W.M. Flinders Petrie
The weather in ancient Egypt
In considering the arrangements of the early monuments, the questions of the invariability of the climate, and the state of the ground when they were built, become of interest. Was the sand as encroaching then as now? And did the builders anticipate the half-buried state of many monuments?
In considering these questions we must first glance at the general course of Egyptian climate. The country has undoubtedly been gradually drying up. The prodigious water-worn ravines in the cliffs of the Nile valley show this and there are remarkable evidences of the Nile having been habitually some 50 feet above its present level, thus filling up the whole valley at all times of the year. At many points of the Nile valley, particularly at Tehneh, the cliffs are all water-worn in holes, exactly in the manner of solution under water; while above this action, over about 50 feet level, the cliffs are worn by aerial denudation in a wholly different manner: also the lower part projects forward as a foot, in front of the upper part, the action by water being apparently much slower than that in air, and tending to prevent aerial denudation afterwards.
Besides this, at the foot of the cliffs, particularly at Beni Hassan, wherever the scour of the current was less, or ravines debouched into the main valley, large banks of debris. have been formed, showing the former power and height of the stream. That it was fed by local rains throughout its course is seen by the deep gorges in the cliffs, often a mile long, and ending in dried-up waterfalls. In the history of the Faium the same drying up is seen ; that district appears to have been originally a large lake, which has been gradually reduced, partly artificially, until it is now not a tenth of its former size.
It therefore appears certain that the general change has been one of desiccation; and the inquiry to be made is, if there be any evidence to show whether this change has been continuing in historic times.
Rain was certainly known in Lower Egypt in the Pyramid times, though there is but one evidence of it in the monuments ; the water-spout carved in stone, leading from the roof of one of the tombs of the fifth dynasty at Gizeh, is a proof that such a feature was known, and perhaps in common use on the mud-brick houses. Nevertheless, the rain can hardly have been much commoner then than now, or more signs of its action on the tombs would remain. In Greek times the rain appears to have been just as rare as it is now, or even rarer, in Upper Egypt. Herodotus says that the last that fell at Thebes was two centuries before his time, under Psamtik, and then only in drops. Now, last year, Mr Tristram Ellis, while at Negadeh, just below Thebes, expected rain one day, but he was told that none had been seen there for 45 years. So there does not appear to have been appreciable climatic change in the Thebaid during the last two thousand years. The pits in the Tombs of the Kings, sometimes supposed to have been intended to arrest any storm-flooding, may as likely have been to arrest or hinder intruders; or may be sepulchral pits abandoned, owing to the changes and amplifications of the plans. Again, it may be observed that neither rain, nor any sign of rain, is shown in the paintings of the tombs; no wide hats, no umbrellas, no dripping cattle, are ever represented. Mud-brick tombs, covered with stucco, still remain from the third or fourth dynasty, when they were built without any apparent fear of their dissolution.
On the whole, the rain-fall does not appear to have perceptibly changed during historic times.
The Nile, though so much higher in pre-historic or geologic times, as just mentioned, does not seem to have sunk at all, in Middle or Lower Egypt, in historic times ; though above the cataracts it has fallen some twenty or thirty feet. Below the cataracts, on the contrary, it has actually risen, owing to silting up; for many of the deepest tomb-shafts at Gizeh have now several feet of water in them at high Nile, and can onty be entered just before the inundation. Also the thickness of mud over the remains both at Memphis and Karnak shows not only the great amount of deposit, but also how much the river must have risen for it to lay down mud so many feet above the old level of deposit.
The rise due to silting up proceeds, then, much faster than any slight diminution of the river which may take place.
The amount of the sand, then, cannot be affected by any variation in moisture ; and on looking back it seems very doubtful if there has been any change in it. The sand over the Serapeum might be supposed to have increased, as it has buried the Sphinxes there. But these are of Greek work, and were only erected shortly before the time of Strabo ; and he, nevertheless mentions them as being nearly buried in his day, though doubtless some attempt was made then to keep them cleared. Before this, in the dream of Tahutmes IV., the Sphinx at Gizeh appears to have been buried very rnuch as at present. And on looking to the remains of the early dynasties at Gizeh and elsewhere, their buried state seems rather to be due to artificial changes accumulating the sand than to any great increase in the general amount of sand.
The usual way in which the sand is moved is by a few high winds in the course of the year. These tear over the ground, as opaque as a London fog, bearing just as much sand as their whirling will support; and as soon as any obstacle checks their velocity the surplus of sand is dropped, and thus accumulates. Now the tombs are either rock-hewn, in which case a face of rock is artificially scarped for the fronts, or else they are built on the surface. In either case an eddy is formed in the wind, and this will cause quantities of sand to be thrown down during a sand storm. Again, the erection of the Pyramids would be sufficient to interrupt the steady blow of the wind by causing numerous oblique currents, and would so produce an increase of wind-borne sand in the neighbourhood. Whatever cause checks the velocity of the wind is sure to lead the sand to accumulate ; the Arabs know this well, and plant frail rows of reeds (even spaced apart) around their gardens bordering the desert these make the wind drop the sand, so as to form a bank outside them, and thus keep the enclosures clear.
The general conclusion as to the climate, then, seems to be that there has been no appreciable change in rain-fall, river-flow, or sand-blow during historic times.
W.M. Flinders Petrie, The pyramids and temples of Gizeh