To the trough of the Bitter Lakes succeed in a northerly direction the lakes of el Themsah, the Birket el Karash, and, lastly, the Birket el Ballak; the two last basins are visited by the inundations of the Nile; which would also be the case with those first mentioned, were the floods not intercepted by some artificial mounds thrown across the Long Yalley.
The Birket el Ballah communicates with the S. E. branch of Lake Menzaleh; and by inspecting the Map it will be seen that the basins or hollows above enumerated form an almost continuous chain of valley land extending from the Mediterranean Sea to the Gulph of Suez, suggesting the probability that at a former period the whole was submerged and constituted a strait, separating Africa from Asia, and that through the same medium a water communication might now easily be effected between the two seas.
The lake of Themsah occurs nearly in the centre of the chain of hollows above mentioned, and forms the western elbow of the series; at this place commences the Wadi of Subabyar, which proceeds westerly and joins the Wadi of Tomilat, which, trending in the same direction, terminates at Abaceh in the Delta of the Nile.
If the straight line indicating the shortest distance between the two seas be considered as a chord, then the line of the above-named chain of hollows will form an arc to that chord, the versed sine of which will amount to about twenty English miles. Within the space contained by this chord and the arc, the most suitable ground occurs for forming a navigable channel between the two seas; and to this space the choice of a line of communication seems to be restricted. The discussions may therefore be limited to three projects:—
1. The most direct line avoiding all the lakes and hollows.—This line passes near Bir Makdal, and is marked