[7]Zeitschrift der Gesellschaft für Erdkunde zu Berlin, Band 20, Heft II, 1885. Also Dr. Schweinfurth’s summary of Ascherson’s results in “Petermann’s Mittheilungen,” 22. Band, 1876, p. 264.
[8]On the Stratigraphy and Physiography of the Libyan Desert of Egypt. Q. J. G. S. Nov, 1894, pp. 531-547.
[9]Vorlaüfiger Bericht über seine im Winter 1899-1900 nach der Oase Siwa und nach Nubien unternommenen Reisen.—Königl. Sächs. Gesellschaft der Wissenschaften zu Leipzig, 1900, p. 226. Steindorff entered the Oasis from Siwa, and returned from it via the Fayum. He appears only to have visited the northern part of Baharia.
CHAPTER II.
Surveying Methods and General Results.
Crossing the Libyan Desert from Maghagha and Minia respectively, the two parties of the Geological Survey met at a joint camp close to Zubbo, one of the chief villages of the oasis. It was desirable to fix this meeting-point as a primary station for the subsequent plotting of the maps. Cailliaud[10] gave the latitude of Zubbo as 28° 21′ 47″, and its longitude as 26° 43′ 46″ E. of Paris, (equivalent to 29° 3′ 55″ E. of Greenwich). Jordan gave for Bawitti the position N. lat. 28° 21′ 12″, long. E. of Greenwich 28° 56′ 45″. Taking the difference of latitude and longitude between Bawitti and Zubbo as found by the Survey, viz., lat. + 55″, long. + 4′ 16″, we have as the equivalent of Jordan’s latitude for Zubbo 28° 22′ 7″, and for his longitude 29° 1′ 1″ E. of Greenwich. Thus, while there is a fair agreement between the two authors as regards latitude, there is a difference of 2′ 54″ in the values of the longitude.
The longitude is of course always the difficult matter in the geographical determination of places not easy of access. Cailliaud’s value rests on the method of distance and azimuths, both roughly determined only; Jordan, on the other hand, used the absolute though not very precise method of lunar distances measured with a sextant. The Survey parties depended entirely on direct measurement by means of measuring-wheels from known points in the Nile Valley; the values obtained in this way are tabulated below[11].
I.—Traverse from Maghagha to Zubbo.