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LAUGHING GAS.

THE above fanciful appellation has been given to nitrous oxide, from the very agreeable sensations excited by inhaling it. In its pure state it destroys animal life, but loses this noxious quality when inhaled, because it becomes blended with the atmospheric air which it meets in the lungs. This gas is made by putting three or four drams of nitrate of ammonia, in crystals, into a small glass retort, which being held over a spirit lamp, the crystals will melt, and the gas be evolved.

Having thus produced the gas, it is to be passed into a large bladder having a stop-cock; and when you are desirous of exhibiting its effects, you cause the person who wishes to experience them, to first exhale the atmospheric air from the lungs, and then quickly placing the cock in his mouth, you turn it, and bid him inhale the gas. Immediately, a sense of extraordinary cheerfulness, fanciful flights of imagination, an uncontrollable propensity to laughter, and a consciousness of being capable of great muscular exertion, supervene. It does not operate in exactly the same manner on all persons; but in most cases the sensations are agreeable, and have this important difference from those produced by wine or spirituous liquors, that they are not succeeded by any depression of mind.

THE LUMINOUS WAND.

Cover a long slip of wood, half-way, with sulphur, by immersion while in a melted state. Having prepared a jar of nitrous oxide gas, as in preceding experiments, light the sulphur, and plunge the wand into the jar. The gas will extinguish the flame. Withdraw the wand, light it again, and when the flame is very brilliant, immerse it again in the jar. It will this time burn with great splendour, and of a beautiful red colour.

TO MAKE CARBONIC ACID GAS.

Put about an ounce of marble in small lumps, into an eight ounce phial, with about an equal quantity of water; pour in a little muriatic acid, and carbonic acid gas will be evolved.

CARBONIC ACID GAS IN WINE OR BEER VESSELS.

The apparently empty or upper part of vessels in which wine or beer is working, is filled with this deleterious gas; for its great weight prevents its ascent from the fermenting liquid. A variety of striking but simple experiments may be made with the gas in this condition. Lighted paper, or a candle dipped into it, will be immediately extinguished; and the smoke remaining in the carbonic acid gas will render its surface visible, which may be thrown into waves by agitation, like water. In consequence of the great weight of the carbonic acid gas, it may be taken from a vat of fermenting liquor, in a jug or bottle, and in the latter, if well corked, it may be conveyed to great distances; or the gas may be drawn out of a vessel by a cock, like a liquid.

TO EXTINGUISH FLAME WITH GAS.

The effects produced by pouring carbonic acid gas from one vessel to another, have a very singular appearance: if a lighted candle be placed in a jar, and the gas be poured upon it, the flame will be extinguished in a few seconds, though the eye is incapable of distinguishing that anything is poured out.

EFFECT OF HYDROGEN ON THE VOICE.

Make a hole through a wine cork of sufficient size to admit a smaller cork; through which make another hole, and fix it into the larger one. Tie the corks thus fixed into the neck of a bullock’s bladder, previously exhausted of air; let a tube from a bottle generating hydrogen pass very tightly through the aperture in the small cork, and the gas will distend and fill the bladder. The instant it is full, withdraw the inner cork, and either prevent the escape of the gas by means of the thumb, or cork it closely, till the operator is ready to breathe the gas; to do which, he should put the open cork into his mouth, and take one inspiration, when, on immediately speaking, his voice will be remarkably shrill. The effect will pass off in a few seconds.

MAGIC TAPER.

Provide a piece of copper wire, about ten inches long, and fix at one end of it a piece of wax taper: take a pint bottle of hydrogen, and place the mouth downwards; light the taper, introduce it into the bottle, and the gas will take fire, and burn slowly towards the mouth, where it is in contact with the air. If, however, the taper be passed up into the bottle, it will be extinguished; but, on gently withdrawing it through the burning hydrogen, the wick will be rekindled. This may be done several times in succession with the same portion of gas.

THE GAS CANDLE.

Provide a strong glass bottle which will contain about eight ounces, or half a pint, into which put a few pieces of zinc; then mix half an ounce of sulphuric acid with four ounces of water, and pour it into the bottle upon the zinc; fit the mouth closely with a cork, through which put a metal tube which ends upward in a fine opening: the mixture in the bottle will soon effervesce, and hydrogen gas will rise through the tube. When it has escaped for about a minute, apply a lighted paper to the tube, and the gas will burn like a candle, but with a pale flame. Its brightness may be increased to brilliance, by sifting over it a small quantity of magnesia.

GAS BUBBLES.

Provide a bladder, fill it with hydrogen gas, to be made as for the last experiment, and fit the end of a tobacco-pipe closely into the bladder; dip the bowl of the pipe into soap and water, and, by pressing the bladder, soap-bubbles will be formed, filled with hydrogen gas; which bubbles, or balloons, will rise in the air, and keep there for some time.

GAS-LIGHT IN THE DAY-TIME.

Light a stream of hydrogen gas, and it will be scarcely visible in the day-light; but place in it a small coil of platinum wire, or project a little oxide of zinc through the flame, and it will become very luminous.

MINIATURE BALLOONS.

One of the simplest and most beautiful experiments in aËrostation, is to take a turkey’s maw, or stomach, properly prepared, and to fill it either with pure hydrogen gas, or the carburetted hydrogen produced from coal. If the balloon be then allowed to escape in the open air, it will ascend rapidly in the atmosphere: but the best method of showing the experiment, is to let the balloon off a high staircase, and observe it ascend to the cupola or light, where it will remain near the highest point till the escape of the gas allow it to descend. The prepared maw for this balloon may be purchased of any optician.

MINIATURE GAS-LIGHTING.

Bicarburetted hydrogen is the principal constituent of the gas burned in the streets: it is procured from coal, and the process may readily be performed on a small scale. Put about two ounces of pounded coal into an earthen retort, and fix a glass tube into the neck, terminating in an aperture of one-fifth of an inch in diameter; heat the retort red-hot, and apply the flame of a taper to the orifice of the tube, when the gas will burn with a bright white light, very different from that afforded by the combustion of hydrogen; a circumstance owing to the presence of particles of carbon in the carburet, which being intensely ignited, are highly luminous.

It is no less strange than true, that bicarburetted hydrogen, the substance which we so largely consume to illuminate our towns, is ether when united to water in one proportion, and spirit when combined with it in another; a fluid which constitutes the strength of all wines, beer, and fermented liquors.

MUSICAL GAS.

Into a half-pint glass bottle, put some zinc, granulated by being melted in a ladle, and then poured gradually into water. Add some sulphuric acid, diluted with eight parts by weight of water. Then pass a glass tube with a capillary bore, through a cork, which you have previously made to closely fit the bottle, and cork the bottle well. In a short time, the atmospheric air will be expelled, and hydrogen gas will rise through the tube; you then apply a light, and the gas will become ignited. If you now hold another glass tube, about eighteen or twenty inches long over the flame sufficiently wide to enclose the other tube very loosely (see engraving), the little speck of flame will sport along the larger tube, and musical sounds will be produced, which may be varied by using other tubes of different dimensions, and made of different materials; the wide tubes forming the lower, and the narrow tubes the upper notes.

MINIATURE WILL O’-THE-WISP.

Put a small piece or two of the phosphuret of lime into a saucer of water, when bubbles of phosphuretted hydrogen gas will rise to the surface, explode into flame, and cause a white smoke; representing, on a small scale, the ignis fatuus, or will o’-the-wisp, as seen over marshy ground, or stagnant pools of water.

PHOSPHORIC ILLUMINATION.

A light so brilliant that the eye can scarcely bear to contemplate it, is produced by the immersion of phosphorus in oxygen gas. To perform this experiment, you place a piece of phosphorus in a copper cup, of the circumference of a sixpence, which is fastened to a thick piece of iron wire, attached to a cork which fits a bottle (as in the foregoing experiment) filled with oxygen gas. Set fire to the phosphorous, and quickly plunge it into the bottle; when the splendour of the combustion will be surpassingly beautiful.

It is necessary to observe, that the heat is so excessive, that if the piece of phosphorous in this experiment be larger than a small pea, there will be great danger of breaking the bottle.

COMBUSTION OF IRON IN OXYGEN GAS.

Twist a piece of fine iron wire, such as is used by piano-forte makers, round a cylindrically-shaped piece of wood or metal, which will give it a spiral form; or a broken watch-spring, which may be bought for a trifle of the watch-makers, will answer the same purpose. Fasten round one end of it some waxed cotton thread or twine, and attach the other end to a cork, which fits a glass jar or bottle, that will hold a quart, filled with oxygen gas. Having made the wire red-hot by setting light to the thread, plunge it into the bottle. Do not cork the bottle, but let the cork merely lay on the mouth, and to prevent its being burned, a small a piece of lead should be fastened to the bottom of it. The iron will instantly begin to burn with great brilliancy, throwing out luminous scintillations.

To prevent the bottle from being broken by the sparks, a small quantity of sand should be previously poured into it.

GLOW-WORM IN OXYGEN GAS.

If a glow-worm be placed in a jar of oxygen gas, in a dark room, it will shine with a far surpassing brilliancy to that which it exhibits in atmospheric air.

LUMINOUS CHARCOAL.

Attach a small piece of charcoal to the end of a copper-wire; make it red-hot, and immerse it in a jar of oxygen gas. The charcoal will burn with great brilliance, throwing out splendid scintillations. The bark of the wood converted into charcoal must be selected, otherwise there will be no scintillations.

BRILLIANT COMBUSTION IN OXYGEN.

Place in a bottle of oxygen gas a lighted taper, and it will burn with a flame of increased brilliancy.

Extinguish the taper immediately; put it into the same or another bottle of oxygen, and it will be again lighted provided a spark remain on the wick.

Bend a piece of iron wire in a spiral form, and tie on to one end some cotton or flax; sprinkle some flour of sulphur on it, set it on fire, dip it into a bottle of oxygen gas, and beautiful corruscations will be thrown off the wire.

FLAME FROM COLD METALS.

Provide a bottle of the gas chlorine, which may be purchased of any operative chemist, and with it you may exhibit some brilliant experiments.

For example, reduce a small piece of the metal antimony to a very fine power in a mortar; place some of this on a bent card, then loosen the stopper of the bottle of chlorine, and throw in the antimony, it will take fire spontaneously, and burn with much splendour; thus exhibiting a cold metal spontaneously bursting into flame.

If, however, a lump of antimony be dropped into the chlorine, there will be no spontaneous combustion, nor immediate change: but, in the course of time, the antimony will become incrusted with a white powder, and no chlorine will be found in the bottle.

Or, provide copper in fine leaves, known as “Dutch metal;” slightly breathe on one end of a glass rod, about ten inches long, and cause one or two leaves of the metal to adhere to the damp end; then open a bottle of chlorine, quickly plunge in the leaves, when they will instantly take fire, and burn with a fine red light, leaving in the bottle a greenish-yellow solid substance.

A small lump of copper, or “Dutch metal,” will not burn as above, but will be slowly acted upon, like the antimony.

Immerse gold leaf in a jar of chlorine gas, and combustion with a beautiful green flame will take place.

PHOSPHORUS IN CHLORINE.

Put into a deflagrating spoon about four grains of phosphorus, and let it down into a bottle of chlorine, when the phosphorus will ignite instantaneously.

Or, fold a slip of blotting-paper into a match five inches long; dip it into oil of turpentine, drain it an instant, drop it into another bottle of chlorine, when it will burst into a flame, and deposit much carbon.

CAOUTCHOUC BALLOONS.

Put a little ether into a bottle of caoutchouc, close it tightly, soak it in hot water, and it will become inflated to a considerable size. These globes may be made so thin as to be transparent.

A piece of caoutchouc, the size of a walnut, has thus been extended to a ball fifteen inches in diameter; and a few years since, a caoutchouc balloon, thus made, escaped from Philadelphia, and was found 130 miles from that city.

TO INCREASE THE LIGHT OF COAL GAS.

Lay a piece of wire-gauze upon the glass chimney of a common argand gas burner, when the flame will be enlarged to twice its former dimensions, and its light fully doubled. If the experiment be made with a common argand oil-lamp, the flame will be often enlarged, but so discoloured as to yield less light.

GAS FROM INDIAN RUBBER.

Put caoutchoucine, or the spirit distilled from caoutchouc, or Indian rubber, into a phial, little more than sufficient to cover the bottom, and the remainder of the phial will be filled with a heavy vapour; pour this off the spirit into another phial, apply to it a piece of lighted paper, and the vapour will burn with a brilliant flame.

ETHER GAS.

Let fall a few drops of ether into a large drinking-glass, and cover it with a plate for a few minutes; during this time the glass will be filled with vapour from the ether, so that, on removing the plate, and applying a piece of lighted paper at the mouth of the glass, the invisible vapour will take fire; thus proving how readily a volatile fluid, such as ether, combines with the air.

MAGIC VAPOUR.

Provide a glass tube, about three feet long and half an inch in diameter, nearly fill it with water, upon the surface of which pour a little coloured ether; then close the open end of the tube carefully with the palm of the hand, invert it in a basin of water, and rest the tube against the wall: the ether will rise through the water to the upper end of the tube; pour a little hot water over the tube, and it will soon cause the ether to boil within, and its vapour may thus be made to drive nearly all the water out of the tube into the basin; if, however, you then cool the tube by pouring cold water over it, the vaporized ether will again become a liquid, and float upon the water as before.

GAS FROM THE UNION OF METALS.

Nearly fill a wine-glass with diluted sulphuric acid, and place in it a wire of silver and another of zinc, taking care that they do not touch each other; when the zinc will be changed by the acid, but the silver will remain inert. But, cause the upper ends of the wires to touch each other, and a stream of gas will issue from them.

INVISIBLE GASES MADE VISIBLE.

Pour a little sulphuric acid upon some common salt in a saucer. Into another saucer put a mixture of about two parts of quick-lime and one of sal ammoniac, both in powder, adding to these a very small quantity of boiling water. Each saucer apart will yield an invisible gas: but the moment they are brought closely together, very visible vapours will be the result.

LIGHT UNDER WATER.

Put into an eau de Cologne bottle two drams of chlorate of potass, and upon that salt about a dozen chips of phosphorous, and fill up the bottle with cold water: provide a glass tube which will reach to the potass, through which pour half-an-ounce, by measure, of strong sulphuric acid, when a gas will instantly rise, give to the liquid a deep yellow colour, and inflame the phosphorous in a striking manner.

GASEOUS EVANESCENCE.

Add a tea-spoonful of fuming nitric acid to two tea-spoonfuls of spirit of wine, in a cup, and the liquids will presently disappear in the form of vapour.

VIOLET-COLOURED GAS.

Put three or four grains of iodine into a small clean Florence oil flask, and close it with a cork. Warm the flask gently over a candle, or before the fire, and the iodine will become converted into a beautiful violet-coloured vapour, which condenses again into brilliant metallic crystals, when the flask is suffered to become cold. The experiment may be repeated with the same flask for any number of times.

Or, upon a small sheet of any metal, place a few grains of iodine, and add a chip of dry phosphorous; when the latter will inflame, and the iodine pass off in a violet vapour.

TO COLLECT GASES.

Provide a moistened bladder, tie a piece of tobacco-pipe firmly into its neck, twisting it so as to expel the common air. This may be fitted to any vessel by means of the pipe, which may be fixed in the cork of a bottle containing gas, and closely luted with putty or clay, or powdered lime and white of egg.

THE DEFLAGRATING SPOON.

To introduce substances into gases, a deflagrating spoon is required. It may be bought for half-a-crown; but an instrument equally useful may be made as follows: cut a piece of sheet copper somewhat larger than a sixpence, and bend it into a shallow, cup-like form; twist four fine brass wires, each nine inches long, tightly together, leaving an inch at the extremities, which must be spread to hold the copper, as the strings or chains of a balance support the scale-pan. To complete it, take a piece of sheet-lead, the size of a penny-piece; make a hole through the centre large enough to admit the twisted wires, but, at the same time, retaining them firmly in their position: then, if the wires will not rest in the lead by adhesion, the hole may be enlarged, the wire put in, and secured by a piece of solder. The spoon being then let down through the mouth of a bottle, the circular piece of lead rests upon and stops the mouth.

WHAT IS STEAM?

Invert a glass goblet over a cup of hot water, when the vapour or steam will be seen to rise in it, to condense upon the cold glass, and then to run down its inside; thus showing that steam is vaporized water, and will, when the heat is abstracted from it, become water again.

THE STEAM-ENGINE SIMPLIFIED.

The steam-engine is much more intelligible than its name first suggests. That part by which the machinery is set in motion, may be compared to a syringe, or squirt, the rod of which is driven up and down by steam admitted above and below, one end of the rod being connected with the machinery to be worked. Thus, the piston is made to turn the wheels of a railway carriage, or the paddles of a steam-boat.

The elastic force of the steam, or vapour, by which the rod is driven up and down, may be explained by this simple experiment. Provide a test tube, put into it a little water, hold the thumb over the mouth, and cause the water to boil by holding it over a spirit-lamp. There will soon be felt a pressure against the thumb; when, if the tube be dipped into cold water, the thumb being still held at the end, a kind of suction will be felt against it. Now, the tube resembles the cylinder of the steam-engine, in which the piston moves up and down; to imitate which, wrap a little tow about the end of a piece of stick, grease it with tallow, and fit it moderately tight into the tube; when the water is made to boil, the stick will be raised, and when the end is dipped into cold water, the stick will fall as the piston rises and falls in the cylinder.

TO BOIL WATER BY STEAM.

Nearly fill a retort with water, and boil it over a lamp; then immerse the beak into a tumbler of cold water, and the disengaged steam will raise the water to the boiling temperature, though it be at a distance from the source of heat.

DISTILLATION IN MINIATURE.

Fill a kettle with water, and set it on the fire; fix a long metal tube to the spout, and as soon as the water boils, the steam will pass into the tube, and being condensed into water, will drip at the other end of the tube, which corresponds with the worm in the still; it soon, however, becomes as hot as the water, and then the condensation will cease: but, were the tube passed through cold water, as is the worm of the still in a tub, the whole water in the kettle might be boiled away, but reproduced in the tube, and collected from it without the loss of a drop. This simple process resembles distillation, and the kettle and tube the still.

CANDLE OR FIRE CRACKERS.

Provide a number of little glass bulbs, put into each a drop of water, and seal it up; if it be then put into the flame of a candle, or the fire, the heat will soon convert the water into steam, and cause the bulb to burst with a loud report.

STEAM FROM THE KETTLE.

Observe attentively the steam that escapes from the spout of a tea-kettle, at the moment the water begins to boil, and you will perceive the steam to be condensed in minute drops on the interior edges of the spout. A few moments afterwards, provided the water continue to boil, the spout of the kettle will become perfectly dry; and, at the same time, close to it, there will be a certain space, say from one-half to three-fourths of an inch, throughout which not a particle of steam will be perceptible. This may be easily explained. When the water in the kettle begins to boil, the spout being cooler than the steam issuing from it, a portion of that steam is condensed. As more steam escapes, the metal soon becomes as hot as the steam, will no longer condense it, and the spout becomes dry. By this time the steam will displace the air immediately opposite the orifice of the spout, whence it will issue dry and invisible. As it is cooled by mixing with the surrounding air, it assumes its well-known cloudy appearance.

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COLOURED FLAMES.

A VARIETY of rays of light is exhibited by coloured flames, which are not to be seen in white light. Thus, pure hydrogen gas will burn with a blue flame, in which many of the rays of light are wanting. The flame of an oil-lamp contains most of the rays which are wanting in sunlight. Alcohol, mixed with water, when heated or burned, affords a flame with no other rays but yellow. The following salts, if finely powdered, and introduced into the exterior flame of a candle, or into the wick of a spirit-lamp will communicate to flame their peculiar colours:

Or, either of the above salts may be mixed with spirit of wine, as directed for Red Fire.

YELLOW FLAME.

Burn spirits of wine on common table salt or saltpetre.

ORANGE-COLOURED FLAME.

Burn spirit of wine on chloride of calcium, a substance obtained by evaporating muriate of lime to dryness.

EMERALD GREEN FLAME.

Burn spirit of wine on a little powdered nitrate of copper.

INSTANTANEOUS FLAME.

Heat together potassium and sulphur, and they will instantly burn very vividly.

Heat a little nitre in a fire-shovel, sprinkle on it flour of sulphur, and it will instantly burn. If iron filings be thrown upon red-hot nitre, they will detonate and burn.

Pound, separately, equal parts of chlorate of potash and lump sugar; mix them, and put upon a plate a small quantity; dip a thread into sulphuric acid, touch the powder with it, and it will burst into a brilliant flame.

Or, put a few grains of chlorate of potash into a table-spoonful of spirit of wine; add one or two drops of sulphuric acid, and the whole will burst into a beautiful flame.

THE CUP OF FLAME.

Put a little newly calcined magnesia into a tea-cup upon the hearth or hob, and suddenly pour in as much concentrated sulphuric acid as will cover the magnesia; in an instant, sparks will be thrown out, and the mixture will become completely ignited. To prevent accidents, the phial containing the sulphuric acid should be tied to the end of a long stick.

TO COOL FLAME BY METAL.

Encircle the very small flame of a lamp with a cold iron wire, which will instantly cause its extinction.

PROOF THAT FLAME IS HOLLOW.

Pour some spirit of wine into a watch-glass, and inflame it; place a straw across this flame, and it will only be ignited and charred at the outer edge; the middle of the straw will be uninjured, for there is no ignited matter in the centre of the flame.

Or, introduce into the middle of the flame one end of a glass tube, when the vapour will rise through it, and may be lighted at the other end of the tube.

CAMPHOR SUBLIMED BY FLAME.

Set a metallic plate over the flame of a spirit-lamp; place upon it a small portion of camphor under a glass funnel; and the camphor will be beautifully sublimed by the heat of the lamp, in an efflorescent crust on the sides of the funnel.

GREEN FIRE.

A beautiful green fire may be thus made. Take of flour of sulphur, thirteen parts; nitrate of baryta, seventy-seven; oxymuriate of potassa, five; metallic arsenic, two; and charcoal, three. Let the nitrate of baryta be well dried and powdered; then add to it the other ingredients, all finely pulverized, and exceedingly well mixed and rubbed together. Place a portion of the composition in a small tin pan, having a polished reflector fitted to one side, and set light to it; when a splendid green illumination will be the result. By adding a little calamine, it will burn more slowly.

BRILLIANT RED FIRE.

Weigh five ounces of dry nitrate of strontia, one ounce and a half of finely-powdered sulphur, five drams of chlorate of potash, and four drams of sulphuret of antimony. Powder the chlorate of potash and the sulphuret of antimony separately in a mortar, and mix them on paper; after which, add them to the other ingredients, previously powdered and mixed. No other kind of mixture than rubbing together on paper is required. For use, mix with a portion of the powder a small quantity of spirit of wine, in a tin pan resembling a cheese-toaster, light the mixture, and it will shed a rich crimson hue: when the fire burns dim and badly, a very small quantity of finely-powdered charcoal or lamp-black will revive it.

PURPLE FIRE.

Dissolve chloride of lithium in spirit of wine; and when lighted, it will burn with a purplish flame.

SILVER FIRE.

Place upon a piece of burning charcoal a morsel of the dried crystals of nitrate of silver, (not the lunar caustic,) and it will immediately throw out the most beautiful sparks that can be imagined, whilst the surface of the charcoal will be coated with silver.

THE FIERY MOUNTAIN.

Put into a glass tumbler fifteen grains of finely granulated zinc, and six grains of phosphorus cut into very small pieces, beneath water. Mix in another glass, gradually, a dram of sulphuric acid with two drams of water. Remove both glasses into a dark room, and there pour the diluted acid over the zinc and phosphorus in the glass: in a short time, beautiful jets of bluish flame will dart from all parts of the surface of the mixture; it will become quite luminous, and beautiful luminous smoke will rise in a column from the glass; thus representing a fountain of fire.

THE ARTIFICIAL CONFLAGRATION.

Put into a small, narrow-necked earthen bottle, half an ounce of muriate of ammonia, an ounce of camphor, and two ounces of highly rectified spirit of wine; set fire to it, and the room will seem to be in flames. This experiment should be performed in the dark.

INFLAMMABLE POWDER.

Heat a small portion of the grey powder of aluminum, and it will ignite, inflame, and burn with great rapidity. Or, blow a little of this powder into the flame of a candle, and it will produce a small shower of sparks, brilliant as those from iron filings.

COMBUSTION WITHOUT FLAME.

Light a small green wax-taper; in a minute or two, blow out the flame, and the wick will continue red-hot for many hours; and, if the taper were regularly and carefully uncoiled, and the room kept free from currents of air, the wick would burn on in this manner until the whole taper were consumed. The same effect is not produced when the colour of the wax is red, on which account, red wax-tapers are safer than green; for the latter, if left imperfectly extinguished, may set fire to any object with which they are in contact.

COMBUSTION OF THREE METALS.

Mix a grain or two of potassium with an equal quantity of sodium; add a globule of quicksilver, and the three metals, when shaken, will take fire, and burn vividly.

TO MAKE PAPER INCOMBUSTIBLE.

Take a smooth cylindrical piece of metal, about one inch and a half in diameter, and eight inches long; wrap very closely round it a piece of clean writing paper, then hold the paper in the flame of a spirit-lamp, and it will not take fire; but it may be held there for a considerable time, without being in the least affected by the flame.

SINGULAR EXPERIMENTS WITH GLASS TUBES.

A most remarkable phenomenon is produced in glass tubes, under certain circumstances. When these are laid before a fire in a horizontal position, having their extremities properly supported, they acquire a rotatory motion round their axis, and also a progressive motion towards the fire, even when their supports are declining from the fire, so that the tubes will move a little way upwards to the fire. When the progressive motion of the tubes towards the fire is stopped by any obstacle, their rotation still continues. When the tubes are placed in a nearly upright posture, leaning to the right hand, the motion will be from east to west; but if they lean to the left hand, the motion will be from west to east; and the nearer they are placed to the upright posture, the less will the motion be either way. If the tube be placed horizontally on a glass plane, the fragment, for instance, of coach window glass, instead of moving towards the fire, it will move from it, and about its axis in a contrary direction to what it had done before; nay, it will recede from the fire, and move a little upwards, when the plane inclines towards the fire. These experiments succeed best with tubes about twenty or twenty-two inches long, which have in each end a pretty strong pin fixed in cork for their axis.

AQUATIC BOMB.

Drop about two grains of potassium into a saucer of cold water. It will instantly burst into flame, with a slight explosion, burn vividly on the surface, and dart about with great violence in the form of a red-hot fire ball.

HEAT NOT TO BE ESTIMATED BY TOUCH.

Hold both hands in water which causes the thermometer to rise to ninety degrees, and when the liquid has become still, you will be insensible of the heat, and that the hand is touching any thing. Then remove one hand to water that causes the thermometer to rise to 200 degrees, and the other in water at thirty-two degrees. After holding the hands thus for some time, remove them, and again immerse them in the water at ninety degrees; when you will feel warmth in one hand and cold in the other. To the hand which had been immersed in the water at thirty-two degrees, the water at ninety degrees will feel hot; and to the hand which had been immersed in the water at 200 degrees, the water at ninety degrees will feel cold. If, therefore, the touch in this case be trusted, the same water will be judged to be hot and cold at the same time.

FLAME UPON WATER.

Fill a wine-glass with cold water, pour lightly upon its surface a little ether; light it by a slip of paper, and it will burn for some time.

ROSE-COLOURED FLAME ON WATER.

Drop a globule of potassium, about the size of a large pea, into a small cup nearly full of water, containing a drop or two of strong nitric acid; the moment that the metal touches the liquid, it will float upon its surface, enveloped with a beautiful rose-coloured flame, and entirely dissolve.

TO SET A MIXTURE ON FIRE WITH WATER.

Pour into a saucer a little sulphuric acid, and place upon it a chip of sodium, which will float and remain uninflamed; but the addition of a drop of water will set it on fire.

WAVES OF FIRE ON WATER.

On a lump of refined sugar let fall a few drops of phosphuretted ether, and put the sugar into a glass of warm water, which will instantly appear on fire at the surface, and in waves, if gently blown with the breath. This experiment should be exhibited in the dark.

EXPLOSION IN WATER.

Throw very small pieces of phosphuret of potassium into a basin of water, and they will produce separate explosions. The same substance will also burn with great brilliancy, when exposed to air.

WATER FROM THE FLAME OF A CANDLE.

Hold a cold and dry bell-glass over a lighted candle, and watery vapour will be directly condensed on the cold surface; then close the mouth of the glass with a card or plate, and turn the mouth uppermost; remove the card, quickly pour in a little lime-water, a perfectly clear liquid, and it will instantly become turbid and milky, upon meeting with the contents of the glass, just as lime-water changes when dropped into a glass of water.

FORMATION OF WATER BY FIRE.

Put into a tea-cup a little spirit of wine, set it on fire, and invert a large bell-glass over it. In a short time, a thick watery vapour will be seen upon the inside of the bell, which may be collected by a dry sponge.

BOILING UPON COLD WATER.

Provide a tall glass jar, filled with cold water, and place in it an air thermometer, which will nearly reach the surface; upon the surface place a small copper basin, into which put a little live charcoal: the surface of the water will soon be made to boil, while the thermometer will show that the water beneath is scarcely warmer than it was at first.

CURRENTS IN BOILING WATER.

Fill a large glass tube with water, and throw into it a few particles of bruised amber; then hold the tube, by a handle for the purpose, upright in the flame of a lamp, and, as the water becomes warm, it will be seen that currents, carrying with them the pieces of amber, will begin to ascend in the centre, and to descend towards the circumference of the tube. These currents will soon become rapid in their motions, and continue till the water boils.

HOT WATER LIGHTER THAN COLD.

Pour into a glass tube, about ten inches long, and one inch in diameter, a little water coloured with pink or other dye; then fill it up gradually and carefully with colourless water, so as not to mix them: apply heat at the bottom of the tube, and the coloured water will ascend and be diffused throughout the whole.

The circulation of warm water may be very pleasingly shown, by heating water in a tube similar to the foregoing; the water having diffused in it some particles of amber, or other light substance not soluble in water.

EXPANSION OF WATER BY COLD.

All fluids, except water, diminish in bulk till they freeze. Thus, fill a large thermometer tube with water, say of the temperature of eighty degrees, and then plunge the bulb into pounded ice and salt, or any other freezing mixture: the water will go on shrinking in the tube till it has attained the temperature of about forty degrees; and then, instead of continuing to contract till it freezes, (as is the case with all other liquids,) it will be seen slowly to expand and consequently to rise in the tube until it congeals. In this case, the expansion below forty degrees, and above forty degrees, seems to be equal: so that the water will be of the same bulk at thirty-two degrees as at forty-eight degrees, that is, at eight degrees above or below forty degrees.

THE CUP OF TANTALUS.

This pretty toy may be purchased at any optician’s for two or three shillings. It consists of a cup, in which is placed a standing human figure, concealing a syphon, or bent tube, with one end longer than the other. This rises in one leg of the figure to reach the chin, and descends through the other leg through the bottom of the cup to a reservoir beneath. If you pour water in the cup, it will rise in the shorter leg by its upward pressure, driving out the air before it through the longer leg; and when the cup is filled above the bend of the syphon, (that is, level with the chin of the figure,) the pressure of the water will force it over into the longer leg of the syphon, and the cup will be emptied: the toy thus imitating Tantalus of mythology, who is represented by the poets as punished in Erebus with an insatiable thirst, and placed up to the chin in a pool of water, which, however, flowed away as soon as he attempted to taste it.

IMITATIVE DIVING BELL.

Nearly fill a basin with water, and put upon its surface a floating lighted wick or taper; over this place a glass goblet, mouth downwards, and push it into the water, which will be kept out, whilst the wick will continue to float and burn under the goblet; thus imitating the living inmate of a diving bell, which is merely a larger goblet, with a man instead of a candle within it.

THE WATER-PROOF SIEVE.

Fill a very fine wire-gauze sieve with water, and it will not run through the interstices, but be retained among them by capillary attraction.

MORE THAN FULL.

Fill a glass to the brim with water, and you may add to it spirit of wine without causing the water to overflow, as the spirit will enter into the pores of the water.

TO CAUSE WINE AND WATER TO CHANGE PLACES.

Fill a small narrow-necked bulb with port wine, or with water and coloured spirit of wine, and put the bulb into a tall, narrow glass jar, which is then to be filled up with cold water: immediately, the coloured fluid will issue from the bulb, and accumulate on the surface of the water in the jar, while colourless water will be seen accumulating at the bottom of the bulb. By close inspection, the descending current of the water may also be observed, and the coloured and the colourless liquids be seen to pass each other in the narrow neck of the bulb without mixing.

The whole of the coloured fluid will shortly have ascended, and the bulb will be entirely filled with clear water.

PYRAMID OF ALUM.

Put a lump of alum into a tumbler of water, and, as the alum dissolves, it will assume the shape of a pyramid. The cause of the alum decreasing in this peculiar form is briefly as follows: at first, the water dissolves the alum very fast, but as the alum becomes united with the water, the solvent power of the latter diminishes. The water, which combines first with the alum, becomes heavier by the union, and falls to the bottom of the glass; where it ceases to dissolve any more, although the water which it has displaced from the bottom has risen to the top of the glass, and is there acting upon the alum. When the solution has nearly terminated, if you closely examine the lump, you will find it covered with geometrical figures, cut out, as it were, in relief, upon the mass; showing, not only that the cohesion of the atoms of the alum resists the power of solution in the water, but that, in the present instance, it resists it more in some directions than in others. Indeed this experiment beautifully illustrates the opposite action of cohesion and repulsion.

VISIBLE VIBRATION.

Provide a glass goblet about two-thirds filled with coloured water, draw a fiddle-bow against its edge, and the surface of the water will exhibit a pleasing figure, composed of fans, four, six, or eight in number, dependent on the dimensions of the vessel, but chiefly on the pitch of the note produced.

Or, nearly fill a glass with water, draw the bow strongly against its edge, the water will be elevated and depressed; and, when the vibration has ceased, and the surface of the water has become tranquil, these elevations will be exhibited in the form of a curved line, passing round the interior surface of the glass, and above the surface of the water. If the action of the bow be strong, the water will be sprinkled on the inside of the glass, above the liquid surface, and this sprinkling will show the curved line very perfectly, as in the engraving. The water should be carefully poured, so that the glass above the liquid be preserved dry; the portion of the glass between the edge and the curved line, will then be seen partially sprinkled; but between the level of the water and the curved line, it will have become wholly wetted, thereby indicating the height to which the fluid has been thrown.

CHARCOAL IN SUGAR.

The elements of sugar are carbon and water, as may be proved by the following experiment: Put into a glass a table-spoonful of powdered sugar, and mix it into a thin paste with a little water, and rather more than its bulk of sulphuric acid; stir the mixture together, the sugar will soon blacken, froth up, and shoot like a cauliflower out of the glass: and, during the separation of the charcoal, a large quantity of steam will also be evolved.

FLOATING NEEDLES.

Fill a cup with water, gently lay on its surface small fine needles, and they will float.

WATER IN A SLING.

Half fill a mug with water, place it in a sling, and you may whirl it around you without spilling a drop; for the water tends more away from the centre of motion towards the bottom of the mug, than towards the earth by gravity.

ATTRACTION IN A GLASS OF WATER.

Pour water into a glass tumbler, perfectly dry, and it may be raised above the edge, in a convex form; because the particles of the water have more attraction for each other than for the dry glass; wet the edge, and they will be instantly attracted, and overflow, and the water will sink into a concave form.

TO PREVENT CORK FLOATING IN WATER.

Place at the bottom of a vessel of water, a piece of cork, so smoothly cut that no water gets between its lower surface and the surface of the bottom, when it will not rise, but remain fixed there, because it is pressed downward by the water from above, and there is no pressure from below to counter-balance it.

INSTANTANEOUS FREEZING.

During frosty weather, let a vessel be half filled with water, cover it closely, and place it in the open air, in a situation where it will not experience any commotion: it will thereby frequently acquire a degree of cold more intense than that of ice, without being frozen. If the vessel, however, be agitated ever so little, or receive even a slight blow, the water will immediately freeze with singular rapidity. The cause of this phenomenon is, that water does not congeal unless its particles unite together, and assume among themselves a new arrangement. The colder the water becomes, the nearer its particles approach each other; and the fluid which keeps it in fusion gradually escapes; but the shaking of the vessel destroys the equilibrium, and the particles fall one upon another, uniting in a mass of ice.

Or, provide a glass full of cold water, and let fall on its surface a few drops of sulphuret of carbon, which will instantly become covered with icy network: feathery branches will then dart from the sulphuret, the whole contents of the glass will become solidified, and the globules will exhibit all the colours of the rainbow.

TO FREEZE WATER WITH ETHER.

Fill a very thin glass tube with water. Close it at one end, and wrap muslin round it: then frequently immerse the tube in strong ether, allowing what the muslin soaks each time to evaporate, and in a short time the water will be frozen.

PRODUCTION OF NITRE.

Dip into the above solution a piece of paper: if its colour be changed to brown, a drop or two more acid must be cautiously applied: if, on the contrary, it reddens litmus paper, a small globule or two of potassium will be required; the object being to obtain a neutral solution: if it then be carefully evaporated to about half its bulk, and set aside, beautiful crystals will begin to form, which will be those of the nitrate of potash, commonly called nitre, or saltpetre.

CURIOUS TRANSPOSITION.

Take a glass of jelly, and place it mouth downward, just under the surface of warm water in a basin: the jelly will soon be dissolved by the heat, and, being heavier than the water, it will sink, while the glass will be filled with water in its stead.

ANIMAL BAROMETER.

Keep one or two leeches in a glass bottle nearly filled with water; tie the mouth over the coarse linen, and change the water every two or three days. The leech may then serve for a barometer, as it will invariably ascend or descend in the water as the weather changes from dry to wet; and it will generally come to the surface prior to a thunder-storm.

MAGIC SOAP.

Pour into a phial a small quantity of oil, with the same of water, and, however violently you shake them, they cannot be mixed, for the water and oil have no affinity for each other; but, if a little ammonia be added, and the phial be then shaken, the whole will be mixed into a liquid soap.

EQUAL PRESSURE OF WATER.

Tie up in a bladder of water, an egg and a piece of very soft wax, and place it in a box, so as to touch its sides and bottom; then, lay loosely upon the bladder a brass or other metal plate, upon which place a hundred pounds weight, or more; when the egg and the wax, though pressed by the water with all its weight, being equally pressed in all directions, will not be in the least either crushed or altered in shape.

TO EMPTY A GLASS UNDER WATER.

Fill a wine-glass with water, place over its mouth a card, so as to prevent the water from escaping, and put the glass, mouth downwards, into a basin of water. Next, remove the card, and raise the glass partly above the surface, but keep its mouth below the surface, so that the glass still remains completely filled with water. Then insert one end of a quill or reed in the water below the mouth of the glass, and blow gently at the other end, when air will ascend in bubbles to the highest part of the glass, and expel the water from it; and, if you continue to blow through the quill, all the water will be emptied from the glass, which will be filled with air.

TO EMPTY A GLASS OF WATER WITHOUT TOUCHING IT.

Hang over the edge of the glass a thick skein of cotton, and the water will slowly be decreased till the glass is empty. A towel will empty a basin of water in the same way.

DECOMPOSITION OF WATER.

The readiest means of decomposing water is as follows: take a gun-barrel, the breech of which has been removed, and fill it with iron wire, coiled up. Place it across a chafing-dish filled with lighted charcoal, and connect to one end of the barrel a small glass retort containing some water; and, to the other, a bent tube, opening under the shelf of a water bath. Heat the barrel red hot, and apply a lamp under the retort: the stream of water, in passing over the red-hot iron of the barrel, will be decomposed, the oxygen will unite with the iron, and the hydrogen may be collected in the form of gas at the end of the tube over the water.

WATER HEAVIER THAN WINE.

Let a tumbler be half-filled with water, and fit upon its surface a piece of white paper, upon which pour wine; then carefully draw out the paper, say with a knitting-needle, so as to disturb the liquids as little as possible, and the water, being the heavier, will continue at the lower part of the glass; whilst the wine, being the lighter, will keep above it. But, if a glass be first half-filled with wine, and water be poured over it, it will at once sink through the wine, and both liquids will be mixed.

TO INFLATE A BLADDER WITHOUT AIR.

Put a tea-spoonful of ether into a moistened bladder, the neck of which tie up tightly; pour hot water upon the bladder, and the ether, by expanding, will fill it out.

AIR AND WATER BALLOON.

Procure a small hollow glass vessel, the shape of a balloon, the lower part of which is open, and place it in water, with the mouth downwards, so that the air within prevents the water filling it. Then fill a deep glass jar nearly to the top with water, and place the balloon to float on its surface; tie over the jar with a bladder, so as to confine the air between it and the surface of the water. Press the hand on the bladder, when more water will enter the balloon, and it will soon sink to the bottom of the jar; but, on removing your hand, the balloon will again ascend slowly to the surface.

HEATED AIR BALLOON.

Make a balloon, by pasting together gores of bank post paper; paste the lower ends round a slender hoop, from which proceed several wires, terminating in a kind of basket, sufficiently strong to support a sponge dipped in spirit of wine. When the spirit is set on fire, its combustion will produce a much greater degree of heat than any ordinary flame: and by thus rarefying the air within the balloon, will enable it to rise with great rapidity, to a considerable height.

THE PNEUMATIC TINDER-BOX.

Provide a small stout brass tube, about six inches long, and half an inch in diameter, closed at one end, and fitted with a hollow air-tight piston, containing in its cavity a scrap of amadou, or German tinder. Suddenly drive the piston into the tube by a strong jerk of the hands; and the compression of the air in the tube will give out so much heat as to light the tinder; and upon quickly drawing out the piston, the glowing tinder will kindle a match.

THE BACCHUS EXPERIMENT.

This experiment, showing the elasticity of air, is performed with a pleasing toy. It represents a figure of Bacchus sitting across a cask, in which are two separate compartments. Put into one of them a portion of wine or coloured liquid, and place the apparatus under the exhausted receiver of an air-pump, when the elastic force of the confined air will cause the liquid to ascend a transparent glass tube, (fitted on purpose,) into the mouth of the Bacchanalian figure. To render the experiment more striking, a bladder, with a small quantity of air therein, is fastened around the figure, and covered with a loose silken robe, when the air in the bladder will expand, and produce an apparent increase in the bulk of the figure, as if occasioned by the excess of liquor drunk.

THE MYSTERIOUS CIRCLES.

Cut from a card two discs or circular pieces, about two inches in diameter; in the centre of one of them make a hole, into which put the tube of a common quill, one end being even with the surface of the card. Make the other piece of card a little convex, and lay its centre over the end of the quill, with the concave side of the card downward; the centre of the upper card being from one-eighth to one-fourth of an inch above the end of the quill. Attempt to blow off the upper card by blowing through the quill, and it will be found impossible.

If, however, the edges of the two pieces of card be made to fit each other very accurately, the upper card will be moved, and sometimes it will be thrown off; but when the edges of the card are on two sides sufficiently far apart to permit the air to escape, the loose card will retain its position, even when the current of air sent against it be strong. The experiment will succeed equally well, whether the current of air be made from the mouth or from a pair of bellows. When the quill fits the card rather loosely, a comparatively light puff of air will throw both cards three or four feet in height. When, from the humidity of the breath, the upper surface of the perforated card has a little expanded, and the two opposite sides are somewhat depressed, these depressed sides may be distinctly seen to rise and approach the upper card, directly in proportion to the force of the current of air.

Another fact to be shown with this simple apparatus, appears equally inexplicable with the former. Lay the loose card upon the hand with the concave side up; blow forcibly through the tube, and, at the same time, bring the two cards towards each other, when, within three-eighths of an inch, if the current of air be strong, the loose card will suddenly rise and adhere to the perforated card. If the card through which the tube passes has several holes made in it, the loose card may be instantly thrown off by a slight puff of air.

For the explanation of the above phenomenon, a gold medal and one hundred guineas were offered, some years since, by the Royal Society. Such explanation has been given by Dr. Robert Hare, of Philadelphia, and is as follows:

Supposing the diameter of the discs of card to be to that of the hole as 8 to 1, the area of the former to the latter, must be as 64 to 1. Hence, if the discs were to be separated, (their surfaces remaining parallel,) with a velocity as great as that of the air blast, a column of air must meanwhile be interposed, sixty-four times greater than that which would escape from the tube during the interim; consequently, if all the air necessary to preserve the balance be supplied from the tube, the discs must be separated with a velocity as much less than that of the blast, as the column required between them is greater than that yielded by the tube, and yet the air cannot be supplied from any other source, unless a deficit of pressure be created between the discs, unfavourable to their separation.

It follows, then, that, under the circumstances in question, the discs cannot be made to move asunder with a velocity greater than one-sixty-fourth of that of the blast. Of course, all the force of the current of air through the tube will be expended on the moveable disc, and the thin ring of air which exists around the orifice between the discs: and, since the moveable disc can only move with one-sixty-fourth of the velocity of the blast, the ring of air in the interstice must experience nearly all the force of the jet, and must be driven outwards, the blast following it in various currents, radiating from the common centre of the tube and discs.

PRINCE RUPERT’S DROPS.

Let fall melted glass into cold water, and it will become suddenly cooled and solidified on the outside before the internal part is changed; then, as this part hardens, it is kept extended by the arch of the outside crust: and, if the finely drawn-out point of the drop be broken off, the cohesion of the atoms of the glass is destroyed, and the whole crumbles to dust with a smart explosion.

VEGETABLE HYGROMETER.

The dampness of the air, and the consequent approach of rain, is denoted by several simple means, which are termed hygrometers. Thus, if an ear of the wild oat be hung up, its awn or bristly points will be contracted by a rotatory motion in damp air, and relaxed by a contrary motion when the air is dry. Similar effects are observable on all cordage, string, and every description of twisted material; as the moisture swells the threads, and increases their diameter, but reduces their length; hence, catgut is used in the construction of a weather-house, in which the man and woman foretel wet or dry weather, moving as the catgut stretches or contracts, according as the air is moist or dry.

To prove the moving power of the awn, separate one from the ear, and, holding the base between the finger and thumb, moisten the awn with the lips, when it will be seen to turn round for some time.

THE PNEUMATIC DANCER.

This amusing pneumatic toy consists of a figure made of glass or enamel, and so constructed as to remain suspended in a glass jar of water. An air-bubble, communicating with the water, is placed in some part of the figure, shown at m, near the top of the jar, A, in the engraving. At the bottom, B, of the vessel is a bladder, which can be pressed upwards by applying the finger to the extremity of a lever, e o, when the pressure will be communicated through the water to the bubble of air, which is thus compressed. The figure will then sink to the bottom; but, by removing the pressure, the figure will again rise, so that it may be made to dance in the vessel, as if by magic. Fishes, made of glass, are sometimes substituted for the human figure. A common glass jar may be used for this experiment, in which case the pressure should be applied to the upper surface, which should be a piece of bladder, instead of being placed at the bottom, as shown in the figure engraved.

THE ASCENDING SNAKE.

To construct this pretty little pneumatic toy, take a square piece of stiff card, or sheet copper or brass, about two and a half or three inches in diameter, and cut it out spirally, so as to resemble a snake, as in the engraving (fig. 1.). Then paint the body on each side of the card the colours of a snake; take it by the two ends, and draw out the spiral till the distance from head to tail is six or seven inches, as in fig. 2. Next, provide a slender piece of wood on a stand, and fix a sharp needle at its summit; push the rod up through the spiral, and let the end of the spiral rest upon the summit of the needle. Now place the apparatus as nearly as possible to the edge of the mantel-shelf above the fire, and the snake will begin to revolve in the direction of its head; and, if the fire be strong, or the current of heated air which ascends from it is made powerful, by two or three persons coming near it, so as to concentrate the current, the snake will revolve very rapidly. The rod a, b, should be painted, so as to resemble a tree, which the snake will appear to climb; or, the snake may be suspended by a thread from the ceiling, over the current of air from a lamp. Two snakes may be made to turn round in opposite directions, by merely drawing out the spiral of one from the upper side, and of the other from the under side of the figure, and fixing them, of course, on separate rods.

THE PNEUMATIC PHIAL.

Provide a phial one-fourth filled with any coloured water, and with a glass tube passing through the cork, or cemented into the neck of the phial, so as to be air-tight; the tube may reach to within a quarter of an inch of the bottom of the phial, so as to dip below the surface of the liquid. Hold this little instrument before the fire, or plunge it into hot water, when the air that is in the phial will expand, and force up the coloured liquor into the tube.

RESIN BUBBLES.

Dip the bowl of a tobacco-pipe into melted resin, hold the pipe in a vertical position, and blow through it; when bubbles of various sizes will be formed, of a brilliant silvery hue, and in a variety of colours.

MOISTURE OF THE ATMOSPHERE.

Moisture is always present in the air, even when it is driest. To prove this, press a piece of sheet copper into the form of a cup; place on it a piece of phosphorus, thoroughly dried between blotting-paper; put the cup on a dry plate, and beside it a small piece of quick-lime; turn over it a glass tumbler, and leave it for ten minutes, that the lime may remove all moisture from the included air; take off the tumbler, touch the phosphorus with a hot wire, and instantly replace the glass; when a dry solid will be formed, resembling snow. As soon as the flame is extinct, examine the plate; when the solid will, in a very short time, attract so much water from the air, that it will pass into small drops of liquid.

CLIMATES OF A ROOM.

The air in a room may be said to resemble two climates: as it is lighter than the external air, a current of colder or heavier air is continually pouring in from the crevices of the windows and doors; and the light air must find some vent, to make way for the heavy air. If the door be set a-jar, and a candle held near the upper part of it, the flame will be blown outwards, showing that there is a current of air flowing out from the upper part of the room; and, if the candle be placed on the floor, close by the door, the flame will bend inwards, showing that there is also a current of air setting into the lower part of the room. The upper current is the warm, light air, which is driven out to make way for the stream of cold, dense air, which enters below.

BUBBLES ON CHAMPAGNE.

Pour out a glass of champagne, or bottled ale, and wait till the effervescence has ceased; you may then renew it by throwing into the liquor a bit of paper, a crumb of bread, or even by violently shaking the glass. The bubbles of carbonic acid chiefly rise from where the liquor is in contact with the glass, and is in greatest abundance at those parts where there are asperities. The bubbles setting out from the surface of the glass are at first very small; but they enlarge in passing through the liquor. It seems as if they proceeded more abundantly from the bottom of the glass than from its sides; but this is an ocular deception.

PROOFS THAT AIR IS A HEAVY FLUID.

Expel the air out of a pair of bellows, then close the nozzle and valve-hole beneath, and considerable force will be requisite to separate the boards from each other. This is caused by the pressure or weight of the atmosphere, which, acting equally upon the upper and lower boards externally, without any air inside, operates like a dead weight in keeping the boards together. In like manner, if you stop the end of a syringe, after its piston-rod has been pressed down to the bottom, and then attempt to draw it up again, considerable force will be requisite to raise it, depending upon the size of the syringe, being about fourteen or fifteen pounds to every square inch of the piston-rod. When the rod is drawn up, unless it be held, it will fall to the bottom, from the weight of the air pressing it in.

Or, fill a glass tumbler to the brim with water, cover it with a piece of thin wet leather, invert it on a table, and try to pull it straight up, when it will be found to require considerable force. In this manner do snails, periwinkles, limpets, and other shells adhere to rocks, &c. Flies are enabled to walk on the ceiling of a room, up a looking-glass, or window-pane, by the air pressing on the outside of their peculiarly-constructed feet, and thus supporting them.

To the same cause must be attributed the firmness with which the oyster closes itself; for, if you grind off a part of the shell, so as to make a hole in it, though without at all injuring the fish, it may be opened with great ease.

TO SUPPORT A PEA ON AIR.

This experiment may be dexterously performed by placing a pea upon a quill, or the stem of a tobacco-pipe, and blowing upwards through it.

PYROPHORUS, OR AIR-TINDER.

Mix three parts of alum with one of wheat flour, and put them into a common phial; set it in a crucible, up to the neck in sand; then surround the crucible with red-hot coals, when first a black smoke, and next a blue sulphureous flame, will issue from the mouth of the phial; when this flame disappears, remove the crucible from the fire, and when cold, stop the phial with a good cork. If a portion of this powder be exposed to the air, it will take fire.

Or, a very perfect and beautiful pyrophorus may be obtained by heating tartrate of lead in a glass tube, over a lamp. When some of the dark brown mass thus formed is shaken out in the air, it will immediately inflame, and brilliant globules of lead cover the ignited surface.

Or, mix three parts of lamp-black, four of burnt alum, in powder, and eight of pearl-ash, and heat them for an hour, to a bright cherry red, in an iron tube. When well made, and poured out upon a glass plate or tile, this pyrophorus will kindle, with a series of small explosions, somewhat like those produced by throwing potassium upon water; but this effect should be witnessed from a distance.

Put a small piece of grey cast-iron into strong nitric acid, when a porous, spongy substance will be left untouched, and will be of a dark grey colour, resembling plumbago. If some of this be put upon blotting paper, in the course of a minute it will spontaneously heat and smoke; and, if a considerable quantity be heaped together, it will ignite and scorch the paper; nor will the properties of this pyrophorus be destroyed by its being left for days and weeks in water.

BEAUTY OF A SOAP BUBBLE.

Blow a soap bubble, cover it with a clean glass to protect it from the air, and you may observe, after it has grown thin by standing a little, several rings of different colours within each other round the top of it. The colour in the centre of the rings will vary with the thickness; but, as the bubble grows thinner, the rings will spread, the central spot will become white, then bluish, and then black; after which the bubble will burst, from its extreme tenuity at the black spot, where the thickness has been proved not to exceed the 2,500,000th part of an inch.

WHY A GUINEA FALLS MORE QUICKLY THAN A FEATHER THROUGH THE AIR.

The resistance of the air to fallen bodies is not proportioned to the weight, but depends on the surface which the body opposes to the air. Now, the feather exposes, in proportion to its weight, a much greater surface to the air than a piece of gold does, and therefore suffers a much greater resistance to its descent. Were the guinea beaten to the thinness of gold-leaf, it would be as long, or even longer in falling than the feather; but, let both fall in a vacuum, or under the receiver of an air-pump, from which the air has been pumped out, and they will both reach the bottom at the same time; for gravity, acting independently of other forces, causes all bodies to descend with the same velocity.

An apparatus for performing this experiment is shown in the engraving: the coin and the feather are to be laid together, on the brass flap, A or B: this may be let down by turning the wire, C, which passes through a collar of leather, D, placed in the head of the receiver.

SOLIDITY OF AIR.

Provide a glass tube, open at each end; close the upper end by the finger, and immerse the lower one in a glass of water, when it will be seen that the air is material, and occupies its own space in the tube, for it will not permit the water to enter it until the finger is removed, when the air will escape, and the water rise to the same level in the inside as on the outside of the tube.

BREATHING AND SMELLING.

Hold the breath, and place the open neck of a phial, containing oil of peppermint, or any other essential oil, in the mouth, and the smell will not be perceived; but, after expiration, it will be easily recognised.

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