Part 119

“5. To change a card without the help of the pack proceed thus: Slip the chosen card to the top, and make a false shuffle. Then take off, apparently only the top one, but really the top two, and hold them up by the edges, so that the top (right) one is completely hidden by the second (wrong) one. Putting the pack quite away behind at some distance from you, bring forward your (double) card in the left hand and show it to the chooser, asking if it is his own. As he will say no, appear confused and let him be quite positive and assertive that it is not his own. Take the (double) card lengthwise and face downwards in the right hand, walk back towards the pack, as you do so draw off the (right) card, leaving the wrong one palmed in the right hand as at _d_. Bring it forward again in the right hand (which in holding, the right will conceal the wrong card), as if to make quite sure, when the chooser will find it to be changed into his own card.

“6. This trick is somewhat similar to the last. Take out the four kings, and spread them out fanwise, _but_ let the second have concealed behind it as in the last trick, two other court cards (court cards are best as being not so noticeable in case of accident). Hold them up, saying, ‘You see I have here the four kings,’ close them up smartly and lay them face downwards on the top of the pack, so that the order is now, 1 king, 2 false ditto, 3 false ditto, 4, 5 and 6 kings. Take off the first (which is real) and apparently unintentionally show its face and place it at the bottom of the pack. Take off the next (false one) _without_ showing it, and place it _into_ the pack near the bottom. Place the next (false one) similarly _into_ the pack near the top. Take off the fourth (real) and apparently unintentionally exposing its face, _commence_ to put it into the middle; when half way, however, change your mind and place it on the top of the pack. Say, ‘Well, these kings are all well separated now, to mix them still further will you kindly cut the pack;’ this operation will of course join all four again in the middle. ‘Ruffle’ the pack and spreading it out fanwise expose them _en masse_ in the centre. If neatly done this is an excellent illusion.”

_Physical Experiments._--There are many illustrations of physical laws which admit of exhibition without the aid of any special apparatus, and which may be made highly instructive. Most of the following examples are borrowed from Max Adeler’s _Curious Company_.

(_a_) Equilibrium.--Stick 2 forks into a cork, and place the cork on the brim of the neck of a bottle (Fig. 100). The forks and the cork form a whole, of which the centre of gravity is fixed over the point of support. You can tip the bottle, empty it even, if it contains fluid, without the little construction over its mouth being in the least disturbed from its balance. The vertical line of the centre of gravity passes through the point of support, and the forks oscillate with the cork, which serves as their support, thus forming a movable structure, but much more stable than one is inclined to suppose. This curious experiment is often performed by conjurors, who inform their audience that they will undertake to empty the bottle without disturbing the cork. (_b_) If a woodcock has been served for dinner, or any other bird with a long beak, take off the head at the extreme end of the neck; then split a cork so that you can insert into it the neck of the bird, which must be tightly clipped to keep it in place; two forks are then fixed into the cork, exactly as in the preceding example, and into the bottom of the cork a pin is inserted. This little contrivance is next placed on a piece of money, which has been put on the opening of the neck of the bottle, and when it is fairly balanced, give it a rotatory movement, by pushing one of the forks as rapidly as you please, but as much as possible without any jerk. You will then see the two forks, and the cork surmounted by the woodcock’s head, turning on the slender pivot of a pin. Nothing can be more comical than to witness the long beak of the bird turning round and round, successively facing all the company assembled round the table, sometimes with a little oscillation, which gives it an almost lifelike appearance. (_c_) Lifting a glass bottle full of water by means of a simple wisp of straw. The straw is bent before being passed into the bottle of water, so that, when it is lifted, the centre of gravity is displaced, and brought directly under the point of suspension. It is well to have at hand several pieces of straw perfectly intact and free from cracks, in case the experiment does not succeed with the first attempt. (_d_) The next experiment, though apparently very difficult, will be found easy enough in practice if the hand be steady. Take a key, and by means of a crooked nail, or “holdfast,” attach it to a bar of wood by a string tied tightly round the bar. To the other extremity of the bar attach a weight, and then drive a large-headed nail into the table. It will be found that the key will balance and even move upon the head of the nail, without falling. The weight is under the table, and the centre of gravity is exactly beneath the point of suspension. Inertia.--(_e_) Take a broomstick, and place it horizontally, passing the ends through two paper rings. Then ask two children to hold the paper rings by means of two razors, so that the rings rest on the blades. This done, take a stout stick, and, with all your strength, strike the broomstick in the centre; it will be broken into shivers, but the paper rings will not be torn in the least, or even cut by the razors! (_f_) A modification of _e_. A needle is fixed at each end of the broomstick, and these needles are made to rest on two glasses, placed on chairs; the needles alone must be in contact with the glasses. If the broomstick is then struck violently with another stout stick, the former will be broken, but the glasses will remain intact. The experiment answers all the better the more energetic the action. (_g_) A wooden ball is suspended from the ceiling by a rather slender thread, and a similar thread is attached to the lower end of the ball. If the lower thread is pulled forcibly it will break with the force of the pull; the movement communicated to it has not time to pass into the ball; if, on the contrary, it is pulled very gradually, and without any shock, the upper thread instead will break, because in this case it supports the weight of the ball. Motion is not imparted simultaneously to all parts of a body, but only to the particles first exposed to a blow, for instance. One might multiply examples of this. If a bullet be shot from a gun, it will make a round hole in a piece of wood or glass, whilst if thrown by the hand--that is to say, with much less force--it will shiver the wood or the pane of glass to pieces. When the celerity of the motive force is very great, the particles directly affected are disturbed so quickly that they separate from the adjacent particles before there is time for the movement to be communicated to the latter. (_h_) It is possible, for the same reason, to extract from a pile of money a piece placed in the middle of the pile without overturning the others. It suffices to move them forcibly and quickly with a flat wooden ruler. The experiment succeeds very well also if performed with draughtsmen piled up on the draught-board. (_i_) Take a strip of paper, and upon it place a coin, on a marble chimney-piece. If, holding the paper in the left hand, you strike it rapidly and forcibly, you will be enabled to draw away the paper without causing the coin (say a five-shilling piece) to fall down. (_j_) It is not impossible to draw away a napkin laid as a tablecloth for one person’s dinner, without disturbing the various articles laid upon it. A quick motion is all that is necessary, keeping the napkin tightly extended by the hands at the same time. This latter experiment, however, is not recommended to boys home for the holidays.

Pressure of Air.--(_k_) The force of air can be shown as acting with considerable pressure upon an egg in a glass. By blowing in a claret glass containing a hard-boiled egg, it is possible to cause the egg to jump out of the glass; and with practice and strength of lungs it is not impossible to make it pass from one glass to another. (_l_) The force of heated air ascending can also be ascertained by cutting up a card into a spiral, and holding it above the flame of a lamp. The spiral, if lightly poised, will turn round rapidly. (_m_) A wine glass, a plate, and water will serve for the next experiment. Pour some water on the plate, light a piece of paper resting on a cork, and cover the flame with the glass, which turn upside down. The water rises in the glass. Why?--Because the burning of the paper having absorbed a part of the oxygen, and the volume of confined gas being diminished, the pressure of the outer air has driven back the fluid. Next fill a goblet with water up to the brim, and cover it with a sheet of paper, which touches both the edge of the glass and the surface of the water. Turn the glass upside down, and the sheet of paper prevents the water running out, because it is held in place by atmospheric pressure. It sometimes happens that this experiment does not succeed till after a few attempts on the part of the operator; thus it is prudent to turn the glass over a basin, so that, in case of failure, the water is not spilt. (_n_) Having obtained a vase and a bottle, both quite full of water, take the bottle, holding it round the neck so that the thumb can be used as a stopper, then turn it upside down, and pass the neck into the water in the vase. Remove your thumb, or stopper, keeping the bottle in a vertical position, and you will see that the water it contains does not escape, but remains in suspension. It is atmospheric pressure which produces this phenomenon. If, instead of water, we put milk in the bottle, or some other fluid denser than water, we shall see that the milk also remains suspended in the bottle. (_o_) Light a piece of paper, and let it burn, plunging it into a water-bottle full of air. When the paper has been burning a few seconds close the opening of the water-bottle by means of a hard-boiled egg, which you have previously divested of its shell, so that it forms a hermetic stopper. The burning of the paper has now caused a vacuum of air in the bottle, and the egg is gradually thrust in by the atmospheric pressure outside. (_p_) Take a thin piece of wood about ⅛ in. thick, 8 in. wide, and 24 in. long, and lay it upon a table so that it shall project over the edge. It is evident that the least pressure will make it tilt and fall. Next spread out a large newspaper over the end that lies upon the table. Now if you strike a sharp blow with your fist on the projecting portion, you will be much surprised to see that the board resists the shock, just as if it were nailed to the table. If you strike hard you may injure your hand, or perhaps the board will break into pieces, but you will not lift the simple paper that holds it. The downward pressure of the atmosphere upon a wide surface explains the phenomenon. In order that the experiment may succeed well, the paper should be spread flat and evenly upon the table, and all the folds should be smoothed out so as to expel the interposed air.

Equilibrium of Floating Bodies.--(_q_) The equilibrium of bodies floating upon liquids is an occurrence of daily observation, but such is not the case as regards aeriform fluids--a soap bubble filled with air and floating upon a stratum of carbonic acid, for example. Although this pretty experiment would seem to require complicated apparatus to carry it out, it may nevertheless be performed very simply, as follows:--Having procured a glass vessel, such as a bell-glass, of medium size, place it, mouth upward, upon a tripod made of coarse wire, or upon any other support. In the bottom of this vessel place a mixture formed of equal parts soda bicarbonate and tartaric acid reduced to powder. The quantity of powder to be employed depends upon the size of the vessel and the thickness of the stratum of carbonic acid that it is desired to have. Soda bicarbonate contains carbonic acid to the amount of half its weight, and consequently it is necessary to decompose 4 grammes (66 gr.) of bicarbonate to produce 1 litre (61 cub. in.) of carbonic acid gas. Over the mouth of the glass vessel place a disc of cardboard of sufficient size to cover it exactly, and, in the centre of this, make a circular aperture to allow of the passage of a glass rod of sufficient length to rest upon the bottom and project externally. Through this tube, and by means of a small funnel, water is introduced in small quantities at a time (so as not to produce too lively an effervescence) until the powder is entirely covered. When the carbonic acid ceases to be given off, the tube is taken out.

Care should be taken to prepare beforehand a solution of soap in water, or, what is better, some of Plateau’s glyceric liquid. With either of these liquids, bubbles about 4 in. in diameter are blown at the extremity of a tube that flares slightly. This tube should be held vertically while carrying the bubble over the cardboard cover, and the latter should be carefully removed by sliding it off horizontally, and the bubble be then detached in such a way that it shall fall in the direction of the vessel’s axis. If the fall occurs from a certain height, the ball will rebound as if it were repelled by a spring. It will then descend and rise again, and finally become immovable. It is at this moment that it is well to replace the cover, so that no disturbance shall occur in the interior of the vessel.

The bubble then resembles a small balloon in equilibrium in the atmosphere of the vessel; but, in reality, it is floating upon the invisible stratum of carbonic acid. This equilibrium, however, is of short duration, since the carbonic acid rapidly dissolves in the liquid envelope of the bubble, and passes into the interior of the latter, and increases its weight to such a degree as to cause it to gradually descend to the bottom of the vessel, where it disappears. But a suspension of several balls may be obtained successively, that is to say, the experiment may be repeated several times, if, on removing the cover, care be taken not to disturb the atmosphere of the vessel.

The soap bubble may be replaced by one of those small rubber balloons that please children so much, and that weigh, on an average, 1 gramme each. Upon inflating one of these to a diameter of about 6 in., we shall obtain an equilibrium that has greater fixedness and duration, and may observe the phenomenon at our leisure.

Chemical Experiments.--It is well known that the vapours of mercury are very diffusive in their nature, and some quite singular experiments have been devised based upon this, and upon the fact that the salts of silver and the chlorides of gold, platinum, iridium, and palladium are affected by these mercurial vapours. If any one, for instance, write upon a sheet of white paper with platinum chloride, no mark would be visible, as the liquid is quite colourless. If, however, the same sheet of paper be held over a little mercury, the metal will be brought out on the paper in dark tints. This magical apparition of a figure or drawing on a sheet of paper which appears to be perfectly white is very astonishing to the spectator.

On the other hand, reversing the experiment, a no less marvellous result is obtained. At first expose the drawing in writing to the gases of mercury; the lines will become charged with mercury, and then by simply bringing the drawing in contact with a sheet of paper previously sensitised with a solution of platinum, the drawing will be reproduced, line for line, on the white paper. Drawings made in this way give a charming effect, the tones being very soft and the lines being distinct and clear.

_Optical Delusions._--Those talking decapitated persons that are so often seen in various kinds of shows are one of the sights that always prove successful. They have already astonished a number of generations past, and will probably prove just as attractive to those that shall succeed our own. These decapitated persons are seen under different aspects according to the tricks employed to produce the illusion, and which all have the same aim in view, that is, to cause the appearance, on a table or tray, of a living head with no visible body. This illusion may be produced in several ways. (_a_) At the Foire aux Pains d’Epices of 1880, one of the side shows exhibited a decapitated person as follows: The small stage, which was draped with a black fabric covered with silver spangles, was feebly lighted by a sort of night lamp attached to the ceiling. To the right and left were seen panoplies of skulls and cross-bones. The spectators were in darkness. In the middle of this grim place a tray was suspended by 3 small chains at about 3 ft. from the floor, and upon this tray there was a living head--that of a young man who an instant before had shown himself to the public. His body lay extended out under the tray, and his head talked, drank, and smoked, while his arms and legs moved. Both, although quite distinct, were perfectly alive.

The trick by which the illusion was obtained consisted in this: The body belonging to the apparently decapitated head was hidden behind, under the tray, and was completely invisible owing to the shadow of the latter, and the partial darkness of the stage. The apparent body was that of another person of exactly the same height, size, and dress, whose head was in the dark and further hidden by black cloth.

(_b_) Recently there was exhibited at Paris, in what is called the “Théâtre des Merveilles,” another example of a decapitated person. A young girl first appears before the audience, accompanied by an executioner clad in red and armed with the traditional axe. Then the curtain drops, but rises in a few moments, and shows the stage a little darkened. Near the executioner, however, can be perfectly distinguished the girl’s head lying on a round table at the back of the stage; her body is seen lying on a bed at a few feet from her head, and at her side is the fatal block that has served for the execution. The effect is dramatic. The trick employed is the same as the preceding, in that it requires two persons of the same size wearing the same costume. One of these--the one who showed herself to the public--makes the head, her body being hidden behind the cloth in the rear of the stage. The other, who makes the body, has her head bent far back and hidden in a sort of box, a false cardboard neck contributing to increase the illusion.

(_c_) Upon entering the room we perceive a black wooden square table having 4 legs. Over one of its angles there is thrown a piece of red fabric whose other end may be perfectly seen hanging from the opposite side. The floor, which is strewn with straw, is continuous to the back of the stage. There is nothing under the table, then--there can be no doubt of it. Still, upon this table there lies on a tray the head of a young girl which smiles and answers questions that are asked it. The ingenuous spectators are almost persuaded that the girl has no body; others ask themselves where it is hidden; and very peculiar suppositions are indulged in on all sides. In a word, the illusion is perfect.

When, through favour or money, we enter the side scene and look at the table sideways, we are almost ashamed of having allowed ourselves to be deceived by so simple a trick; for the apparatus consists, in fact, only of a mirror fixed obliquely to two legs of the table. This mirror hides the body of the girl, who is on her knees or seated on a small stool, and reflects the straw which covers the floor so as to make it appear continuous under the table, and likewise reflects the front leg of the table so as to make it appear at an equal distance from the other side and thus produce the illusion of a fourth leg. It also reflects the end of the red fabric hanging in front of the table, and thus makes it appear to hang down also from behind. It should be remarked that during the exhibition the spectator stands only a few inches away from the table and head, being separated therefrom by a wooden railing from which hangs a curtain reaching to the ground. Such proximity of the spectator and actor would seem to favour a discovery of the trick; but, on the contrary, it is indispensable to its success. Were the spectator placed at a distance, and did the curtain not exist, he might by stooping see his legs reflected in the mirror. The curtain, then, prevents any one from looking under the railing, and the rays that might reach him from the curtain, by being reflected in the glass, are lost beneath the table, owing to the proximity of the latter.

As may be seen, the trick is easily understood, and, moreover, it is one of those that gives the best results, since it deceives the public the best. Besides, it has the merit of great age.

(_d_) The living half-woman is a very ingenious improvement on the decapitated individual. On entering, we perceive, when the curtain is drawn aside, an elegant little room decorated with flowers and lights and hung with curtains and tapestry. In front there are two railings, and the floor is covered with a carpet. In the centre is seen a small square table, on which rests a sort of three-legged stool supporting a cushion and the half body. The latter is the body of a young woman apparently cut in two just beneath the thighs. Naturally, this young person shows that she is alive by moving her arms and head, and speaking and singing. Now, as we can see the 4 legs of the table and can perfectly distinguish the space under the stool, and that too in full light, we naturally ask by what means the lower part of the girl’s body is hidden. On raising the stool, it will be seen that it is formed only of a hollowed-out disc whose supports are connected by two mirrors, that make with each other an angle of 45°. These mirrors rest on the top of the table, which is decorated with regular designs in mosaic, and reflect the latter in such a way that they seem to continue uninterruptedly under the stool. The table presents an analogous arrangement, two legs being connected with the foremost one by two mirrors (the table is placed cornerwise to the audience). These mirrors reflect not only the designs of the carpet, which by their continuity produce the illusion of a vacancy, but also 2 table legs located on each side behind the railings. The mirror to the left transmits to the spectators on that side the image of the leg placed on the left, and this image seems to them to be the fourth leg of the table. The mirror to the right plays the same rôle with regard to the spectators on that side. These mirrors, in addition, hide the lower portion of the girl’s body.

(_e_) The Dircksian phantasmagoria, which was more generally known as “Pepper’s Ghost,” is another example of the illusive effects of mirrors suitably arranged. On a moderate scale the same spectral apparitions can be produced as an entertainment for the drawing-room.