7. Summary of Principal Geographical Positions and Levels

Latitude N.Longitude E.Meters above seaRemarks
°′″°′″
Jaghbub (mosque)29444124311132Position from previous determination byDr. Ball.
Jalo (El Erg)292332128361
Bir Buttafal28542621451598
El Harrash Well (Zieghen)252629221055310
Taj (Kufra)241347232341475
Boema (Kufra. Rohlfs’s camp)24138232440400Short compass traverse from Taj
Arkenu221232244415598
Ouenat215229245416616
Erdi (camp 8 km. north of well)183539231029906
Agah175238231555744
Enebah1721242314281100
Bao16282423147969
Furawia152151233810857Longitude from Sudan map

8. Construction of the Route Map on Scale 1:2,000,000

In the process of utilizing the dead-reckoning for the determination of the longitudes of the principal camps, the whole route had been provisionally plotted on to a scale of 1:500,000 direct from the field-books, on a series of sheets each comprising one section of the route. To these plottings of the actual route were now added the computed levels of all camps, the geographical features fixed by cross-bearings on either side of the route, and notes on the nature of the ground. The various sections thus provisionally mapped on 1: 500,000 were then reduced to the scale of 1:2,000,000, allowance being made for the small departures of the original plottings from the 1:500,000 scale as found by the latitude-observations, and the various sections so reduced were drawn in on the final map between the finally adopted positions of the principal camps. It was found practicable to show all the principal geographical features on the final scale, though many notes on the nature of the ground had perforce to be omitted in order not to overcrowd the map. These notes are however carefully preserved on the 1:500,000 manuscript sectional maps in the Desert Survey Office in Cairo, so as to be available for future reference, while the principal of them are incorporated in Hassanein Bey’s narrative of the expedition.

The main portion of the route, namely that from Jaghbub to Furawia, has been mapped entirely from Hassanein Bey’s journals and note-books. The portions of his route from Sollum to Jaghbub in the north, and from Furawia to El Obeid in the south, have been copied from the latest official survey maps of Egypt and the Sudan, as being more accurate than any route survey could be.

The fixing of the positions of El Harrash and Taj by Hassanein Bey’s observations has enabled the course of his former expedition to Kufra (with Mrs. Forbes) in 1920-21 to be delineated more accurately than was possible from the original records of that journey, which were unaccompanied by any astronomical observations; and the course of the former route, adjusted to newly determined positions, has been indicated on the new map by a dotted line.

9. Additions to Geographical Knowledge Resulting from the Expedition

Jalo.—The first portion of Hassanein Bey’s route from Jaghbub to Jalo appears to be identical with that trodden by Rohlfs in 1869. At Gara Matan Sidi, about half-way between Jaghbub and Jalo, the track forks and Hassanein Bey went by the northern (Zawaiya) branch, which passes Hiseila Wells and enters Jalo from a more northerly direction than the southern (Majabra) branch taken by Rohlfs.

Hassanein Bey’s position for Jalo is almost identical with that of Rohlfs, but peculiar interest attaches to the former’s determination of its level at sixty-one meters above sea. Rohlfs, visiting the place in 1869 and 1879, had found the aneroid to indicate a level below the sea in 1869, and above it in 1879, and had ultimately concluded that both Aujila and Jalo lay about at sea-level.[4] Hassanein Bey’s determination is based on ten days’ aneroid readings and comparison with Siwa, and it is noteworthy that exactly the same altitude (sixty-one meters) for Jalo results whether the comparison is made with the readings of the standard barometer in the meteorological station at Siwa during the same period, or with the readings taken by Hassanein Bey with the same aneroid on four days at Siwa two months earlier (allowance being made, of course, for the annual variation of pressure over the intervening period). There can, I think, be hardly any doubt of the greater accuracy of Hassanein Bey’s determination, since it is unlikely that Rohlfs’s readings extended over so long a period, and it is practically certain that no comparisons were made by him with simultaneous observations at a place of known level. It should however be mentioned that Hassanein Bey’s level probably refers to a somewhat higher observation point than that of Rohlfs; for owing to sand-drifts enveloping the houses, the inhabitants of El Erg are gradually rebuilding their dwellings on higher ground, and his observations were taken in one of the most recently constructed of these. Another point worthy of remark is that although Hassanein Bey’s determination is to a certain extent checked by the exact agreement of the two methods of comparison above referred to, the day-to-day variations of pressure observed at Jalo are much in excess of those at Siwa during the same ten-day period. The extreme range shown by the aneroid at Jalo was 10 mm. against 5 mm. of the standard barometer at Siwa, and the 7 mm. average difference of pressure between the two places for the ten days of comparison, which has been used to calculate the new value of the level, is the mean of difference ranging from 1 to 12 mm. on different days. The relatively great variability of atmospheric pressure at Jalo, which readily explains the discordant results noted by Rohlfs on different dates, may be closely connected with the sand-storms which are so frequent in the neighborhood.

Bir Buttafal.—Bir Buttafal (“Battifal” of Rohlfs) is of importance as being the last watering-place for caravans proceeding on the weary desert march of nearly 400 km. to Zieghen. The position found for Bir Buttafal by Hassanein Bey agrees fairly well with that given by Rohlfs:[5]