CHAPTER IV.

PHENOMENA OF THE DESERT.

The desert has its own meteorology; it is the theatre of peculiar phenomena, which one observes in no other part of the globe. Its climate, at least in the sandy region, is remarkably uniform; it varies only, according to latitude, in a greater or less elevated thermometrical mean. Hippocrates, the ancient philosopher, rightly called "the Father of Medicine," states the three elements of climate to be, the atmosphere, the soil, and the waters. Throughout the desert these are identically similar, and consequently originate identically similar phenomena.

The atmosphere, in fact, is everywhere of an almost unchanging purity. It is only in the neighbourhood of mountains that clouds accumulate, to spend themselves at periodical seasons in more or less abundant rains. In the plains it never rains, and during the day no veil is interposed between the earth and the sun's burning glare, nor during the night do any refreshing dews weaken the force of the terrestrial radiation. There result constant alternations of devouring heat while the sun is above the horizon, and of rapid and frequently intense cooling when he has disappeared.

The soil is everywhere as smooth as "the liquid main." This uniformity contributes, in addition to its silicious, argillaceous, or calcareous character, to render more abrupt the changes of temperature which occur from morning to evening and from evening to morning. In truth, the earth reflects the sun's heat in proportion as it receives it; it absorbs but insignificant quantities, which it loses in a few minutes when the calorific source begins to fail. On the other hand, in these immense plains where no inequality of surface can oppose the atmospheric movements, the wind acquires an increasing force and swiftness, _vires acquirit eundo_, and soon assumes all the characteristics of a tempest. Hence arise those terrible typhoons, those appalling hurricanes, of whose destructive effects history records so many instances, and of which I shall presently be called upon to speak. As for water, we have seen that its entire absence is a characteristic feature of the Sandy Desert.

To sum up, an overpowering degree of heat during the day,--a freshness, often even an excessive cold, during the night (in the Sahara the thermometer frequently rises above 120° F. at noon, and not infrequently sinks below 32° about two or three o'clock A.M.); an ever transparent and azure sky,

"Darkly, deeply, beautifully blue;"

the absence of rains and dews, of gales and thunder; but a frequent recurrence of terrible hurricanes: such is the meteorological constitution of the arid zone, which embraces all the northern districts of Africa, except the Mediterranean region--that is, from the snowy heights of Atlas to the fertile pastures of Soudan--and which extends in Asia from the west to the north-east, for all but one narrow belt, as far as the 119th meridian of longitude.

* * * * *

Foremost among the phenomena peculiar to this zone we must place those famous tempests which, in default of humid clouds, traverse with startling swiftness the changing surface of the Desert, driving before them whirlwinds of burning sand, and striking the traveller's heart with a sense of unconquerable awe. The wind of the Desert is called by the Arabs the _choum_ or _khamsin_; but is more generally known in European books as the _Simoun_, _Simoom_, or _Samoun_. It is the _Samiel_ of the Turks; and, under a somewhat milder form, the _Scirocco_ of the Mediterranean. Wherever, or however it blows, it is a pernicious and hateful wind; the blast, in all probability, which destroyed the hosts of Sennacherib at the bidding of the Divine Word,--

"The angel of Death spread his wings on the blast, And breathed in the face of the foe as he passed. And the eyes of the sleepers waxed deadly and chill, And their hearts but once heaved, and for ever grew still."

Torrents of burning sand sweep before it, a thick veil of darkness envelopes the firmament, and the sun assumes a blood-red hue.

"That crimson haze By which the prostrate caravan is awed In the red desert when the wind's abroad."[58]

When the Simoom rises, says M. Martins,[59] the air is filled with dust of such extreme fineness that it makes its way through objects hermetically sealed, penetrates into the eyes, the ears, and the organs of respiration. A burning heat, like that which breathes from the mouth of a furnace, possesses the air, and paralyzes the strength of men and animals. Seated on the sand, with their backs turned to windward, the Arabs, wrapped in their burnous, wait with fatalistic resignation the end of the torment; their camels crouching, exhausted, panting, stretch their long necks upon the scorching soil. Seen through this powdery haze, the sun's disc, shorn of its beams, shows pale and ghastly as that of the moon.

Fortunately, the phenomenon never prevails over any very considerable area, and beyond its limits the atmosphere remains serene and calm; so that travellers who have watched it approaching in the form of a reddish cloud, without being able to calculate on its direction, have often escaped with no worse result than a panic, and have only witnessed its terrible effects at a distance.

It must not, however, be confounded with the sand-storms which the pilgrim encounters in the Arabian Desert, and which seem confined to that region. Dean Stanley, on his route from Suez to Sinai, met with one which prevailed the whole day. "Imagine," he says, "the caravan toiling against this,--the Bedouins each with his shawl thrown completely over his head, half of the riders sitting backwards,--the camels, meantime thus virtually left without guidance, though from time to time throwing their long necks sideways to avoid the blast, yet moving straight onwards with a painful sense of duty truly edifying to behold. Through the tempest, this roaring and driving tempest, which sometimes made me think that this must be the real meaning of 'a _howling_ wilderness,' we rode on the whole day."[60]

A French cavalier, M. Trémaux, while crossing the Desert of Korosko, had the good fortune to witness the course of a Simoom, while himself in a position of safety.

It was the 8th of February 1848. The horizon in the south-west wore a hue of the evillest augury. Gusts of wind, which seemed to have issued from some red-hot brazier, beat in the face of the travellers. The camel-drivers, accustomed to interpret these sinister signs, and assured that a tempest was at hand, felt themselves called upon to give M. Trémaux a few counsels, which were by no means reassuring.

"As soon as the storm darkens the air," said one of them, "by surrounding us with a cloud of sand, we must throw ourselves prone on the ground, wrap our heads in our finest stuffs, to protect our respiration from this sand, which burns the throat. It will be useless to trouble ourselves about the camels; they will lie down of their own accord, bend their head against their burden, and never stir so long as the tempest lasts. If the sand accumulates by our side, we must move in such a manner as to prevent it from covering us, making it roll under itself, but without exposing our heads. Remember these things carefully; and the will of God be done!"

"That is not all," added another; "when the water-bags are partly shrunken, as are ours at this moment, and the Khamsin blows for some time, it finishes by completely drying them up."

Thus warned, M. Trémaux was compelled to face, with all the resignation he was capable of, the melancholy alternative of perishing suffocated by the sand, or, a little later, of succumbing to the tortures of thirst. He continued to journey, or rather to drag himself towards the centre of the choking atmosphere, and to watch the scourge which rapidly drew near. This lasted a couple of hours, after which the travellers had the satisfaction of seeing the Simoom glide by on their right, and depart with the same rapidity.

A column of the French army, commanded by the Dukes of Aumale and of Montpensier, had met with a less happy chance on the 7th of March 1844, in the Souf, or Algerine Sahara; it was attacked by a Simoom, which prolonged its furious assaults during fourteen hours. On the day following, M. Fournel, a mining engineer who accompanied the expedition, ascertained that the meteor had swept but a narrow zone parallel to the Aurès range, and that at the mountain base the tranquillity of the atmosphere had been undisturbed.

The Simoom, or Khamsin, is, however, more troublesome and painful than really dangerous. M. Martins speaks of the annihilated army of Cambyses, the Persian king, which perished in the Libyan Desert (B.C. 524),[61] and of whole caravans engulfed in the sepulchral sands. "The numerous skeletons of camels," he adds, "which we met with on our way prove that these catastrophes are still of frequent occurrence." It is more probable, however, that they died from dearth of water and want of food. As for the Persian host, it was probably swallowed up in one of those quicksands, those hidden treacherous gulfs, which are found in the deserts of Libya, as well as in those of Persia and Arabia. The evil effects of the Simoom have, in fact, been exaggerated by the Arabs, whose highly-coloured narratives have been too easily adopted by credulous travellers. It heats the blood, it dries the skin, it renders respiration troublesome; but it does not kill.

It is not always a single wind which blows in the Deserts; but sometimes two or three currents, from opposite directions, cross and clash and drive against one another with increasing fury. Then is produced the singular phenomenon of the sand-spout, often witnessed on a magnificent scale in the sandy plains of Eastern Asia and Southern America. The sand is not now driven in voluminous masses in a rectilineal direction; but raised aloft in the form of long tortuous columns, which whirl to and fro like gigantic spectres in the mazes of a wild demon-dance. At the same time, the azure of the sky grows pale and troubled, the sun's light obscured, the boundaries of the horizon seem to meet together; the burning dust held in suspension in the air renders it irrespirable, and if one of these whirlwinds encounters any object which offers a resistance, it carries it upward and hurls it a considerable distance. Fortunately the phenomenon is one of brief duration. The atmospheric equilibrium is speedily restored; the heavens recover their serenity; the atmosphere grows clear, and the sand columns, falling in upon themselves, form a number of little hills or cones, apparently constructed with great care, like those mimic edifices of sand or snow built up by children in their pastimes.

It is said that these furious whirlwinds have occasionally engulfed whole caravans in their tremendous vortex,--

"Man mounts on man, on camels camels rush, Hosts march on hosts, and nations nations crush; Wheeling in air the wingèd islands fall, And one great sandy ocean covers all."

Whether this be true or not, there can be no doubt that the spectacle is one of great magnificence, and calculated to inspire the traveller with emotions of awe and dread. Mr. Atkinson describes it as seen by him, on one occasion, when traversing the Mongolian Desert:--

"As we passed," he says,[62] "in the middle of a space sown with innumerable hillocks of sands, we saw about thirty of them suddenly raise themselves around us, lengthen into long elliptical columns, and glide with many a whirl and sweep over the surface of the Desert with the hissings and contortions of gigantic serpents which had awakened at our approach. These spouts, for the phenomenon was no other, varied in diameter; the smallest measured between twenty and thirty feet; a few attained to a hundred; and one, which absorbed in its vortex all that it approached, rose to nearly two hundred. One might have said, on seeing them bending, rising again and crossing one another in space amidst an atmosphere of dust, that they were antediluvian monsters emerging from their geological bed, and returning into the feverish activity of existence. But soon, the atmospheric forces which had raised them beginning to fail, we saw these sand-spouts fall away one after another, and form on the surface of the Desert a number of moving hillocks similar to those from which we had just emerged."

* * * * *

The poet, invoking the judgment of Heaven on the traitor, would fain doom him to the misery of cherishing hopes that shall never be realized. "May he," cries the minstrel--

"May he, at last, with lips of flame, On the parched desert thirsting die, While lakes that shone in mockery nigh Are fading oft, untouched, untasted."[63]

The image here is borrowed from that most singular phenomenon of the Desert, the _Mirage_; an atmospheric illusion due to the refraction of the sun's rays upon the sand, and the intense expansion of the lower strata of the air,--in other words, it arises from the total reflection of the rays of light from the lower surface of a stratum of air. "This occurs when, from any cause, such a stratum of air possesses a higher refractive power than the one immediately below it. Such a condition of the atmosphere causes remote objects to be seen as if reflected in a mirror, or to appear as if suspended in the air. When the effect is confined to apparent elevation, the English sailors call it _looming_; when inverted images are formed, the Italians give it the name of _Fata Morgana_. The Arabs call it _Serab_, or _Suhrab_, the 'Water of the Desert;' and the Hindus, _Tchittram_, or 'the Picture.'"

The effects of the illusion are extraordinary, but undoubtedly they are heightened by the imagination of observers, generally over-excited by fatigue, by privations, or sometimes by fever. These causes contribute to vary the nature of the phenomenon as seen by different eyes. Thus some gaze enraptured on verdurous islands bright as Armida's enchanted garden, with feathery palms and blooming flowers, and delicious sparkling lakes; others see, in that dim far-off which is never reached, the laughing waves of ocean, with ships resting calmly at anchor, or

"Veering up and down, they know not why,"

and camels browsing quietly upon its shores; others, again, see before them the rolling river, its banks studded with groves and palaces; and all this, while there is not a solitary real object on the horizon whose presence might serve in some degree as a foundation for their visions. It is the very phantasmagoria of nature; her wildest, most wayward, and most fantastic sport. The reflection of the sky, modified by the inequalities of the soil and the vibratory movements of the air, can alone account for the singular deception. Imagination shows its victim, in the reflected image of the cloudless sky, a sheet of water, which is variously taken for a sea, a lake, or a river; it invests the slightest objects on the earth's surface with forms, colours, and dimensions, which are easily metamorphosed into houses, ships, men, animals; and it seems certain that those which in Nubia our fancy converts into camels would, in the Soudan, be transformed into elephants, and at Venice into gondolas. Imagination makes us its dupes, and gives to airy nothings

"A local habitation and a name."

It becomes absolutely necessary, therefore, to distinguish these wholly personal illusions born of a heated brain, from those which are really due to a definite physical cause. The latter necessarily suppose the existence of _actual objects_, below or very little above the horizon. Under such conditions, the most frequent illusion is that which shows the sky or rocks reflected in the expanse of rarified air superincumbent on the earth's surface, and which through this cause alone resembles water. It is then that the ignorant or inexperienced traveller, overwhelmed with fatigue and devoured by thirst, hastens his eager steps to reach more quickly that limpid water, where he hopes to refresh and reinvigorate himself, but which flies before his advance, and speedily vanishes altogether. Sometimes it is an inverted representation of terrestrial objects which appears in the air; or rather, these same objects, several times reflected, appear to multiply themselves. M. Trémaux relates that he saw the latter form of mirage in Nubia. He observed a row of doum-palms, which were about two thousand yards distant, repeated in several similar rows, each with a like number of trees, so as to produce the effect of a quincunx; among these trees floated several seeming sheets of water.

We must remember, moreover, that the immensity, uniformity, and vacuity of the Desert, singularly contribute to render optical illusions frequent. The very serenity of the air assists in destroying the perspective to which we are accustomed in temperate climates, which are always more or less misty. Objects appear much nearer than they are in reality, because they are more distinctly visible, and also because nothing intervenes between them and the observer. Their dimensions, too, become arbitrary, for want of standards of comparison by which to measure them. So the trees and the mountains where the weary traveller hopes to obtain a temporary repose and a passing shelter from the Pythian's fiery arrows, seem constantly to recede before him, like the rainbow when pursued by the ignorant peasant; and, until experience has taught him to rectify the apparent testimony of his senses, he is doomed, like Tantalus, to be the victim of continual deceptions,--

"Ev'n in the circling floods refreshment craves, And pines with thirst amidst a sea of waves; When to the water he his lip applies, Back from his lip the treacherous water flies."[64]

Nor is this all; hunger, thirst, weariness, and especially the action of the solar heat upon the brain, determine a peculiar pathological condition, a species of mental intoxication or delirium which powerfully predisposes the victim to hallucinations, and deprives the mind of that self-control which would enable it to chase away the phantoms that haunt it. To this affection, whose symptoms are frequently but erroneously confounded with those of the mirage, the Arabs have given a specific name. They call it _Ragle_. A distinguished French traveller has described it with exhaustive fulness,[65] and he attributes it to fatigue, excessive heat, and want of sleep.

It shows itself most commonly at night, and in dreams, attacks of nightmare, and a somnambulism of which the sufferer is perfectly conscious, without being able to throw it off. By day strange hallucinations affect the sight, the hearing, and even, though less powerfully, the senses of taste and smell. The aberration extends, as far as the sight is concerned, to the objects which we are in the habit of seeing; a small stone, for instance, expands into a rock; the rut of a carriage-wheel enlarges into the furrow of a freshly ploughed field; a tuft of grass or a bush will assume the grand proportions of a forest; and, what is remarkable, these objects seem always close at hand. Another frequent error is the elevation of horizontal surfaces; the horizon becomes a wall or a mountain. "It has happened to myself," says M. d'Escayrac, "to meet with walls constantly reappearing before me. My extended arm has plunged into the masonry, but my body never encountered any obstacle; the rampart opened to give me a free passage."

Hearing is, in its turn, affected. Then, any sound whatsoever, such as a footfall, the blow of a stone, the whisper of the wind, is changed into melodious sounds, keen cries of distress, the murmur of woods, the harmony of familiar songs.

One day, says M. d'Escayrac, I heard the click-clack of a village mill. Endeavouring to collect my senses, and to obtain an explanation of the sound, I perceived that it arose from the clink of my sword-belt against the pommel of my saddle, to which I had buckled my sabre.

Jomard, the savant, who experienced the effects of the ragle during his travels in Egypt, confirms in every respect the foregoing description. On his way from Rosetta to Alexandria, he kept along the border of the sea, and found his feet painfully staggering in the thick fine sand. Such a journey is necessarily one of extreme fatigue. After the first night, this fatigue grew overwhelming; the traveller lost all accurate perception of objects, or of the form of places. The surface of the lake Medeah appeared not so much a sheet of water as a monotonous plain. Constantly pressing forward, he maintained a hard fight against the overpowering sense of slumber. Half-asleep, half-awake, his brain was dazzled with the most fantastic phantoms, and the hallucination was so great that he plunged into the lake before him, without perceiving it, though the water was very deep. But the freshness caused by the evaporation of the water warned him of his error, and the vision suddenly passed away.

Such being the phenomena of the Desert, one can understand the dreary picture which Dante paints in his "Inferno," of--

"The plain Which from its bed rejecteth every plant;"

whose soil is--

"Of an arid and thick sand;"

and where--

"With a gradual fall Are raining down dilated flakes of fire. As of the snow on Alp, without a wind."[66]