The sea sands then have long ceased to accumulate, and the fact may be explained by assuming that the destruction of the coasts of Morocco, Algeria, Candia, and other parts,—which destruction, we repeat, alone furnishes the materials of maritime alluvium, —has abated from some cause or other. It may also be assumed, that the sands which were formerly driven by winds and currents into the Gulf of Pelusium, are now cast on the African coast between Tripoli and Alexandria, and driven inland in the shape of downs. The fact is, that no new downs are now seen forming in the Isthmus; those on the seashore being of ancient formation, and nearly all naturally fixed by vegetation. In conclusion, the extension of the Pelusiac shore, if such extension there be, is too insignificant to be taken into consideration. Now, the direction of the jetties being nearly perpendicular to the shore, in order to be at right angles with the prevailing wind from W. N. W., the sand, when the wind is perpendicular to the shore, will be driven on to the coast and increase its height, as hitherto, no change being occasioned by the jetties. During the parallel winds, which mostly prevail, the littoral current, finding an obstacle in the jetties, will form an eddy to windward, which will increase the force of the current between the points of the jetties and the mole, so that the sand will be carried far away; and the probability is, that the bottom will become deeper. It is only the oblique winds then, that will carry the sand into the angles formed by the shore and the windward jetty. In calm weather, the sea-current which flows along the coast from west to east has not sufficient force to affect the equilibrium of the beach. Thus, to sum the matter up, the most that can be feared is the accumulation of a small quantity of the loose sand in the Gulf at the angle of the windward jetty. Supposing that even 10,000 _cubic metres per ann._ should be so deposited, which, according to what we have said, is an exaggeration, it would take 100 years to advance the beach 400 _metres_, and such an advance would produce no perceptible effect at the extremities of the jetties. It may be objected, that by all these movements of the sands, some portion will necessarily find its way into the channel, and thus, by degrees, end in obstructing it. To obviate this inconvenience we have at our disposal dredging machines, and the most powerful means of clearance derived from a mass of 700,000,000 _cubic metres_ of water, which can be stored up, above the level of low water in the two Seas, throughout the whole extent of the Canal, and in the immense reservoir of the Bitter Lakes. But are jetties extending 6000 _metres_ into the sea possible? and if possible, would they not require so much time and such an expenditure of money as, practically, to cause the undertaking to be given up?