Chapter I: Part 1

Transcriber’s Notes:

Text enclosed by underscores is in italics (_italics_), text enclosed by equal signs is in bold (=bold=), and _{} encloses subscripted material.

The whole number part of a mixed fraction is separated from the fractional part with -, for example, 2-1/2.

Additional Transcriber’s Notes are at the end.

How to Become a Scientist.

GIVING
Interesting and Instructive Experiments
IN
CHEMISTRY,
Mechanics, Acoustics
AND
PYROTECHNICS.

ALSO CONTAINING
MATHEMATICAL PROBLEMS and PUZZLES
BOTH
USEFUL AND AMUSING.

NEW YORK:
FRANK TOUSEY, Publisher,
24 UNION SQUARE.

* * * * *

Entered according to Act of Congress, in the year 1900, by

FRANK TOUSEY,

in the Office of the Librarian of Congress at
Washington, D. C.

How to Become a Scientist.

Chemistry, optics, pneumatics, mechanics, and mathematics, all contribute their share towards furnishing recreation and sport for the social gathering, or the family fireside. The magical combinations and effects of chemistry have furnished an almost infinite variety of pleasant experiments, which may be performed by our youthful friends with great success if a little care be taken; and the other branches of natural science are nearly as replete with interest.

The following _repertoire_ of such tricks and illusions will be found exceedingly complete, although pains have been taken to select only the best and most startling of them. A large number are entirely new, but are described with sufficient clearness to enable any person of ordinary intelligence to become expert in them, with a little practice.

Chemical Amusements.

Chemistry is one of the most attractive sciences. From the beginning to the end the student is surprised and delighted with the developments of the exact discrimination, as well as the power and capacity, which are displayed in various forms of chemical action. Dissolve two substances in the same fluid, and then, by evaporation or otherwise, cause them to reassume a solid form, and each particle will unite with its own kind, to the entire exclusion of all others. Thus, if sulphate of copper and carbonate of soda are dissolved in boiling water, and then the water is evaporated, each salt will be reformed as before. This phenomenon is the result of one of the first principles of the science, and as such is passed over without thought; but it is a wonderful phenomenon, and made of no account, only by the fact that it is so common and so familiar.

It is by the action of this same principle, “chemical affinity,” that we produce the curious experiments with

Sympathetic Inks.

By means of these, we may carry on a correspondence which is beyond the discovery of all not in the secret. With one class of these inks, the writing becomes visible only when moistened with a particular solution. Thus, if we write to you with a solution of the sulphate of iron, the letters are invisible. On the receipt of our letter, you rub over the sheet a feather or sponge, wet with a solution of nut-galls, and the letters burst forth into sensible being at once, and are permanent.

2. If we write with a solution of sugar of lead, and you moisten with a sponge or pencil, dipped in water impregnated with sulphureted hydrogen, the letters will appear with metallic brilliancy.

3. If we write with a weak solution of sulphate of copper, and you apply ammonia, the letters assume a beautiful blue. When the ammonia evaporates, as it does on exposure to the sun, the writing disappears, but may be revived again as before.

4. If you write with the oil of vitriol very much diluted, so as to prevent its destroying the paper, the manuscript will be invisible except when held to the fire, when the letters will appear black.

5. Write with cobalt dissolved in diluted muriatic acid; the letters will be invisible when cold, but when warmed they will appear a bluish green.

We are almost sure that our secrets thus written will not be brought to the knowledge of a stranger, because he does not know the solution which was used in writing, and, therefore, does not know what to apply to bring out the letters.

To Light a Candle Without Touching the Wick.

Let the candle burn until it has a good long snuff; then blow it out with a sudden puff, a bright wreath of white smoke will curl up from the hot wick. Now, if a flame be applied to this smoke, even at a distance of two or three inches from the candle, the flame will run down the smoke and rekindle the wick in a very fantastic manner. To perform this experiment nicely, there must be no draught or “banging” doors while the mystic spell is rising.

Magic Milk.

Lime-water is quite transparent, and clear as common spring water; but if we breathe or blow into it, the bright liquid becomes opalescent and as white as milk.

The best way to try this simple experiment is to put some powdered quicklime into a wine bottle full of cold water; shake them well together, now and then, for a day; then allow the bottle to remain quiet till the next day, when the clear lime-water may be poured off from the sediment. Now fill a wine-glass or tumbler with the lime-water thus made, and blow through the liquid with a glass tube, a piece of new tobacco-pipe, or a clean straw, and in the course of a minute or so--as the magicians say--“the water will be turned into milk.” By means of this pastime “Wise Men” can ascertain which young ladies are in love and which young gentlemen are not. With a shrewd guess they present, as a test, a glass of lime-water to the one and of pure water to the other, with unerring effect.

The Mimic Vesuvius.

This experiment is a demonstration of the heat and light which are evolved during chemical combination. The substance phosphorus has a great affinity for oxygen gas, and wherever it can get it from it will, especially when aided by the application of heat. To perform this experiment, put half a drachm of solid phosphorus into a Florence oil-flask, holding the glass slantingly, that the phosphorus may not take fire and break the glass; pour upon it a gill and a half of water, and place the whole over a tea-kettle lamp, or any common lamp filled with spirits of wine; light the wick, which should be about half an inch from the flask; and as soon as the water is boiling hot, streams of fire, resembling sky-rockets, will burst at intervals from the water; some particles will also adhere to the sides of the glass, immediately displaying brilliant rays, and thus continue until the water begins to simmer, when a beautiful imitation of the aurora borealis will commence and gradually ascend until it collects into a pointed cone at the mouth of the flask; after a half a minute, blow out the flame of the lamp, and the apex of fire that was formed at the mouth of the flask will rush down, forming beautiful illumined clouds of fire, rolling over each other for some time; and when these disappear, a splendid hemisphere of stars will present itself. After waiting a minute or two, light the lamp again, and nearly the same phenomena will be displayed as at the beginning. Let a repetition of lighting and blowing out the lamp be made for three or four times, so that the number of stars may be increased; and after the third or fourth act of blowing out the lamp, the internal surface of the flask will be dry. Many of the stars will shoot with great splendor from side to side, while others will appear and burst at the mouth of the flask. What liquid remains in the flask will serve for the same experiment three or four times, without adding any water. Care should be taken, after the operation is over, to put the flask in a cool and secure place.

The Real Will-o’-the-Wisp.

Into a small retort place about an ounce of strong liquor of potash; that is, pure potash dissolved in water, together with about a drachm of phosphorus. Let the neck or beak of the retort dip into a saucer of water, say half an inch deep; now very gently heat the liquid in the retort with a spirit-lamp until it boils. In a few minutes the retort will be filled with a white cloud; then the gas generated will begin to bubble at the end of the saucer; a minute more, each bubble, as it issues from the boiling fluid, will _spontaneously take fire_ as it comes into the air, forming at the same time the philosopher’s ring of phosphoric acid. Care is required in handling phosphorus; but our young chemical readers will, we think, not forego this wonderful experiment for the want of due attention; for, without proper care on their part, we must give up showing them wonders even greater than these.

The Paper Oracle.

Some amusement may be obtained among young people by writing, with common ink, a variety of questions, on different bits of paper, and adding a pertinent reply to each, written with nitro-muriate of gold. The collection should be suffered to dry, and put aside, until an opportunity offers for using them. When produced, the answers will be invisible; desire different persons to select such questions as they may fancy, and take them home with them; then promise, if they are placed near the fire during the night, answers will appear written beneath the questions in the morning; and such will be the fact, if the paper be put in any dry, warm situation.

The Mimic Gas-House.

This shows a simple way of making illuminating gas, by means of a tobacco-pipe. Bituminous coal contains a number of chemical compounds, nearly all of which can, by distillation, be converted into an illuminating gas; as with this gas nearly all our cities are now lighted in the dark hours of night. To make it, obtain some coal-dust (or walnut or butternut meats will answer), and fill the bowl of a pipe with it; then cement the top over with some clay; place the bowl in the fire, and soon smoke will be seen issuing from the end of the stem; when that has ceased coming apply a light and it will burn brilliantly for several minutes; after it has ceased, take the pipe from the fire and let it cool, then remove the clay, and a piece of coke will be found inside: this is the excess of carbon over the hydrogen contained in the coal, for all the hydrogen will combine with carbon at a high temperature, and make what are called hydrocarbons--a series of substances containing both these elemental forms of matter.

Alum Basket.

Make a small basket, about the size of the hand, of iron wire or split willow; then take some lamp-cotton, untwist it, and wind it around every portion of the basket. Then mix alum, in the proportion of one pound with a quart of water, and boil it until the alum is dissolved. Pour the solution into a deep pan, and in the liquor suspend the basket, so that no part of it touch the vessel or be exposed to the air. Let the whole remain perfectly at rest for twenty-four hours; when, if you take out the basket, the alum will be found prettily crystallized over all the limbs of the cottoned frame.

In like manner, a cinder, a piece of coke, the sprig of a plant, or any other object, suspended in the solution by a thread, will become covered with beautiful crystals.

If powdered tumeric be added to the hot solution, the crystals will be of a bright yellow; if litmus be used instead, they will be of a bright red; logwood will yield them of a purple, and common writing-ink, of a black tint; or, if sulphate of copper be used instead of alum, the crystals will be of fine blue.

But the colored alum crystals are much more brittle than those of pure alum, and the colors fly; the best way of preserving them is to place them under a glass shade, with a saucer containing water. This keeps the atmosphere constantly saturated with moisture, the crystals never become too dry, and their texture and color undergo but little change.

The Magic Bottle.

This trick, if well managed, is one of the most wonderful that can be performed in a drawing-room without apparatus; but it requires dexterity at the conclusion.

The person performing the trick offers to pour from a common wine-bottle, port-wine, sherry, milk, and champagne, in succession, and in any order.

To accomplish the trick, you must make solutions of the following chemicals, and label the bottles with numbers, thus:

No. 1. A mixture of two parts perchloride of iron, and one part sulphuric acid (vitriol).

No. 2. A strong solution of the sulphocyanate of potash.

No. 3. A strong solution of acetate of lead.

No. 4. A solution of bicarbonate of soda, or potash.

No. 5. A clear solution of gum arabic.

Procure a champagne-bottle, and wash it out well; then pour three teaspoonfuls of No. 1 into it. As the quantity is very small, it will not be observed, especially if you are quick in your movements. Pour some distilled or rain water into a common water-bottle, or jug, and add a tablespoonful of No. 5 to it; then set it aside, ready for use.

Provide some wine-glasses, of four different patterns, and into one pattern put one drop of solution No. 2; into another, three drops of solution No. 2; rinse the third with solution No. 3, and the fourth with solution No. 4.

Arrange the glasses on a small tray, remembering the solutions that were poured into each pattern.

Everything being ready, take the champagne bottle that you have prepared, from two or three others, and holding it up, to show the company that it is clear and empty; you must desire some person to hand you the water-bottle or jug, and then fill up the bottle with the water.

Pour some of the contents of the bottle into an unprepared glass, in order to show that it is water; then say: “Change to champagne,” and pour the liquid from the bottle into one of the glasses rinsed with No. 4; then pour into the glass containing _three drops_ of No. 2, and it will change to port wine; but if poured into the glass rinsed with No. 3, it will change to milk; and if into the glass with one drop of No. 2, it will produce sherry.

Be careful in pouring the fluid from the bottle, not to hold it high above the glasses, but to keep the mouth of it close to the edges, otherwise persons will observe that it undergoes change of color after it is poured into them; and, on this account, the glasses should be held rather high.

As all the solutions used in the above trick are deleterious, they should not be left about in the way of children, and, of course, the fluid in the wine-glasses must not even be tasted; but if any of the company wish to drink the wines you have made, then the tray must be adroitly exchanged for another with the proper wines placed on it.

The Faded Rose Restored.

Take a rose that is quite faded, and throw some sulphur on a chafing-dish of hot coals; then hold the rose over the fumes of the sulphur, and it will become quite white; in this state dip it into water, put it into a box, or drawer, for three or four hours, and when taken out it will be quite red again.

The Protean Liquid.

A red liquor, which, when poured into different glasses, will become yellow, blue, black, and violet, may be thus made: Infuse a few shavings of logwood in common water, and when the liquor is red, pour it into a bottle; then take three drinking-glasses, rinse one of them with strong vinegar, throw into the second a small quantity of pounded alum, which will not be observed if the glass has been newly washed, and leave the third without any preparation. If the red liquor in the bottle be poured into the first glass it will assume a straw color; if into the second, it will pass gradually from bluish-gray to black, provided it be stirred with a bit of iron, which has been privately immersed in good vinegar; in the third glass the red liquor will assume a violet tint.

The Changeable Ribbon.

Dip a rose-colored ribbon into nitric acid, diluted with eight or ten parts of water, and as soon as the color disappears, which it will do in a short time, take out the ribbon and put it into a very weak alkaline solution, when the alkali will quickly neutralize the acid, and the color will reappear.

The Chemical Chameleon.

Put a drachm of powdered nitrate of cobalt into a vial, containing an ounce of the solution of caustic potash, when the decomposition of the salt, and precipitation of a blue oxide of cobalt will take place. Cork the vial, and the liquid will assume a blue color, from which it will pass to a lilac, afterward to a peach tint, and finally to a light red.

Musical Flame.

Fit a good cork into a wine-bottle; burn a hole through the cork with a round iron skewer, and into it fix a piece of tobacco pipe about eight inches long. Put into the bottle about two or three ounces of zinc, in slips, such as the waste cuttings from a zinc-worker; now pour water on to the zinc until the bottle is more than half full; then add about three parts of a wine-glassful of sulphuric acid (oil of vitriol); this causes a rapid effervescence at first, but which subsides to a moderate and continuous boiling for a lengthened period; as soon as the boiling is regular, the cork with the pipe through it may be inserted into the bottle. If a light be placed to the end of the pipe, a flame will be produced, which will continue to burn so long as there is any visible action in the bottle. This flame is the ignited hydrogen gas (water gas), resulting from the decomposition of water by the acid and zinc, and as such is an exceedingly interesting experiment. Now, to be musical, procure a glass or metal pipe, about sixteen or eighteen inches long, and from half to three-quarters of an inch in diameter; place the tube over the flame, and allow the pipe to be about three to five inches up the tube, which will act as a kind of high chimney; it must be held perfectly steady and upright, at a particular distance up the tube, which varies according to the size of the flame. A beautiful sound is thus produced, similar to an organ-pipe. This sound, or “musical flame,” varies in note according to the diameter of the tube, being deeper or more bass as the tube is increased in size. By using various-sized tubes, different sounds are thus readily produced. The true explanation of this singular experiment remains yet to be solved.

Optical Amusements.

The science of optics affords an infinite variety of amusements, which cannot fail to instruct the mind, as well as delight the eye. By the aid of optical instruments we are enabled to lessen the distance to our visual organs between the globe we inhabit and “the wonders of the heavens above us;” to watch “the stars in their courses,” and survey at leisure the magnificence of “comets importing change of times and states;” to observe the exquisite finish and propriety of construction which are to be found in the most minute productions of the earth;--to trace the path of the planet, in its course around the magnificent orb of day, and to detect the pulsation of the blood, as it flows through the veins of an insect. These are but a few of the powers which this science offers to man; to enumerate them all would require a space equal to the body of our work; neither do we propose to notice the various instruments and experiments which are devoted to purposes merely scientific; it being our desire only to call the attention of our juvenile readers to such things as combine a vast deal of amusement with much instruction, to inform them as to the construction of the various popular instruments; to show the manner of using them, and to explain some of the most attractive experiments which the science affords. By doing thus much, we hope to offer a sufficient inducement to extend inquiry much further than the information which a work of this nature will enable us to afford.

The Camera Obscura.

This is a very pleasing and instructive optical apparatus, and may be purchased for a small sum. But it may be easily made by the young optician. Procure an oblong box, about two feet long, twelve inches wide, and eight high. In one end of this a tube must be fitted containing a lens, and be made to slide backward and forward, so as to suit the focus. Within the box should be a plain mirror, reclining backward from the tube at an angle of forty-five degrees. At the top of the box is a square of unpolished glass, upon which, from beneath, the picture will be thrown, and may be seen by raising the lid. To use the camera, place the tube with the lens on it opposite to the object, and having adjusted the focus, the image will be thrown upon the ground glass, as above stated, where it may be easily copied by a pencil or in colors.

The Magic Lantern.

The object of this ingenious instrument is to represent, in a dark room, on a white wall or cloth, a succession of enlarged figures of remarkable, natural, or grotesque objects. It consists of a tin box, with a funnel on the top, and a door on one side of it. This funnel, by being bent, serves the double purpose of letting out the smoke and keeping in the light. In the middle of the bottom of the box is placed a movable lamp, which must have two or three good lights, at the height of the center of the polished tin reflector. In the front of the box, opposite the reflector, is fixed a tin tube, in which there slides another tube. The sliding tube has, at its outer extremity, a convex lens fixed in it, of three inches in diameter. The focus of the smaller of these lenses may be about five inches. Between the stationary tube and the lamp, there must be a split or opening to admit of the passage of glass sliders, mounted in paper or wooden frames, upon which sliders it is that the miniature figures are painted, which are intended to be shown upon the wall. The distinctness of the enlarged figures depends not only upon the goodness of the magnifying glass, but upon the clearness of the light yielded by the lamp. It may be purchased ready made of any optician.

_To Paint the Glasses._--The slides containing the objects usually shown in a magic lantern are to be bought of opticians with the lantern, and can be procured cheaper and better in this way than by any attempt at manufacturing them. Should, however, the young optician wish to make a few slides, of objects of particular interest to himself, he may proceed as follows: Draw on a paper the subject you desire to paint. Lay it on a table or any flat surface, and place the glass over it; then draw the outlines with a very fine pencil, in varnish mixed with black paint, and, when dry, fill up the other parts in their proper colors. Transparent colors must be used for this purpose, such as carmine, lake, Prussian blue, verdigris, sulphate of iron, tincture of Brazil wood, gamboge, etc.; and these must be tempered with a strong white varnish, to prevent their peeling off. Then shade them with black, or with bistre, mixed with the same varnish.

_To Exhibit the Magic Lantern._--The room for the exhibition ought to be large, and of an oblong shape. At one end of it suspend a large sheet, so as to cover the whole of the wall. The company being all seated, darken the room, and placing the lantern with its tube in the direction of the sheet, introduce one of the slides into the slit, taking care to invert the figures; then adjust the focus of the glasses in the tube, by drawing it in or out, as required, and a perfect representation of the object will appear.

_Effects of the Magic Lantern._--Most extraordinary effects may be produced by means of the magic lantern; one of the most effective of which is a tempest at sea.

This is effected by having two slides painted, one with the tempest as approaching on one side, and continuing in intensity till it reaches the other. Another slide has ships painted on it, and while the lantern is in use, that containing the ships is dexterously drawn before the other, and represents ships in the storm.

The effects of sunrise, moonlight, starlight, etc., may be imitated also, by means of double sliders; and figures may be introduced sometimes of fearful proportions.

Heads may be made to nod, faces to laugh; eyes may be made to roll, teeth to gnash; crocodiles may be made to swallow tigers; combats may be represented; but one of the most instructive uses of the slides is to make them illustrative of astronomy, and to show the ratio of the seasons, the cause of the eclipses, the mountains in the moon, spots on the sun, and the various motions of the planetary bodies and their satellites.

The Phantasmagoria.

Between the phantasmagoria and the magic lantern there is this difference: in common magic lanterns the figures are painted on transparent glass; consequently the image on the screen is a circle of light, having figures upon it; but in the phantasmagoria all the glass is opaque, except the figures, which, being painted in transparent colors, the light shines through them, and no light can come upon the screen except that which passes through the figure.

There is no sheet to receive the picture, but the representation is thrown on a thin screen of silk or muslin, placed between _the spectators and the lantern_. The images are made to appear approaching and receding, by removing the lantern further from the screen, or bringing it nearer to it. This is a great advantage over the arrangements of the magic lantern, and by it the most astonishing effects are often produced.

Dissolving Views.

The dissolving views, by which one landscape or scene appears to pass into the other while the scene is changing, are produced by using two magic lanterns, placed side by side, and that can be inclined towards each other when necessary, so as to mix the rays of light, proceeding from the lenses of each, together, which produces that confusion of images, in which one view melts, as it were, into the other, which gradually becomes clear and distinct.

How to Raise a Ghost.

The magic lantern or phantasmagoria may be used in a number of marvelous ways, but in none more striking than in raising an apparent specter. Let an open box, about three feet long, a foot and a half broad, and two feet high, be prepared. At one end of this place a small swing dressing-glass, and at the other let a magic lantern be fixed, with the lenses in a direction towards the glass. A glass should now be made to slide up and down in the groove to which a cord and pulley should be attached, the end of the cord coming to the lower part of the left hand side. On this glass the most hideous specter that can be imagined may be painted, but in a squat or contracted position, and when all is done, the lid of the box must be prepared by raising a kind of gable at the end of the box, and in its lower part an oval hole should be cut sufficiently large to suffer the rays reflected from the glass to pass through them. On the top or the box place a chafing-dish, upon which put some burning charcoal. Now light the lamp in the lantern, sprinkle some powdered camphor or white incense on the charcoal, adjust the slide on which the specter is painted, and the image will be thrown upon the smoke. In performing the feat the room must be darkened, and the box should be placed on a high table, that the hole through which the light comes may not be noticed.

To Imitate a Mirage.

Provide a glass tumbler two-thirds full of water, and pour spirits of wine upon it; or pour into a tumbler some syrup, and fill it up with water; when mixed, the object seen through it will be inverted.

Two-fold Reflections.

Provide a circular piece of glass, and with a common awl, moistened with spirits of turpentine, pierce the center of the glass; hold it encircled with the fingers and thumb in the sunshine, or the strong light of a lamp, when these striking effects will be produced: If the glass be _red_, the hole pierced in the middle will be reflected _green_; if the glass be _green_, the spot will be _red_; if _blue_, _orange_; and if _yellow_, _indigo_.

The Thaumatrope.

Cut out a piece of card-board of circular form, and affix to it six pieces of string, three on each side. Paint on one side of the card a bird, and on the other a cage, taking care to paint the bird upside down, or the desired effect will not be produced. When showing the toy, take hold of the center strings, between the forefinger and thumb, and twirl the card rapidly around, and the bird will appear snugly ensconced in its cage. The principle on which this effect is produced is, that the image of any object received on the retina or optic nerve is retained on the mind about eight seconds after the object causing the impression is withdrawn, being the memory of the object; consequently, the impression of the painting on one side of the card is not obliterated ere the painting on the other side is brought before the eye. It is easy to understand from this fact how both are seen at once. Many objects will suit the thaumatrope, such as a juggler throwing up two balls on one side, and two balls on the other; and according to the pairs of strings employed, he will appear to throw up two, three, or four balls; the body and legs of a man on one side, and the arms and head on another; a horse and his rider; a mouse and trap. But we leave it to the ingenuity of our readers to devise for themselves.

PNEUMATIC AMUSEMENTS.

The branch of the physical sciences which relates to the air and its various phenomena is called Pneumatics. By it we learn many curious particulars. By it we find that the air has weight and pressure, color, density, elasticity, compressibility, and some other properties with which we shall endeavor to make the young reader acquainted, by many pleasing experiments, earnestly impressing upon him to lose no opportunity of making physical science his study.

To show that the air has weight and pressure, the common leather sucker by which boys raise stones will show the pressure of the atmosphere. It consists of a piece of soft but firm leather, having a piece of string drawn through its center. The leather is made quite wet and pliable, and then its under part is placed upon the stone and stamped down by the foot. This pressing of the leather excludes the air from between the leather and the stone, and by pulling the string a vacuum is left underneath its center; consequently the weight of the air about the edges of the leather not being counterbalanced by any air between it and the stone, enables the boy to lift it.

The Magic Tumbler.

The air which for about forty miles surrounds our earth has a definite weight; and although we can neither see nor feel it, we are conscious of its presence by the momentary operation of breathing. The weight of a column of air one inch square, and forty miles high, is about fifteen pounds.

The reason why we are not crushed down by this enormous weight is because we are surrounded on all sides by it, and as the pressure of weight is equal all around, it becomes, as far as we are personally concerned, insensible.

That the air _does_ exert a definite pressure, in consequence of its weight, may be easily proved by any one with the above simple apparatus--only a tumbler and a sheet of paper. Fill a tumbler quite full of water, and carefully draw over its top a sheet of clean letter paper, and be careful to see that there are no bubbles of air in the water; place your hand over the paper while inverting it, and when the glass is mouth downward the water will be kept in, until the paper becomes wet through. The air pressing against the mouth of the tumbler is of greater weight than the contained water, and so, until some air can get in to supply the place of the water, it cannot fall out.

The Weight of the Air Proved by a Pair of Bellows.

Shut the nozzle and valve-hole of a pair of bellows, and after having squeezed the air out of them, if they are perfectly air-tight, we shall find that a very great force, even some hundreds of pounds, is necessary for separating the boards. They are kept together by the weight of the heavy air which surrounds them, in the same manner as if they were surrounded by water.

The Revolving Serpent.

This illustration represents an amusing and instructive experiment, which proves the ascension of heated air by rendering its effects visible, and it may also be used to test the direction of the currents in our rooms and dwellings. To construct one, a piece of card-board is taken and cut in the form of a spiral, and to give effect it may be painted to represent a serpent. Then prepare a stand, having a needle in its upper end, and suspend the serpent from its center on the needle. If this be now placed over a stove, or the tail of the serpent suspended by a bit of thread over a lamp, the heated air ascending through it will cause it to revolve in a very amusing manner. Two serpents may be made to turn in opposite directions, by pulling out one from the one side, and the other in the reverse direction, so that their heads may point toward each other when suspended.

To Put a Lighted Candle Under Water.

Procure a good-sized cork, or bung; upon this place a small, lighted taper; then set it afloat in a pail of water. Now, with a steady hand, invert a large drinking glass over the light, and push it carefully down into the water. The glass being full of air, prevents the water from entering it. You may thus see the candle burn _under_ water, and bring it up again to the surface, still alight. This experiment, simple as it is, serves to elucidate that useful contrivance called the diving-bell, being performed on the same principle.

The largest drinking-glass holds but half a pint, so that your diving light soon goes out for the want of air. As an average, a burning candle consumes as much air as a man, and he requires nearly a gallon of air every minute, so that, according to the size of the glass over the flame, you can calculate how many seconds it will remain alight; of course, a large flame requires more air than a small one. For this, and several other experiments, a quart bell-glass is very useful, but being expensive it is not found in every parlor laboratory: one is, however, easily made from a green glass pickle-bottle; get a glazier to cut off the bottom, and you have a bell-glass that Chilton would not reject.

To Place Water in a Drinking-Glass Upside Down.

Procure a plate, a tumbler, and a small piece of tissue or silver paper. Set the plate on a table, and pour water in it up to the first rim. Now slightly crumple up the paper, and place it in the glass; then set it on fire. When it is burnt out, or rather just as the last flame disappears, turn the glass quickly upside down into the water. Astonishing! the water rushes with great violence into the glass! Now you are satisfied that water can be placed in a drinking-glass upside down. Hold the glass firm, and the plate also. You can now reverse the position of the plate and glass, and thus convince the most skeptical of the truth of your pneumatic experiment. Instead of burning paper, a little brandy or spirits of wine can be ignited in the glass; the result of its combustion being invisible, the experiment is cleaner.

AMUSEMENTS IN MECHANICS.

There is no subject so important as mechanics, as its principles are founded upon the properties of matter and the laws of motion; and, knowing something of these, the tyro will lay the foundation of all substantial knowledge.

The properties of matter are the following: Solidity (or impenetrability), divisibility, mobility, elasticity, brittleness, malleability, ductility and tenacity.

The laws of motion are as follows:

1. Every body continues in a state of rest, or uniform rectilineal motion, unless affected by some extraneous force.

2. The change of motion is always proportionate to the impelling force.

3. Action and reaction are always equal and contrary.

Experiment of the Law of Motion.

In shooting at “taw,” if the marble be struck “plump,” as it is called, it moves forward exactly in the same line of direction; but if struck sideways, it will move in an oblique direction, and its course will be in a line situated between the direction of its former motion and that of the force impressed. It is called the resolution of forces.

Balancing.

The center of gravity in a body is that part about which all the other parts equally balance each other. In balancing a stick upon the finger, or upon the chin, it is necessary only to keep the chin or finger exactly under the point which is called the center of gravity.

The Balanced Coin.

It seems to be an astounding statement that a quarter, or other piece of money, can be made to spin on the point of a needle. To perform this experiment, procure a bottle, cork it, and in the cork place a needle. Now take another cork and cut a slit in it, so that the edge of the coin will fit into the slit; next place two forks in the cork, and placing the edge of the coin on the needle, it will spin around without falling off. The reason is this: that the weight of the forks projecting as they do so much below the coin, brings the center of gravity of the arrangement much below the point of suspension, or the point of the needle, and therefore the coin remains perfectly safe and upright.

The Spanish Dancer.

The laws which govern the motion of bodies are capable of many pleasing illustrations, and the example which we now give of causing rotary motion is very interesting and easily performed.

Take a piece of card, and cut out a little figure, and paste or gum it in an erect position on the inside of a watch-glass. Then procure a black japanned waiter, or a clean plate will do, and, holding it in an inclined position, place the figure and watch-glass on it, and they will, of course, slide down. Next let fall a drop of water on the waiter, place the watch-glass on it, and again incline the waiter, and instead of the watch-glass sliding down, it will begin to revolve. It will continue to revolve with increasing velocity, obeying the inclination and position of the plane, as directed by the hand of the experimentalist. The reason of this is, in the first place, in consequence of the cohesion of the water to the two surfaces, a new force is introduced, by which an unequal degree of resistance is imparted to different parts of the watch-glass in contact with the waiter, and, consequently, in its effort to slide down, it revolves. Again, if the drop of water be observed, it will be seen that it undergoes a change of figure; a film of water, by capillary action, is drawn to the foremost portion of the glass, while, by the centrifugal force, a body of water is thrown under the under part of it. The effect of both these actions is to accelerate the motion, or, in other words, to gradually increase the speed.

The Mechanical Bucephalus.

The illustration of the horse furnishes a very good solution of a popular paradox in mechanics: Given, a body having a tendency to fall by its own weight; required, how to prevent it from falling by adding to it a weight on the same side on which it tends to fall. Take a horse in an erect position, the center of gravity of which is somewhere about the middle of its body. It is evident, therefore, that were it placed on its hinder legs, on a table, the line of its direction, or center, would fall considerably beyond its base, and the horse would fall on the ground; but to prevent this, there is a stiff wire attached to a weight or bullet, connected with the body of the horse, and by this means a horse prances on a table without falling off; so that the figure that was incapable of supporting itself, is actually prevented from falling by adding a weight to its unsupported end. This seems almost impossible, but when we consider that in order to have the desired effect, the wire must be bent, and the weight be further under the table than the horse’s feet are on it, the mystery is solved, as it brings the total weight of bullet and horse in such a position that the tendency is rather to make it stand up than to let it fall down.

The Revolving Image.

This little figure may be made to balance itself amusingly. Get a piece of wood, about two inches long; cut one end of it into the form of a man’s head and shoulders, and let the other end taper off to a fine point. Next furnish the little gentleman with a pair of wafters, shaped like oars, instead of arms, but they must be more than double the length of his body; stick them in his shoulders, and he is complete. When you place him on the tip of your finger, if you have taken care to make the point exactly in the center, he will stand upright. By blowing on the waiters he may be made to turn around very quickly. It is explained by the reasons that were given in the experiment of the “balanced coin.”

The Bridge of Knives.

Place three glasses in the form of a triangle, and arrange the handles of three knives upon them. Nos. 1, 2, and 3, the blade of No. 1 over that of No. 2, and that over No. 3, which rests on No. 1. The bridge so made will be self-supported.

The Parlor Boomerang.

The boomerang is a weapon used by the savages of Australia. By them it is made of a flat piece of hard wood. The peculiarity of this instrument is, that in whatever direction it is thrown, it will return to the place from whence it started, in a curve. The Australian aborigines use it with great dexterity, making it travel around a house and return to their feet, or they can throw it on the ground so that it will fly into the air, form a perfect arc over their heads, and strike them on the back. This curious instrument can be made in miniature, and is a very amusing toy for the parlor.

Get a piece of tolerably stiff cardboard, and cut from it a figure resembling a boomerang.

The next thing is to propel it through the air so that it will return to your feet; to do this, lay the boomerang on a flat book, allowing one end to project about an inch; then, holding the book to a slight angle, strike the projecting end of the boomerang with a piece of stick, or heavy pen-holder, when it will fly across the room and return to your feet.

The Balanced Turk.

A decanter or bottle is first obtained, and in its cork is placed a needle; on this is balanced a ball of wood, having a cork or wooden figure cut out, standing on the top. From the ball project two wires, bent semicircularly, having at their extremities two bullets. Push the bullets, and the whole will turn around on the needle, the figure standing upright all the while; and, twist it about from side to side as much as you like, it will always regain its erect position. The two bullets in this case cause the center of gravity to fall below the ball on which the figure is placed, and, in consequence, as the center of gravity always assumes the lowest position, it cannot do so without making the figure stand erect, or, in other words, until the bullets themselves are equally balanced. Any boy may whittle one of these toys out with a jack-knife.

The Complacent Vizier.

Among the novelties which scientific investigation has added to our toys, are several figures which will raise themselves upright when thrown down, and regain the erect position, notwithstanding their equilibrium is disturbed. The figures themselves are made of the pith of elder trees, or any other very light substance. Each is placed on half a bullet, or may be made to stand on its head, by making its cap of lead. Their appearance is very droll when they are moved about, as they seem every moment to be falling over, and yet continually right themselves. The philosophy of this is, that the center of gravity being in the base, and always trying to assume the lowest position, it keeps the figures upright. However much the equilibrium is disturbed, it will always try to regain its original position.

ARITHMETICAL AMUSEMENTS.

As the principal object of these articles is to enable the young reader to learn something in his sports, and to understand what he is doing, we shall, before proceeding to the curious tricks and feats connected with the science of numbers, present him with some arithmetical aphorisms, upon which most of the following examples are founded:

Aphorisms of Number.

1. If two even numbers be added together, or subtracted from each other, their sum or difference will be an even number.

2. If two uneven numbers be added or subtracted, their sum or difference will be an even number.

3. The sum or difference of an even and an uneven number added or subtracted will be an uneven number.

4. The product of two even numbers will be an even number, and the product of two uneven numbers will be an uneven number.

5. The product of an even and uneven number will be an even number.

6. If two different numbers be divisible by any one number, their sum and their difference will also be divisible by that number.

7. If several different numbers, divisible by 3, be added or multiplied together, their sum and their product will also be divisible by 3.

8. If two numbers divisible by 9, be added together, their sum of the figures in the amount will be either 9 or a number divisible by 9.

9. If any number be multiplied by 9, or by any other number divisible by 9, the amount of the figures of the product will be either 9 or a number divisible by 9.

10. In every arithmetical progression, if the first and last term be each multiplied by the number of terms, and the sum of the two products be divided by 2, the quotient will be the sum of the series.

11. In every geometric progression, if any two terms be multiplied together, their product will be equal to that term which answers to the sum of these two indices. Thus, in the series:

1 2 3 4 5
2 4 8 16 32

If the third and fourth terms, 8 and 16, be multiplied together, the product, 128, will be the seventh term of the series. In like manner, if the fifth term be multiplied into itself, the product will be the tenth term; and if that sum be multiplied into itself, the product will be the twentieth term. Therefore, to find the last, or twentieth term of a geometric series, it is not necessary to continue the series beyond a few of the first terms.

Previous to the numerical recreations, we shall here describe certain mechanical methods of performing arithmetical calculations, such as are not only in themselves entertaining, but will be found more or less useful to the young reader.

To Find a Number Thought of.

FIRST METHOD.

EXAMPLE.
Let a person think of a number, say 6
1. Let him multiply by 3 18
2. Add 1 19
3. Multiply by 3 57
4. Add to this the number thought of 63

Let him inform you what is the number produced; it will always end with 3. Strike off the 3, and inform him that he thought of 6.

SECOND METHOD.

EXAMPLE.
Suppose the number thought of to be 6
1. Let him double it 12
2. Add 4 16
3. Multiply by 5 80
4. Add 12 92
5. Multiply by 10 920

Let him inform you what is the number produced. You must then, in every case, subtract 320; the remainder is, in this example, 600; strike off the 2 ciphers, and announce 6 as the number thought of.

THIRD METHOD.

Desire a person to think of a number--say 6. He must then proceed:

EXAMPLE.
1. To multiply this number by itself 36
2. To take 1 from the number thought of 5
3. To multiply this by itself 25
4. To tell you the difference between this product
and the former 11
You must then add 1 to it 12
And halve this number 6

Which will be the number thought of.

FOURTH METHOD.

Desire a person to think of a number--say 6. He must then proceed as follows:

EXAMPLE.
1. Add 1 to it 7
2. Multiply by 3 21
3. Add 1 again 22
4. Add the number thought of 28
Let him tell you the figures produced 28
5. You then subtract 4 from it 24
6. And divide by 4 6

Which you can say is the number he thought of.

FIFTH METHOD.

EXAMPLE.
Suppose the number thought of be 6
1. Let him double it 12
2. Desire him to add to this a number you
tell him--say 4 16
3. To halve it 8

You can then tell him that if he will subtract from this the number he thought of, the remainder will be, in the case supposed, 2.

NOTE.--The remainder is always half the number you tell him to add.

To Discover Two or More Numbers that a Person has Thought of.

FIRST CASE.

Where each of the numbers is less than 10. Suppose the numbers thought of were 2, 3, 5.

EXAMPLE.
1. Desire him to double the first number, making 4
2. To add one to it 5
3. To multiply by 5 25
4. To add the second number 28

There being a third number, repeat the process.

5. To double it 56
6. To add 1 to it 57
7. To multiply by 5 285
8. To add the third number 290

And to proceed in the same manner for as many numbers as were thought of. Let him tell you the last sum produced (in this case, 290). Then, if there were two numbers thought of, you must subtract 5; if three, 55; if four, 555. You must here subtract 55; leaving a remainder of 235, which are the numbers thought of, 2, 3, and 5.

SECOND CASE.

Where one or more of the numbers are 10, or more than 10, and where there is an _odd_ number of numbers thought of.

Suppose he fixes upon five numbers, viz., 4, 6, 9, 15, 16.

He must add together the numbers as follows, and tell you the various sums:

1. The sum of the 1st and 2d 10
2. The sum of the 2d and 3d 15
3. The sum of the 3d and 4th 24
4. The sum of the 4th and 5th 31
5. The sum of the 1st and last 20