CHAPTER III.

MISCELLANEOUS TRICKS OF AN AMUSING NATURE. INTERESTING TRICKS IN ELASTICITY. [Illustration: SCIENTIFIC TRICKS WITH BILLIARD BALLS AND COINS.] The clever trick with billiard balls shown in Figs. 1 and 2 depends for its success on a truly scientific principle. A number of billiard balls are placed in a row against the cushion of the table. The player asks one of the spectators to name a certain number of balls to be pocketed without any apparent disturbance of the others. Suppose the number to be three. Then at the will of the player three balls separate from the others and roll into the pocket. The number is perfectly controllable, and when the hand of the player and one end of the row of balls is covered, the trick appears mysterious. It is hardly less so when the entire experiment is visible. The feat is accomplished by removing from one end of the series as many balls as are to be projected from the opposite end, and rolling them forward against the end of the row remaining. An equal number of balls fly off from the opposite end of the row and roll into the pocket. Three balls driven against one end of the series will cause three to roll off, two will drive off two, one will drive off one, and so on. The principle of this trick is illustrated in the well-known classroom experiment in which a series of contacting suspended balls of highly elastic material are made to transmit a blow delivered on the first of the series to the last ball of the series, so that the last ball will fly off without any apparent disturbance of the other balls. In this experiment, the first ball of the series is drawn back and allowed to fall against the first one of those remaining in contact. The impact of this ball will slightly flatten the ball with which it comes in contact, and each ball in turn transmits its momentum to the next, and so on through the entire series, the last of the series being thrown out as indicated. In the case of the experiment with the billiard balls it is found by careful observation that separate blows are given to the series, corresponding in number to the number of balls removed, so that while the separation of the three balls at the end of the series is apparently simultaneous, in reality they are separated one at a time. In Fig. 3 is illustrated a method of repeating the experiment with coins in lieu of balls. Dollars or half dollars may be used, and the effect is produced by sliding the coins. NOVEL PUZZLE. Our engraving shows a single perforated piece of wood having the form of a conventional heart, and in the perforation is inserted an arrow, also formed of a single piece of wood, the barb and head being much larger than the perforation in which the shank of the arrow is received. The heart is made of one kind of wood and the arrow of another. The question is, How did the arrow get into the heart? We have heard of the philosopher who was unable to rightly place a horse collar; and we have seen philosophers who could readily harness a horse, but who could not explain how the arrow got into the heart. The puzzle illustrated is one of many thousands distributed gratuitously upon the streets of New York as an advertisement. The heart is of black walnut and the arrow is of basswood. Now we fear that the secret is out; for any one familiar with the properties of basswood knows that it may be enormously compressed, after which it may be steamed and expanded to its original volume. One end of the arrow was thus compressed, and in its compressed state was passed through the aperture of the heart, after which it was expanded. Advantage has been taken of this principle in the manufacture of certain kinds of moldings. The portions of the wood to be left in relief are first compressed or pushed down by suitable dies below the general level of the board, then the board is planed down to a level surface, and afterward steamed. The compressed portions of the board are expanded by the steam, so that they stand out in relief. [Illustration: A NOVEL PUZZLE.] SIMPLE MATCH TRICK. [Illustration: A SIMPLE MATCH TRICK.] To lift three matches by means of one, it is necessary to make an incision in the end of a match and insert the pointed end of a second match into this incision. Place them on the table, with a third match resting against them for a support, as shown at the left of the figure. Then present a match to any one who may be looking on, and ask him to raise the three together by means of the match in his hand. The solution is given at the right of the figure. Bear lightly against the two matches that are joined until the third falls against the one held in the hand. Then raise it, and all three will be lifted together. Although this trick, which we find described in a French paper, “_Le Chercheur_,” is probably as ancient as the art of making matches, our juvenile readers may find it of interest, and possibly it may afford them a half hour’s amusement at recess time. CRYSTALLIZED ORNAMENTS. A beautiful ornament, which is very easily made, consists of a wooden cross covered with canton flannel, with the nap side out, and crystallized by immersion in a solution of alum. The nap retains the crystals so that they are not readily loosened or detached. The flannel should be attached to the wood by means of brass wire nails, and the cross should be suspended in a solution formed by dissolving a pound of alum in a gallon of warm water. The cross should be suspended in the solution while it is still warm and allowed to remain in until the solution cools, when it will be found covered with bright crystals. [Illustration: FIG. 1.--GROTTO.] Fig. 1 is a perspective view, and Fig. 2 a longitudinal section, of a grotto formed by crystallizing alum in a box containing jagged points covered with canton flannel, or wrapped about in various directions with coarse thread or twine. The box may be of wood or metal. It should have apertures in the top, ends, and sides. These apertures are stopped with corks while the box is filled with solution. After the crystallization the corks are removed, and the holes in the top, sides, and one end are covered with colored glass, and over the front aperture is secured a convex spectacle lens, having a focus about equal to the length of the box. When the interior of the box is illuminated by a strong light passing through the colored windows, the effect is fine. The solution used in this case is the same as that given for the cross. After the crystals are formed and the liquid is poured from the box, the interior should be allowed to dry thoroughly before closing the apertures. [Illustration: FIG. 2.--SECTION OF GROTTO.] MAGICAL APPARITION OF A DRAWING ON WHITE PAPER. It is well known that the vapors of mercury are very diffusive in their nature, and some quite singular experiments have been devised, based upon this knowledge, and upon the fact that the salts of silver and the chlorides of gold, platinum, iridium, and palladium are affected by these mercurial vapors. If any one, for instance, should write upon a sheet of white paper with platinum chloride, no mark would be visible, as the liquid is quite colorless. If, however, the same sheet of paper should 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. [Illustration: MAGICAL APPARITION OF A DRAWING ON WHITE PAPER.] Reversing the experiment, a no less marvelous result is obtained. At first expose the drawing or 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 sensitized 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 distinct and clear. MAGIC PORTRAITS. An able chemist, C. Wideman, has recently devised a curiosity in the way of engraving. It is a square piece of transparent glass in which absolutely nothing can be seen, even on the closest examination. If the glass be breathed upon, so as to cover its surface with moisture, a face like that shown in the cut makes its appearance. As soon as the moisture leaves the glass, the image disappears. [Illustration: MAGIC PORTRAITS.] A piece of glass is obtained similar to that used for making mirrors. The glass may be transparent, tinned, or silvered; that makes no difference as to the final result. Then a small quantity of fluorspar is placed in a porcelain capsule and moistened with sufficient sulphuric acid to make the proper chemical reaction to write with. With this liquid and a quill pen the desired drawing or writing is executed on the previously well-cleaned glass. In about five minutes, or ten at the most, the glass is to be washed in common water and dried with a cloth. The plate will then be ready, and it will only be necessary to breathe upon it to see the figures that have thus been traced make their appearance. A little practice will show the exact time necessary to leave the fluid lines on the glass. Too long a biting of the acid would be accompanied by so deep an engraving of the glass that the lines would always be perceptible, even on the dry glass. A TRICK OPERA GLASS. [Illustration: A TRICK OPERA GLASS.] We present an engraving of a trick opera glass which may be new to some of our readers, although the principle involved is very old. One tube of the opera glass is constructed in the ordinary manner, being provided with lenses, while the other tube is arranged to give a view of any object at right angles to the line of vision of the normal tube, or considerably to the rear of it. The trick tube has no eyepiece, and the objective is done away with, a piece of japanned wood taking its place. A portion of the tube and its leather cover is cut away, and a mirror is inserted at an angle in the tube. When the observer wishes to use the trick glass at short range, he covers up a portion of the opening in the tube with his fingers, but at longer range this precaution would not be necessary. The practical uses of the glass are apparent. Our engraving shows a plan view of a theater, with the stage, boxes, and seats. The gentleman in the box and the one on the right of the center aisle both appear to be observing the actor on the stage, but in reality they are observing the lady on the left of the center aisle. Of course each of the gentlemen has his glasses turned a different way around. A TOY BIRD THAT FLIES. [Illustration: A TOY BIRD THAT EFFECTIVELY SIMULATES A BIRD FLYING.] The naturalness and the easy movement of the wings of the little toy bird shown in the accompanying illustration, as the operator pulls gently on the end of the supporting string over which the bird moves, in accordance with the movement of the wings, always attracts observers when this toy is shown on the streets, as it has been by numerous venders within a short time. The toy is one of the latest of the many novelties which are constantly being exhibited by the wide-awake salesmen in the streets of New York and other large cities, and in the construction of some of which a surprising degree of skill and ingenuity are displayed. The cord leading from the aperture below the mouth of the bird is attached at its outer end to a hook in the wall or other support, while its inner portion passes over an idler and around a pulley, to which it is attached. This pulley is a little smaller than another at its side, as shown in Fig. 2, both pulleys being fast on the same shaft, and a cord from the larger pulley passes over an idler and out rearwardly, having at its end a finger-piece, on which the operator pulls in manipulating the toy. The cords are wound in opposite directions on their pulleys, so that the unwinding of the cord from the larger pulley, and the rotation of the same, winds up the cord on the smaller pulley, and causes the bird to move forward on what seems to be only a single length of cord, the backward movement taking place by gravity when the pull on the string is released. The movement of the wings is effected by a crank on each outer end of the pulley shaft, the crank being pivotally connected with an extension of a member of the inner one of two pairs of lazy tongs, and this member having also a pivotal bearing on a crossbar which turns in bearings on the outer side of the toy, just under where the wings are hinged to the body. The larger pair of lazy tongs is pivotally connected to the outer portion of the wing, giving a longer sweep thereto than to the inner portion, with which the smaller lazy tongs are connected; and the pivotal connection of the lazy tongs with the bearing in the crossbar gives an oscillatory movement to the wings, which constitutes a very good simulation of the natural movement of the wings of a bird in flight. A high degree of mechanical skill is shown in the putting together of this little toy. THE PLANCHETTE TABLE. This curious toy was popular as far back as 1867. Marvelous tales were told by the credulous about it, and even as distinguished scientists as Professor Tyndall and Professor Faraday were drawn into controversies concerning it. Many think there is some hidden secret in the construction of the planchette table. All that is necessary is that it should stand firmly and move readily on its legs. All that is needful is a heart-shaped cedar board with two nicely turned metal legs carrying well-oiled casters, and in the point of the board an aperture of suitable size for the insertion of a lead pencil, which serves as the third leg, and rests upon the paper. Many believe that humbug was stamped over every movement of the planchette board, and that one or the other of those whose hands bore upon it conspired with the little board in the formulation of its reply. Certain it is that planchette has performed some curious feats and has made for itself a position in the world of mysteries. Probably the most generally accepted explanation is that advanced by Lewes and others, that although there is no intentional movement of the hands of those who are subjecting planchette to the influence, still there is, in spite of this, an unconscious pressure of the finger tips upon the board, which directs the movement of the pencil. Nor does it seem that such can be at all unlikely, for unconscious movement is by no means an unusual phase of our existence. The somnambulist who nightly takes a promenade from cellar to garret, or whose steps by chance have led him to the border of a precipice, has as little knowledge of the peril he has escaped, when the morning beams have awakened him, as planchette is conscious of its movements. How often also in mercantile pursuits do those who are accustomed to a certain routine perform it unconsciously, and after the work has been finished would be unable to tell you of many of the details of the work which custom has taught them to perform correctly, even while in a state of abstraction. Much has been said at times of planchette’s prophetic nature. Under the influence of certain people of a highly nervous temperament, or having to a certain extent the qualities of mediums, future events are said to be foretold. Secrets of which the person touching planchette is in ignorance have been divulged in a remarkable way, and many anecdotes shrouding planchette in mystery are repeated and believed. [Illustration: PLANCHETTE.] Were the testimony, however, more universal, were planchette more consistent, and were it more generally truthful and less given to uttering remarkable sayings only occasionally, there would be more reason for according it a place for thorough and systematic investigation. Perhaps the day will come, when mesmerism is understood and mind reading is more satisfactorily explained, in which there will be occasion for looking upon planchette more seriously, and of regarding it as a wonderful means of displaying a rational nervous action independent of conscious mental cerebration. JAPANESE MAGIC MIRRORS. Mr. R. W. Atkinson, of the University of Tokio, Japan, communicates to “Nature” the following interesting account of these curious mirrors: “A short time ago a friend showed me a curious effect, which I had previously heard of, but had never seen. The ladies of Japan use, in making their toilet, a small round mirror about one-twelfth to one-eighth of an inch in thickness, made of a kind of speculum metal, brightly polished, and coated with mercury. At the back there are usually various devices, Japanese or Chinese written characters, badges, etc., standing out in strong relief, and brightly polished like the front surface. Now, if the direct rays of the sun are allowed to fall upon the front of the mirror, and are then reflected on a screen, in a great many cases, though not in all, the figures at the back will appear to shine through the substance of the mirror as bright lines upon a moderately bright ground. “I have since tried several mirrors as sold in the shops, and in most cases the appearance described has been observed with more or less distinctness. [Illustration: JAPANESE MAGIC MIRROR.] “I have been unable to find a satisfactory explanation of this fact, but on considering the mode of manufacture I was led to suppose that the pressure to which the mirror was subjected during polishing, and which is greatest on the parts in relief, was concerned in the production of the figures. On putting this to the test by rubbing the back of the mirror with a blunt-pointed instrument, and permitting the rays of the sun to be reflected from the front surface, a bright line appeared in the image corresponding to the position of the part rubbed. This experiment is quite easy to repeat; a scratch with a knife or with any other hard body is sufficient. It would seem as if the pressure upon the back during polishing caused some change in the reflecting surface corresponding to the raised parts whereby the amount of light reflected was greater; or supposing that of the light which falls upon the surface, a part is absorbed and the rest reflected, those parts corresponding to the raised portions on the back are altered by the pressure in such a way that less is absorbed, and therefore a bright image appears. This, of course, is not an explanation of the phenomenon, but I put it forward as perhaps indicating the direction in which a true explanation may be looked for.” The following account of the manufacture of the Japanese mirrors is taken from a paper by Dr. Geerts, read before the Asiatic Society of Japan, and appearing in their “Transactions” for 1875-76, p. 39: “For preparing the mold, which consists of two parts put together with their concave surfaces, the workman first powders a kind of rough plastic clay, and mixes this with levigated powder of a blackish ‘tuff-stone’ and a little charcoal powder and water, till the paste is plastic and suitable for being molded. It is then roughly formed by the aid of a wooden frame into square or round cakes; the surface of the latter is covered with a levigated half-liquid mixture of powdered ‘_chamotte_’ (old crucibles which have served for melting bronze or copper) and water. Thus well prepared, the blackish paste in the frame receives the concave designs by the aid of woodcuts, cut in relief. The parts of the mold are put together in the frame and dried. Several of these flat molds are then placed in a melting box made of clay and ‘chamotte.’ This box has on the top an opening into which the liquid bronze is poured after it has been melted in small fireproof clay crucibles. The liquid metal naturally fills all openings inside the box, and consequently also the cavities of the moulds. For mirrors of first quality the following metal mixture is used in one of the largest mirror foundries in Kioto: Lead 5 parts. Tin 15 „ Copper 80 „ --- 100 “For mirrors of inferior quality are taken: Lead 10 parts. Natural sulphide of lead and antimony 10 „ Copper 80 „ --- 100 “After being cooled, the melting box and molds are crushed and the mirrors taken away. These are then cut, scoured, and filed until they are roughly finished. They are then first polished with a polishing powder called _to-no-ki_, which consists of the levigated powder of a soft kind of whetstone (_to-ishi_) found in Yamato and many other places. Secondly, they are polished with a piece of charcoal and water, the charcoal of the wood _ho-no-ki_ (_Magnolia hypoleuca_) being preferred as the best for the purpose. When the surfaces of the mirrors are well polished they are covered with a layer of mercury amalgam consisting of quicksilver, tin, and a little lead. The amalgam is rubbed vigorously with a piece of soft leather, which manipulation must be continued for a long time, until the excess of mercury is expelled and the mirrors have a fine, bright reflecting surface.” MAGIC MIRRORS. The following article on magic mirrors by MM. Bertin and Dubosq outlines several interesting experiments. “The people of the Far East, the Chinese and the Japanese, in bygone times were acquainted with metallic mirrors only; and even to-day they make only these. They are made of speculum metal, of various forms and sizes, but always portable. One of the faces is polished and always slightly convex, so that its reflection gives images which are reduced in size; the other face is plane or slightly concave, and always has cast on it ornaments which are in relief. Among the many mirrors thus constructed there are a few which possess a wonderful property: when a beam of the sun’s light falls upon the polished surface and is reflected on a white screen, we see in the disk of light thus formed the image of the ornamentation which is on the back of the mirror. The Chinese have long known of these mirrors and value them highly; they call them by a name which signifies ‘mirrors which are permeable to the light.’ We, of the West, call them ‘magic mirrors.’ “Very few persons had seen magic mirrors till Mr. Ayrton, professor of the Polytechnic School at Yeddo, exhibited several which he had brought with him from Japan, and he experimented with them as already mentioned. “In the meantime I received a visit from M. Dybowski, my former pupil, who had returned from Japan, where for two years he had been the colleague of Professor Ayrton. He brought back with him as objects of curiosity four _temple mirrors_, that is to say, antique mirrors; these are far superior to those of modern production, for their manufacture has been nearly abandoned by reason of the introduction of the silvered mirrors of Europe. We tried them together; three were circular, and the thinnest of them, which is a disk of 15.3 centimeters in diameter, was found to be slightly magic. “To try such a mirror we reflect a sunbeam from its polished surface to a white cardboard about one meter distant. But to obtain the very best effects we must illuminate the mirror with a diverging pencil of light; this pencil is made still further divergent by reflection from the mirror, because its reflecting surface is convex. We can now receive the reflected rays on a screen at a greater distance, and we at once see distinctly the magnified image of the ornamentation on the back of the mirror. These raised designs appear on the screen in white on a dark ground. The image thus made by our mirror was confused, because it was not a good one; had it been properly made, the image would have been sharply defined. I then knew of no means by which I could make it give better effects. “The means by which the mirror could have been improved were first pointed out by M. Govi in the second of his two papers. It is a consequence of the true theory of magic mirrors. The theory was not reached at once. I proposed to M. Dubosq to associate himself with me in order, first, to repeat the experiments of the learned Italian, Govi, and then to study generally the interesting phenomena of magic mirrors, in the hope of being able eventually to reproduce them in his workshops. At first we had only at our disposal the mirror brought from Japan by M. Dybowski, and which gave confused images with the reflected solar rays. These images became very sharply defined when we had heated the back of the mirror with a gas lamp, and it gave very magic effects. [Illustration: THE MAGIC MIRROR.] “We then made a mold and reproduced this mirror, not in Japanese bronze, but in ordinary gun metal. The first copy was roughly worked on the lathe, after the Japanese manner, in order to render it magical, but this was broken. The second was worked carefully on an optical grinding tool; the surface was then polished and nickel plated, but it was not magical; it acquired this property in a high degree when it was heated, and even retained traces of it after it had been repeatedly heated. Several Japanese mirrors which we have procured have given analogous results. “We then engraved letters on the back of little rectangular Japanese mirrors. On heating these the letters appeared in black in the reflected image. When we cut lines around the design on the back of the mirror, heat rendered them very magical, for the design stood out, framed in the black lines which bordered the figures. “Thus it is seen that heat is very efficacious in rendering mirrors magical, but it is not without its inconveniences. First of all, it injures the mirrors, which thus lose their polish, especially when they have been amalgamated; also, the mirror is often not heated equally, and the images are deformed. It occurred to us that the change of curvature which was required could be obtained more uniformly by means of pressure. M. Dubosq therefore constructed a shallow cylinder of metal, closed at one end by the metallic mirror, and at the other by a flat plate of brass, having in its center a stopcock which we could attach, by means of a rubber tube, to a little hand pump. This pump could be made either to condense or rarefy air. If the rubber tube was attached to the pump, arranged as a condenser, a few strokes of the piston sufficed to compress sufficiently the air in the shallow cylinder; the mirror became more and more convex, the cone of reflected rays became more and more open, and in the image on the screen the design on the back of the mirror became more and more distinct. Our Japanese mirror when thus treated gave very fine images, and the copy which we had made, and which gave no result as ordinarily experimented with, now became a magic mirror as perfect as any of those which Professor Ayrton had exhibited before us. A mirror in brass, nickel plated, on whose back was soldered tin-plate figures, around whose borders were cut lines, became very magical by pressure, and gave the design on its back in light surrounded by dark borders. “This is what I call the _positive image_. We can also obtain the _negative image_, or the inverse of the preceding one, by rarefying the air in the shallow box. To do this we have only to attach the rubber tube to the pump arranged as an ordinary air pump. On now working the piston the air in the shallow box is rarefied; the mirror becomes concave; the cone of the diverging reflected rays closes up; the image of the design is reduced in size, changes its appearance, and becomes an image of the design on the back of the mirror; but this now shows in shade edged with bright borders. “These experiments require an intense light. A jet of coal gas is insufficient, but the oxyhydrogen light is sufficiently intense. We intercept it with a screen perforated with a small hole, so that the diverging pencil which falls on the mirror may not spread too much. The mirror is mounted on the top of a column so that it can be made to face in any required direction. The effects are most brilliant and the best defined when we experiment with the rays of the sun. When we expose the mirror to the beam of the _porte-lumière_ it is generally not entirely covered by the light; in this case it is best to use a diverging beam, obtained by means of a lens placed between the _porte-lumière_ and the mirror. “Thus we have seen that we can now make copies of the Japanese mirrors, some of which may be magical, but all may be rendered so by making them covers of the shallow box containing either compressed or rarefied air. This pressure box and its mirror, made in the Japanese style, certainly forms one of the most curious pieces of apparatus which is to be found in the cabinet of physics. “We shall not, however, stop here. One of these days, while our mirror is magical under the influence of pressure, we will take a cast of its surface, and then reproduce this by means of galvano-deposition. This surface will have all the irregularities of that of the magic mirror, and will produce by its reflected rays the image of a design which no longer exists on its back.”