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.