The Isthmus of Suez Question

by Ferdinand de Lesseps

As to the Meuse and the Rhine, the following deductions have been made.

The abrasion of the coasts of the channel supplies the sea with fragments of chalk and siliceous rocks, which being rolled about by the sea become shingle. This shingle forms banks along the English and French coasts, and forced by the double action of flood and wind towards the straits it approaches them; but the shingle on the coast of France continually decreasing in size, reaches the mouth of the Somme, where it finds the point of Cayeux formed by its accumulation. Stopped at this point by the waters of the Somme, and by the change in the direction of the current of the sea which turns towards the Pas de Calais, this shingle increases the point of Cayeux, so long as its continual collision has not sufficiently reduced the size of the stones for them to be carried away by the sea; but when they are small enough, the flood bears them away and distributes them on the numerous banks which are found between the Somme and the Pas de Calais. From the inspection of Marine Charts, it is seen that the fineness of the deposit increases in proportion as these banks are nearer to the straits, and if the banks disappear in the Straits, it is because the force of the current does not allow the sands, which from being sifted for a long time have become finer and finer, to stop in that passage. They pass it therefore and some go to form the downs between Dunkirk and the Scheld, others in like manner to form downs on the English coast, others remaining in the strongest currents are carried as far as the mouths of the Humber in England, and of the Meuse and Rhine on the Continent.

If the shape of the English and French coasts to the north and south of the Straits is observed attentively, it will strike every one that those to the south are cut out into concave indentations, while those to the north all affect the convex form. It is because the coasts to the south of the Straits are abraded by the tide, and those to the north, on the contrary, are fed by the accretions. As for the muddy matters in this long course, they can only be deposited in a few perfectly tranquil creeks, or in the basins of open ports on either coast. Wherever the tide penetrates they are carried with it, and, when finally it has entered the northern sea, and made a course sufficiently long to abate its swiftness, it finds itself in an excellent condition for depositing these muddy matters, which it holds in suspension. This is what it does at the mouth of the Humber, where it completely chokes up the port of Hull.

In like manner, the muddy matters form at the mouth of the Rhine, of the Meuse, and of the Scheld, those immense polders, which constitute such an essential part of the territory of Holland, and the numerous banks at the mouth of these rivers are only composed of sand and carbonate of lime. Now the rapidity of the current, long before reaching the mouth, is not sufficiently great to carry down the sands; in fact, no trace of them is perceived; these banks are therefore the production of the sea.

Finally, in order to appreciate at the maximum the power of the fluviatile deposit in the formation of the coasts, observations have been made upon the Yssel, that branch of the Rhine which discharges itself into the Zuyderzee. This sea has but very feeble tides, 0 met., 40, at ordinary high water, and very much resembles the Mediterranean, the Black Sea, and the Adriatic Gulf in this respect. A muddy Delta has also been formed at the mouth of the Yssel, of the same shape as those of the Rhone, the Po, the Nile, &c. &c. This Delta cannot be exclusively owing to the Yssel, because, although it is true that the tides of the Zuyderzee are very feeble, on the other hand the shores which surround it are of an exceedingly friable nature; now, however feeble the tides may be, they yet attack the banks, and what proves it, is, that the Hollanders are obliged to defend them. By considering the Delta of the Yssel as a fluviatile deposit solely, we shall therefore have an extreme case. Now, this Delta has a superfice of only 1500 hectares, while the superfice of the land in Holland, which is evidently of modern deposit, is at least 1,000,000 hectares. If it is observed that the Yssel only emits a fifteenth of the whole volume of the Rhine and the Meuse united, it will give 22,500 hectares for the deposit of the river, against 1,000,000 deposited by the sea; which is scarcely two per cent. of what the sea has furnished in the formation of the polders of Holland.

From the examination of all these facts, it evidently results, as we have said, that in seas with tides, the rivers not only do not form banks, alluvium, or deltas at their mouths, but farther, that the alluvium found in the regions of these rivers submitted to the action of the tide, is deposited by the sea.

We shall now prove that these conclusions are equally true for the rivers of the Mediterranean, notwithstanding the opinion of the Italian engineers, who have considered the fluviatile origin of their deltas as demonstrated.

To give an idea of the propagation of the waves or billows of the sea agitated by the wind, they have been compared to a field of corn under the action of the air. It seems as if the ears of corn had an impulsive swiftness, which however does not exist, since they do not quit their places. Farther, if the wind is feeble, it is only the ears which waver without the stalks being shaken; but, in proportion as the wind rises, the stalks take part in the movement to a greater and greater depth down to the root.

The waves have been again compared to the movements of a cord, which is made to undulate by shaking one of its extremities in the hand. It seems as if the cord was going at a rapid rate, while in reality it does not quit the hand that shakes it, only each point of it rises and falls alternately, and this movement is the greater according as the impulse is stronger; if the extremity of the cord opposite to that which receives this impulse encounters an obstacle, as the surface of a wall for instance, it will strike it at each movement of the hand.