ODD EXPERIMENTS
TO WHILE AWAY WINTER HOURS
THE famous King Belshazzar was much dismayed to see the mysterious
writing upon the wall of his palace. Without reducing your friends to a
similar state of terror, a very easy experiment can be performed
productive of the same effect, and if it does not exactly make their
knees strike together, it will astonish them very much.
The appliances are such as can be found in any home, and the strange
writing can be produced in the following way.
[Illustration: FIG. 1.--Showing relative positions of candle and mirror
so that patch of light is thrown on the wall.]
At one end of a dark room erect a screen that shall conceal you and your
apparatus effectually from the spectators. Upon a table behind this
screen place a large mirror, such as can be found upon any
dressing-table. Put a lighted candle in front of this glass, placing the
latter at such an angle that a large patch of light is thrown upon the
wall before you, as in Fig. 1.
The screen must, of course, hide all this from the company, who will see
nothing but the light on the wall.
To write your message is now a very simple matter. Dip a coarse brush
into some lamp-black water color, and, writing backwards, inscribe what
you wish upon the face of the mirror. The message will then appear
legibly upon the wall, seemingly written by a mysterious hand.
By dipping the brush into clean water and washing out what you have
written upon the glass, the message on the wall will disappear as
inexplicably as it appeared in the first place.
[Illustration: FIG. 2.--Thread passed round prongs of the bone.]
[Illustration: FIG. 3.--Match through twisted thread.]
A peculiar optical illusion is accomplished as follows. The wishbone of
a fowl or duck should be thoroughly cleaned, and a thread passed several
times around the prongs of the fork, as shown in Fig. 2. Having secured
the thread tightly, pass a strong wooden match between the strands,
twisting it several times until the prongs of the bone have been drawn
closer together (Fig. 3).
Now, pulling out the match sufficiently to allow of one end catching
against the fork, hold the bone firmly. Releasing the match it
immediately describes a circle, striking against the under part of the
fork, but so rapidly has it completed this revolution that the eye has
been quite unable to follow it. This causes an illusion that induces all
who witness the experiment to imagine that the match passes through the
fork of the bone at A.
But if the eye was too slow in the last experiment, it is so officious
in what is next to be described that it sees something which really does
not take place.
[Illustration: FIG. 4.--The lion and his cage.]
Draw a lion and a cage, as in Fig. 4. If you place a visiting card upon
the line A B, and put your face so near that the right eye looks upon
the lion whilst the left can see only the cage, you will observe the
lion walking into his cage as naturally as if he were at the Zoo!
A rather amusing experiment, and one which will afford immense pleasure
to the juvenile members of your party, is as follows:--
Cut a circular disc of stout cardboard 12″ in diameter. In the center
make a hole to allow the disc to revolve easily, but not loosely, upon a
wooden penholder, which should be fixed at right angles to a wooden
stick (Fig. 5).
[Illustration: FIG. 5.--Disc of cardboard kept in place with penholder.]
[Illustration: FIG. 6.--Showing box in correct position.]
Upon the center of the disc fasten a cylindrical cardboard box (A, Fig.
6), with the penholder passing right through it. This box should be
roughly 3″ high and 2″ in diameter.
At a radius of 4¹⁄₂″ from the center describe a semicircle upon the disc
at E F (Fig. 6), whilst upon the same half of the cylinder describe a
line as G H in the same figure. Now pierce about twenty-five equidistant
holes in E F and G H, joining them with thread, as in Fig. 7.
Cover these threads with little strips of paper in such a manner as to
make a plane surface, as shown in Fig. 8. Then fasten a cork upon the
end of a wire attached to the stick, and in a cleft in this cork put a
little cardboard figure as in the illustration.
Make the disc revolve by a rapid turn of the hand, and if a candle be so
placed as to cast the shadow of the little man upon the disc, he will
be seen engaged in making sundry passes and lunges in the manner of the
perfect fencer.
[Illustration: FIG. 7.--Mode of joining thread.]
[Illustration: FIG. 8.--The toy complete.]
Various other figures can be made in a similar way with great success,
and when cleverly managed the toy will be found most amusing.
LIFE PARTNERS
If at any time it should happen that an engaged couple are amongst the
friends whom you wish to entertain, a very simple piece of apparatus can
be made that will give these good people much pleasure.
In the four sides of a cube box, measuring 18″ each way, make an oval
opening, 9″ by 7″, as A, B, C, D in Fig. 9. Inside the box place two
mirrors, back to back, diagonally from G to E (Fig. 10), and contrive
four curtains to draw up simultaneously over the holes.
[Illustration: FIG. 9.--Showing box with oval openings.]
[Illustration: FIG. 10.--Showing box with oval openings and mirrors.]
You must now get two couples to look through the holes, arranging the
two men opposite each other, as at A and C, and the ladies at B and D,
promising them that by looking into the simple but magical box they
shall see the future partners of their lives and pleasures.
As soon as they are in position raise the curtains, when A will see B,
and C will be gazing at D, so that if you have sorted the parties
aright, they will feel so pleased with themselves and with you that no
inquiry will be made as to how the trick is done.
To turn from sight to hearing, the following is a simple experiment
which can be exhibited without any special apparatus.
Cut a plain cross from a sheet of notepaper, as in Fig. 11, and place it
over a wine-glass, bending the ends to prevent it slipping off. Almost
fill the glass with water, taking great care to leave the sides and rim
perfectly dry.
If you damp your finger and pass it over any part of the glass outside,
a distinct humming will be heard, but the more remarkable thing to
observe is that the cross will begin to revolve very slowly so long as
your finger rubs a portion of the glass between the arms of the
cross--as at A in Fig. 11. Yet when you begin to rub beneath one of the
arms the paper will remain perfectly still. A complete revolution of the
paper can be produced by rubbing round the glass in a circle.
[Illustration: FIG. 11.--Showing paper cross and glass almost filled
with water and cross placed over the top.]
The vibration of the glass when emitting the notes explains this
phenomenon, although the reason that the cross should remain still when
you rub beneath one of its arms is too technical for explanation here.
[Illustration: FIG. 12.--A “light” experiment.]
A LIGHT EXPERIMENT
Why do we wear white clothes in extreme heat and dark clothes in the
winter? To this question every one will answer that white clothes absorb
less heat than black, and that we therefore feel the rays of the sun
less.
Quite true; and yet, how is it that Polar bears and other Arctic
creatures exposed to such extreme cold are clothed in white?
The fact is that not only does white absorb less heat, but it serves to
retain heat, and a white coat preserves the natural warmth in the
animal’s body. This is exemplified by the following experiment, for
which only a tumbler is required.
Choose a glass with the lower part faced, as in Fig. 12. Color these
faces black and white alternately, a little India ink serving for the
former and some crushed chalk and water for the latter.
With a very small knob of wax fasten a pin to each face, as shown in the
figure. Having done this place a lighted candle within the glass.
The heat, striking the interior equally, is modified by the colors
painted on the outside to such an extent that after some little while
the wax supporting the pins of the BLACK faces is melted, whilst the
pins on the white parts remain unaffected. This shows very clearly that
the white prevents the escape of internal heat, as surely as it prevents
the penetration of external warmth.
THE PYROMETER
We all know that metals expand under heat. The amount of such expansion
may be measured by a simple little apparatus called a pyrometer.
[Illustration: FIG. 13.--Showing how to make a pyrometer.]
On a wooden base, B, C (Fig. 13), make two uprights, A and D, of which A
must be a half inch higher than D. Bore a hole a quarter of an inch from
the top of A, but not right through the wood.
A couple of pins must be bent into the shape of a Y and driven into the
top of D, as in Fig. 13. With a little sealing-wax fasten a paper
pointer to the eye end of a needle and lay the needle across the pins,
P, P (Fig. 14). Next place an ordinary knitting-needle in the hole at A,
and rest it over the small needle with the pointer. The pyrometer is now
complete.
Put a lighted candle under the knitting-needle between D and A, as in
the figure, taking care that the flame plays freely upon the needle. As
the latter grows hot you will notice that the pointer moves slowly from
left to right, being acted upon by the hot knitting-needle passing over
the axle at X.
[Illustration: FIG. 14.--Showing needle laid in position across pins.]
If a small paper dial be made against the pointer, the amount of the
expansion can be even more clearly observed. Of course two or even more
candles may be used, the result being that the needle shows more and
more expansion as it becomes hotter.
THE BROKEN BOTTLE
An interesting and useful experiment with a broken bottle is depicted in
Fig. 15.
Fill the broken piece with oil to whatever level you desire it to be
cut, and stand it upon a perfectly level table. Now plunge a red-hot
poker into the oil and hold it there for a few seconds, when there will
be a loud crack, and the top of the broken part will come off, even and
smooth, as in Fig. 16.
[Illustration: FIG. 15.--Portion of broken bottle for experiment.]
[Illustration: FIG. 16.--Showing smooth break after red-hot poker has
been plunged into the oil.]
It may not be generally known that a sheet of glass may be cut regularly
and evenly with a pair of strong scissors.
A glance at Fig. 17 will give an idea of how this is done. The apparatus
required is a large pail of cold water and a pair of strong scissors.
Plunge the glass, the scissors, and the hands, right into the water so
that no part of either scissors or glass escapes immersion. You will now
find that the scissors cut cleanly without the glass cracking or
splintering.
The reason for this is that the water deadens the vibrations both of the
scissors and the glass, thus insuring a neat and clean fracture.
[Illustration: FIG. 17.--A glass-cutting experiment.]
COMPRESSED AIR
An interesting and effective experiment may be performed with compressed
air. The arrangements are very simple and the requirements few.
[Illustration: FIG. 18.--Walnut shell with necessary holes bored.]
Divide a walnut shell into two, and bore a hole in the bottom of each
half. In one of the cups thus obtained make another hole half-way up the
side, as in Fig. 18. Now, with a little sealing-wax fasten three straws
into these holes.
In the cork of a fair-sized jar, which should be of some opaque glass,
bore two holes, through which the straws must be placed at unequal
heights, as shown in Fig. 19. Having almost filled the jar with clear
water, place the cork with the straws so tightly that no air can
possibly enter either at the sides or by any other means than through
the straws.
The following strange effect will now be obtained. Pouring some colored
liquid into the top shell A, plain clear water will come from the spout
C of the lower shell B, and will continue as long as you pour from above
(Fig. 20).
The reason of this is that the compressed air in the jar forces the
clear water through the straw at B, which, being plunged deep into the
clear liquid, carries off none of the colored matter passed into the jar
by means of A.
[Illustration: FIG. 19.--Showing positions of straws for experiment.]
[Illustration: FIG. 20.--Pouring the colored liquid into the top shell.]
This experiment may be performed with red wine and water, but the result
is not quite so satisfactory on account of the ease with which wine and
water mix.