Sir John Herschel has pronounced the

the beach, to which a sandy plain extending consequently to the larger quantities that with a gentle rise to their base connects them. rolled down the slope. The same sounds, Its height, about 400 feet, as well as the mate- he found, were produced when the wind rial of which it is composed, a light colored friable sandstone, is about the same as the rest was sufficiently high to set the sand in moof the chain; but an inclined plane of almost tion. He does not venture to explain this impalpable sand rises at an angle of 40° with phenomenon; but he rejects without hesitathe horizon, and is bounded by a semi-circle tion the generally received opinion, that of rocks, presenting broken, abrupt, and pin- the effects are originated by this sand fallnacled forms, and extending to the base of this ing into cavities, "because sounds thus remarkable hill. Although their shape and produced would be dull, and wholly defiarrangement in some respects may be said to resemble a whispering gallery, yet I deter-cient in the vibrations he has noticed." mined by experiment that their irregular surface renders them but ill adapted to the pro- phenomenon of El Narkous, as described by duction of an echo. Seated on a rock at the Seetzen and Gray to be a very surprising base of the sloping eminence, I directed one of one, and to him "utterly inexplicable," and the Bedowins to ascend, and it was not till he we should doubtless have found ourselves had reached some distance that I perceived in the same dilemma had we not perused the sand in motion rolling down the hill to the depth of a foot. It did not, however, descend the narrative of Lieutenant Wellstedt, in one continued stream, but as the Arab become acquainted with an analogous phescrambled upwards it spread out laterally, nomenon recently observed in our and upwards, until a considerable portion of country by Mr. Hugh Miller. the surface was in motion. At their comThis able geologist and accurate obsermencement the sounds might be compared to the faint strains of an Eolian harp when its ver, when visiting in the course of last sumstrings first catch the breeze; as the sand be-mer, the interesting island of Eigg, in the came more violently agitated by the increased Hebrides, observed that a musical sound velocity of the descent, the noise more nearly was produced while he walked over the resembled that produced by drawing the white dry sand which forms the sea beach moistened fingers over glass. As it reached of the island. At each step the sand was the base the reverberations attained the loud-driven from his foot print, and the noise ness of distant thunder, causing the rock on which we were seated to vibrate; and our camels, animals not easily frightened, became so alarmed that it was with difficulty their drivers could restrain them."-Vol. ii., p. 23.

In continuing his observations, Lieutenant Wellstedt remarked that the noise did not issue alike from every part of the hill. The loudest was produced by disturbing the sand on the north side, about twenty feet from the base, and about ten from the rocks which bound it in that direction. The sounds fell quicker on the ear at one time, and were prolonged at another, apparently depending on the velocity with which the Bedowin descended. The sounds are said to have an inconceivably melancholy effect, and the tradition given by Burckhardt that the bells of the convent were heard here, was often repeated by the Arabs to Lieutenant Wellstedt.

Our author visited the Jebel Narkous on two other occasions. The first time the sounds were barely audible, and rain having fallen before his second visit, the surface of the sand was so consolidated by the moisture that they could not be produced at all. Hence Lieutenant Wellstedt ascribed the gratification of his curiosity at his third visit to the perfect dryness of the sand, and

and

own

sand. We have here, therefore, the phenomwas simultaneous with the scattering of the enon in its simple state, disembarrassed from reflecting rocks, from a hard bed beneath, and from cracks and cavities that might be supposed to admit the sand, and indicating as its cause either the accumulated vibrations of the air when struck by the driven sand, or the accumulated sounds occasioned by the mutual impact of the particles of sand against each other. If a musket ball passing through the air emits a whistling note, each individual particle of sand must do the same, however faint be the note which it yields, and the accumulation of these infinitesimal vibrations must constitute an audible sound, varying with the number and velocity of the moving particles. In like manner, if two plates of silex or quartz, which are but large crystals of sand, give out a musical sound when mutually struck, the impact or collision of two minute crystals or particles of sand must do the same, in however inferior a degree, and the union of all these sounds, though singly imperceptible, may constitute the musical notes of the Bell Mountain or the lesser sounds of the trodden sea-beach of the Eigg.

The thirteenth chapter of the work be

fore us is devoted to the discussion of pernatural exhibitions. The ancients had those prodigies which are supposed to have particular places (Nekyomantion) specially been produced by optical combinations. consecrated to the raising of the dead, and This class of wonders is perhaps the most the apparition of their images or shades. interesting of any of those which have a These were images either formed on the purely scientific origin. As the science wall, or any white ground, and were genof optics deals especially with images either erally dumb representations, unless when of animate or inanimate objects which can the ventriloquist added his science to perbe diminished or enlarged, multiplied or fect the illusion. Sometimes they were inverted, thrown upon smoke, into the formed on the wreaths or clouds of smoke air, or upon the ground, or upon the walls which rose from the burning incense. The or ceiling of an apartment, it is obvious objects from which these optical pictures that the magician may apply these resour- were obtained, were either painted like ces in effecting the most extraordinary ex- nesses, or busts, or they might be living hibitions. It is to the eye, rendered sensi- persons themselves, dressed and painted so tive or faithless by fear, or even when in the as to resemble the god or the hero who full possession of its powers of scrutiny and was to be summoned from his retreat. In detection, that the spectres and apparitions one of these magical abodes, Homer makes which form the staple of the supernatural, Ulysses converse with his friends raised invariably present themselves. The illu- from the dead, and a crowd of apparitions sions of the ear we may question; and even those of the taste, the touch, and the smell, may be liable to suspicion; but we never doubt the existence of what stands fully before us, whether it appeals to our individual observation, or to the concurring senses of our associates.

might enable him to dispense with his laughing friend: The grave image of the grave statue of Hecate might have been quickly replaced by a laughing image from a laughing statue of the same personage.

and a frightful noise interrupt the conversation. We are informed by Jamblichus that the gods, when evoked by the magician, appeared among the vapors disengaged from the fire; and when the statue of Hecate was made to laugh amid the smoke of burning incense, it was probably the image It is universally admitted that the an- of a living person wearing the sorcerer's cients used mirrors of silver, steel, and of costume. But even this supposition is not speculum metal, composed of copper and necessary. The resources of the magician tin. It appears from a passage in Pliny, that mirrors of glass were manufactured at Sidon, though we have no reason to believe that they possessed the art of increasing the reflective power of their posterior surface; and therefore they could be used only when a very faint image was required, or when the person or object was highly illuminated. Aulus Gellius has mentioned another kind of mirror which, though it gave distinct images in one place, lost its power of reflexion, or rather of forming images, when carried to another place (aliorsum translatum). M. Salverte regards this property as either the result of sleight of hand, or of "something analogous to the phenomena of polarized light, which ceases to be reflected when it falls at a certain angle upon a reflecting body." The last of these suppositions is clearly inadmissible, and without having recourse to the magician's wand we may deprive any mirror of its reflective power, by merely breathing upon it, or conveying it to a film of vapor which will disappear quickly or slowly, according to the temperature of the mirror, or the dryness of the atmosphere in which it is placed.

With mirrors and specula for his utensils, the magician is prepared for the most su

But the same, and even more astonishing effects, might be produced by simpler means. It was stated by Sir David Brewster, at the British Association at York, that the rigid features of a white bust might be made to move and vary their expression, sometimes smiling and sometimes frowning, by moving rapidly in front of the bust a bright light, so as to make the lights and shadows take every possible direction, and various degrees of intensity. Hence, if such a bust is placed before a concave mirror, its image, like that of Hecate, may be made to do more than smile when it is cast upon the smoky wreaths.

The employment of phantasmagoric exhibitions by the ancients is clearly indicated by Damascius, in his account of the manifestation of Osiris by the Alexandrian priests. "There appeared," says he, "on the wall of the temple, a mass of light, which seemed at first very remote. It transformed itself, while contracting its dimensions, into a face evidently divine

and supernatural, with a severe aspect, yet age of the figures on the back, and has no blended with gentleness, and extremely connexion with them whatever, excepting beautiful." This is precisely the manner in which the figures of the modern phantasmagoria, produced by mirrors or lenses, rise out of the luminous image, when put out of focus.

in their resemblance. The figures on the back are merely a copy of a concealed picture which is somehow or other formed or impressed in the polished surface which reflects it. The figure of the dragon, for example, may be delineated in shallow lines on the surface of the mirror previous

The celebrated feat of modern necromancy described by Benvenuto Cellini, in which he himself was an actor, though to its being polished; or it may be eaten perplexed with unnecessary and misleading details, was clearly the work of a magic lantern which threw the pictures of gods and demons upon the wreaths of smoke, while the spectators were stupefied or intoxicated with noisome or exciting odors, which increased their liability to deception, if they did not add the phantasms of the imagination to the crowd of apparitions with which they were previously encircled.

out by a diluted acid, so as to remove only the smallest portion of the metal. The surface must then be polished upon cloth, which will polish the slightly depressed parts of the metal as highly as the rest, so that the picture of the dragon will be wholly invisible to the eye. A curious example of this may be seen in highly polished gilt buttons, upon which no figure whatever can be seen by the most careful examination, and yet when they are made to reMirrors of a kind different from any of flect the light of the sun or of a candle those we have described, and acting upon upon a piece of paper held close to them, a different principle, may have been used they give a beautiful geometrical figure, by the ancients. A mirror of this kind with ten rays issuing from the centre, was, about 15 years ago, sent to India from and terminating in a luminous rim. If, China, where they were very uncommon. in place of the sun or candle, we were They are said to have been brought by a to use a small bright luminous point, Dutch ship from Japan several years before, we have no doubt that the figure given by and to have excited general notice. One the Chinese mirror and the button would of these mirrors, which was described to be much more distinct.* us by George Swinton, Esq., was five inches in diameter, and made of copper and tin. On the back of it there is stamped in relief certain circles with a kind of Grecian border. Its polished face is so convex as to give an image of the human face half its natural size, and when it was made to reflect from that surface the rays of the sun upon a white ground, the image of the circles with the Grecian border, as stamped upon the back was distinctly seen in the luminous area on the white ground. On the back of another mirror was a dragon, the image of which was, in like man- In accounting for the enchanted garner, reflected from the polished side. This dens and magnificent palaces, the resiis doubtless a very magical result, and the dence of the gods, which were exhibited instrument which produces it might be during the initiation of his aspirant, M. made a fertile source of deception. There Salverte supposes that a method similar to is here no object to be concealed. The that used in the diorama was employed. elements of deception all lie within the In this beautiful invention a fine painting, mirror itself, and the apparition requires visible only by transmitted light, rises into only a strong light to be evoked. Like existence during the disappearance of the ablest conjurers, the artist has contrived another on the same canvass, visible only to make the observer deceive himself the by reflected light. In this manner a cathemost insurmountable of all kinds of decep- dral, perfect in all its parts, gradually tion. The figures stamped on the back passes into one destroyed by fire, and the are the source of this self-deception. The * See London and Edinburgh Philosophical picture in the luminous area is not an im-Magazine, Vol. i., p. 438. Dec. 1832

A similar illusion might be produced by drawing a figure with weak gum water upon the surface of a convex mirror. The thin film of water thus deposited on the outline or details of the figure would not be visible in dispersed day light, but when made to reflect the rays of the sun, or those of a divergent pencil, would be beautifully displayed by the lines and tints occasioned by the diffraction of light, or the interference of the rays passing through the film with those which pass by it.

splendid abbey of Notre Dame, at first illu- feet; but M. Zeiher of St. Petersburgh, minated by the setting sun, gradually by adopting a better process, succeeded in passes through its different phases after bending a Venetian plate of glass, 2 lines sunset, till its interior is illuminated with thick and 20 Rhinland inches in diameter, artificial lights, and the appearance of so as to have a focal length of 15 feet. the moon and the stars completes the He did this by placing a bar of iron across midnight representation of the scene. the centre of the plate when placed in a The dissolving views, another beautiful ring. The plate was kept in its place optical combination of the present day, but by a thin bar of iron stretched across it, which was not known when M. Salverte and having a female screw in the centre. wrote, would have been, or perhaps was, This thin bar was again pressed against a valuable auxiliary in ancient mysteries. the glass by a screw passing through the By means of two magic lanterns, in one of centre of the cross bar and working in the which is the summer representation, and female screw. An apparatus similar to in another the winter representation of that of Buffon has, we understand, been the same landscape, the one is made to lately constructed by our ingenious counpass into the other with a beauty and effect tryman, Mr. Nasmyth, who produces the which it is impossible to describe. The vacuum by simply sucking out the air same effect might be produced, though less from behind the plate of glass. perfectly, by mirrors, so that the ancients might have effected any metamorphosis they chose by such an apparatus; they might have thus summoned the dead man from his grave or given to the pallid corpse both life and motion.

But of all the wonders of modern science the art of Photography furnishes us with the most striking. Beyond the violet extremity of the solar spectrum there exist certain invisible rays which, though not appreciable by their incidence on the Another optical apparatus which we be- human retina, have yet the power of exerlieve has not yet been made an instrument cising a chemical action upon a Daguerreof imposture, might be made available by otype plate or upon a sheet of paper renthe skilful conjurer. Could we alter the dered sensitive by the Calotype process of focal length of a large concave mirror, we Mr. Talbot. If these rays, as suggested might make the image of a statue or a liv- by Mr. Talbot, were introduced into a ing object move or walk backwards and dark apartment so as to fall upon the perforwards in the air, or through a lengthen- sons and objects which it contained, the ed wreath or a series of contiguous clouds sharpest eye within would descry nothing of smoke suited to its reception. Now athwart the thick darkness which surBuffon has actually taught us how to bend rounded it. But if a camera, furnished a large plate of glass into a concave mir- with the sensitive retina of an iodised plate, ror. He took glass plates two or three or a sheet of calotype paper, were directed feet in diameter, and by means of a screw to the party in the rocm, it would, in a few acting upon a piece of metal in the centre seconds, take their portraits, record their of the plate, he bent it by mechanical pressure into different degrees of concavity. He improved upon this idea by making the glass plate a part of an air-tight drum, and by exhausting the air with an air-pump, the pressure of the atmosphere forced the glass into a concave form. He next proposed to grind the central part of the plate into the shape of a small convex lens,* and in its focus to place a sulphur match, so that when the plate was directed to the sun, his rays, concentrated by the lens, would inflame the match, produce an absorption of the air, and consequently a Buffon produced mirrors whose shortest focal length was 25

vacuum.

In this

way

It is singular that Buffon did not think of the simpler method of cementing a lens on the centre of the plate.

passions, and reveal their deeds. Were this dark abode the locality of crime, and the shroud of night the cover of the criminal, the blank yet pregnant tablet would surrender to the astonished sage its embosomed phantoms-the murderer and his bleeding victim.

Nor is this the only contribution which the photogenic art has made to natural magic. Professor Moser of Königsberg has discovered that all bodies, even in the dark, throw out invisible rays, and that these bodies, when placed at a small distance from polished surfaces of all kinds, depict themselves upon such surfaces in forms which remain invisible till they are developed by the human breath, or by the vapors of mercury or iodine. Even if the sun's image is made to pass over a plate of glass,

the light tread of its rays will leave behind it an invisible track which the human breath will instantly reveal. Had the gigantic bird which, in the primæval age, left its footprints upon the now indurated sea beach as a stereotype of its existence and its character-had that bird marched over a surface of glass without leaving any visible trace of its path, and had that surface been exempted from other agencies, the breath of the modern geologist would have revealed, upon the vitreous pavement, the foot-weeping statues of the ancients, and the print and the stride of the feathered colos

But while visible objects thus leave behind them invisible phantoms, which may at any time be summoned into view, invisible objects may also impress, or leave behind them, visible and persistent images. The ascending vapor of fluids, as well as The portraiture of the unseen and the un-their downward tendency, was summoned known may be made upon surfaces with to the aid of superstition. Anthemius of which the objects neither are, nor have Tralles, the architect of Justinian, being been, in contact; and even in our very desirous to play a trick to the orator Zeno, dwellings may this transmigration of forms, like the hand-writing on the wall, surprise