ancient canal was open*, and since that time one part has continued to retain a depth of 16 feet, notwithstanding the effects of drift sand and torrents falling into it.
Adjoining the Gulph of Suez, and for three miles northward, it is true the drift sand has not only filled the bed of the canal, but has risen to a height of three feet above the high-water-mark of the Red Sea; but even this circumstance shews no great flow of sand, if we consider the period of its formation, say 25 feet in one thousand years, or one foot in forty years; to counteract which, a very slight current in the channel would be sufficient. It may, indeed, be alleged that the height of sand now observed is a maximum result of natural causes, which might have obtained in one hundred years, as easily as in one thousand; but, if we grant this allegation, it is satisfactory to know the maximum effect is of such small amount.
The selection of the best line of canal for the remainder of the distance must remain in a great degree arbitrary, until detailed surveys, levellings, and borings have been made on which we can entirely rely. In the mean time it may be admitted, that, if no obstacles of a serious] character intervene, we should prefer to conduct the navigable channel by the straightest and shortest line between the two seas. See the line marked blue on the Map.
The shortest line would give the greatest velocity and scouring property to the stream; and, under equal circumstances, would cost least money. A nearly straight line would also be most controllable, and with the least expence ; for, as soon as bends and angles are introduced to the channel of a large body of running water, an action immediately and inevitably commences on the banks, which would have to be provided against by a heavy ex-
* The canal was re-opened by the Caliph Omar about the year 644, and it remained navigable for 120 years.