The position of the Gulf, is thus adjusted:
Capt. White, by two observations of eclipses of Jupiter’s first satellite, found the longitude of Suez to be 30° 28′ 30″ east of Greenwich: and a mean of 76 lunar observations differed less than a minute from the former.
The difference of longitude between Suez and Mocha, near the entrance of the Gulf, is, by the mean of five different accounts, 11° 4′, which added to 32° 28′ gives 43° 32′ for the longitude of Mocha: and which is nearly a mean between the different results, by timekeepers. But until a greater number of celestial observations are taken at the mouth of the Gulf, its position cannot be deemed exact.
Cape Guardafui, is placed by timekeeper observations, in 51° 12′ longitude: 11° 43′ of latitude.
The adjustment of the lower part of the course of the Nile, to the shores of the Red Sea, differs very much from M. D’Anville’s map. He supposed that the Nile, in its course from the lower Cataract (near Syene) to Cairo, gradually approached towards the Arabian Gulf: but late observations shew that it runs nearly parallel to it, throughout that extent, which is about 7 degrees of latitude. Hence the distance across, between the port of Kosire and Ghinna, on the Nile, is much less than M. D’Anville supposed; he having allowed about 110 G. miles, although 90 is about the truth.[92]
It may be proper to state, that the line between Kosire and Ghinna is by no means the shortest, that can be drawn between the Nile and the Red Sea, because it runs obliquely between them. The distance appears to be no greater than 72 miles on an ENE course, from Ghinna to the nearest part of the coast.
Cairo, by the mean of several accounts, is about 59 G. miles to the west of Suez, equal to 1° 8′ of longitude.[93] So that Cairo should stand in 31° 20′. The Con. de Temps has 31° 29′; but it is probable that Suez is the best determined of the two places.
Mr. Bruce had observations of longitude at Kosire and Syene (or Assuan). The first he gives at 34° 4′: and Capt. White at 34° 3′. But as Capt. White gives its latitude at 26° 18′, whilst Mr. Bruce found it only 26° 8′, we may suppose that the former did not approach the coast near enough to discriminate particulars. Mr. Bruce’s parallel intersects the coast in Capt. White’s chart, in lon. 34° 8′: and I have adopted that for the place of Kosire. Capt. White may perhaps have mistaken the old for new Kosire.
Syene is given at 33° 30′ by Mr. Bruce, making 2° 10′ east from Cairo; whereas M. D’Anville has no more than 41 minutes of easting. Hence arises a difference of 12 degrees in the bearing: M. D’Anville’s being about N 9 W; Bruce’s N 21 W: or nearly parallel to the shore of the Red Sea.
The longitude of Sennar is 33° 30′ 30″ according to Mr. Bruce. In this particular is found the widest difference between D’Anville and Bruce; the former placing it no less than 3° 50′ more to the west; that is, D’Anville has it, 1° 41′ west of Cairo, Bruce 2° 9′ east of it.