Now at last the expectation was gratified with a vengeance, for I smoked until my throat was sore.

Bukara, with a handful of the newly arrivedcigarettes, put on his long-tasseled redtarboosh, got on the guide’s horse, and did a littlefantasiaof joy. But it was when we camped at the government rest-house at Marahig that general rejoicing broke loose with singing and dancing. The corporal, looking on while the men set the sugar-loaf on the ground and executed a wild dance about it, thought us all a little mad.

“Why all this rejoicing?” he demanded.

“Because for a month we have had no sugar, and now our tea is sweetened again,” said Abdullahi.

Until one has tried going without any sugar whatever, one does not realize how keenly it will be missed.

The corporal shook his head and smiled. “I must return at once to Kuttum and bring you more provisions,” he said. “We never realized that you were so short of food.” Before he left he was kind enough to go to a camp near-by and bring us a sheep and butter, which were to be paid for by themoawinof Kuttum, since the seller refused to accept Egyptian paper money. The corporal then left with letters from me for Mr. Dupuis and themoawin, the deputy Governor of Kuttum.

The provisions which he had brought us were good as far as they went, but we should very soon be in need of more. I decided to push on at once. We made our midday halt at the government rest-houseat Marahig Well and our stop for the night only a few kilometers farther on. The camels were in very bad condition. The backs and sides of some of them were sore and bleeding, and two camels refused to move until their loads were taken off. It rained for an hour that evening, but it could not dampen our spirits. The men sang and danced around a big fire. The humidity and the smell of the wet grass reminded me of my walks in English country.

We made an early start the next morning in order to reach Mutarrig Well for the midday halt. We lunched at the rest-house near the well and received a visit from thesheikhof Mutarrig, who brought a few chickens asdiafa. He wanted us to stop the night so that he could entertain us properly the next day, but I felt the necessity of going on as fast as possible.

The camels were getting steadily worse. We had to leave one of them with thesheikhof the village on the understanding that if it recovered he was to get a quarter of the price it brought when sold, while if it died he was not to be held responsible.

An hour and a half after starting the next day another soldier on horseback appeared. He brought a letter from themoawinof Kuttum and a small quantity of rice and sugar. They are gratefully received, for once more we were on short rationsand without sugar for our tea. I gave him a letter to take back to Kuttum. A little later we camped in the small valley of Boa. In the afternoon, soon after we had started again, it came on to rain with a strong southeast wind, and I thought it might be wise to camp until the storm was over. But through my glasses I made out ahead of us the row of straw huts of the Markas—the government house—of Kuttum, and spurred on by the sight we drove the camels faster.

Soon a group of horsemen were seen approaching us, and my Bedouins impulsively raised a cheer. When I recognized the uniform of Sudanese troops, it was the most cheering sight that I had seen for many weeks. Riad Abu Akla Effendi and Nasr El Din Shaddad Effendi, the twomoawinsof Kuttum, approached with a detachment of ten soldiers, thekadi, the head clerk, and other officials and notables of Kuttum. I shook hands warmly with them all, and under their escort the caravan moved on through the village. As we approached, the Markas women clothed in white and beating drums greeted us with singing and “lu-lias.” We settled ourselves in and about the rest-house, and the women came again to offer greetings. In a long line they sang and danced, much to the delight of my Bedouins, who asked permission to empty gunpowder in acknowledgment ofthe courtesy. I could not refuse my consent, and one by one, beginning with Bukara, the men performed the ceremony of singeing the girls’ slippers. The Sudanese women were not so accustomed to the Bedouin manner of paying homage as the girls of the northern desert, and flinched a little as the powder flashed at their feet. But they accepted it all in good part, the whole line swaying and dancing to the rhythm of the drums while one by one my men singled them out for the “slipper-singeing honor.” It was a wonderful reception, and the pleasure of it dispersed like magic the fatigue and lassitude of the journey.

More hospitality was to come. Four sheep, butter, and fresh vegetables, to say nothing of sugar, were brought to us asdiafafrom themoawinsand officials, and we spent a pleasant evening feasting.

Our arrival at Kuttum at this particular moment had seemed to the inhabitants there an especially auspicious one, for we came with the first rain of the season.

We stopped there for two days, entertained generously by themoawinsin the absence of the inspector, Mr. Arkell, who was at El Fasher.

One afternoon we attended a soccer match between two teams of soldiers. It was played with energy if not with finesse. At times a player, strivingto give the ball an especially vigorous kick, would miss it and send his Sudanese slipper shooting high into the air. Thecamaraderiebetween officers and men, playing this not exactly gentle game together, was interesting to see.

Dinner that night with Riad Effendi and Nasr El Din Effendi, themoawins, was the first meal I had eaten in a house since leaving Kufra. My hosts gave me Egyptian newspapers to read, the first I had seen in nearly six months.

We left Kuttum at six o’clock on the morning of June 17, cheered by the generous hospitality we had enjoyed and the friendly send-off our friends gave us. The two days’ journey to El Fasher was a joy-ride. We all felt the thrill and exhilaration of getting in touch with the world again.

But as I went to bed on the eighteenth I realized with a stab of regret that this was my last day in the real desert. I thought how I should miss my men and my camels, the desolateness and the beauty, the solitude and the companionship; in two words, the desert and its life. I thanked God for His guidance across this vast expanse of pathless sand and found myself adding a prayer, half wistfully, that I might come back to it again.

I had given orders for an early start the next morning. In their eagerness my men somewhat exaggeratedmy idea of “early,” but I was excited myself and did not mind getting under way at half-past two.

Three hours’ march from El Fasher we camped to make preparations for entering the place. We all shaved and put on our best clothes. Mr. Dupuis had sent a supply of white cloth to Kuttum for us, and my men were able to appear once more in decent raiment. They crowded around my remnant of a mirror to see how they looked. Rifles were cleaned, and the luggage, which was in a very shabby state, was tidied as much as possible. I wished that I might be able to do something for the camels as well, which were thin and dejected-looking. But rest and attention to their sore backs were what they needed, and we had no time or facilities for giving them that. Nevertheless they too seemed to be infected with the spirit of eagerness felt by all of us and walked forward briskly. Abdullahi and Zerwali got into their silks, and the caravan moved gaily toward its destination.

As we reached the outskirts of El Fasher, cheers of rejoicing rose throughout the caravan. A cavalcade of men in khaki was coming toward us. I put spurs to Baraka, and he responded willingly. He saw the horses before us, pricked his ears forward, and dashed toward them.

EL FASHERThe capital of Darfur Province

EL FASHER

The capital of Darfur Province

Mr. Dupuis came forward on his horse to meet me, and we shook hands warmly. The greetings were repeated by the English and Egyptian officers of his staff, and we went on to his house, a part of which he generously made over to me and the men of my caravan. The weary camels were promptly taken in hand by Bimbashi Andas, who gave them food, water, and the medical treatment for their wounds they so much needed.

The officer in charge of the wireless station kindly got me the exact Greenwich time from Paris by radio. I was pleased to discover that my chronometer had lost only twenty-three minutes and twenty-three seconds in eight months.

For ten days I was the guest of Mr. Dupuis and was lavishly entertained by the officers and officials of the garrison, both English and my own compatriots, and the notables of the town. Hospitality was showered upon me, and every kind of assistance that could possibly be needed was eagerly rendered. This was civilization again. I enjoyed once more the luxuries of life, especially vegetables and fruits. It is only when one has gone through the austere régime of the desert that one looks upon these things as luxuries and not necessities. There was in particular a brand of prunes, the pride of Major Smith, and of peculiar lusciousness. He called them “IfWinter Comes,” and I have never tasted their like anywhere.

At last the day came when I must take leave of my companions of the trek from Kufra. When Bukara and his brother and Hamid and Senussi Bu Jaber came to my room to say good-by, it was a moment full of real emotion and crowded with memories. These rugged men of the desert burst into tears, and I found my own eyes wet. We had been through thick and thin together and came out fast friends. I could never wish for better companions on a journey into desolate regions, more able, more manly, or more loyal.

We read the “Fat-ha,” the sound of the familiar sacred phrases punctuated by Bukara’s sobbing. I exchanged a final handclasp with each of them, and we parted, to meet one day, I hope, in that desert that I love as much as they.

One more camel-trek before me eastward to El Obeid. There I took train for Khartum and thence home to Cairo, where I arrived on August 1, 1923.

I had been away from home seven months and twenty-three days, having trekked twenty-two hundred miles across the desert by caravan.

I had determined finally the position of the Zieghen Wells and of Kufra on the map of Africa, in the placing of which there had been hitherto errorsof one hundred and of forty-five kilometers respectively.

I had also had the great good fortune to put the “lost” oases of Arkenu and Ouenat definitely on the map of the Libyan Desert.

To A. M. H.

I crave no statue in a public street,Nor page of history to give my name:A desert flower on my winding sheetIs all I ask to mark the way I came.There were no jewels buried in the sand,The treasure that I sought was little worth:I went—but oh, how few will understand—To tread an unworn carpet of the earth.Wide spaces called me, and the way was free;Feet falter not upon a road unknown:How languish, one who, looking back, can see—A thousand miles—no footsteps but his own?Not half a hundred voyagings for goldCould make me rich as many times I’ve beenWhen, weary-eyed, I’ve watched the dawn unfoldAnd spread soft radiances o’er a desert scene.Thoughts were my treasure; where may thoughts be sold?My world was empty, but my world was clean.G. F.Foley.El Fasher,June 30, 1923.

I crave no statue in a public street,Nor page of history to give my name:A desert flower on my winding sheetIs all I ask to mark the way I came.

I crave no statue in a public street,

Nor page of history to give my name:

A desert flower on my winding sheet

Is all I ask to mark the way I came.

There were no jewels buried in the sand,The treasure that I sought was little worth:I went—but oh, how few will understand—To tread an unworn carpet of the earth.

There were no jewels buried in the sand,

The treasure that I sought was little worth:

I went—but oh, how few will understand—

To tread an unworn carpet of the earth.

Wide spaces called me, and the way was free;Feet falter not upon a road unknown:How languish, one who, looking back, can see—A thousand miles—no footsteps but his own?

Wide spaces called me, and the way was free;

Feet falter not upon a road unknown:

How languish, one who, looking back, can see—

A thousand miles—no footsteps but his own?

Not half a hundred voyagings for goldCould make me rich as many times I’ve beenWhen, weary-eyed, I’ve watched the dawn unfoldAnd spread soft radiances o’er a desert scene.Thoughts were my treasure; where may thoughts be sold?My world was empty, but my world was clean.G. F.Foley.

Not half a hundred voyagings for gold

Could make me rich as many times I’ve been

When, weary-eyed, I’ve watched the dawn unfold

And spread soft radiances o’er a desert scene.

Thoughts were my treasure; where may thoughts be sold?

My world was empty, but my world was clean.

G. F.Foley.

El Fasher,June 30, 1923.

El Fasher,

June 30, 1923.

Note on the Cartographical Results of Hassanein Bey’s Journey

John Ball, O.B.E.,D.Sc., Director of Desert Surveys, Egypt

THE cartographical data brought back by Hassanein Bey consist of:

(1) Note-books containing the records of astronomical observations for the determination of time, latitude, and compass-variation at nineteen principal camps, with records of watch-comparisons.

(2) A journal giving a continuous record of observed compass-bearings and estimated distances from Siwa Oasis to Lameina Wells, near El Fasher, a distance of about 2430 kilometers.

The journal also contains a considerable number of observed compass-bearings to conspicuous features on either side of the route, with a few rough trigonometrical estimations of the altitudes of mountains passed, a large number of readings of an aneroid barometer and sling thermometer for the estimation of altitudes along the route, daily observations of maximum and minimum temperatures, observations on the character of the country passed through, and notes on the meteorological conditions.

These observational data have been reduced in the Desert Survey Office, Cairo, and utilized in the preparation of the map on a scale of 1:2,000,000 which accompanies Hassanein Bey’s account of his travels. The objects of the present note are, first, to give an account of the critical examination to which the records were subjected in the course of the reduction of the observations, so as to enable an estimate to be formed of the degree of precision which may be fairly assigned to the geographical positions, altitudes, and other results used in the construction of the map; and, secondly, to indicate the additions to existing geographical knowledge concerning a little-known region of northeast Africa which have accrued from the expedition.

Theodolite observations of altitudes of the sun or of stars were made at all the principal camps for determining the error on local mean time of the half-chronometer watch which was used in the latitude observations. In all, thirty-four complete time determinations were made at seventeen camps. The observations were made with a three-inch Troughton & Simms theodolite, the vertical circle of which could be read by two verniers to 1′, and which was provided with a sensitive level on the microscope arm. The theodolite was invariably set up in the magnetic meridian by its trough compass, and the method used was to note the times of passage of the sun’s limb or of the star over each of the three horizontal wires of the stadia-graticule, reading the level and circle at each pointing, face-right and face-left. In the case of stars, the magnetic bearing of the star was also noted from the horizontal circle, and a note made of the color and brightness of the star, for the identification of the stars subsequently in the office, and thus to free theobserver from the necessity of knowing the stars’ names. The barometer and thermometer were carefully read at each observation for calculating the refraction.

No difficulty was experienced in subsequently identifying the stars. In only a single case was it found necessary to reject an observation, and this because the observer had accidentally sighted different stars on the two faces of the instrument. On many days two or more observations were taken at the same place, and comparisons of the results at these places indicated that the observations are remarkably accurate for so small an instrument. In seven cases where the sun has been observed shortly before sunset and a star soon after sunset, for example, the maximum difference between the results given by the two observations is only seven seconds, while the average is under four seconds. It is thus apparent that the precision of the time observations is amply sufficient to insure that no sensible error in the latitudes can be due to errors of the adopted local times.

As the only use made of the time observations in the preparation of the map has been in the determination of latitude, it would serve no useful purpose to give a list of the watch errors. But it may interest future geographers, undertaking long desert journeys, to note some of Hassanein Bey’s experiences in the transport of watches, and the hazard of relying on constancy of rate for long periods with even the best watch.

Of the six watches carried, only a single one remained in going order throughout the journey. The timekeeper which thus successfully resisted the vicissitudes of the seven months of desert travel was fortunately the one with which Hassanein Bey took all his observations, and was carried in his pocket during the entire journey; it was a large-sized half-chronometer “explorer’s” watch of English manufacture,with a dust-proof cap to the winding mechanism. It had been awarded an “especially good” certificate at the National Physical Laboratory of England, and was consequently the most expensive of all the six watches taken on the journey. Even this watch failed to maintain a sufficiently constant rate to be of any service in the determination of longitudes, though it amply sufficed for the latitudes, even in two cases when reliance had to be placed on the constancy of its rate for one or two days owing to latitude alone being observed without corresponding observations for local time. Thus, for instance, the following were the average rates of the principal watch deduced from local time observations at places of previously known latitudes:

Rate of Principal Watch

The above table fails, however, to bring out fully the actual variations of the watch. So long as the other five watches remained in order, Hassanein Bey made frequent comparisons with his principal watch, and between March 21 and 23 there is strong evidence that the principal watch made an abnormal gain of about fifty seconds. A similar abnormal gain of twenty-nine seconds by the principal watch is evidenced in the twenty-four hours between comparisons of March 24 and 25. Both these abnormalities occurred between Jalo and El Harrash, at an early stage of the journey, while all the watches appeared to be behaving tolerably well, and it is quite possible that other abnormalitiesoccurred at later stages, when, owing to some or all of the other watches having stopped or broken down, no satisfactory control by comparison was possible.

Of the other five watches carried, one was an English half-chronometer, similar to the principal watch but of smaller size; three were high-class Swiss lever (“Peerless”) watches with very tight-fitting cases; and the fifth was a small Swiss lever-watch with luminous dial, carried on the wrist for noting the times of marching. The small half-chronometer stopped on April 3, after going for over four months; and though it was restarted, its rate changed considerably after the stoppage. The three “Peerless” watches, though they failed to continue going to the end of the journey, showed by no means a bad record. One was found stopping and unreliable on May 6, after going for over five months; the two others continued to go for over a month longer; and so far as can be judged from the comparisons made on the route, their variations of rate were about of the same order as those of the half-chronometers. The wrist-watch, from the manner in which it was carried, was of course liable to much greater variations of rate, and was occasionally reset by the principal watch; but it kept going till nearly the end of the journey.

As regards dust-resisting power, which must always be one of the principal aims in selection of watches for desert exploration, there appears to be nothing to choose between good English half-chronometers and the highest class of Swiss watches, the cases of the latter being remarkably close-fitting. The most probable cause either of stoppage or of abnormal changes of rate appears to be the sudden shocks which may arise either to a watch carried on the person when jumping on or off a camel, or to one carried in the baggage by sudden movements of the camel.The most likely explanation of the abnormal gains of the principal watch for short periods on the two occasions above noted would seem to be that, owing to a jerk in mounting or dismounting, two contiguous coils of the hair-spring may have been made to touch each other for a short time, with consequent temporary shortening of the period of vibration of the balance-wheel. It is noteworthy that the watch which remained going throughout the journey was the largest of all those taken, and its greater resisting-power may have been to some extent due to its size, permitting of greater strength in its component parts.

Observations for latitude by altitudes of the pole-star were carried out on thirty-five nights at nineteen principal camps, using the same three-inch theodolite as was employed for the time-observations. Three readings of altitude were made on each face, using each of the three horizontal stadia-wires in turn, the corresponding times being noted on a half-chronometer watch whose error on local time was accurately known from sun or star-observations carried out just before the latitude-observation. Particular care was taken with the level-adjustment, and the air-pressure and temperature at the time of the observation were recorded.

The following table gives the results of the observations:

Astronomical Latitudes

Of six of the above places (Sollum, Siwa, Jaghbub, Kuttum, El Fasher, and El Obeid) the latitudes are accurately known from the Egyptian and Sudan official surveys, and the agreement in these cases is very satisfactory, though a very close comparison is not generally possible owing to uncertainty as to Hassanein Bey’s precise observation-spot. At Jaghbub, Hassanein Bey records that his observation-spot was 200 meters S.S.W. of the dome of the mosque. Applying the corresponding difference of latitude (− 6″) to my own determination of the latitude of the dome in 1917 (29° 44′ 41″) we obtain 29° 44′ 35″, showing a difference of only 9″ from Hassanein Bey’s observed latitude.

A further test of the degree of precision of the latitude-observations can be made by comparison of the latitudes found for the same camp by observations taken on different nights. The following gives the average deviation of a single observed latitude from the mean at all the camps where two or more observations for latitude were made:

It thus appears unlikely that any observed latitude can be as much as 1′ in error, and consequently in the preparation of the map, Hassanein Bey’s observed latitudes have been accepted as fundamental data for all the places for which no previous determinations are known to exist, viz., El Harrash, Taj, Arkenu, Ouenat, Erdi, Agah, Enebah, and Bao. His latitudes for Jalo (El Erg), Bir Buttafal, and Furawia have also been adopted for the map, the first because it is possibly better than that of Rohlfs, with whose mapped position it is however in very close agreement; the second because while differing by about 2′ from Rohlfs’s value (28° 36′ 22″) it is doubtless more exact, because it checks admirably well with Hassanein Bey’s dead reckoning; and the third because, although the position of Furawia is shown on the Sudan maps, it is outside the present limits of the Sudan triangulation and is possibly liable to some slight error.[1]

For finding the pole-star easily when the sky was not very dark or was partially obscured by clouds, and also for obtaining the approximate bearings of time-stars for their subsequent identification, the theodolite was invariably set up in the magnetic meridian by its trough-compass, and the magnetic bearing of the pole-star was read on the horizontal circle after each latitude-observation and the time noted. In this way approximate compass-variation was determined at each camp, with the following results:

Variation of the Compass

The method of estimating the compass-variation with the theodolite is, of course, only rough; but the values found are probably correct at most places within half a degree, and they serve to show that there is no likelihood of any serious errors of dead-reckoning owing to local irregularities of the compass-variation. They have accordingly been utilized in reduction of the compass-bearings of the traverse to true bearings over the major portion of the route, where no previous determinations exist, and where in consequence the distribution of the isogonic lines is not known with any exactitude.

The probability of some watches breaking in the course of seven months’ travel had been foreseen, and from the outset it appeared improbable that any use could be made of the watches in the direct determination of longitude of so long and difficult a journey. We had decided accordingly to depend ultimately on dead-reckoning for longitude, making every effort to obtain an unbroken chain of compass-bearings and estimated distances between Jaghbub and some known place in the Sudan, the bearings to be taken with a good compass with all possible precision, at very frequent intervals, and the estimates of distance to be carefully made each day from the marching time of the baggage-camels, assuming a normal rate of 4 km. per hour over average desert, and making allowance for the variations in speed over ground of varying character. The journey being predominantly north to south, the estimates of distance could mostly be well controlled by the latitudes, while errors of bearing would not be cumulative, and would tend to cancel out over any considerable stretch of route. The primary reason for taking six watches was therefore not to determine longitude,for which at best they could afford only somewhat uncertain values, but to make sure of at least one watch being available throughout the journey for latitude-observations, without which no proper control of the all-important distances could be obtained.

The doubts about the possibility of safely transporting the watches proved justified, for all but one broke down before the end of the journey. But fortunately on the one hand the watch which survived sufficed amply for the determination of latitude (though its rate was insufficiently constant for it to be used uncontrolled in finding longitudes), and on the other hand the program of a continuous chain of very careful bearings and estimation of distances was scrupulously adhered to from the departure of the caravan from Jaghbub, the last known place in Egypt, to Furawia, the first known place in the Sudan—a journey of 2430 kilometers—and from this chain of bearings and estimated distances, combined with the observed latitudes, it was possible to estimate the longitudes of all places on the route with a fairly high probability of accuracy.

For the estimation of the longitude of Jalo (El Erg) a slightly different procedure was followed from that adopted for the other principal camps on the route. It will be noticed from the map that the general direction of the march from Jaghbub to Jalo was predominantly from east to west, instead of from north to south as in the rest of the journey. Consequently the observed latitudes do not afford so good a means of correcting the estimated distances in this stretch as elsewhere. But fortunately the observed latitude at Jalo does enable us to correct the previous estimation by Hassanein Bey (in 1920) of the distance of that place from Jedabia, and this combined with the then observed bearings would lead to one value for the longitudefor Jalo, while if we can assume the accuracy of the estimated distances from Jaghbub to Jalo, we may use the observed latitude of the latter place to correct the bearings and thus arrive at another value for its longitude.

From careful consideration of all the available data, the two methods appear likely to be about equal in degree of approximation. The position at present accepted for Jedabia (Lat. 30° 48′ 10″ N., Long. 20° 13′ 30″ E.) is open to a little uncertainty,[2]and the bearings taken by Hassanein Bey on his former expedition are probably a little less accurate than those of the present one. On the other hand, the estimations of the distances from Jaghbub to Jalo, as gaged by the latitude-control of the other portions of the route of the present expedition, are remarkably close to the truth, while a uniform correction to his bearings of less than half a degree would swing his dead-reckoning position for Jalo on to its observed parallel of latitude.

For the longitude of Jalo on the map I have therefore taken the mean of the two longitudes found (1) by assuming Hassanein Bey’s bearings correct from Jedabia and correcting his distances by the latitudes, and (2) by assuming his distances from Jaghbub correct and using the observed latitudes to correct his bearings. The results are:

It may be remarked in passing that the result placesJalo almost precisely where it is shown on Rohlfs’s map of 1880.

As regards the longitudes adopted for the other principal camps along the route, the procedure has been as follows. The route was divided into the following nine sections between principal camps where latitudes had been observed: Jalo, El Harrash, Taj, Arkenu, Ouenat, Erdi, Agah, Enebah, Bao, Furawia; and the compass-traverse for each section was plotted on a scale of 1:500,000 from the recorded bearings and estimated distances. A true meridian was then drawn on each section from the mean of the observed compass-variations at its two ends, and the total difference of latitude of each section was scaled off and compared with the difference of latitude given by the latitude-observations. This comparison gave, of course, the average error of estimation of distance along each section, assuming the bearings correct. The results of the comparison for the various sections are tabulated below:

Correction to Estimated Distances

The average error of distance-estimation in each sectionof the route having been thus found, the next step was to scale off the various departures from the plotted traverses, correcting for the errors of distance-estimation, and then to convert the departures into differences of longitude. When this was done, the resulting total difference of longitude between Jalo and Furawia was 2° 25′ 55″. But assuming the true longitude of Jalo to be that found above, and the true longitude of Furawia to be as shown on sheet 53 D of the 1:250,000 Sudan survey map of 1921,[3]we have:

So that the difference of longitude found by the dead-reckoning requires correction by 15′ 48″. This correction, which implies an average error in the observed compass-bearings of less than a degree, and a negligible correction to the adjusted distances, was distributed along the entire traverse in proportion to the difference of latitude between the principal camps, leading to the finally adopted longitudes shown in the following table:

Concluded Longitudes

In attempting to estimate the probable degree of accuracy of the concluded longitudes, we are faced with the difficulty that while we may be certain that theaverageerror of the compass-bearings was less than 1°, which average error has been allowed for in the adjustment, we have no proof that in some of the individual sections the errors may not have been considerably greater. But in view of the great number of the observed compass-bearings (339) which make up the directional data of the 1754 kilometers of traverse from Jalo to Furawia (an average of thirty-eight observed bearings for each of the nine sections), and bearing in mind also the remarkable accuracy of the estimations of distance as evidenced by the latitude-observations, it would seem unlikely that any of the above-adopted longitudes for the principal camps can be in error by more than three or four miles. This implies a degree of accuracy which it would have been difficult to insure by transport of even a considerable number of chronometers over a land journey lasting more than three months. It may, I think, be concluded that no better values for the longitudes can be obtained without the aid of wireless time-signals.

For the barometric estimations of altitudes above sea-level, a two-inch aneroid by Steward was used. This instrument, which was one of two specially made for the expedition,was very carefully compensated for temperature, and provided with a fairly open pressure-scale, a millimeter of pressure being represented by very nearly a millimeter of actual scale-length, so that estimations to half-millimeters of pressure could be readily made.

The aneroid was read morning and evening at each camp, and at numerous other points on the route, the air-temperatures being as a rule recorded at the same time, as given by sling-thermometer. The aneroid behaved very satisfactorily throughout the journey. There had unfortunately been no opportunity of testing the instrument before Hassanein Bey’s departure, but it was in perfect order on his return, and was then tested in the laboratory of the Physical Department at Cairo, when it was found to require the following corrections (at about 25° C.):

That the above corrections had remained sensibly constant throughout the journey is rendered extremely probable by the close agreement noted further on (p. 329) between the levels found for Jalo directly from the aneroid readings (corrected, of course, on the assumption of constancy of the table) and those found indirectly from readings of the mercurial barometer in the meteorological station at Siwa.

The first step in the calculation of the barometric levels was to collect the whole of the readings of the barometer and sling-thermometer at each of the nine principal camps, where a halt of at least several days had been made, and a considerable number of readings taken. The means of all the recorded pressures and air-temperatures were taken for each of these principal camps, and the pressure corrected for instrumental error from the table above given. The readingsbeing taken at various times of the day, the diurnal variation of pressure could safely be neglected, as it would most probably disappear on taking the mean of the readings. To allow for the annual variation, the mean pressures were next reduced to the mean of the year by applying a correction based on the mean of the normal annual variations at Siwa and El Obeid, as found from the recent volume of “Climatological Normals” issued by the Physical Department of Egypt and shown in the following table:

Corrections to Reduce Monthly Mean Pressures to Annual Means

A further correction to allow for the distribution of the sea-level isobars over the region traversed was desirable, but no sufficient data exist for estimating its amount; the distribution is, however, probably nearly linear, and such a distribution was approximately allowed for by assuming the previously accepted levels at Siwa (− 17 m.) and El Fasher (793 m.) to be correct and distributing any residual difference found by the otherwise corrected barometer readings between these two places uniformly among the different sections.

The difference of height corresponding to each difference of mean corrected barometer-readings was calculated by the tables ofBarometrische Höhenstufenin Jordan’s “Mathematische und Geodätische Hülfstafeln,” for the air-temperature corresponding to the mean of the thermometer-readings at the two ends of the line.

The adopted levels of thirteen principal camps as found in the above manner are tabulated below. It is interesting to note that the residual difference of height which had to be distributed between Siwa and El Fasher, and which is presumably mainly due to systematic pressure-gradient, was sixty-three meters, corresponding to a normal fall of sea-level pressure between the two places of about 5 mm., and this is from other considerations probably very near the truth; also that the resulting adjustment which had to be made in the levels in any single main section of the route did not exceed five meters.

Concluded Altitudes above Sea

After thus determining the levels for the principal camps, those of intermediate camps and other places were computed in a similar manner, adjusting each section to the adopted levels at its terminal points. The maximum adjustment which it was found necessary to apply to thedifference of height given by the barometer between points a day’s journey apart was five meters, and the average three meters.

An exception was made in the stretch between Jaghbub and Jalo, where no intermediate levels were adopted for the map, owing to the extremely unstable state of the atmosphere during the journey between these two places; sand-storms of great violence occurred on several days of marching, with such rapid fluctuations of air-pressure that no heights could safely be deduced from the barometer-readings.

As regards the degree of reliability of the deduced levels, some little uncertainty exists in the levels adopted for the terminal points Siwa and El Fasher, while the temperature-compensation of the aneroid has not been tested and may not be quite perfect. Taking everything into account, it may be estimated that the levels of the principal camps are probably correct to within about twenty meters, while those of the intermediate camps and other points, for which only one or two readings of the barometer are available, may possibly be in error by twice that amount.

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