Provide two cylindrical vessels, A B and C D, as in Fig. 6. Connect them by four tubes open at each end, as H I, &c., so that the air may descend out of the higher into the lower vessel. To these tubes fix candlesticks, and to the hollow cover, E F, of the lower vessel, fit a tube, K, reaching almost to the bottom of the vessel. At G let there be an aperture with a screw, whereby water may be poured into C D, which, when filled, must be closed by the screw.

[Ill.u.s.tration: Fig. 6.]

When the candles are lighted, the air in the upper cover and contiguous pipes will be thereby rarefied, and the jet from the small tube, K, will begin to play: as the air becomes more rarefied, the force of the jet will increase, and it will continue to play till the water in the lower vessel is exhausted. As the motion of the jet is caused by the heat of the candles, when they are extinguished the fountain will stop.

_A Fountain which acts by the heat of the Sun._

In the annexed engraving, Fig. 7, G N S is a thin hollow globe of copper, eighteen inches diameter, supported by a small inverted basin, placed on a stand with four legs, A B C D, which have between them, at the bottom, a basin of two feet diameter. Through the leg C pa.s.ses a concealed pipe, which comes from G, the bottom of the inside of the globe. This pipe goes by H V, and joins the upright pipe _u_ I, to make a jet, as I. The short pipe, _u_ I, which goes to the bottom, has a valve at _u_, under the horizontal pipe H V, and another valve at T, above that Horizontal pipe, under the c.o.c.k at K. The use of this c.o.c.k is to keep the fountain from playing in the day, if you think proper.

The north pole N of the globe has a screw that opens a hole, whereby water is poured into the globe.

[Ill.u.s.tration: Fig. 7.]

The machine being thus prepared, and the globe half filled with water, put it in an open place, when the heat of the sun rarefying the air as it heats the copper, the air will press strongly against the water, which, coming down the pipe, will lift up the valve at V, and shut the valve at u. The c.o.c.k being opened, the water will spout out at I, and continue to play a long while, if the sun shines.

_Inflammable Phosphorus._

Take the meal of flour of any vegetable, put it into an iron pan over a moderate fire, and keep it stirring with an iron spoon till it changes to a black powder; to one part of this add four parts of raw alum. Make the whole into a fine powder; put it again into the iron pan, and keep stirring it till it almost catches fire, to prevent its forming into lumps, as it is apt to do when the alum melts; in which case it must be broken again, stirred about, and accurately mixed with the flour, till it emits no more fumes, and the whole appears a fine black powder.

Put this powder in a clean dry phial with a narrow neck, filling it to about one-third of the top. Then stop the mouth of the phial with loose paper, so as to let the air pa.s.s freely through it, and leave room for the fumes to come through the neck. Place the phial in a crucible, encompa.s.sed on all sides with sand, so that it may not touch any part of the crucible, but a considerable s.p.a.ce everywhere left between. The phial must be covered up with sand, leaving only a small part bare, by which you can discern whether the powder is ignited. In this state, the crucible is to be surrounded with coals, kindled slowly till it is well heated on all sides, and then the fire is to be raised, till the crucible and every thing in it is red-hot; keep it in this state an hour; after this, the fire still burning as fiercely, close up the orifice of the phial with wax, to exclude the air. Leave it to cool, and you will find in it a black dusty coal formed of the flour and alum.

Shake a small quant.i.ty of this out of the phial into the cool air, and it will immediately take fire, but will not burn any thing. Keep the bottle dry, as even the air will spoil it effectually.

_The Magical Mirrors._

Make two holes in the wainscot of a room, each a foot high and ten inches wide, and about a foot distant from each other. Let these apertures be about the height of a man's head, and in each of them place a transparent gla.s.s in a frame, like a common mirror.

Behind the part.i.tion, and directly facing each aperture, place two mirrors enclosed in the wainscot, in an angle of forty-five degrees.[B] These mirrors are each to be eighteen inches square: and all the s.p.a.ce between them must be enclosed with pasteboard painted black, and well closed, that no light can enter; let there be also two curtains to cover them, which you may draw aside at pleasure.

When a person looks into one of these fict.i.tious mirrors, instead of seeing his own face he will see the object that is in front of the other; thus, if two persons stand at the same time before these mirrors, instead of each seeing himself; they will reciprocally see each other.

There should be a sconce with a lighted candle, placed on each side of the two gla.s.ses in the wainscot, to enlighten the faces of the persons who look in them, or the experiment will not have so remarkable an effect.

[B] That is, half-way between a line drawn perpendicularly to the ground and its surface.

_To cause a brilliant Explosion under Water._

Drop a piece of phosphorus, the size of a pea, into a tumbler of hot water; and, from a bladder furnished with a stop-c.o.c.k, force a stream of oxygen directly upon it. This will afford a most brilliant combustion under water.

_Fulminating Mercury._

Dissolve 100 grains of mercury by heat, in an ounce and a half of nitric acid. This solution being poured cold upon two measured ounces of alcohol previously introduced into any convenient gla.s.s vessel, a moderate heat is to be applied, till effervescence is excited. A white fume then begins to appear on the surface of the liquor, and the powder will be gradually precipitated when the action ceases. The precipitate is to be immediately collected on a filter, well washed with distilled water, and cautiously dried in a heat not exceeding that of a water-bath. Washing the powder immediately is material, because it is liable to the re-action of the nitric acid; and, while any of the acid adheres to it, it is very subject to the action of light. From 100 grains of mercury, about 130 of the powder are obtained.

This powder, when struck on an anvil with a hammer, explodes with a sharp stunning noise, and with such force as to indent both hammer and anvil. Three or four grains are sufficient for one experiment.

_The Iron Tree._

Dissolve iron filings in aqua fortis, moderately concentrated, till the acid is saturated; then add to it gradually, a solution of fixed alkali, (commonly called oil of tartar per deliquum.) A strong effervescence will ensue, and the iron, instead of falling to the bottom of the vessel, will afterwards rise so as to cover the sides, forming a mult.i.tude of ramifications heaped one upon the other, which will sometimes pa.s.s over the edge of the vessel, and extend themselves on the outside, with all the appearance of a plant.

_To make any Number divisible by Nine, by adding a Figure to it._

If (for example) the number named be 72,857, you tell the person who names it to place the number 7 between any two figures of that sum, and it will be divisible by 9; for if any number be multiplied by 9, the sum of the figures of the product will be either 9, or a number divisible by 9.

_Arithmetical Squares._

An arithmetical magical square consists of numbers so disposed in parallel and equal lines, that the sum of each, taken any way of the square, amounts to the same.

Any five of these sums taken in a right line make 65. You will observe that five numbers in the diagonals A to D, and B to C, of the magical square, answer to the ranks E to F, and G to H, in the natural square, and that 13 is the centre number of both squares.

_A Natural Square._ _A Magical Square._ A G B A B +--+--+--+--+--+ +--+--+--+--+--+

1

2

3

4

5

11

24

7

20

3

+--+--+--+--+--+ +--+--+--+--+--+

6

7

8

9

10

4

12

25

8

16

+--+--+--+--+--+ +--+--+--+--+--+ E

11

12

13

14

15

F

17

5

13

21

9

+--+--+--+--+--+ +--+--+--+--+--+

16

17

18

19

20

10

18

1

14

22

+--+--+--+--+--+ +--+--+--+--+--+

21

22

23

24

25

23

6

19

2

15

+--+--+--+--+--+ +--+--+--+--+--+ C H D C D

To form a magical square, first transpose the two ranks in the natural square to the diagonals of the magical square; then place the number 1 under the central number 13, and the number 2 in the next diagonal downward. The number 3 should be placed in the same diagonal line; but as there is no room in the square, you are to place it in that part it would occupy if another square were placed under this. For the same reason, the number 4, by following the diagonal direction, falling out of the square, it is to be put into the part it would hold in another square, placed by the side of this. You then proceed to numbers 5 and 6, still descending; but as the place 6 should hold is already filled, you then go back to the diagonal, and consequently place the 6 in the second place under the 5, so that there may remain an empty s.p.a.ce between the two numbers. The same rule is to observed, whenever you find a s.p.a.ce already filled.

You proceed in this manner to fill all the empty cases in the angle where the 15 is placed: and as there is no s.p.a.ce for the 16 in the same diagonal, descending, you must place it in the part it would hold in another square, and continue the same plan till all the s.p.a.ces are filled. This method will serve equally for all sorts of arithmetical progressions composed of odd numbers; even numbers being too complicated to afford any amus.e.m.e.nt.

_To find the Difference between two Numbers, the greatest of which is unknown._

Take as many nines as there are figures in the smallest number, and subtract that sum from the number of nines. Let another person add that difference to the largest number, and, taking away the first figure of the amount, add it to the last figure, and that sum will be the difference of the two numbers.

For example: Robert, who is 22, tells George, who is older, that he can discover the difference of their ages; he therefore privately deducts 22 from 99, and the difference, which is 77, he tells George to add to his age, and to take away the first figure from the amount, and add it to the last figure, and that last sum will be the difference of their ages. Thus, the difference between

Robert's age and 99, is 77 To which George adding his age 35 ---- The sum will be 112 ---- 12 1 ---- Then by taking away the first figure, 1, } and adding it to the last figure, 2, } 13 the sum is } Which added to Robert's age 22 ---- Gives George's age, which is 35

_The Boundless Prospect._

Take a square box, about six inches long and twelve high, or of any other proportionate dimensions. Cover the inside with four flat pieces of looking-gla.s.s placed perpendicular to the bottom of the box. Place at the bottom any objects you please, as a piece of fortification, a castle, tents, soldiers, &c. On the top, place a frame of gla.s.s shaped like the bottom of a pyramid, as in Fig. 8, and so formed as to fit on the box like a cover. The four sides of this cover are to be composed of ground gla.s.s, or covered inside with gauze, so that the light may enter, and yet the inside be invisible, except at the top, which must be covered with transparent gla.s.s: when you look through this gla.s.s, the inside will present a pleasing prospect of a boundless extent; and, if managed with care, will afford a deal of amus.e.m.e.nt.

[Ill.u.s.tration: Fig. 8.]

_To set Fire to a combustible Body by Reflection._

Place two concave mirrors at about twelve feet distance from each other, and let the axis of each be in the same line. In the focus of one of them place a live coal, and in the focus of the other some gunpowder. With a pair of strong bellows keep blowing the coal, and notwithstanding the distance between them, the powder will presently take fire.

The mirror may be either made of gla.s.s, metal, or pasteboard gilt.

_To find the Number of Changes that may be rung on Twelve Bells._