He relates the rise and persecution of a prophet and preacher, the catastrophe of a falling mountain and submergence of a great city, followed by a general inundation, and the claim of the prophet to have foretold these disasters; adding physical descriptions of the Euphrates river and the marvellous effects of sunset light on the Taurus range.
Raised shore-lines, occasional earthquakes, and slow measurable elevation of the land about active volcanoes, indicate that elevation is now in progress, but the geological evidence shows no sign of former submergence of a connecting isthmus.
Conclusive proofs, however, of a later submergence under a post-Glacial Littorina sea (containing shells now living in the Baltic) are found up to 150 ft.
It had been at first intended to raise the dam to a height which would have involved the submergence, for some months of every year, of the Philae temples, situated on an island just upstream of the dam.
The greater the depth of submergence the less the disturbance made by the submarine on the surface of the water, and the greater the immunity from gun-fire, ramming, etc.; also in a sea-way the deeper the submarine the more readily is it con trolled.