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dry places by what desire or necessity we know not, found seeps and flowing springs immediately under the great scarps or cliffs, which were the center of all of the wild life of the region. In addition to the flow coming up through distinct openings and crevices, the water in other places diffused upward through the loose crust, giving sufficient moisture for a characteristic vegetation, but not in such volume as to bring the liquid to the surface. This may not be accomplished by the most expert engineering in most places of this kind. The sand, loosened from the surface by heat and cold and the action of the wind, was driven as a cutting blast which carved deeply into the exposed cliffs, planing and polishing the surfaces of exposed limestone into scroll like mirrors of karafesh, leaving knobs and mounds of clay and marl here and there in the depressions and on the higher slopes.

If a section of sandstone moistened by water was encountered, this was held together by the moisture, and was not cut down, remaining as a hill. In other cases the water flowing from a spring caught and held moving sand, which was in time cemented and built up into little hills as much as a hundred feet in height, and it is on these elevations that the most interesting historical records may be

found. Man on the Libyan Desert has always built his dwellings of mud and stone on the moist hills, and some of these yield at a glance the sequence of paleolithic man, Berber, Egyptian, Roman, Persian, and modern pagan, Copt, and Moslem, in records from the rudest pottery of baked mud to the products of the finer arts of the present.

The golden sands of the Egyptian desert cover great areas on the long slopes, in the shape of ridges which run fifteen degrees west of north and east of south for a distance as great as three hundred miles in some places. Under a westerly wind the crests of the dunes take on a knife-edge sharpness. The northerly winds of winter, however, blowing the length of the dunes, break down the sharp crests and build crescents which give the summits of the ridges a toothed effect like a saw. In addition minor ridges may connect two parallel dunes, but it is possible to ride for many miles along a clean-swept lane of sogag a quarter to a half mile wide, between the dunes which rise on either hand to a height of a hundred feet or more.

The first section of the journey lay along the sandstone escarpment from the village of Nadura in Kharga to the little villages of Tenida, Smint, Mut, Rashida, and Dahkla, in the oasis of Dahkla,

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about one hundred miles to the westward. Both oases are in the same general depression not many feet above sea-level, and it was on the track between them that the first opportunity for close examination of the desert was afforded. First of all, the reader is asked to join in relegating to the scrap-heap travelers' tales of dry places utterly devoid of life. The intricate pattern of living things which characterizes the moister regions becomes simplified in the desert and many threads disappear, but the areas of land surface not used or occupied by plants or animals are limited in extent and remote, indeed, from sources of water.

Regions in southwestern America that convey the impression of extreme aridity are, in fact, rich in life, and that part of Arizona contiguous to the domain of the Desert Laboratory bears as many species of plants per square mile as the densest tropical jungle: the number of individuals representing each form is, of course, very small. The same is probably true of the eastern desert of Egypt between the Nile and the Red Sea. Conditions conspire against the traveler who looks casually for evidence of living things in the Libyan Desert. The caravan track consists of a network of trails which spread out in a band from a few yards to a mile in width. The camel plodding along these trails ravages everything but rock and sand, and the traveler will be carried along the bared strip. If he should attempt to lean upon information gathered from the Bedouins, he will find that they know but little of the country on either side of the caravan track, and remember only those plants affording camel food. The widest interval between clumps of vegetation on our journey was crossed on the first and second days, when a distance of forty miles of gravel, sand, and broken rock was traversed, in which no vestige of any kind of a plant dead or alive was found between the bunches of grass near Nadura, and the crop of dead stems of an annual plant which had grown up after some vagrant rain-storm two or three years before in a depression near some sandstone knobs. The branches crumbled in the dry air, but a profusion of shiny, lens-shaped seeds were falling to the ground; and these, capa

ble of withstanding desiccation for many years, would spring quickly into life with the first supply of moisture.

We were not allowed to think that the bare area was circular in outline, because the scarp rose a short distance to the northward, and the sand-dunes not far away promised vegetation at their bases. In the middle of this stretch a rodentlike mouse crept into the circle of the camp-light in search of food, and probably scores of its kind found sustenance near the track. Lizards were seen near the carcasses of camels, and these also must have some general distribution in the region or they could not take advantage so quickly of this and other windfalls. Gazelles ranged several days' journey from water, and might be seen fifty miles away from any available supply. Fragments of ostrich egg - shells with rounded and smooth edges were found on the sand dunes south and east of Farafra, far to the northward of the present range of the species, and in places where they have not been known to exist for a long time. Foxes and jackrabbits also ranged widely in the desert, and no day passed that opportunities were not afforded for seeing the adaptations of form and habit displayed by plants and animals which occupy these driest of all dry places. Plants have steadily developed structures more suitable for existence in arid regions ever since the first simple forms found a footing above the reach of the tides, so that one has the consciousness of seeing this particular evolutionary tendency at its very highest expression in the indurated species of the desert.

The adaptations made by man to conditions of aridity are none the less interesting, and when one attempts to visualize the way in which these deserts have been used in the past, the principal points in the current discussions as to possible changes of climate in this and other parts of the world are brought forcibly to mind. The oases visited did not in our brief examination give evidence of greater fertility in the past, although skilful engineering may have made the water supply of greater efficiency. The water from the wells comes from sea-level and lower, and probably has no direct connection with the rain

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fall of any part of the country within a thousand miles. Fluctuations of climate which would double the present precipitation would have but little temporary effect and leave no lasting signs, and it is doubtful whether tenfold the amount of rain would result in appreciably greater fertility, since the present amount is very slight. Sections of caravan tracks leading toward the westward and interior of Africa, now unused, suggest changes in trade routes or extinguished oases of which there are indeed traditions. Legends of villages buried in the sand, of unknown swamps and wadies, are rife, and the reputed loss of the army of King Cambyses in the desert sands must have had some fatality for its foundation. Whatever may have been the climatic conditions, the weapons and mementoes to be picked up show that paleolithic man plodded along the wearisome trails from one watering-place to another, and that later people who carried water and food in clay vessels followed some of the same routes, as evinced by the thickly strewn

fragments of pottery illustrative of the art of several thousands of years. Their presence midway of the long-dry tangents indicates accidents to water stores and consequent suffering. The camel skeletons and oblong mounds which dot the track at frequent intervals suggest that while some riders may have walked to safety, not all who leave one oasis may reach the cooling shade of the next one.

A man afoot in the American deserts uses from twelve to twenty pints of water daily; and a horse, one of the most unadaptive of all animals taken out into the dry places, consumes ten times as much. In such places the water-bottle and tank is the most carefully lookedafter part of the traveler's outfit, while but little attention is paid to the sun or to temperatures. Much less water appears to be needed in the Libyan Desert, while here and all through the hot countries of the East extraordinary precautions are taken to shield the head and neck from the sun and wind. One may walk for hours in the hottest part of

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America without special regard to the direct effects of the sun, and a member of the staff of the Desert Laboratory spends as much as a month in the field with no head covering. Whether real differences are to be found between the physiological effects of light in Eastern and in American deserts is not established. It is apparent, however, that the yellowish, glittering sand of the Egyptian desert and the effect of the almost continuous winds result in marked "sunburning" effects.

Sand as a feature of desert landscapes is not so prominent as ordinarily supposed. Dunes of size are to be found in but few places in America away from the sea - shore, but in northern Africa more extensive areas are occupied by huge ridges. One may travel for days without seeing either a mound or the unbroken stretches of sand which figure so largely in literature. Despite these facts, there is enough of fine particles of dust and broken rock present everywhere to become unpleasantly noticeable in a wind. One soon becomes accustomed to grit in the pockets, made aware of its presence by the roughened pages of the note-book, and may even

come to enjoy the titillation of having it sift down inside collar and belt, but when it finds a resting-place in footgear it becomes really obtrusive. The least motion of the air disturbs the finer dust on the surface of the ground, and with increasing force of the wind larger particles are lifted and moved along, pelting and abrading everything in their path. The downward action of rain and streams carves mountains and hills into ridges and gullies, which afford shelters from the direct action of storms in moister regions. The wearing action of the horizontally moving sand - blast results in rounded contours much like half an egg, behind which there is no real shelter. When looking for a campingplace at the close of the day, Abou Salem would maneuver to leeward of a small hill, seeking the spot in which the least sand was falling, for no place would be entirely free from it if there was any wind motion. When he came to a quieter place, which might be directly against the base of a cliff or out some distance from it, a few moments' pause would be made, and if the occasional eddy which reached the place did not carry too much grit, the baggage would be arranged for

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the night. One might begin dinner or unfold a camera in fancied security, when a disconcerting blast would deluge everything with a shower of sand which penetrated into the mechanism of shutters and plate - holders of cameras well as into the recesses of "waterproof" baggage. The experience of only a day or two was needed to learn that the least discomfort would be met by facing the wind with a fold of cloth before the face, an expedient readily used when riding, but making difficulties for the man afoot.

Our own experience left nothing to be desired in the way of opportunities for seeing the action of a Saharan sandstorm. A leisurely journey from Mut in the oasis of Dahkla took us northward, one day in February, to Qasr Dahkl, which lies under a scarp rising fifteen hundred feet above it. A breeze rose steadily during the day and night, and when the morning call to prayers sounded from a near-by house-top in the chill dawn, the roar of the wind passing high overhead was distinct and ominous. A steep ravine piled deep with sand gave passage up the slope, and when we had toiled up this, reaching the rim at noon, the full violence of a gale of thirty-five or forty miles an hour came

directly in our faces. Pebbles as large as peas were being moved along near the ground, while finer particles were carried so high as to strike a camelrider in the face. A halt was soon necessary. A second essay was made; but the track was almost obliterated, and it was prudent to keep the animals and men in close order. Presently the characteristic smell of wet sand came to the nostrils, followed by scattering rain-drops, which added to the cooling effect of the wind. It was necessary to make camp, and this was done directly, in the open, with no shelter except the lee of the baggage and two sleeping bags. The wind abated somewhat by morning, but our muslin - clad cameleers must have found the temperature of several degrees below freezing point quite uncomfortable, since we suffered, though clothed as if for an arctic climate. The breeze continued during the day, but with diminished force, much to our good fortune, as we entered high dunes through which we were to travel for three days. The sand was disposed in ridges as much as a hundred feet in height, with stretches of sogag between.

Once you had entered one of these lanes, you followed it for fifty miles before a convenient crossing to another

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