Endless Amusement Part 10

Procure a circle of wood or ivory, about 5 or 6 inches diameter, which must turn quite free on a stand with a circular border; on the ivory or wood circle fix a pasteboard, on which you place, in proper divisions, the hours, as on a dial. There must be a small groove in the circular frame, to receive the pasteboard circle; and observe, that the dial must be made to turn so free, that it may go round without moving the circular border in which it is placed.

Between the pasteboard circle and the bottom of the frame, place a small artificial magnet, that has a hole in its middle. On the outside of the frame, place a small pin, which serves to show when the magnetic needle is to stop. This needle must turn quite free on its pivot, and its two sides should be in exact equilibrium.

Then provide a small bag, with five or six divisions, like a lady's work-bag, but smaller. In one of these divisions put small square pieces of pasteboard, on which are written the numbers from 1 to 12.

In each of the other divisions put twelve or more similar pieces, observing that all the pieces in each division must be marked with the same number. The needle being placed upon its pivot, and turned quickly about, it will necessarily stop at that point where the north end of the magnetic bar is placed, and which you previously know, by the situation of the small pin in the circular border.

You then present to any person that division of the bag which contains the several pieces on which is written the number opposite to the north end of the bar, and tell him to draw any one he pleases. Then placing the needle on the pivot, you turn it quickly about, and it must necessarily stop at that particular number.

_The Magnetic Cards._

Draw a pasteboard circle; you then provide yourself with two needles, similar to those used in the foregoing experiment, (which you must distinguish by some private mark,) with their opposite points touched with the magnet. When you place that needle whose pointed end is touched, on the pivot described in the centre of the circle, it will stop on one of the four pips, against which you have placed the pin in the frame; then take the needle off, and, placing the other, it will stop on the opposite point.

Having matters thus arranged, desire a person to draw a card from a piquet pack, offering that card against which you have placed the pin of the dial, which you may easily do, by having a card a little longer than the rest. If he should not draw it the first time, as he probably may not, you must make some excuse for shuffling them again, such as letting the cards fall, as if by accident, or some other manoeuvre, until he fix on the card. You then tell him to keep it close, and not let it be seen. Then give him one of the two needles, and desire him to place it on the pivot, and turn it round, when it will stop at the colour of the card he chose; then taking that needle off, and exchanging it, unperceived, for the other, give it to a second person, telling him to do the same, and it will stop at the name of the identical card the first person chose.

_The Magnetic Orrery._

Construct a round box, Fig. 16, about eight inches diameter, and half an inch deep. On the bottom fix a circular pasteboard drawn like the figure. You are likewise to have another pasteboard, drawn exactly the same, which must turn freely in the box, by means of an axis placed on a pivot, one end of which is to be fixed in the centre of the circle.

On each of the seven smaller circles on the pasteboard, which you have fixed at the bottom of the box, place a magnetic bar, two inches long, in the same direction with the diameters of those circles, and their poles, in the situations expressed in the figure.

There must be an index like the hour hand of a dial, fixed on the axis of the central circle, by which the pasteboard circle in the box may be turned about; also a needle (forming in the figure the other hand) that will turn freely on the axis, without moving the circular pasteboard.

In each of the places where the word _question_ is, write a different question; and in each of the seven circles where the planetary signs are, write two answers to each question; observing, that there must only be seven words in each question: for instance,

In division No. 1, of the circle G, which stands opposite question No. 1, write the first word of the first answer. In the division No.

2, of the next circle, write the second word; and so on to the last, which will be in the seventh division of the seventh circle.

[Ill.u.s.tration: Fig. 16.]

In the eighth division of the first circle, write the first word of the second answer; in the ninth, the second word of the same answer; and so on to the fourteenth division of the seventh circle, which must contain the last word of that answer.

The same must be done for all the seven questions, and to each of these must be a.s.signed two answers, the words of which are to be dispersed through the seven circles.

At the centre of each of these circles place a pivot, and have two sets of magnetic needles like the hands of a watch, the pointed end of one set being north, and the other south.

Now, the index of the central circle being directed to any one of the questions, if you place one of the two magnetic needles on each of the seven lesser circles, they will fix themselves according to the directions of the bars on the corresponding circles at the bottom of the box, and consequently point to the seven words that compose the answer. If you place one of the other needles on each circle, it will point to the words that are diametrically opposite to those of the first answer, the north pole being in the place of the south pole of the other.

You therefore present this orrery to any person, and desire him to choose one of the questions there written. You then set the index of the central circle to that question; and, putting one of the needles on each of the seven circles, you turn it about, and when they all settle, the seven words they point to compose the answer.

The moveable needle, whose point in the figure stands at September, is to place against the names of the months; and when the party has fixed upon a question, you place that needle against the month in which he was born, which will make the ceremony appear a sort of magic divination. The planetary signs are merely intended to aid this deception, and give it the appearance of astrology.

_The Magic Verse._

The eight words which compose this Latin verse,

"_Tot sunt tibi dote, quot coeli sidera, virgo,_"[F]

being privately placed in any one of the different combinations of which they are susceptible, and which are 40,320 in number, to tell the order in which they are placed.

[F] "Thy charms, O, Virgin! are as numerous as the stars of heaven."

Provide a box that shuts with hinges, and is eight inches long, three wide, and half an inch deep, Fig. 17. Have eight pieces of wood, about one-third of an inch thick, two inches long, and one and a half wide, which will therefore, when placed close together, exactly fill the box. In each of these pieces or tablets place a magnetic bar, with their poles, as is expressed in Fig. 18. The bars being covered over, write on each of the tablets, in the order they then stand, one of the words of the foregoing Latin verse.

[Ill.u.s.tration: Fig. 17.]

[Ill.u.s.tration: Fig. 18.]

[Ill.u.s.tration: Fig. 19.]

On a very thin board of the same dimensions with the box, draw the eight circles, Fig. 19, A B C D E F G H, whose centres should be exactly over those of the eight tablets in the box, when the board is placed upon it. Divide each of those circles into eight parts, as in the figure, and in each of those divisions write one of the words of the Latin verse, and in the precise order expressed in the plate, so that when the board is placed over the box, the eight touched needles placed at the centre of the circles may be regulated by the poles of the bars in the box, and consequently the word that the needle points to in the circle will be the same with that inscribed on the tablet.

Cover the board with a gla.s.s, to prevent the needles from rising off their pivots, as is done in the sea-compa.s.s.

Over the board place four plates of gla.s.s, I L M N, Fig. 17, which will give the machine the figure of a truncated pyramid, of eight inches high. Cover it with a gla.s.s, or rather a board, in which are placed two lenses, O, of eight inches focus, and distant from each other about half an inch. Line the four plates of gla.s.s that compose the sides with very thin paper, that will admit the light, and at the same time prevent the company from seeing the circles on the board.

These preparations being made, you give the box to any one, and tell him to place the tablets, on which the words are written privately, in what position he thinks proper, then to close the box, and, if he please, to wrap it up in paper, seal it, and give it to you. Then placing the board with the pyramid upon it, you immediately tell him the order in which the tablets are placed, by reading the words to which the needles on the circles point.

INTERESTING EXPERIMENTS WITH THE AIR-PUMP.

We shall not occupy the time of our readers by describing the form and nature of the air-pump; since those persons whose circ.u.mstances will enable them to have it, can purchase it properly made at an optician's, at less expense, and with far less trouble, than they can construct, or cause it to be constructed, themselves.

_Bottles broken by Air._

Take a square bottle of thin gla.s.s, and of any size. Apply it to the hole of the air-pump, and exhaust the air. The bottle will sustain the weight of the external air as long as it is able, but at length it will suddenly burst into very small particles, and with a loud explosion.

An opposite effect will be produced, if the mouth of a bottle be sealed so close that no air can escape; then place it in the receiver, and exhaust the air from its surface. The air which is confined within the bottle, when the external air is drawn off, will act so powerfully as to break the bottle into pieces.

_Gla.s.s broken by Air._

Lay a square of gla.s.s on the top of an open receiver, and exhaust the air. The weight of the external air will press on the gla.s.s, and smash it to atoms.

_The Hand fixed by Air._

If a person hold his hand on an open receiver, and the air be exhausted, it will be fixed as if pressed by a weight of sixty pounds.

_Water boiled by Air._