But to this it was answered, That, were this the cause, all rivers running in a northern direction, to the sea, would be subject to the same accident; and this it was known they were not. And we may further add, that were this really the cause, the inundation of the Nile would be very irregular; for the winds at this season often blow from the south-west for two or three days together, and then the inundation would be interrupted. To this it must be added, that a very considerable part of Egypt, and that the most fertile, the Delta, is under the dominion of variable winds, which last long, from one point, at no time.
I shall trespass upon my reader’s patience, on this head, by no more than one additional observation. If the Etesian winds, by opposing the stream, occasioned the inundation, they could effect this no longer than they continued to blow. Now, it was an observation we made when on the Nile, and it was almost without exception, that as often as the Etesian winds blew throughout the day, the night was either calm, or the wind blew gently from the south or east, so that it is morally impossible the river could have overflowed at all, without a much more powerful and constant agent than the Etesian winds:—
——Zephyros quoque vana vetustas
His adscripsit aquis,——
Lucan.
Vain, indeed! A philosopher of the present age would be thought mad who should rely on a system so contrary to experiment and observation; though Thales, the propagator of this now mentioned, was so highly esteemed for his knowledge.
The next opinion quoted is that of Anaxagoras, who attributes the inundation of the Nile to snow melting in Ethiopia; and this Diodorus contradicts, for a very substantial reason, that there is no snow in Ethiopia to melt. But supposing all the mountainous part of Ethiopia north of the Line, that is all Abyssinia, were covered with snow, then the inundation must happen in other months, as it must begin in January, for the sun being then within few degrees of being vertical, it must have been the very height of flood when the sun passed over that country in April; whereas its increase is not discerned till about June, when the sun has left the zenith of all Abyssinia, having then passed over Nubia, and is standing vertical to Syene, or as far to the northward as it can proceed.
It is not my meaning to maintain that there never was snow in Abyssinia, as climates have wonderfully changed. In Cæsar’s time, the greatest rivers in the Gaul almost every year were frozen over for months, so that armed nations, with their families, cattle, and incumbrances, passed regularly over them upon the ice without fear; an event that happens not now once in a century. In Prussia[138] also were found white bears, an animal now confined to the severest snowy regions of the north; and, what comes still nearer to the present subject, in the inscription found in Abyssinia by Cosmas Indoplaustes, Ptolomæus Evergetes, speaking there, in the first person, of his own conquests in Ethiopia, says, that he had passed the river Siris, and had entered the kingdom of Samen, a country intolerable on account of cold and deep snow.
This account I think almost incredible. Ptolemy parted from Egypt, his fleet coasting along the Red Sea, opposite to his army, and carrying provisions for it; we know, moreover, the time his ships sailed, the beginning of June, when the Nile was overflowed, and consequently of great utility to his army on the first part of his expedition, while he was in Egypt and part of Nubia. Now supposing him to pass the desert as quickly as possible, and come to Axum, it must have been then Summer, or near it; and as it was necessary his fleet should return by the monsoon in October, so it must have then rained continually, and the sun been perpendicular to the country when he found the deep snows in Samen, which is not very probable. The river Tacazzé, moreover, which Ptolemy crossed, was really not passable at that time, and no Abyssinian army did ever attempt it during a flood, though, without, scruple at all seasons they cross the Nile when most deep and rapid.
I remember that when I first ascended Lamalmon, the highest mountain of that ridge, running the whole length of the province of Samen, it was in the depth of winter; the thermometer stood at 32°, wind N. W. clear and cold, but attended with only hoar frost, though at that height, and at that season; the grass scarcely was discoloured, and only felt crisp below my feet, with this small degree of freezing; but this vanished into dew after a quarter of an hour’s sun, nor did I ever see any sign of congelation upon the water, however shaded and stagnant, upon the top of that, or any other hill. I have seen hail indeed lie for three hours in the forenoon upon the mountains of Amid Amid.
The opinion of Democritus was, that the overflowing of the Nile was owing to the sun’s attraction of snowy vapour from the frozen mountains of the north, which being carried by the wind southward, and thawed by warmer climates, fell down upon Ethiopia in deluges of rain: and the same is advanced by Agatharcides of Cnidus in his Periplus of the Red Sea. This opinion of Democritus, Diodorus attempts to refute, but we shall not join him in his refutation, because we are now perfectly certain, from observation, that Democritus and Agatharcides both of them had fallen upon the true causes of the inundation.
I shall now mention a treatise of a modern philosopher, wrote expressly upon this subject, I mean a discourse on the causes of the inundation of the Nile, by M. de la Chambre, printed at Paris in quarto, 1665, where, in a long dedication, he modestly assures the king, he is persuaded that his majesty will consider, as one of the glories of his reign, the discovery of the true cause of the Nile’s inundation, which he had then made, after it had baffled the inquiry of all philosophers for the space of 2000 years; and, indeed, the cause and the discovery would have been both very remarkable, had they been attended with the least degree of possibility. M. de la Chambre says, that the nitre with which the ground in Egypt is impregnated, ferments like a kind of paste, occasioning the Nile to ferment likewise, and thus increases the mass of water so much, that it spreads over the whole land of Egypt.