that to describe it would be superfluous; particularly as it can now
be purchased at a very reasonable expense, at any of the opticians':
but as many persons who have a taste for drawing might not be pleased
with the designs to be had at the shops, or might wish to indulge
their fancy in a variety of objects, which to purchase would become
expensive, we here present our readers, in the first place, with the
method of drawing them, which will be succeeded by a plain
description of some very diverting experiments.
_Of Painting the Glasses._
You first draw on a paper, the size of the glass, the subject you mean
to paint; fasten this at each end of the glass with paste, or any
other cement, to prevent it from slipping. Then with some very black
paint mixed with varnish, draw with a fine camels'-hair pencil, very
lightly, the outlines sketched on the paper, which, of course, are
reflected through the glass. Some persons affirm that those outlines
can be more readily traced with japan writing ink, and a common pen
with a fine nib; but this, even if it succeeds in making a delicate
black outline, is sure to be effaced by damp or wet.
It would improve the natural resemblance, if the outlines were drawn
with a strong tint of each of the natural colours of the object; but
in this respect you may please your own fancy. When the outlines are
dry, colour and shade your figures; but observe, to temper your
colours with strong white varnish. A pleasing effect will be produced,
if you leave strong lights in some parts of the drapery, &c., without
any colours. The best colours for this purpose are transparent ones;
opaque or mineral colours will not do. The following are in most
repute.
For Pink and crimson Lake or carmine.
Blue Prussian blue.
Green Calcined verdigris, or distilled ditto.
Yellow Gamboge.
_To represent a Storm at Sea._
Provide two strips of glass, whose frames are thin enough to admit
both strips freely into the groove of the lantern. On one of these
glasses paint the appearance of the sea from a smooth calm to a
violent storm. Let these representations run gradually into each
other, as in Fig. 9, and you will of course observe, that the more
natural and picturesque the painting is, the more natural and pleasing
will be the reflection.
[Illustration: Fig. 9.]
[Illustration: Fig. 10.]
On the other glass, Fig. 10, paint various vessels on the ocean,
observing to let that end where the storm is, appear in a state of
violent commotion, and the vessels as if raised on the waves in an
unsettled position, with heavy clouds about them.
You then pass the glasses slowly through the groove, and when you come
to that part where the storm is supposed to begin, move them gently up
and down, which will give the appearance of the sea and vessels being
agitated; increase the motion till they come to the height of the
storm. You will thus have a very natural representation of the sea and
ships in a calm and storm; and as you gradually draw the glasses back,
the tempest will subside, the sky appear clear, and the vessels glide
gently over the waves.
By the means of two or three glasses, you may also represent a battle
on land, or a naval engagement, with a variety of other pleasing
experiments.
_To produce the appearance of a Spectre on a Pedestal in the middle of
a Table._
Enclose a small magic lantern in a box, Fig. 11, large enough to
contain a small swing dressing-glass, which will reflect the light
thrown on it by the lantern in such a way, that it will pass out at
the aperture made at the top of the box; which aperture should be
oval, and of a size adapted to the cone of light to pass through it.
There should be a flap with hinges, to cover the opening, that the
inside of the box may not be seen.
[Illustration: Fig. 11.]
There must be holes in that part of the box which is over the lantern,
to let the smoke out; and over this must be placed a chafing-dish of
an oblong figure, large enough to hold several lighted coals. This
chafing-dish, for the better carrying on the deception, may be
enclosed in a painted tin box, about a foot high, with a hole at top,
and should stand on four feet, to let the smoke from the lantern
escape.
There must also be a glass planned to rise up and down in the groove
_a b_, and so managed by a cord and pulley, _c d e f_, that it may be
raised up and let down by the cord coming through the outside of the
box. On this glass, the spectre, (or any other figure you please,)
must be painted in a contracted or equal form, as the figure will
reflect a greater length than it is drawn.
When you have lighted the lamp in the lantern, and placed the mirror
in a proper direction, put the box on a table, and, setting the
chafing-dish in it, throw some incense, in powder, on the coals. You
then open the trap door and let down the glass in the groove slowly,
and when you perceive the smoke diminish, draw up the glass, that the
figure may disappear, and shut the trap door.
This exhibition will afford a deal of wonder; but observe, that all
the lights in the room must be extinguished; and the box should be
placed on a high table, that the aperture through which the light
comes out may not be seen.
There are many other pleasing experiments which may be made with the
magic lantern, but the limits of our work will not permit us to
specify them, without excluding many other equally interesting
subjects of a different nature.
_The Artificial Landscape._
Procure a box, as in Fig. 12, of about a foot long, eight inches wide,
and six inches high, or any other dimensions you please, so they do
not greatly vary from these proportions. At each of its opposite ends,
on the inside of this box, place a piece of looking-glass that shall
exactly fit: but at that end where the sight hole A is, scrape the
quicksilver off the glass, through which the eye can view the objects.
[Illustration: Fig. 12.]
Cover the box with gauze, over which place a piece of transparent
glass, which is to be well fastened in. Let there be two grooves at
each of the places C D E F, to receive two printed scenes, as follow:
On two pieces of pasteboard, let there be skilfully painted, on both
sides, any subject you think proper, as woods, bowers, gardens,
houses, &c.; and on two other boards, the same subjects on one side
only, and cut out all the white parts: observe also, that there ought
to be in one of them some object relative to the subject, placed at A,
that the mirror placed at B may not reflect the hole on the opposite
side.
The boards painted on both sides are to slide in the grooves C D E F,
and those painted on one side are to be placed against the opposite
mirrors A and B; then cover the box with its transparent top. This box
should be placed in a strong light, to have a good effect.
When it is viewed through the sight hole, it will present an unlimited
prospect of rural scenery, gradually losing itself in obscurity; and
be found well worth the pains bestowed on its construction.
_To draw, easily and correctly, a Landscape, or any other Object,
without being obliged to observe the Rules of Perspective, and without
the Aid of the Camera Obscura._
[Illustration: Fig. 13.]
Procure a box of pasteboard, A B C D, Fig. 13, of about a foot and a
half long, and made in the shape of a truncated pyramid, whose base, B
D F G, is eight inches wide, and six inches high. Fix to the other end
of it a tube of four or five inches long, and which you can draw out
from the box more or less. Line the inside of the box with black
paper, and place it on a leg or stand of wood, H, and on which it may
be elevated or depressed by the hinge I.
Take a small frame of wood, and divide it at every inch by lines of
black silk drawn across it, forming forty-eight equal parts; divide
these into still smaller equal parts, by lines of finer silk:[C] fix
this frame at the end of B D, as the base of the pyramid.
Provide a drawing-paper, divided into the same number of parts as in
the frame, by lines, lightly drawn in pencil. It is not material of
what size these divisions are; that will depend entirely on the size
you propose to draw the objects by this instrument.
Place this instrument opposite a landscape, or any other object that
you want to draw, and fix the leg firmly on, or in the ground, that it
may not shake; then turning it to the side you choose, raise or
incline it, and put the tube further in or out, till you have gained
an advantageous view of the object you intend to draw.
Place your eye, E, by the instrument, which you have adjusted to the
height of your eye, and, looking through the tube, carefully observe
all that is contained in each division of the frame, and transpose it
to the corresponding division in your paper; and if you have the least
knowledge in painting or even drawing, you will make a very pleasing
picture, and one in which all the objects will appear in the most
exact proportion.
By the same method you may draw all sorts of objects, as architecture,
views, &c., and even human figures, if they remain some time in the
same attitude, and are at a proper distance from the instrument.
[C] The different thicknesses of the silk serve to
distinguish more readily the corresponding divisions.
_Illuminated Prospects._
Provide yourself with some of those prints that are commonly used in
optical machines, printed on very thin white paper; taking care to
make choice of such as have the greatest effect from the manner in
which the objects are placed in perspective. Place one of these on the
borders of a frame, and paint it carefully with the most lively
colours, making use of none that are terrestrial. Observe to retouch
those parts several times where the engraving is strongest,[D] then
cut off the upper part or sky, and fix that on another frame.
[Illustration: Fig. 14.]
[Illustration: Fig. 15.]
The prints being thus prepared, place them in a box, A B C D, Figs. 14
and 15, the opening to which, E F G H, should be a little less than
the print. Cover this opening with a glass, and paint all the space
between that and the prints, which should be about two or three
inches, black. The frame that contains the sky should be about an inch
behind the other. In the back part of this box, which is behind the
prints, and which may be about four inches deep, place four or five
small candlesticks to hold wax lights, and cover that part entirely
with tin, that it may be the more luminous.
When the print is placed between the wax lights and the opening in the
front of the box, and there is no other light in the room, the effect
will be highly pleasing; especially if the lights are at a sufficient
distance from each other, and not too strong, that they may not
occasion any blots in the print. Those prints that represent the
rising or setting of the sun will have a very picturesque appearance.
Such as represent conflagrations have also a striking effect.
There should be two grooves for the print next the glass, that you may
insert a second subject before you draw away the first; and that the
lights in the back of the box may not be discovered.
You must not, thinking to make the print more transparent, cover it
with varnish; for that will prevent the gradation of the colours from
being visible. The frame should enter the side of the box by a groove,
that a variety of subjects may be introduced.
[D] When you colour a print, place it before you, against a
piece of glass, in a position nearly erect, that it may be
enlightened by the sun. You may also colour both sides of the
print.
EXPERIMENTS IN MAGNETISM.
_The Magnetic Wand._
Bore a hole three-tenths of an inch in diameter, through a round stick
of wood; or get a hollow cane about eight inches long, and half an
inch thick. Provide a small steel rod, and let it be very strongly
impregnated with a good magnet: this rod is to be put in the hole you
have bored through the wand, and closed at each end by two small ends
of ivory that screw on, different in their shapes, that you may better
distinguish the poles of the magnetic bar.
When you present the north pole of this wand to the south[E] pole of a
magnetic needle, suspended on a pivot, or to a light body swimming on
the surface of the water, (in which you have placed a magnetic bar,)
that body will approach the wand, and present that end which contains
the south end of the bar: but if you present the north or south end of
the wand to the north or south end of the needle, it will recede from
it.
[E] For the more clearly explaining this, it is to be
observed, that the two ends of a magnet are called its poles.
When placed on a pivot, in just equilibrium, that end which
turns to the north is called the north pole, and the other
end the south pole.
_The Mysterious Watch._
You desire any person to lend you his watch, and ask him if it will go
when laid on the table. He will, no doubt, say it will; in which case,
you place it over the end of the magnet, and it will presently stop.
You then mark the precise spot where you placed the watch, and, moving
the point of the magnet, you give the watch to another person, and
desire him to make the experiment; in which he not succeeding, you
give it to a third (at the same time replacing the magnet) and he will
immediately perform it.
This experiment cannot be effected, unless you use a very strongly
impregnated magnetic bar, (which may be purchased at the opticians',)
and the balance of the watch must be of steel, which may be easily
ascertained by previously opening it, and looking at the works.
_The Magnetic Dial._
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.
[Illustration: 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 assigned 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.
[Illustration: Fig. 17.]
[Illustration: Fig. 18.]
[Illustration: 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 glass, to prevent the needles from rising off
their pivots, as is done in the sea-compass.
Over the board place four plates of glass, 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 glass, 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 glass 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 circumstances 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 glass, 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.
_Glass broken by Air._
Lay a square of glass on the top of an open receiver, and exhaust the
air. The weight of the external air will press on the glass, 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._
Take water made so warm that you can just bear your hand in it, but
that has not been boiled; put it under the receiver, and exhaust the
air. Bubbles of air will soon be seen to rise, at first very small,
but presently become larger, and will be at last so great, and rise
with such rapidity, as to give the water the appearance of boiling.
This will continue till the air is let into the receiver, when it will
instantly cease.
_Aerial Bubbles._