ART. V. THE COAST OF EGYPT AND THE SUEZ CANAL.

IT is with the consent of Professor Peirce, the Superintendent of the Coast Survey, that I offer, in advance of an of ficial report, selections from notes compiled in a recent professional visit to Egypt. I have been moved to do this by the thought that at this time, when public interest is somewhat drawn to the subject of the Suez Canal by the approach of the date of its formal opening, the leading features of this great work, set forth, however crudely, by one who has made a regular inspection of it, under authority from M. Lesseps, may be of interest to the general reader. The construction of this canal has added some new features to our knowledge of the geography of Egypt, and opens anew the problems presented in the physical history of the delta of the Nile.

Lower Egypt, "the gift of the Nile," has been regarded by most authorities, ancient and modern, as a territory reclaimed from a gulf or arm of the Mediterranean Sea, and not as a deposit superimposed upon the sands of the desert.*

The manner in which the sediments of rivers reclaim territory from the sea differs according to the degree of exposure at the embouchures. If the river empties into a great basin, the mud elevates the bottom of the latter pretty uniformly over a large area; but if it empties into the ocean, the waves break up the outflow, and cause an abrupt deposit, so that only the lightest material — that which is mechanically mixed with the river water, rendering it turbid actually escapes into the sea. In the first case the displacement is caused by a nearly vertical accumulation, and in the second by a horizontal encroachment. The Alabama discharges itself at the head of a sheltered bay, and we find for many miles beyond the uncer

* Herodotus, Book II., repeats this theory, which he learned of the priests of Egypt; and recent authors, like Dolomien and L. Elie de Beaumont, accept it fully. Sir Gardner Wilkinson takes the opposite view.

† For the character of deep-sea deposits, see "Law of Deposit of the FloodTide," by Lieutenant Charles H. Davis. Smithsonian Contributions, 1851.

tain shore-line of its delta a submerged bank of mud.* The Ganges and the Mississippi, on the other hand, push out long moles of earth against the waves of the sea. The history of the harbor of Greytown illustrates both of these conditions. Formerly it was an exposed bend in the coast, at the head of which the San Juan River made a bold delta. By the gradual advance of Point Arenas this bend took the form of a bight, and finally became a lagoon. It was not, however, until the shelter from the waves was made complete, that a general elevation of the bottom of the basin commenced.‡

Exposed deltas are usually bordered by sands— the residuum from the long-continued sifting action of the waves. These sands, in tideless seas, usually form an apron which is scarcely interrupted by navigable channels. The delta of the Danube offers an example of this class. In seas subject to considerable tides, the bordering sands are broken into slender banks, between which navigable channels occur. The Ganges and Burrampooter construct, at the head of the Bay of Bengal, the most remarkable delta of the latter class. The Mississippi delta, visited by a small diurnal tide, holds a somewhat intermediate position between these two classes, and advances its mud so rapidly upon the sea that the sand is not thoroughly disintegrated from other deposits. The Nile delta belongs to the tideless class. In view of its very slow progress, and of the exposure of its coast to prevailing winds from the north, the sands along its border, and the sand-bars at the mouths of the river, seem to offer no anomalies.

The accomplished L. Elie de Beaumont evidently entertains the notion that the sandy border of Egypt is a formation antecedent to the river delta; that it was a "cordon littoral," separating a gulf or lagoon from the Mediterranean, within the shelter of which the Nile has made a homogeneous deposit of mud. He says, indeed, that he believes the present outlets of the Nile

*The rivers of China distribute their mud over the bed of the shallow and sheltered Yellow Sea without forming visible deltas.

† I am informed by Major-General Humphreys, that the Mississippi bars advance after the manner of submerged dunes; by the rolling of grains of sand up a long rear slope and down a steep fore slope.

For the first complete history of the formation of a lagoon, see "Report of the Committee of the National Academy on Greytown Harbor, Nicaragua." 1866.

are the first that have ever discharged their waters directly upon the sea. He cites the testimony of classical history to strengthen this statement, as showing that none of the seven ancient branches of the Nile sensibly emptied directly upon the sea; but that their waters reached the Mediterranean only after traversing the lagoons. When we consider that these lagoons, so vast in superficial area, are but thin sheets of water, whose beds lie but little below the level of the sea, the testimony loses its significance. No one, looking from a physical point of view at a chart of the Bay of Bengal, could say that the shore-line of the Sunderbunds is the boundary of the delta of the Ganges. On the contrary, he would point to the bold extremities of the great submerged moles of sand and say, "Here the river suddenly enters the sea,"more than twenty miles below its "sensible" mouths.

The littoral sandy cordon is a physical feature which Beaumont discusses at length in his descriptions of various countries, and he everywhere regards it as due to external causes, to the waves and currents which abrade the projections of the coast, and drive the sands across the indentures of the shore. Many hooks, bights, and even lagoons have fallen under my own observation, which I know to have been formed in this manner. The instance of Sandy Hook is one in point. It is rapidly extending, under the action of the waves, which deposit at its extremity material torn from the New Jersey coast in the neighborhood of Long Branch. The case of Greytown, which I have already referred to, is similar and more perfect. But the sandy shore of Egypt does not appear to me to belong to this class of phenomena. I see no reason to believe that it existed before the outflows of the Nile, or that it has been formed under the action of external forces. Its form, curving outward from the general trend of the coast, indicates, not the action of the waves in front, but of a force in the rear. Upon our own coast we find the slender "littoral cordons" which separate lagoons from the ocean gradually moving in towards the continent; and, in the instances I have cited, of Sandy Hook and Greytown, the drifts of sand have been bent inward as they advanced. It is difficult to conceive of any external forces which could have formed a convex coast like that of the Nile

delta. In digging the canal through the beach at Port Saïd the pure sand was found to be but a superficial border. At about seventeen feet below the mean level of the sea (which is about the limit of wave action) a material is found apparently corresponding with that excavated, further on, from Lake Menzaleh.

I fall back, then, upon the primitive idea, which every one entertains on first looking upon a map of Egypt; viz., that a bank of mud has projected itself upon the sea. I have been confirmed in this view by an inquiry into which I have been led by my surprise at finding in all the authorities upon Egypt a statement that Cape Bourlos, midway between the present outlets of the Nile, is the most advanced point of the delta, — which it certainly is not. Its geographical position more seaward and in higher latitude than the adjacent coasthas led to this error; but if we look at this shore as a creation of the Nile we are undeceived. We discover that the coast forms very nearly the arc of a circle of which the delta is a sector; that Cape Bourlos is not as distant from the centre as the present mouths of the river; and that the waters of the Nile are performing longer journeys to reach the sea by the Rosetta and Damietta outlets than by any other routes we could project within the sector.*

Is it unreasonable to suppose that the Nile has changed its outlets whenever these have become so prolonged as to present great resistance to its floods, and that before the occupation of the country by dike-builders the river was in some degree free to seek the shortest route to the sea, especially in periods of inundation? The conclusion is forced upon my mind that, in ages past, the coast-line, while slowly advancing upon the sea, must, in its general sweep, have oscillated about the arc of a circle, of which the centre was somewhere in the main artery of the great floods.

My search for this central point led to a curious result. I took a string and pencil, and described upon Linant's chart successive circles, continually altering the position of my centre and the length of my radius, till I was satisfied that I had

*One of the Greek authorities cited by Rawlinson describes Egypt as shaped like a battle-axe. The Arabs call it Er Rif, the pear.

plotted the arc which best conformed to the general sweep of the coast from the Tower of the Arabs to Peluse. Watching my arc, I had not perceived in what direction I had been shifting my centre, but now, lifting my finger to mark the point, I discovered beneath it the Pyramids of Gizeh! Subsequently I plotted the Great Pyramid upon the recent coast-chart of the Suez Canal Company, and found my previous result confirmed.* Situated upon the last rock that confines the floods of the Nile, this structure occupies a more important physical position than any other artificial object upon the face of the earth, since it is the centre from which radiated the waters of the river, and from which, from age to age, the coast may be supposed to have advanced in concentric arcs. With no predisposition to believe in the scientific purposes of the pyramid-builders, I nevertheless cannot help thinking that, if there ever existed a comprehensive and economical system of irrigation in Lower Egypt, this initial point must have been to the engineer one of primary importance.†

To return to the subject under discussion, I must remark finally that the hypothesis of a pre-existing sheltered bay or grand lagoon is not necessary to explain the absence of sands upon the delta, since these sands do exist in great masses to bear witness of the past. About eighteen miles north of Cairo, surrounded by fertile lands, there is a pair of "sand islands,”

The latitude of the Great Pyramid (the more important element for this) was not long ago carefully re-determined by Professor Smyth, Royal Astronomer of Scotland. The longitude I took from Linant. I required my circles, as I drew them, to touch the outer rocks (contemporaneous formations) at Alexandria and Abou-Kir; to clear Cape Bourlos (which has, according to Beaumont, slightly retrograded under the action of the sea), and to fall in with the shore at Peluse, where the beach under the action of waves from the westward has advanced fifteen hundred feet since the days of Strabo, i. e. since the closing of the ancient Pelusic and Tanitic branches. Although my arc is over one hundred degrees, I do not pretend to distinguish between the Great Pyramid and its immediate neighbors of the same group.

↑ Since writing the above, I have discovered the following passage in Girard (of the French expedition): "The coast of Egypt, from Alexandria to Peluse, presents a great curve, turning its convexity to the north, upon which the point of Abou-Kir and the two outlets of the Nile are salients. Precisely in the middle of the distance which separates them (the outlets) we find Cape Bourlos, the most northern point of Egypt, situated upon the same meridian as the pyramids." Except the allusion to Abou-Kir, this is correct.