PARLOUR MAGIC

PARLOUR MAGIC

REVISED AND IMPROVED.
PHILADELPHIA: H. PERKINS, 134 CHESTNUT STREET.
MDCCCXXXVIII.

Entered, according to Act of Congress, in the year 1838, by Henry Perkins, in the Clerk’s office of the District Court for the Eastern District of Pennsylvania.

Printed by Haswell, Barrington, and Haswell.

PREFACE.

To furnish the ingenious youth with the means of relieving the tediousness of a long winter’s or a wet summer’s evening,—to enable him to provide for a party of juvenile friends, instructive as well as recreative entertainment, without having recourse to any of the vulgar modes of killing time,—to qualify the hero of his little circle to divert and astonish his friends, and, at the same time, to improve himself, are the principal objects of the following little Work.

The boy whose wonder and curiosity have been excited by the experiments of the scientific lecturer, or the illusions of the ventriloquist, will here find many of these mysteries unveiled, and plain directions for performing them, divested, as far as possible, of scientific or technical language. Many of the descriptions are strictly original, and now, for the first time, appear in print; and especial care has been taken to introduce only such Experiments as are adapted for performance at the parlour or drawing-room table, or fire-side, and such as are practicable without expensive chemical or mechanical apparatus, and require no implements beyond those which any ingenious youth may readily furnish from his own resources, or at a trifling expense.

Another object of these pages is to inform, without being dryly scientific,—by imparting interesting facts, to stimulate the young experimentalist to inquire into the laws that regulate them,—by aiding him to acquire dexterity of practice, to smooth the road to the development of principles,—and, above all, to enable him to escape an imputation which every boy of spirit would consider the depth of disgrace,—that of being “No Conjuror!”

CONTENTS.

TRANSMUTATIONS.

TRANSMUTATIONS.

THE SPECTRAL LAMP.

MIX some common salt with spirit of wine in a platinum or metallic cup; set the cup upon a wire frame over a spirit-lamp, which should be inclosed on each side, or in a dark-lantern: when the cup becomes heated, and the spirit ignited, it will burn with a strong yellow flame; if, however, it should not be perfectly yellow, throw more salt into the cup. The lamp being thus prepared, all other lights should be extinguished, and the yellow lamp introduced, when an appalling change will be exhibited; all the objects in the room will be but of one colour, and the complexions of the several persons, whether old or young, fair or brunette, will be metamorphosed to a ghastly, death-like yellow; whilst the gayest dresses, as the brightest crimson, the choicest lilac, the most vivid blue or green—all will be changed into one monotony of yellow: each person will be inclined to laugh at his neighbour, himself insensible of being one of the spectral company.

Their astonishment may be heightened by removing the yellow light to one end of the room, and restoring the usual or white light at the other; when one side of each person’s dress will resume its original colour, while the other will remain yellow; one cheek may bear the bloom of health, and the other, the yellow of jaundice. Or if, when the yellow light only is burning, the white light be introduced within a wire sieve, the company and the objects in the apartment will appear yellow, mottled with white.

Red light may be produced by mixing with the spirit in the cup over the lamp, salt of strontian instead of common salt; and the effect of the white or yellow lights, if introduced through a sieve upon the red light, will be even more striking than the white upon the yellow light.

CURIOUS CHANGE OF COLOURS.

Let there be no other light than a taper in the room; then put on a pair of dark green spectacles, and having closed one eye, view the taper with the other. Suddenly remove the spectacles, and the taper will assume a bright red appearance; but, if the spectacles be instantly replaced, the eye will be unable to distinguish any thing for a second or two. The order of colours will, therefore, be as follows:—green, red, green, black.

THE PROTEAN LIGHT.

Soak a cotton wick in a strong solution of salt and water, dry it, place it in a spirit lamp, and, when lit, it will give a bright yellow light for a long time. If you look through a piece of blue glass at the flame, it will lose all its yellow light, and you will only perceive feeble violet rays. If, before the blue glass, you place a pale yellow glass, the lamp will be absolutely invisible, though a candle may be distinctly seen through the same glasses.

THE CHAMELEON FLOWERS.

Trim a spirit-lamp, add a little salt to the wick, and light it. Set near it, a scarlet geranium, and the flower will appear yellow. Purple colours, in the same light, appear blue.

TO CHANGE THE COLOURS OF FLOWERS.

Hold over a lighted match, a purple columbine, or a blue larkspur, and it will change first to pink, and then to black. The yellow of other flowers, held as above, will continue unchanged. Thus, the purple tint will instantly disappear from a heart’s-ease, but the yellow will remain; and the yellow of a wall-flower will continue the same, though the brown streak will be discharged. If a scarlet, crimson, or maroon dahlia be tried, the colour will change to yellow; a fact known to gardeners, who by this mode, variegate their growing dahlias.

CHANGES OF THE POPPY.

Some flowers which are red, become blue by merely bruising them. Thus, if the petals of the common corn-poppy be rubbed upon white paper, they will stain it purple, which may be made green by washing it over with a strong solution of potash in water. Put poppy petals into very dilute muriatic acid, and the infusion will be of a florid red colour; by adding a little chalk, it will become the colour of port wine; and this tint, by the addition of potash, may be changed to green or yellow.

TO CHANGE THE COLOUR OF A ROSE.

Hold a red rose over the blue flame of a common match, and the colour will be discharged wherever the fume touches the leaves of the flower, so as to render it beautifully variegated, or entirely white. If it be then dipped into water, the redness, after a time, will be restored.

LIGHT CHANGING WHITE INTO BLACK.

Write upon linen with permanent ink, (which is a strong solution of nitrate of silver,) and the characters will be scarcely visible; remove the linen into a dark room, and they will not change; but expose them to a strong light, and they will be indelibly black.

THE VISIBLY GROWING ACORN.

Cut a circular piece of card to fit the top of a hyacinth glass, so as to rest upon the ledge, and exclude the air. Pierce a hole through the centre of the card, and pass through it a strong thread, having a small piece of wood tied to one end, which, resting transversely on the card, prevents its being drawn through. To the other end of the thread attach an acorn; and, having half filled the glass with water, suspend the acorn at a short distance from the surface.

The glass must be kept in a warm room; and, in a few days, the steam which has generated in the glass will hang from the acorn in a large drop. Shortly afterwards, the acorn will burst, the root will protrude and thrust itself into the water; and, in a few days more, a stem will shoot out at the other end, and, rising upwards, will press against the card, in which an orifice must be made to allow it to pass through. From this stem, small leaves will soon be observed to sprout; and, in the course of a few weeks, you will have a handsome oak plant, several inches in height.

CHANGES IN SAP GREEN.

Sap green is the inspissated juice of the buckthorn berries: if a little carbonate of soda be dropped into it, the colour will be changed from green to yellow; it may be reddened by acids, and its green colour restored by chalk.

TO REVIVE APPARENTLY DEAD PLANTS.

Make a strong dilution of camphor in spirit of wine, which add to soft water, in the proportion of a dram to a pint. If withered, or apparently dead plants be put into this liquid, and allowed to remain therein from two to three hours, they will revive.

SINGULAR EFFECT OF TEARS.

If tears are dropped on a dry piece of paper, stained with the juice of the petals of mallows or violets, they will change the paper to a permanently green colour.

BEAUTIES OF CRYSTALLIZATION.

Dissolve alum in hot water until no more can be dissolved in it; place in it a smooth glass rod and a stick of the same size; next day, the stick will be found covered with crystals, but the glass rod will be free from them: in this case, the crystals cling to the rough surface of the stick, but have no hold upon the smooth surface of the glass rod. But, if the rod be roughened with a file at certain intervals, and then placed in the alum and water, the crystals will adhere to the rough surfaces, and leave the smooth bright and clear.

Tie some threads of lamp-cotton irregularly around a copper wire or glass rod; place it in a hot solution of blue vitriol, strong as above, and the threads will be covered with beautiful blue crystals, while the glass rod will be bare.

Bore a hole through a piece of coke, and suspend it by a string from a stick, placed across a hot solution of alum; it will float; but, as it becomes loaded with crystals, it will sink in the solution according to the length of the string. Gas-coke has mostly a smooth, shining, and almost metallic surface, which the crystals will avoid, while they will cling only to the most irregular and porous parts.

If powdered tumeric be added to the hot solution of alum, the crystals will be of a bright yellow; litmus will cause them to be of a bright red; logwood will yield purple; and common writing ink, black; and the more muddy the solution, the finer will be the crystals.

To keep coloured alumn crystals from breaking, or losing their colour, place them under a glass shade with a saucer of water; this will preserve the atmosphere moist, and prevent the crystals getting too dry.

If crystals be formed on wire, they will be liable to break off, from the expansion and contraction of the wire by changes of temperature.

TO CRYSTALLIZE CAMPHOR.

Dissolve camphor in spirit of wine, moderately heated, until the spirit will not dissolve any more; pour some of the solution into a cold glass, and the camphor will instantly crystallize in beautiful tree-like forms, such as we see in the show-glasses of camphor in druggists’ windows.

CRYSTALLIZED TIN.

Mix half an ounce of nitric acid, six drams of muriatic acid, and two ounces of water; pour the mixture upon a piece of tin plate previously made hot, and, after washing it in the mixture, it will bear a beautiful crystalline surface, in feathery forms. This is the celebrated moirée metallique, and, when varnished, is made into ornamental boxes, &c. The figures will vary according to the degree of heat previously given to the metal.

CRYSTALS IN HARD WATER.

Hold in a wine-glass of hard water, a crystal of oxalic acid, and white threads will instantly descend through the liquid, suspended from the crystal.

VARIETIES OF CRYSTALS.

Make distinct solutions of common salt, nitre, and alum; set them in three saucers in any warm place, and let part of the water dry away or evaporate; then remove them to a warm room. The particles of the salts in each saucer will begin to attract each other, and form crystals, but not all of the same figure: the common salt will yield crystals with six square and equal faces, or sides; the nitre, six-sided crystals; and the alum, eight-sided crystals; and if these crystals be dissolved over and over again, they will always appear in the same forms.

HEAT FROM CRYSTALLIZATION.

Make a strong solution of Epsom salts in hot water, and while warm, bottle it, cork it closely, and it will remain liquid: draw out the cork, when the salts will immediately crystallize, and in the process, the remaining liquid and the bottle will become very warm.

SPLENDID SUBLIMATION.

Put into a flask a small portion of iodine; hold the flask over the flame of a spirit-lamp, and, from the state of rich ruby crystals, the iodine, on being heated, will become a ruby-coloured transparent gas; but, in cooling, will resume its crystalline form.

ARTIFICIAL ICE.

Mix four ounces of nitrate of ammonia, and four ounces of subcarbonate of soda, with four ounces of water, in a tin vessel, and in three hours the mixture will produce ten ounces of ice.

MAGIC INKS.

Dissolve oxide of cobalt in acetic acid, to which add a little nitre; write with this solution, hold the writing to the fire, and it will be of a pale rose colour, which will disappear on cooling.

Dissolve equal parts of sulphate of copper and muriate of ammonia in water; write with the solution, and it will give a yellow colour when heated, which will disappear when cold.

Dissolve nitrate of bismuth in water; write with the solution, and the characters will be invisible when dry, but will become legible on immersion in water.

Dissolve, in water, muriate of cobalt, which is of a bluish-green colour, and the solution will be pink; write with it, and the characters will be scarcely visible; but, if gently heated, they will appear in brilliant green, which will disappear as the paper cools.

CHAMELEON LIQUIDS.

Put a small portion of the compound called mineral chameleon into several glasses, pour upon each water at different temperatures, and the contents of each glass will exhibit a different shade of colour. A very hot solution will be of a beautiful green colour; a cold one, a deep purple.

Make a colourless solution of sulphate of copper; add to it a little ammonia, equally colourless, and the mixture will be of an intense blue colour; add to it a little sulphuric acid, and the blue colour will disappear; pour in a little solution of caustic ammonia, and the blue colour will be restored. Thus, may the liquor be thrice changed at pleasure.

THE MAGIC DYES.

Dissolve indigo in diluted sulphuric acid, and add to it an equal quantity of solution of carbonate of potass. If a piece of white cloth be dipped in the mixture, it will be changed to blue; yellow cloth, in the same mixture, may be changed to green; red to purple, and blue litmus paper to red.

Nearly fill a wine-glass with the juice of beet-root, which is of a deep red colour; add a little lime water, and the mixture will be colourless; dip into it a piece of white cloth, dry it rapidly, and in a few hours, the cloth will become red.

WINE CHANGED INTO WATER.

Mix a little solution of subacetate of lead with port wine; filter the mixture through blotting paper, and a colourless liquid will pass through; to this add a small quantity of dry salt of tartar, when a spirit will rise, which may be inflamed on the surface of the water.

TWO COLOURLESS TRANSPARENT LIQUIDS BECOME BLACK AND OPAQUE.

Have in one vessel some sulphuric acid, and in another an infusion of nut-galls; they are both colourless and transparent; mix them, and they will become black and opaque.

TWO COLOURLESS FLUIDS MAKE A COLOURED ONE.

Put into a wine-glass of water, a few drops of prussiate of potash; and into a second glass of water, a little weak solution of sulphate of iron in water: pour the colourless mixtures together into a tumbler, and they will be immediately changed to a bright deep blue colour.

Or, mix the solution of prussiate of potash with that of nitrate of bismuth, and a yellow will be the product.

Or, mix the solution of prussiate of potash with that of sulphate of copper, and the mixture will be of a reddish brown colour.

CHANGE OF COLOUR BY COLOURLESS FLUIDS.

Three different colours may be produced from the same infusion, merely by the addition of three colourless fluids. Slice a little red cabbage, pour boiling water upon it, and when cold, decant the clear infusion, which divide into three wine-glasses: to one, add a small quantity of solution of alum in water; to the second, a little solution of potash in water; and to the third, a few drops of muriatic acid. The liquor in the first glass will assume a purple colour, the second, a bright green, and the third a rich crimson.

Put a dram of powdered nitrate of cobalt into a phial containing an ounce of the solution of caustic potass; cork the phial, and the liquid will assume a blue colour, next a lilac, afterwards a peach colour, and lastly a light red.

TO CHANGE A BLUE LIQUID TO WHITE.

Dissolve a small lump of indigo in sulphuric acid, by the aid of moderate heat, and you will obtain an intense blue colour: add a drop of this to half a pint of water, so as to dilute the blue; then pour some of it into strong chloride of lime, and the blue will be bleached with almost magical velocity.

VERITABLE “BLACK” TEA.

Make a cup of strong green tea; dissolve a little green copperas in water, which add to the tea, and its colour will be black.

RESTORATION OF COLOUR BY WATER.

Water being a colourless fluid, ought, one would imagine, when mixed with other substances of no decided colour, to produce a colourless compound. Nevertheless, it is to water only that blue vitriol, or sulphate of copper, owes its vivid blueness; as will be plainly evinced by the following simple experiment. Heat a few crystals of the vitriol in a fire shovel, pulverize them, and the powder will be of a dull and dirty white appearance. Pour a little water upon this, when a slight hissing noise will be heard, and at the same moment, the blue colour will instantly re-appear.

Under the microscope, the beauty of this experiment will be increased, for the instant that a drop of water is placed in contact with the vitriol, the powder may be seen to shoot into blue prisms. If a crystal of prussiate of potash be similarly heated, its yellow colour will vanish, but re-appear on being dropped into water.

THE MAGIC WRITING.

Dissolve a small portion of green-copperas in water, and soak in it sheets of writing paper, so as to allow them to be taken out whole, and then dried; then, cover the paper with very finely powdered galls, and write on it with a pen dipped in water; when dry, brush off the galls, and the writing will appear.

TWO LIQUIDS MAKE A SOLID.

Dissolve muriate of lime in water until it will dissolve no more; make also a similar solution of carbonate of potash; both will be transparent fluids; but if equal quantities of each be mixed and stirred together, they will become a solid mass.

TWO SOLIDS MAKE A LIQUID.

Rub together in a mortar, equal quantities of the crystals of Glauber’s salts and nitrate of ammonia, and the two salts will slowly become a liquid.

A SOLID OPAQUE MASS MADE A TRANSPARENT LIQUID.

Take the solid mixture of the solutions of muriate of lime and carbonate of potash, pour upon it a very little nitric acid, and the solid opaque mass will be changed to a transparent liquid.

TWO COLD LIQUIDS MAKE A HOT ONE.

Mix four drams of sulphuric acid, (oil of vitrol,) with one dram of cold water, suddenly, in a cup, and the mixture will be nearly half as hot again as boiling water.

QUADRUPLE TRANSMUTATION.

Dissolve a small piece of nickel in nitric acid, and it will appear of a fine grass-green colour; add to it a little ammonia, and a blue precipitate will be formed; this will change to a purple-red in a few hours, and the addition of any acid will convert it to an apple-green.

QUINTUPLE TRANSMUTATION.

Heat potassium over the flame of a spirit-lamp, and the colour will change from white to a bright azure, thence to a bright blue, green, and olive.

COMBINATION OF COLOURS.

Cut out a disc or circle of pasteboard, and cover it with paper half green and half black: cause the disc to be rapidly turned round, (like the shafts of a toy wind-mill,) and the colours will combine and produce white.

UNION OF TWO METALS WITHOUT HEAT.

Cut a circular piece of gold-leaf, called “dentist’s gold,” about half an inch in diameter; drop upon it a globule of mercury, about the size of a small pea, and if they be left for a short time, the gold will lose its solidity and yellow colour, and the mercury its liquid form, making a soft mass, of the colour of mercury.

MAGIC BREATH.

Half fill a glass tumbler with lime-water; breathe into it frequently, at the same time stirring it with a piece of glass. The fluid, which before was perfectly transparent, will presently become quite white, and, if allowed to remain at rest, real chalk will be deposited.

TWO BITTERS MAKE A SWEET.

It has been discovered, that a mixture of nitrate of silver with hypo-sulphate of soda, both of which are remarkably bitter, will produce the sweetest known substance.

VISIBLE AND INVISIBLE.

Write with French chalk on a looking-glass; wipe it with a handkerchief, and the lines will disappear; breathe on it, and they will re-appear. This alteration will take place for a great number of times, and after the lapse of a considerable period.

SIGHT & SOUND.

ARTIFICIAL MIRAGE.

THE mirage is an optical phenomenon, produced by the refractive power of the atmosphere. The appearance presented is that of the double image of an object in the air; one of the images being in the natural position, and the other inverted, so as to resemble a natural object and its image in the water. The mirage is commonly vertical, or upright, that is, presenting the appearance, above described, of one object over another, like a ship above its shadow in the water. Sometimes, however, the image is horizontal, or upon the water, and at other times, it is seen on the right or left hand of the real object, or on both sides.

All the effects of the mirage may be represented artificially to the eye. For this purpose, provide a glass tumbler two-thirds full of water, and pour spirit of wine upon it; or pour into a tumbler some syrup, and fill it up with water: as the water and spirit, or the syrup and water incorporate, they will produce a refractive power; then, by looking through the mixed or intermediate liquids at any object held behind the tumblers, its inverted image may be seen. The same effect, Dr. Walloston has shown, may be produced, by looking along the side of a red-hot poker at a word or object ten or twelve feet distant. At a distance less than three-eighths of an inch from the line of the poker, an inverted image was seen; and within and without that, an erect image.

The above phenomena may likewise be illustrated, by holding a heated iron above a tumbler of water, until the whole becomes changed; then withdraw the iron, and, through the water, the phenomena of the mirage may be seen in the finest manner.

Or, look directly above the flame of a candle, or over the glass of a lighted lamp, and a tremulous motion may be observed; because the warm air rises, and its refracting power being less than that of the colder air, the currents are rendered visible by the distortion of objects viewed through them. The same effect is observable over chimney pots, and slated roofs which have been heated by the sun.

MOTION OF THE EYE.

On entering a room, we imagine that we see the whole side of it at once, as the cornice, the pattern of the paper-hanging, pictures, chairs, &c., but we are deceived; for each object is rapidly, but singly presented to the eye, by its constant motion. If the eye were steady, vision would be lost. For example, fix the eye on one point, and you will find the whole scene become more and more obscure, till it vanishes. Then, if you change the direction of the eye ever so little, at once the whole scene will be again perfect before you.

SINGLE VISION WITH TWO EYES.

As we have two eyes, and a separate image of every external object is formed in each, it may be asked, why do we not see double? The answer is, it is a matter of habit. Habit alone teaches us, that the sensations of sight correspond to any thing external, and shows to what they correspond. Thus, place a wafer on a table before you; direct your eyes to it, that is, bring its image on both retinæ to those parts which habit has ascertained to be the most sensible, and best situated for seeing distinctly, and you will see only the single wafer. But, while looking at the wafer, squeeze the upper part of one eye downwards, by pressing on the eyelid with the finger, and thereby forcibly throw the image on another part of the retina of that eye, and double vision will be immediately produced; that is, two wafers will be distinctly seen, which will appear to recede from each other as the pressure is stronger, and approach, and finally blend into one, as it is relieved. The same effect maybe produced without pressure, by directing the eyes to a point nearer to, or farther from them, than the wafer; the optic axes, in this case, being both directed away from the object seen.

TWO OBJECTS SEEN AS ONE.

On a sheet of black paper, or other dark ground, place two white wafers, having their centres three inches distant. Vertically above the paper, and to the left, look with the right eye, at twelve inches from it, and so that, when looking down on it, the line joining the two eyes shall be parallel to that joining the centre of the wafers. In this situation, close the left eye, and look full with the right perpendicularly at the wafer below it, when this wafer only will be seen, the other being completely invisible. But, if it be removed ever so little from its place, either to the right or left, above or below, it will become immediately visible, and start, as it were, into existence. The distances here set down may, perhaps, vary slightly in different eyes.

Upon this curious effect, Sir John Herschel observes: “It will cease to be thought singular, that this fact of the absolute invisibility of objects in a certain point of the field of view of each eye, should be one of which not one person in ten thousand is apprised, when we learn, that it is not extremely uncommon to find persons who have for some time been totally blind with one eye, without being aware of the fact.”

ONLY ONE OBJECT CAN BE SEEN AT A TIME.

Look at the pattern of the paper-hanging of a room, a picture, or almost any other object in it; then, without altering your position, call to mind the magnificent dome of St. Paul’s Cathedral; the pattern of the paper-hanging, or the subject of the picture, though actually impressed on the retina of the eye, will be momentarily lost sight of by the mind; and, during the instant, the recollected image of the dome rising from the dingy roofs of London, will be distinctly seen, but in indistinct colouring and outline. When the object of the recollection is answered, the dome will quickly disappear, and the paper-hanging pattern, or the picture, again resume the ascendancy.

STRAIGHT OBJECTS SEEN CROOKED.

Look through a series of vertical bars, as those of a palisade, or of a Venetian window-blind, at the wheel of a carriage passing along the street, and the spokes of the wheel, instead of appearing straight, as they naturally would do, if no bars intervened, seem to be of a curved form. The velocity of the wheel must not be so great as to prevent the eye from following the spokes as they revolve.

Again, when the disk of the wheel, instead of being marked by a number of radiant lines, has only one radius marked upon it, it presents the appearance, when rolled behind the bars, of a number of radii, each having the curvature corresponding to its situation, their number being the same as that of the bars through which you look at the wheel. It is, therefore, evident that the several portions of one and the same line, seen through the intervals of the bars, form on the retina of the eye so many different radii.

OPTICAL ILLUSION.

Shut one eye, direct the other to any fixed point, as the head of a pin, and you will indistinctly see all other objects. Suppose one of these to be a strip of white paper, or a pen lying upon a table covered with a green cloth: either of them will disappear altogether, as if taken off the table; for the impression of the green cloth will entirely extend itself over that part of the retina which the image of the pen occupied. The vanished pen will, however, shortly re-appear, and again vanish; and the same effect will take place when both eyes are open, though not so readily as with one eye.

PIN-HOLE FOCUS.

Make a pin-hole in a card, which hold between a candle and a piece of white paper, in a dark room, when an exact representation of the flame, but inverted, will be seen depicted upon the paper, and be enlarged as the paper is drawn from the hole; and if, in a dark room, a white screen or sheet of paper be extended at a few feet from a small round hole, an exact picture of all external objects, of their natural colours and forms, will be seen traced on the screen; moving objects being represented in motion, and stationary ones at rest.

OPTICAL DECEPTIONS.

Prick a hole in a card with a needle; place the same needle near the eye, in a line with the card-hole, look by daylight at the end of the needle, and it will appear to be behind the card, and reversed.

Prick a hole with a pin in a black card, place it very near the eye, look through it at any small object, and it will appear larger as it is nearer the eye; while, if we observe it without the card, it will appear sensibly of the same magnitude at all parts of the room.

ACCURACY OF SIGHT.

Rule a short line upon a slate, and upon another slate rule another line, one-eleventh longer than the first: a person possessing what is called “a true eye,” may perceive the difference in length, even though fifty or sixty seconds elapse between looking at the first and the second lines. If they differ only one-twentieth, then an interval of thirty-five seconds may elapse without destroying the judgment; but, if it be longer, the estimate will be incorrect. When the difference between the lines amounts only to one-fiftieth, an interval of three seconds between the examination of each, is the longest that can be allowed without interfering with the correctness of the comparison.

VISUAL DECEPTION.

Let a room be only lit by the feeble gleam of a fire, almost extinguished, and the eye will see with difficulty the objects in the apartment, from the small degree of light with which they happen to be illuminated. The more exertion is made to ascertain what these objects are, as by fixing the eye more steadily upon them, the greater will be the difficulty in accomplishing it. The eye will be painfully agitated, the object will swell and contract, and partly disappear, but will again become visible when the eye has recovered from its delirium.

HAND-WRITING UPON THE WALL.

Cut the word or words to be shown, out of a thick card or pasteboard, place it before a lighted lamp, and the writing will be distinctly seen upon the wall of the apartment.

IMITATIVE HALOES.

Look at a candle, or any other luminous body, through a plate of glass, covered with vapour, or dust in a finely divided state, and it will be surrounded with a ring of colours, like a halo round the sun or moon. These rings increase with the size of the particles which produce them; and their brilliancy and number depend on the uniform size of these particles.

Or, haloes may be imitated by crystallizing various salts upon thin plates of glass, and looking through the plate at a candle or the sun. For example, spread a few drops of a strong solution of alum over a plate of glass so as to crystallize quickly, and cover it with a crust scarcely visible to the eye. Then place the eye close behind the smooth side of the glass plate, look through it at a candle, and you will perceive three fine haloes at different distances, encircling the flame.

TO READ A COIN IN THE DARK.

By the following simple method, the legend or inscription upon a coin may be read in absolute darkness. Polish the surface of any silver coin as highly as possible; touch the raised parts with aqua-fortis, so as to make them rough, taking care that the parts not raised retain their polish. Place the coin thus prepared upon red-hot iron, remove it into a dark room, and the figure and inscription will become more luminous than the rest, and may be distinctly seen and read by the spectator. If the lower parts of the coin be roughened with the acid, and the raised parts be polished, the effect will be reversed, and the figure and inscription will appear dark, or black upon a light or white ground.

This experiment will be more surprising if made with an old coin, from which the figure and inscription have been obliterated; for, when the coin is placed upon the red-hot iron, the figure and inscription may be distinctly read upon a surface which had hitherto appeared blank.

This experiment may be made with small coins upon a heated poker, a flat iron, or a salamander. The effect will be more perfect if the red-hot iron be concealed from the eye of the spectator: this may be done by placing upon the iron a piece of blackened tin, with a hole cut out, the size of the coin to be heated.

TO MAKE A PRISM.

Fig. 1.

Provide two small pieces of window-glass and a lump of wax. Soften and mould the wax, stick the two pieces of glass upon it, so that they meet, as in the cut, where w is the wax, g and g the glasses stuck to it, (Fig. 1.) The end view (Fig. 2) will show the angle, a, at which the pieces of glass meet; into which angle put a drop of water.

To use the instrument thus made, make a small hole, or a narrow horizontal slit, so that you can see the sky through it, when you stand at some distance from it in the room. Or a piece of pasteboard placed in the upper part of the window-sash, with a slit cut in it, will serve the purpose of the hole in the shutter. The slit should be about one-tenth of an inch wide, and an inch or two long, with even edges. Then hold the prism in your hand, place it close to your eye, and look through the drop of water, when you will see a beautiful train of colours, called a spectrum; at one end red, at the other violet, and in the middle yellowish green.

Fig. 3.

The annexed figure will better explain the direction in which to look: here, e, is the eye of the spectator, p, is the prism, h, the hole in the shutter or pasteboard, s, the spectrum. By a little practice, you will soon become accustomed to look in the right direction, and will see the colours very bright and distinct.

By means of this simple contrivance, white light may be analysed and proved to consist of coloured rays, and several of its properties be beautifully illustrated.

OPTICAL AUGMENTATION.

Take a glass rummer that is narrow at bottom and wide at top, into which put a half-sovereign, and fill the glass three-fourths with water; place on it a piece of paper, and then a plate, and turn the glass upside down quickly, that the water may not escape: by looking sideways at the glass, you will perceive a sovereign at the bottom, and higher up the half-sovereign, floating near the surface. Fill the glass with water, and the large piece only will be visible.

GOLD FISH IN A GLASS GLOBE.

A single gold fish in a globe vase, is often mistaken for two fishes, because it is seen as well by the light bent through the upper surface of the water, as by straight rays passing through the side of the vase.

COLOURS PRODUCED BY THE UNEQUAL ACTION OF LIGHT UPON THE EYES.

If we hold a slip of white paper vertically, about a foot from the eye, and direct both eyes to an object at some distance beyond it, so as to see the slip of paper double, then, when a candle is brought near the right eye, so as to act strongly upon it, while the left eye is protected from its light, the left-hand slip of paper will be of a tolerably bright green colour, while the right-hand slip of paper, seen by the left eye, will be of a red colour. If the one image overlaps the other, the colour of the overlapping parts will be white, arising from a mixture of the complementary red and green. When equal candles are held equally near to each eye, each of the images of the slip of paper is white. If, when the paper is seen red and green by holding the candle to the right eye, we quickly take it to the left eye, we shall find that the left image of the slip of paper gradually changes from green to red, and the right one from red to green, both of them having the same tint during the time that the change is going on.

OPTICAL DECEPTION.

Look steadily at a carpet having figures of one colour, green, for example, upon a ground of another colour, suppose red, and you will sometimes see the whole of the green pattern as if the red one were obliterated; and at other times, you will see the whole of the red pattern, as if the green one were obliterated. The former effect takes place when the eye is steadily fixed on the green part, and the latter, when it is steadily fixed on the red portion.

COLOURED SHADOWS.

Provide two lighted candles, and place them upon a table before a whitewashed or light papered wall: hold before one of the candles a piece of coloured glass, taking care to remove to a greater distance the candle before which the coloured glass is not placed, in order to equalize the darkness of the two shadows. If you use a piece of green glass, one of the shadows will be green, and the other a fine red; if you use blue glass, one of the shadows will be blue, and the other a pale yellow.

COLOURS OF SCRATCHES.

An extremely fine scratch on a well-polished surface, may be regarded as having a concave, cylindrical, or, at least, a curved surface, capable of reflecting light in all directions; this is evident, for it is visible in all directions. Hence, a single scratch or furrow in a surface, may produce colours by the interference of the rays reflected from its opposite edges. Examine a spider’s thread in the sunshine, and it will gleam with vivid colours. These may arise from a similar cause, or from the thread itself, as spun by the animal, consisting of several threads agglutinated together, and thus presenting, not a cylindrical, but a furrowed surface.

OCULAR SPECTRA.

One of the most curious affections of the eye is that, in virtue of which it sees what are called ocular spectra, or accidental colours. If we place a red wafer on a sheet of white paper, and, closing one eye, keep the other directed for some time to the centre of the wafer, then, if we turn the same eye to another part of the paper, we shall see a green wafer, the colour of which will continue to grow fainter and fainter, as we continue to look at it.

By using differently coloured wafers, we obtain the following results:

BEAUTIFUL COLOURS OF MOTHER-OF-PEARL.

This substance, obtained from the shell of the pearl oyster, is much admired for the fine play of its colours. To observe them accurately, select a plate of regularly formed mother-of-pearl, with its surface nearly parallel, and grind this surface upon a hone, or upon a plate of glass, with the powder of slate, till the image of the candle, reflected from the surfaces, is of a dull reddish white colour, when it will glow with all the colours of the rainbow. The colours of mother-of-pearl may be communicated to soft black wax; and to clean surfaces of lead and tin by hard pressure, or the blow of a hammer. Or, dissolve gum arabic, or isinglass, in water, and allow it to harden upon a surface of mother-of-pearl, when it will take a perfect impression from it, and exhibit all the colours in the finest manner. Or, place the isinglass between two finely-polished surfaces of mother-of-pearl, and you may obtain a film of artificial mother-of-pearl, which, when seen by the light of a candle, or by an aperture in the window, will shine with the brightest hues.

WHITE LETTERS SEEN FURTHER THAN BLACK.

Paint the same letters of the same size precisely on two boards, the one white on a black ground, and the other a black on a white ground; the white letters will appear larger, and be read at a greater distance than the black.

ARTIFICIAL RAINBOW.

Observe the various colours which are reflected from the glass drops usually suspended from a lustre or chandelier, and you will witness a mimic rainbow. A rainbow may also be made by a garden engine, if the water be thrown high in the air, and the spectator stand between it and the sun.

FRINGE ABOUT A CANDLE.

Provide two small pieces of plate glass, moisten two of their sides with water, and put them together; then look through them at a candle, and you will perceive the flame surrounded with beautifully coloured fringes: these are the effect of moisture, intermixed with portions of air, and exhibiting an appearance similar to dew.

THE DOUBLE-COLOURED REFLECTION.

Provide a circular piece of coloured glass, and pierce its centre by means of a common awl, well moistened with oil of turpentine: encircle the glass with the fingers and thumb, hold it in the sunshine or the strong light of a lamp, and the following beautiful effects will be produced. If the glass be red, the luminous spot in the centre will be reflected green; if the glass be green, the spot will be red; if blue, orange; and if yellow, indigo.

LUMINOUS CROSS.

Place a lighted candle before a looking-glass, and there will appear a luminous cross radiating from the flame of the candle. This is produced by the direction of the friction by which the glass is polished; the scratches placed in a horizontal direction, exhibiting the perpendicular part of the cross, and the vertical scratches the horizontal part.

RINGS OF COLOURS ROUND A CANDLE.

Look at a candle through a plate of glass, upon which you have gently breathed, or over which are scattered particles of dust, or any fine powder, and you will perceive the flame surrounded with beautiful rings of colours. By using the seed of the lycopodium, or by placing a drop of blood diluted with water between two pieces of glass, the rings of colour will be still more finely exhibited. Round the luminous body there will be seen a light area, terminating in a reddish dark margin; this will be succeeded by a ring of bluish-green, and then by a red ring; these two last colours succeeding each other several times when the particles are of uniform diameter, as are the seeds of the lycopodium, each of which is but the 850th part of an inch in diameter.

SIMPLE AND CHEAP OPERA-GLASS.

In this new instrument, no tubes are necessary, as in the ordinary opera-glass; their place being supplied by a slender elastic conical spring of wire, into the upper extremity of which is inserted the eye-glass; the object-glass being fixed to the other extremity, as shown in the engraving. The two glasses must, of course, be kept parallel to each other when in use; which is very easily effected.

In using this opera-glass, rest the finger and thumb of one hand on the rim of the object-glass, B, whilst, with the thumb and finger of the other hand you hold the rim of the eye-glass, A. The spring tube may then be drawn out or shut up to very minute distances. Thus, the ordinary sliding tubes are superseded; nor is any external covering necessary, as the hand in grasping the instrument serves the purpose. If, however, a covering be preferred, a piece of silk may be sewn to the spirals of the spring.

This kind of opera-glass may be made very cheaply; it may be shut into a small space for the pocket, merely by pressing the object-glass and eye-glass together.

MULTIPLYING THEATRES.

Place two pieces of looking-glass, one at each end, parallel to one another, and looking over, or by the edge of one of them, the images of any objects placed on the bottom of the box, will appear continued to a considerable distance.

Or, line each of the four sides of the box with looking-glass, and the bottom of the box will be multiplied to an astonishing extent, there being no other limitation to the number of images but what is owing to the continued loss of light from reflection. The top of the box may be almost covered with thin canvas, which will admit sufficient light to render the exhibition very distinct.

The above experiments may be made very entertaining, by placing on the bottom of the box some toy, as sentry soldiers, &c.; and, if these be put in motion, by wires attached to them, or passing through the bottom or side of the box, it will afford a still more entertaining spectacle. Or the bottom of the box may be covered with moss, shining pebbles, flowers, &c.; only, in all cases, the upright figures between the pieces of looking-glass should be slender, and not too numerous, else they will obstruct the reflected light.

In a box with six, eight, or more sides, lined with looking-glass, as above, the different objects in it will be multiplied to an almost indefinite extent.

APPARATUS FOR WRITING IN THE DARK.

In this ingenious contrivance, A is a frame of wood, into the back and front of which are inserted two thin boards, the front one, B, reaching about half the height of the frame, and the back one being movable, by sliding in grooves, for better fixing the paper to be written on, C, to a roller at top, with a handle and ratchet working into a spring.

To use the apparatus, the paper is to be fixed on the roller, and a strip of lead, or other weight, suspended from the bottom of the paper, to keep it smooth: then, by resting the right hand on the edge of the board B, and turning, with the left hand, the ratchet, the distance of the lines may be regulated by the number of clicks caused by the spring on the ratchet. D, is a foot to support the apparatus, which, however, should be light enough to be held in the hand as a slate.

PORTABLE MICROSCOPE.

This cheap and useful instrument consists of a handle of hard wood, a, which is screwed into a brass piece, d, having, at its top, a ring, with screws on back and front, into which are to be screwed two cells with lenses of different foci. There is also a projecting piece formed on the side of the brass piece, d, in which is a hole to receive the screwed end of a cylindrical rod of brass, c. Upon this rod, a springing slit socket, e, slides backwards and forwards, and is also capable of being turned round. This socket has affixed to it, on one side, a projecting part, with a screwed cavity in it, to receive a short screwed tube, with a small hole in its centre, made to fit the steel stem of the spring forceps; a corresponding hole being made at the bottom of the screwed cavity, where is lodged a piece of perforated cork; which, being pressed upon by the action of the screw, closes upon the steel stem of the forceps, and steadies them, and the objects held in them. The stem of the forceps being removed from its place in the short tube; the handles and lenses, and the rod, c, and the sliding socket upon it, being unscrewed from its place in the handle; they can all three be packed in a black paper case, which is only three and a half inches long, one inch broad, and half an inch thick.

This microscope possesses three different magnifying powers, namely, those of two lenses separately, and the two in combination.

Microscopes of a still simpler nature are small globules of glass, formed by smelting the ends of fine threads of glass in the flame of a candle; and small globular microscopes of great magnifying power, made of hollow glass about the size of a small walnut, may be purchased very cheaply at the opticians’.

THE PHENAKISTISCOPE, OR STROBOSCOPE.

This amusing instrument consists of a turning wheel, upon which figures are seen to walk, jump, pump water, &c. The disc or wheel should be of stout card-board, upon which should be painted, towards the edge, figures in eight or ten postures. Thus, if it is wished to represent a man bowing, the first position is a man standing upright; in the second, his body has a slight inclination; in the third, still more; and so on, to the sixth position, where the body is most bent: the four following, represent the figure recovering its erect posture, so that the fifth and seventh, the fourth and eighth, the third and ninth, and second and tenth figures, have the same posture. Between each of the figures on the wheel, should be a slit, three-fourths of an inch long, and one-fourth of an inch wide, in a direction parallel with the radii of the wheel, and extending to an equal distance from the centre.

To work this instrument, place the figured side of the wheel before a looking-glass, and cause it to revolve upon its centre; then look through the slits or apertures, and you may observe, in the glass, the figures bowing continually, and with a rapidity proportionate to the rate at which the wheel turns. The illusion depends on the circumstance, that the wheel between each aperture is covered, while the figure goes further. That the deception may be complete, it is necessary that every part of the figures not bowing shall be at an equal distance from the centre of the wheel, and from the slits; also that the figures possess equal thickness and colour.

TO LOOK AT THE SUN WITHOUT INJURY.

Provide a wine-glass filled with plain water, which will keep off the heat so effectually, that the brightest sun may be viewed some time through it without any inconvenience. If a little black ink be added to the water, the image of the sun will appear through it, as white as snow; and when the ink is still more diluted, the sun will be of a purple hue.

BRILLIANT WATER MIRROR.

Nearly fill a glass tumbler with water, and hold it, with your back to the window, above the level of the eye, as in the engraving. Then look obliquely as in the direction E, a, c, and you will see the whole surface shining like burnished silver, with a strong metallic reflection; and any object, as a spoon, A C B, immersed in the water, will have its immersed part C B, reflected on the surface, as in a mirror, but with a brilliancy far surpassing that which can be obtained from quicksilver, or from the most highly-polished metals.

OPTICAL ILLUSION UNDER WATER.

Procure a large gallipot; place on the bottom, next the side furthest from you, a sixpence, and next to it, but towards the centre, a shilling; move to such a distance as will render the coins invisible; then let another person pour water gently in, and as it rises in the gallipot, it will cause both the sixpence and shilling to be seen, without your approaching nearer to the gallipot, or moving it towards you.

THE MAGIC WHEELS.

Cut out two card-board cog-wheels of equal size; place them upon a pin, and whirl them round with equal velocity in opposite directions; when, instead of producing a hazy tint, as one wheel would do, or as the two would if revolving in the same direction, there will be an extraordinary appearance of a fixed wheel. If the cogs be cut slantwise on both wheels, the spectral wheel, as it may be called, will exhibit slanting cogs; but if one of the wheels be turned, so that the cogs shall point in opposite directions, then the spectral wheel will have straight cogs. If wheels with radii, or arms, be viewed when moving, the deception will be similar; and however fast the wheels may move, provided it be with equal velocity, the magic of a fixed wheel will be presented.

Or, cut a card-board wheel with a certain number of teeth or cogs at its edge; a little nearer the centre, cut a series of apertures resembling the cogs in arrangement, but not to the same number; and still nearer the centre cut another series of apertures, different in number, and varying from the former. Fix this wheel upon another, with its face held two or three yards from an illuminated mirror; spin it round, the cogs will disappear, and a greyish belt, three inches broad, will become visible; but, on looking at the glass through the moving wheel, appearances will entirely change; one row of cogs, or apertures, will appear fixed, as if the wheel were not moving, whilst the other two will appear as if in motion; and, by shifting the eye, other and new effects appear.

These amusing deceptions were first experimented by Mr. Faraday. The simple apparatus for their exhibition may be purchased, for a trifling sum, of any respectable optician.

ACOUSTIC RAINBOW.

A sounding-plate, made of brass, nine inches long, and half a line in thickness, covered with a layer of water, may be employed to produce a rainbow in a chamber which admits the sun. On drawing a violin bow strongly across the plate, so as to produce the greatest possible intensity of tone, numerous drops of water fly perpendicularly and laterally upwards. The size of the drops is smaller as the tone is higher. The inner and outer rainbows are very beautifully seen in these ascending and descending drops, when the artificial shower is held opposite to the sun. When the eyes are close to the falling drops, each eye sees its appropriate rainbow; and four rainbows are perceived at the same time, particularly if the floor of the room is of a dark colour. The experiment succeeds best, if, when a finger is placed under the middle of the plate, and both of the angular points at one side are supported, the tone is produced at a point of the opposite side, a fourth of its length from one of its angles. An abundant shower of drops is thus obtained.

TRANSMISSION OF SOUND.

Suspend any sonorous body, as a bell, a glass, a silver spoon, or a tuning-fork, from a double thread, and put with the finger the extremities of the thread, one in each ear; if the body be then struck, the apparent loudness and depth of the sound will be surprising.

Again, if you shut your ears altogether, you will yet feel very sensible of the impression of any sound conveyed through the mouth, the teeth, or the head: if you put one end of a small stick or rod in the mouth, and touch with the other extremity a watch lying on the table, the beatings will become quite audible, though the ears be actually shut. So, also, if a log of wood be scratched at one end with a pin, a person who applies his ear to the other end will hear the sound distinctly.

Fogs and falling rain, but especially snow, powerfully obstruct the free propagation of sound; and the same effect is produced by a coating of fresh-fallen snow on the ground, though when glazed and hardened at the surface by freezing, it has no such influence.

Over water, or a surface of ice, sound is propagated with remarkable clearness and strength. Dr. Hutton relates, that on a quiet part of the Thames, near Chelsea, he could hear a person distinctly at 140 feet distance, while on the land the same could only be heard at 76 feet. Lieutenant Forster, in the third Polar expedition of Captain Parry, held a conversation with a man across the harbour of Port Bowen, a distance of 6696 feet, or about a mile and a quarter. This, however remarkable, falls short of what is related by Dr. Young, on the authority of the Rev. W. Derham, viz. that, at Gibraltar, the voice has been heard ten miles, perhaps, across the strait.

The cannonade of a sea-fight between the English and Dutch, in 1672, was heard across England as far as Shrewsbury, and even in Wales, a distance of upwards of 200 miles from the scene of action.

At Carisbrook Castle, in the Isle of Wight, is a well 210 feet in depth, and twelve feet in diameter, into which if a pin be dropped, it will be distinctly heard to strike the water. The interior is lined with very smooth masonry.

PROGRESS OF SOUND.

A stretched string, as that of a piano-forte, may be made to vibrate not only from end to end, but in aliquot parts, the portions being separated by points of rest which interrupted the progress of the sound. This kind of effect may be shown by shaking a long piece of cane in the air, when there will be one, two, or three points of rest, according to the mode of vibrating it.

An elastic surface has, likewise, some parts in motion and others at rest; and these parts may be made visibly distinct, by strewing pieces of bristle over them upon the sounding-board of an instrument.

When a bow is drawn across the strings of a violin, the impulses produced may be rendered evident by fixing a small steel bead upon the bow; when looked at by light or in sunshine, the bead will seem to form a series of dots during the passage of the bow.

SOUND TURNING CORNERS.

Take a common tuning-fork, strike it, and hold it, (when set in vibration,) about three or four inches from the ear, with the flat side towards it, when the sound will be distinctly heard; let a strip of card, somewhat longer than the flat of the tuning-fork, be interposed at about half an inch from the fork, and the sound will be almost entirely intercepted by it; and, if the card be alternately removed and replaced in pretty quick succession, alternations of sound and silence will be produced; proving that sound is by no means propagated with so much intensity round the edge of the card, as straight forward. Indeed, to be convinced of this fact, you have only to listen to the sound of a carriage turning a corner from the street in which you happen to be, into an adjoining one. Even where there is no obstacle in the way, sounds are by no means equally audible in all directions from the sounding body; as you may ascertain, by holding a vibrating tuning-fork or pitch-pipe near your ear, and turning it quickly on its axis.

TO TELL THE DISTANCE OF THUNDER.

Count, by means of a watch, the number of seconds that elapse between seeing the flash of lightning and hearing the report of the thunder; allow somewhat more than five seconds for a mile, and the distance may be ascertained. Thus, say the number of seconds is

or the distance may be estimated by remarking the number of beats of the pulse in the above interval; provided, of course, that we know the rate at which the pulse beats in a certain time. In a French work, it is stated that if the pulse beat six times, the distance of the thunder will be about 30,000 feet, or five miles and a half; thus reckoning 5000 feet for each pulsation.

In a violent thunder-storm, when the sound instantly succeeds the flash, the persons who witness the circumstance are in some danger; when the interval is a quarter of a minute, they are secure.

HEARING BY THE TOUCH.

If a deaf person merely place the tips of his finger-nails on the window-shutters or door of a room in which instruments are playing, he may enjoy their concert of harmony.

CONVERSATION FOR THE DEAF.

If two persons stop their ears closely, they may converse with each other by holding a long stick between their teeth, or by resting their teeth against them. The person who speaks may rest the stick against his throat or his breast; or he may rest the stick, which he holds in his teeth, against a glass tumbler or china basin into which the other speaks. The sound may also be heard when a thread is held between the teeth by both persons, so as to be somewhat stretched.

GLASS BROKEN BY THE VOICE.

On vibrating bodies, which present a large surface, the effects of sounds are very surprising. Persons with a clear and powerful voice have been known to break a drinking-glass, by singing the proper fundamental note of their voice close to it. Looking-glasses are also said to have been broken by music, the vibrations of the atoms of the glass being so great as to strain them beyond the limits of their cohesion.

FIGURES PRODUCED BY SOUND.

Stretch a sheet of wet paper over the mouth of a glass tumbler, which has a footstalk, and glue or paste the paper at the edges. When the paper is dry, strew dry sand thinly upon its surface. Place the tumbler on a table, and hold immediately above it, and parallel to the paper, a plate of glass, which you also strew with sand, having previously rubbed the edges smooth with emery powder. Draw a violin bow along any part of the edges, and as the sand upon the glass is made to vibrate, it will form various figures, which will be accurately imitated by the sand upon the paper; or, if a violin or flute be played within a few inches of the paper, they will cause the sand upon its surface to form regular lines and figures.

TRANSMITTED VIBRATION.