Part 5

Provide two glass bottles, and tune them by pouring water into them, so that each corresponds to the sound of a different tuning-fork. Then apply both tuning-forks to the mouth of each bottle alternately, when that sound only will be heard, in each case, which is reciprocated by the unisonant bottle, or, in other words, by that bottle which contains a column of air susceptible of vibrating in unison with the fork.

THEORY OF WHISPERING.

Apartments of a circular or elliptical form are best calculated for the exhibition of this phenomenon. If a person stand near the wall, with his face turned to it, and whisper a few words, they may be more distinctly heard at nearly the opposite side of the apartment, than if the listener was situated nearer to the speaker.

THEORY OF THE VOICE.

Provide a species of whistle, common as a child’s toy or a sportsman’s call, in the form of a hollow cylinder, about three-fourths of an inch in diameter, closed at both ends by flat circular plates, with holes in their centres. Hold this toy between the teeth and lips; blow through it, and you may produce sounds varying in pitch with the force with which you blow. If the air be cautiously graduated, all the sounds within the compass of a double octave may be produced from it; and, if great precaution be taken in the management of the wind, tones even yet graver may be brought out. This simple instrument or toy, has, indeed, the greatest resemblance to the larynx, which is the organ of voice.

A speaking-machine has been invented in Germany, with which have been distinctly pronounced the words, _mamma_, _papa_, _mother_, _father_, _summer_. This instrument consists of a pair of bellows, to which is adapted a tube terminating in a bell, the aperture of which is regulated by the hand, so as to produce the articulate sounds.

SOUND ALONG A WALL.

Whisper along the bare wall of an apartment, and you will be heard much further than in the middle of the room; for the trough or angle between the wall and the floor, forms two sides of a square pipe which conveys the sound.

SOUNDS MORE AUDIBLE BY NIGHT THAN BY DAY.

The experiment with the glass of champagne (page 40) has been employed by Humboldt, in explanation of the greater audibility of distant sounds by night than by day. This he attributes to the uniformity of temperature in the atmosphere by night, when currents of air no longer rise and disturb its equilibrium; as the air-bubbles in the champagne interfere with the vibration within the glass. Again, the universal and dead silence generally prevalent at night, renders our auditory nerves sensible to sounds which would otherwise escape them, and which are inaudible among the continual hum of noises which is always going on in the day time.

MUSICAL ECHO.

If a noise be made in a narrow passage, or apartment of regular form, the echoes will be repeated at equal very small intervals, and will always impress the ear with a musical note. This is, doubtless, one of the means which blind persons have of judging of the size and shape of any room they happen to be in.

VENTRILOQUISM.

The main secret of this surprising art simply consists in first making a strong and deep inspiration, by which a considerable quantity of air is introduced into the lungs, to be afterwards acted upon by the flexible powers of the larynx, or cavity situated behind the tongue, and the trachea, or windpipe: thus prepared, the expiration should be slow and gradual. Any person, by practice, can, therefore, obtain more or less expertness in this exercise; in which, though not apparently, the voice is still modified by the mouth and tongue; and it is in the concealment of this aid, that much of the perfection of ventriloquism lies.

But the distinctive character of ventriloquism consists in its imitations being performed by the voice _seeming_ to come from the stomach: hence its name, from _venter_, the stomach, and _loquor_, to speak. Although the voice does not actually come from that region, in order to enable the ventriloquist to utter sounds from the larynx without moving the muscles of his face, he strengthens them by a powerful action of the abdominal muscles. Hence, he speaks by means of his stomach; although the throat is the real source from whence the sound proceeds. It should, however, be added, that this speaking distinctly, without any movement of the lips at all, is the highest perfection of ventriloquism, and has but rarely been attained. Thus, MM. St. Gille and Louis Brabant, two celebrated French ventriloquists, appeared to be absolutely mute while exercising their art, and no change in their countenances could be discovered.

It has lately been shown, that some ventriloquists have acquired by practice the power of exercising the veil of the palate in such a manner, that, by raising or depressing it, they dilate or contract the inner nostrils. If they are closely contracted, the sound produced is weak, dull, and seems to be more or less distant; if, on the contrary, these cavities are widely dilated, the sound will be strengthened, the voice become loud, and apparently close to us.

Another of the secrets of ventriloquism, is the uncertainty with respect to the direction of sounds. Thus, if we place a man and a child in the same angle of uncertainty, and the man speaks with the accent of a child, without any corresponding motion in his mouth or face, we shall necessarily believe that the voice comes from the child. In this case, the belief is so strengthened by the imagination; for if we were directed to a statue, as the source from which we were to expect sounds to issue, we should still be deceived, and refer the sounds to the lifeless stone or marble. This illusion will be greatly assisted by the voice being totally different in tone and character from that of the man from whom it really comes. Thus, we see how easy is the deception when the sounds are required to proceed from any given object, and are such as they actually yield.

The ventriloquists of our time, as M. Alexander and M. Fitz-James, have carried their art still further. They have not only spoken by the muscles of the throat and the abdomen, without moving those of the face, but have so far overcome the uncertainty of sound, as to become acquainted with modifications of distance, obstruction, and other causes, so to imitate them with the greatest accuracy. Thus, each of these artists has succeeded in carrying on a dialogue; and each, in his own single person and with his own single voice, has represented a scene apparently with several actors. These ventriloquists have likewise possessed such power over their faces and figures, that, aided by rapid changes of dress, their personal identity has scarcely been recognised among the range of personations.

Vocal imitations are much less striking and ingenious than the feats of ventriloquism. Extraordinary varieties of voice may be produced, by speaking with a more acute or grave pitch than usual, and by different contractions of the mouth. Thus may be imitated the grinding of cutlery on a wheel, the sawing of wood, the frying of a pancake, the uncorking of a bottle, and the gurgling noise in emptying its contents.

FLASHES OF LIGHT UPON REVOLVING WHEELS.

PROVIDE a circle of card-board, six inches in diameter; divide it into sixteen parts, and paint them alternately red and black. Provide a second circle or disc of the same size, and paint on it, in large characters, the words “At rest,” on a white ground. Connect both discs with the simple apparatus for causing them to turn round, used in the construction of a toy windmill. Next fill a basin with water, and provide a few small pieces of phosphuret of lime: darken the room, hold the discs over the basin, and turn them round; let the phosphuret of lime be put into the water, and bubbles of light will rise to its surface. If they come up slowly, both discs will appear stationary during their turning round; but when the bubbles come up quickly, the black and red spaces will exhibit a dancing motion, and sometimes two black spaces will seem joined into one, to the exclusion of the intervening red, and _vice versâ_: the words on the second disc will also cross each other in various directions, when the flashes of light interfere; and, in both cases, confusion will be excited by an impression being made on the retina, before preceding impressions have departed.

DECOMPOSITION OF LIGHT.

Sir Isaac Newton first divided a white ray of light, and found it to consist of an assemblage of coloured rays, which formed an image upon a wall, and in which were displayed the following colours: red, orange, yellow, green, blue, indigo, and violet. Sir Isaac then showed that these seven colours, when again put together or combined, recomposed white light. This may be proved by painting a card wheel in circles with the above colours, and whirling it rapidly upon a pin, when it will appear white.

Light may also be decomposed by the following beautiful experiment: Form a tube about ten inches long and one inch in diameter, of paper, one side of which is of a bright blue colour. This may be done by wrapping the paper once round a cylinder of wood, and securing the edges of the paper with paste. The coloured side of the paper must be the interior of the tube. Apply this tube to one eye, the other being closed, and on looking at the ceiling, a circular orange spot will be seen, which is the result of decomposition: the white light from the ceiling enters the tube, the blue is retained, and the red and yellow rays enter the eye, and produce the impression of orange.

SOLAR REFRACTION.

The theory of solar refraction may be beautifully illustrated as follows: Put a shilling into a basin, and pour some water on it, when the silver will be refracted through the medium; and, if the vessel be filled, you may withdraw to any distance from which the surface of the water will be visible, and, by the refraction from it, you can still observe the shilling.

INCANTATIONS.

Dissolve crystals of nitrate of copper in spirit of wine; light the solution, and it will burn with a beautiful emerald-green flame: pieces of sponge soaked in this spirit, lighted and suspended by fine wires, produce the lambent green flames now so common in incantation scenes: strips of flannel saturated with it, and applied round copper swords, tridents, &c., produce, when lighted, the flaming swords and fire-forks, brandished by the demons in such scenes: indeed, the chief consumption of nitrate of copper is for these purposes.

TO IMITATE THE LIGHT OF THE SEA.

It is well known, that on dark, stormy nights, the sea emits a brilliant light, the effect of which may be thus imitated. Scrape off four drams of the substance of putrefying fish, as whiting, herring, or mackerel, and put it into a white glass bottle, containing two ounces of sea-water, or of pure water with two drams of common salt dissolved in it; set the bottle in a dark place, and in three days a ring of light will be seen on the surface of the liquid, and the whole, if shaken, will become luminous, and continue so for some time. If it be set in a warm place, the light will be brighter; if the liquid be frozen, the light will disappear, but will re-appear on being thawed.

If more salt be added to the solution, the light will disappear, but instantly burst forth from absolute darkness by dilution with water. Lime-water, common water, beer, acids, even very dilute alkaline leys, as pearl-ash or soda and water, will permanently extinguish this spontaneous light.

INSTANTANEOUS LIGHTS.

The oxygenated, or _chlorate matches_, are first dipped in melted sulphur, and then tipped with a paste made of chlorate of potass, sulphur, and sugar, mixed with gum-water, and coloured with vermilion: frankincense and camphor are sometimes mixed with the composition, and the wood of the match is pencil-cedar, so that a fragrant odour is diffused from the matches in burning. To obtain light, a match is very lightly dipped in a bottle containing a little asbestos soaked in oil of vitriol.

_Lucifers_ consist of chips of wood tipped with a paste of chlorate of potass mixed with sulphuret of antimony, starch, and gum-water: when a match is pinched between the folds of glass-paper, and suddenly drawn out, a light is instantly obtained.

_Prometheans_ consist of small rolls of waxed paper, in one end of which is a minute quantity of vitriol, in a glass bulb, sealed up, and surrounded with chlorate of potass: when the end thus prepared is pressed so as to break the bulb, the vitriol comes in contact with the composition, and produces light instantly.

For cigar-smokers, Prometheans are made with touch-paper; this ignites from the composition, and glows without flame, like a slow match; and as the wind will not extinguish it, a dry cigar may be readily lighted at it.

Lucifers and Prometheans must be used with caution, and should never be carelessly left about: by letting them fall upon a sanded floor, and being accidentally trod upon, they may take fire, and thus do great mischief.

TO COLOUR THE FLAME OF A CANDLE.

Take a piece of packthread, or cotton thread, boil it in clean water to free it from saline particles, and dry it; wet one end, and take upon it a little of either of the salts hereafter named, in fine powder, or strong solution. Then dip the wetted end of the thread into the cup of a burning wax candle, and apply it to the exterior of the flame, not quite touching the luminous part, but so as to be immersed in the cone of invisible but intensely heated air which envelopes it. Immediately, an irregular sputtering combustion of the wax on the thread will take place, and the invisible cone of heat will be rendered luminous, with a peculiarly coloured light, according to the salt employed.

Thus, common salt will give a bright yellow; muriate of potass will give a beautiful pale violet; muriate of lime will give a brick red; muriate of strontia will give a magnificent crimson; muriate of lithia will give a red; muriate of baryta will give a fine pale apple green; muriate of copper will give a beautiful bluish green; and green copperas will give a white light.

TO DIVIDE THE FLAME OF A CANDLE.

Provide about a foot square of brass or iron wire gauze, of the fineness of thirty meshes to the square inch: lower the gauze upon the flame of a wax candle, which will not rise through the meshes, but in its place will be the inflammable smoke of the flame; apply to this a piece of lighted paper, and it will be kindled, and the candle will burn with flame above and beneath the gauze. In this case, the gauze so cools the flame, as to extinguish it; and upon this principle is constructed the Davy Safety Lamp, in which the light is surrounded with wire-gauze.

To vary this experiment, place a chip of camphor in the centre of a piece of wire-gauze about a foot square, and hold it over the flame of a candle or lamp; when the vapour of the camphor will burn brightly upon the lower surface of the gauze, but cannot rise through it in consequence of its cooling power. Thus, the camphor lies upon the gauze in an uninflamed state, though it is sufficiently heated to yield inflammable vapour to feed a flame beneath.

CANE WICK LAMP.

Cut a piece of cane about one inch long: set it upright in spirit of wine, with a small portion just above the surface: the spirit will then rise through the tube of the cane, which being lighted, will burn as a wick.

CAMPHOR AND PLATINUM LAMP.

Place a small piece of camphor, or a few fragments, upon the bottom of a glass, and lay upon the camphor a piece of coiled or pressed up platinum wire, heated in the flame of a lamp; when the platinum will glow brilliantly as long as any camphor remains, and frequently light up into flame.

PLATINUM AND ETHER LAMP.

Put into a small hyacinth-glass a teaspoonful of ether, and suspend in it, by wire, a coil of fine platinum wire, first heated in the flame of a spirit-lamp; the wire will then glow with a red heat, and some of it may become white hot; in the latter case, flame will be produced by the ether burning.

FLOATING LIGHT.

Cut a chip of camphor; light it, and set it on a basin of water, when it will continue to burn and float, until it is consumed.

SUBSTITUTE FOR A WAX TAPER.

Steep a loosely twisted cotton skein in a solution of nitre; dry it, and it will readily kindle by the sparks produced from the flint and steel. If, however, the cotton be further prepared by coating portions of it, at regular intervals, alternately with sulphur and white wax, and the sparks be struck upon the sulphur, it will readily kindle, and as readily light the wax; and the flame will endure long enough for sealing a letter.

PHOSPHORESCENT FISH.

Place a very stale fish in a dark room, and it will give out a strong light, because of the numerous animalculæ, whose growth the putrefaction has promoted.

THE LUMINOUS SPECTRE.

Phosphorus in its pure state should be very cautiously handled; as, unless used very moderately, it will burn the skin. By adding to it, however, six parts of olive oil, it may be employed with perfect safety. If every part of the face, except the eyes and mouth, which should be kept shut while applying it, be anointed with this mixture, it will give the party a most frightful appearance in the dark. The eyes and mouth will seem black, and all the other parts of the face will appear lighted with a sickly, pale-bluish flame.

LIGHT, A PAINTER.

Strain a piece of paper or linen upon a wooden frame, and sponge it over with a solution of nitrate of silver in water; place it behind a painting upon glass, or a stained window-pane, and the light, traversing the painting or figures, will produce a copy of it upon the prepared paper or linen; those parts in which the rays were least intercepted being the shadows of the picture.

EFFECT OF LIGHT UPON CRYSTALLIZATION.

Place a solution of nitre in a small basin of water, in a room which has the light admitted only through a small hole in the window-shutter; crystals will then form most abundantly upon the side of the basin exposed to the aperture through which the light enters; and often the whole mass of crystals will turn towards it. This peculiar effect may also be seen in the crystals in camphor glasses in druggists’ windows, which are always most copious upon the side exposed to the light.

EFFECT OF LIGHT ON PLANTS.

Shut a plant up in a room into which light is only admitted through a small hole in the window-shutter, and set the plant out of the direction of this light; it will, in a short time, turn itself, and even grow downwards, that it may expose its leaves to the light.

If plants be kept in darkness, they will soon become bleached; then, if they be exposed to the sun for three, four, or five hours, the leaves and stalks will become as intensely green as if the plants had been reared in the sun. Again, if a lighted lamp be introduced into a dark room, wherein a plant has been shut up and bleached, it will become green, and direct itself towards the lamp. If such a plant be removed from the room, exposed for some time to the sun, and then returned to darkness, it will no longer support the privation of light, but will fade and perish.

INSTANTANEOUS LIGHT UPON ICE.

Throw upon ice a small piece of potassium, and it will burst into flame. In one experiment, the operator pressed the potassium on the ice with a penknife, when the whole length of the ice became ignited.

WHITE LIGHT FROM ZINC.

As a substance for light, zinc is far superior to any of the metals. The light which it yields on burning is as bright as that of the sun, and as white, so that the eye can scarcely endure it; and the effect is much increased by the great quantity of silvery smoke which reflects the fire, and thus widely increases the sphere of illumination. Zinc may be used in thin sheets, or in filings.

BRILLIANT LIGHT FROM TWO METALS.

Wrap a small piece of platinum in a piece of tin-foil of the same size, and expose them upon charcoal to the action of the blow pipe; when the union of the two metals will be accompanied by a rapid whirling, and by a remarkably brilliant light. If the globule thus melted be allowed to drop into a basin of water, it will remain for some time red hot at the bottom of it.

BRILLIANT LIGHT FROM STEEL.

Pour into a watch-glass a little sulphuret of carbon, and light it; hold in the flame a brush of steel-wire, and it will burn beautifully. A watch-spring may also be burnt in it.

LIGHTED TIN.

Place upon a piece of tinfoil a few powdered crystals of nitrate of copper; moisten it with water; fold up the foil gently, and wrap it in paper so as to keep out the air: lay it upon a plate, and the tin will soon inflame.

LIGHT FROM GILT BUTTONS.

Provide a new and highly-polished gilt button, and hold it in a strong light, closely but obliquely, over a sheet of white paper, when it will present radiations exactly like the spokes of a carriage-wheel; the radiations being sixteen in number, and a little contracted in the centre opposite the eye of the button, and presenting altogether a beautiful appearance.

LIGHT FROM A FLOWER.

Hold a lighted candle to the flower of the _fraxinella_, and it will dart forth little flashes of light. This beautiful appearance is caused by the essential and inflammable oil contained in small vessels at the extremities of the flower, which vessels burn at the approach of any inflamed body, setting at liberty the essential oil, as that contained in orange-peel is discharged by pressure.

LIGHT FROM SUGAR.

Simply break a bit of lump sugar between the fingers in the dark, and light will be produced at the moment of fracture.

Or, if powdered loaf sugar be put into a spoon, fused, and kindled in the flame of a lamp, it will exhibit a fine jet of flame.

LIGHT FROM THE POTATO.

Place a few potatoes in a dark cellar, and when they become in a state of putrefaction, they will give out a vivid light sufficient to read by. A few years since, an officer on guard at Strasbourg thought the barracks were on fire, in consequence of the light thus emitted from a cellar full of putrefying potatoes.

LIGHT FROM THE OYSTER.

Open an oyster, retain the liquor in the lower or deep shell, and if viewed through a microscope, it will be found to contain multitudes of small oysters, covered with shells, and swimming nimbly about; one hundred and twenty of which in a row would extend but one inch. Besides these young oysters, the liquor contains a variety of animalculæ, and myriads of three distinct species of worms, which shine in the dark like glow-worms. Sometimes their light resembles a bluish star about the centre of the shell, which will be beautifully luminous in a dark room.

LIGHT FROM DERBYSHIRE SPAR.

Pound, coarsely, some of the dark blue or the fetid variety of Derbyshire spar; heat it in a dark room, in a platinum spoon, over the low flame of a spirit-lamp, and the spar will shine with a beautiful purple tint.

Pounded swinestone, calcareous spar, and powdered quartz, will also give out light, if strewn upon a fire-shovel which has been heated red-hot, and has just ceased glowing.

A variety of fluor spar, found in granite in Siberia, will shine in the dark when warmed, with a remarkably strong phosphorescent light, increasing as the temperature is raised. The light augments when the spar is plunged into water; and in boiling water, the spar becomes so luminous that the letters of a printed book can be seen in a dark room near the glass containing it.

Another variety of fluor spar, also found in Siberia, is of a pale violet colour, and emits a white light merely by the heat of the hand; and when put into boiling water, it will give out a green light.

LIGHT FROM OYSTER-SHELLS.