in all bodies, and is exhibited by various means, one of which, and the
most generally employed, is friction; but the bodies rubbed together must
consist of different substances; for, if they are alike, electricity
will not be evolved. Some substances, such as soot, charcoal, iron,
gold, silver, copper, and other metals, water, &c., are called _good
conductors_, because they transfer with great facility to other bodies
the electric fluid, which glides over the surface with the velocity of
light; while others, such as silk, wool, hair, feathers, dry paper,
leather, glass, wax, &c., are called _non-conductors_, because they resist
the progress of the fluid, which accumulates all the time the friction
continues. It is from these media that are obtained the usual phenomena
of electricity, as exhibited in the experiments which we shall hereafter
describe. Its effects are felt in almost every part of nature; the awful
lightning is the exhibition of the electric fluid, which accumulates in
the clouds, and which is discharged when the heavy lurid masses come in
contact with each other; the mysterious sweeping whirlwind, the terrific
rising and rolling of the sand in the desert wilds of Africa, and the
beautiful yet evanescent Aurora Borealis of the northern climes, are
amongst a few of its effects.
The next branch of the science of Electricity is GALVANISM, or, as it is
sometimes called, Voltaic Electricity; it is obtained through the simple
contact of different conducting bodies with each other. It was first
discovered at Bologna, in the year 1791, by the lady of Louis Galvani,
an Italian philosopher of great merit, and professor of anatomy; from
whom, indeed, the science received its name. His wife being possessed of
a penetrating understanding, and passionately loving him, took a lively
interest in the science which so much occupied his attention. At the time
the incident we are about to narrate took place, she was in a declining
state of health, and taking soup made of frogs, by way of restorative.
Some of these animals, skinned for the purpose, happened to be lying on
the table of Galvani's laboratory, where also stood an electrical machine,
when the point of a knife was unintentionally brought into contact with
the nerves of one of the frog's legs, which lay close to the conductor
of the machine, and immediately the muscles of the limb were violently
agitated. Madame Galvani having observed the phenomenon, instantly
informed her husband of it, and this incident led to the experiments
and interesting discoveries which will transmit his name to the latest
posterity.
The uses of Galvanic Electricity for scientific purposes are incalculable;
and its phenomena are so various and extraordinary, as to render the study
of this science exceedingly interesting. Through means of a galvanic
battery, substances are decomposed, colors changed, water is made
inflammable, and motion is given to lifeless bodies.
The experiments we give on Galvanism show the effect of the combination
which forms what is called a simple galvanic circle, by means of two
metals, zinc and silver, or zinc and copper, and water.
Galvanic action is always accompanied by chemical action, and all that is
necessary to disturb the galvanic fluid is to unite two metals together,
and subject them to the action of a fluid, which will act chemically upon
one of them, differently to what it does upon the other.
A galvanic circle may also be formed of one metal, and two different
fluids, which have a different action upon the metal.
Magnetism is a modification of electricity: at least, there is sufficient
evidence that these causes are intimately connected, if not identical; but
philosophers are as yet ignorant of its nature.
The property designated by the word magnetism is found in an iron ore
of a certain composition, and of a dark gray color and peculiar luster.
This ore alone is the local habitation of magnetism, whilst all others
are subject to its influence, or to be attracted by it. Still, so little
difference is there between the magnetic ore, or loadstone, and those
which do not possess the property, that only practiced mineralogists
can discern one from the other; and an experienced eye may see two ores
join each other by the principle of attraction, without knowing in which
resides the power, until another ore, non-magnetic, is brought within the
sphere of attraction, when it will adhere only to that which contains the
principle.
This singular property of the loadstone is imparted to other metallic
substances, by rubbing and keeping them close together for some length
of time: if a metal be of a hard texture like steel, it retains the
magnetic principle permanently; but if soft, it loses the power as soon
as separated from the magnet. The metals thus prepared, acquire the same
directive and attractive power as the loadstone or natural magnet, and are
employed for purposes of the utmost importance.
We proceed to give the youthful amateur the opportunity of exemplifying
the principles of electricity, galvanism, and magnetism, by several simple
experiments.
[Illustration]
EXPERIMENTS IN ELECTRICITY.
[Illustration]
1.--Lay a watch down upon a table, and on its face balance a tobacco-pipe
very carefully. Next take a wine-glass, rub it quickly with a silk
handkerchief, and hold it for half a minute before the fire; then apply it
near to the end of the pipe, and the latter, attracted by the electricity
evolved by the friction and warmth in the former, will immediately follow
it; and by carrying the glass around, always in front of the pipe, the
latter will continue its rotatory motion; the watch-glass being the center
or pivot on which it acts.
2.--Warm a glass tube, rub it with a warm flannel, and then bring a downy
feather near it. On the first moment of contact, the feather will adhere
to the glass, but soon after will fly rapidly from it, and you may drive
it about the room by holding the glass between it and the surrounding
objects; should it, however, come in contact with anything not under the
influence of electricity, it will instantly fly back to the glass.
3.--A stick of sealing-wax rubbed against a warm piece of flannel or
cloth, acquires the property of attracting light substances, such as small
pieces of paper, lint, &c., if instantly applied at the distance of about
an inch.
4.--Suspend two small pith balls, by fine silken threads of about six
inches in length, in such a manner, that when at rest they may hang in
contact with each other; on applying a piece of sealing wax, excited as in
the former experiment, they will repel each other.
5.--Take a piece of common brown paper, about the size of an octavo book,
hold it before the fire till quite dry and hot, then draw it briskly under
the arm several times, so as to rub it on both sides at once by the coat.
The paper will be found so powerfully electrical, that if placed against
a wainscoted or papered wall of a room, it will remain there for some
minutes without falling.
6.--And if, while the paper adheres to the wall, a light fleecy feather be
placed against it, it will be attracted to the paper, in the same way as
the paper is attracted to the wall.
7.--If the paper be again warmed, and drawn under the arm as before, and
hung up by a thread attached to one corner of it, it will hold up several
feathers on each side; should these fall off from different sides at the
same time, they will cling together very strongly; and if after a minute
they be all shaken off, they will fly to one another in a very singular
manner.
8.--Warm and excite the paper as before, lay it on a table, and place
upon it a ball made of elder pith, about the size of a pea; the ball will
immediately run across the paper, and if a needle be pointed towards it,
it will again run to another part, and so on for a considerable time.
9.--Support a pane of glass, previously warmed, upon two books, one at
each end, and place some bran underneath; then rub the upper side of the
glass with a black silk handkerchief, or a piece of flannel, and the bran
will dance up and down under it with much rapidity.
10.--Place your left hand upon the throat of a cat, and with the middle
finger and the thumb, press slightly the bones of the animal's shoulders;
then, if the right hand be gently passed along the back, perceptible
shocks of electricity will be felt in the left hand. Shocks may also be
obtained by touching the tips of the ears after rubbing the back. If the
color of the cat be black, and the experiment be made in a dark room,
the electric sparks may be very plainly seen. Very distinct charges of
electricity may also be obtained by touching the tips of the ears after
applying friction to the back, and the same may be obtained from the
foot. Placing the cat on your knees, apply the right hand to the back;
the left fore paw resting on the palm of your left hand, apply the thumb
to the upper side of the paw, so as to extend the claws, and by this
means, bring your fore finger into contact with one of the bones of the
leg, where it joins the paw; when, from the knob or end of this bone, the
finger slightly pressing on it, you may feel distinctly successive shocks,
similar to those obtained from the ears. It is, perhaps, unnecessary to
add, that, in order to this experiment being conveniently performed, the
experimenter must be on good terms with the cat.
ELECTRICAL SHOCK FROM A SHEET OF PAPER.
Place an iron japanned tea tray on a dry, clean, beaker glass; then take a
sheet of foolscap writing paper, and hold it close to the fire until all
its hygrometric moisture is dissipated, but not so as to scorch it; in
this state it is one of the finest electrics we have. Hold one end down on
a table with the finger and thumb, and give it about a dozen strokes with
a large piece of India rubber from the left to the right, beginning at the
top. Now take it up by two of the corners and bring it over the tray, and
it will fall down on it like a stone; if one finger be now brought under
the tray, a sensible shock will be felt. Now lay a needle on the tray
with its point projecting outwards, remove the paper, and a star sign of
the negative electricity will be seen: return the paper, and the positive
brush will appear. In fact, it forms a very extemporaneous electrophorus,
which will give a spark an inch long, and strong enough to set fire to
some combustible bodies, and to exhibit all the electric phenomena not
requiring coated surfaces. If four beaker glasses are placed on the
floor, and a book laid on them, a person may stand on them insulated; if
he then holds the tray vertically, the paper will adhere strongly to it,
and sparks may be drawn from any part of his body; or he may draw sparks
from any other person, as the case may be; or he may set fire to some
inflammable bodies, by touching them with a piece of ice.
LIGHT UNDER WATER.
Rub two pieces of fine lump sugar together in the dark, and a bright
electric light will be produced. The same effect, but in a more intense
degree, may be produced with two pieces of silex or quartz, the white
quartz being best for this purpose. The same effect may also be witnessed
by rubbing the pieces of quartz together, _under water_.
SIMPLE MEANS OF PRODUCING ELECTRICITY.
[Illustration]
To show the nature of electrical action, rub a piece of sealing-wax or
amber upon the coat sleeve, and it will be found that while warm by the
friction, it attracts light bodies, such as straws or small pieces of
paper. In our experiments we have shown that if a clean glass tube be
rubbed several times through a silken or leather cloth, and presented to
any substance, it will immediately attract or repel them; and if a poker
suspended by a dry silk string be presented to its upper end, then the
lower end of the poker will exhibit the same phenomena as the tube itself,
which shows that the electrical fluid passes through the metal. But if
for a metallic body a stick of glass or sealing wax be substituted, these
phenomena will not occur, which proves that the electrical fluid does not
pass through these substances.
By this it will be perceived that besides the class of bodies called
electrics, there is another which we call conductors. These bodies cannot
be excited themselves, but have the power of transmitting the electric
fluid through them. These bodies comprise all the metals, some metal and
metallic ores; the fluids of animal bodies; water, and other fluids,
except oil; ice, snow, earthy substances, smoke, steam, and even a vacuum.
[Illustration]
When any electrified conductor is wholly surrounded by non-conductors, so
that the electric fluid cannot pass from the conductor along conductors to
the earth, it is said to be insulated. Thus the human body is a conductor
of electricity; but if a person standing on a glass stool (as represented
in the drawing) be charged with electricity, the electric fluid cannot
pass from him to the earth, and he is said to be _positively electrified_,
because he has more than his natural share; he is also _insulated_, and
if he be touched by another person standing on the ground, sparks will be
exhibited at the point of contact, where also the person touching will
feel a pricking sensation.
ATTRACTION AND REPULSION EXHIBITED.
[Illustration]
In order to illustrate certain remarkable facts in this science of an
amusing character, attention must be directed to the figure A B, which
is a metal stand; C is a small piece of cork or pith, which is suspended
from the hook by a dry silken thread. Having rubbed an electron, as a dry
rod of glass, and presented it to C, the ball will be instantaneously
attracted to the glass, and will adhere to it. After they remain in
contact for a few seconds, if the glass be withdrawn without being
touched by the fingers, and again presented to the ball, the latter will
be _repelled_ instead of attracted, as in the first instance. By being
touched with the finger, the ball can be deprived of its electricity, and
if, after this has been done, we present a piece of sealing-wax in place
of the glass formerly employed, the very same phenomena will take place.
On the first application the ball will be _attracted_, and on the second
_repelled_.
Before the young reader can perform any very important experiments with
electricity, he must become possessed of an ELECTRICAL MACHINE, which is
an instrument contrived for the purpose of rubbing together the surfaces
of electrics and non-electrics. They generally consist of a cylinder, or
plate of glass, and a piece of silk for it to rub against, covered with an
amalgam, the method of preparing which we shall hereafter describe.
HOW TO MAKE AN ELECTRICAL MACHINE.
[Illustration]
It is very easy to make a glass machine of the cylindrical form, if the
maker cannot afford to buy one. First procure a common wine bottle of
good dimensions, and thickish glass Drill a hole through its bottom, by
igniting a piece of worsted tied round round it, dipped in turpentine,
which will do this. Through this hole and the mouth pass a spindle, as
represented in the cut. The end of B should be squared to fix a handle on,
and the spindle should be fixed firmly in the bottle. The bottle is then
to be fixed in a frame, in the following manner: The end of the spindle
C passes through a hole at B; and the other end at C has the handle for
turning the machine.
[Illustration]
[Illustration: CUSHION.]
Next make a cushion of wash-leather, stuffed with wool, and fastened to
the top of a frame of the following figure. This frame is to be of such
a height that the cushion shall press against the sides of the bottle,
and a piece of black silk is sewn on to the top of the cushion, and hangs
over the bottle D. The cushion should be smeared with an amalgam, formed
by melting together in the bowl of a tobacco pipe, one part of tin with
two of zinc; to which, while fluid, should be added six parts of mercury.
These should be stirred about till quite cold, and then reduced to a fine
powder in a mortar, and mixed with a sufficient quantity of lard to form a
thickish paste. When all is done, the machine is complete.
CONDUCTOR.
The electricity being generated by the friction produced between the
rubber and the bottle from the motion imparted by the handle, it is
necessary to draw it off for use. This is performed by what is called a
conductor. This is made in the following manner: At right angles to one
end of a cylinder of wood, about two inches and a half in diameter, and
six inches long, fix a small wooden cylinder about three quarters of an
inch in diameter, and three inches long, rounded at both ends--the other
end of the larger cylinder is also to be rounded. Cover the whole with
tinfoil, and mount it on a stand on a glass rod. When used, it is to be
placed with the even piece in a line even with, and about half an inch
from the bottle, and it should be of such a height as to come just below
the silk apron. When it is wished to charge a Leyden jar, it is to be
placed at the round end of the conductor. By these simple means a great
variety of pleasing experiments may be performed; but to show the various
phenomena connected with this interesting study, we shall now describe an
electrical machine of the newest construction, and perform our experiments
with it.
THE PLATE ELECTRICAL MACHINE.
[Illustration]
Formerly the electrical machine was made in the form of a cylinder,
but now it consists of a plate A, as seen in the engraving. The plate
is turned by the handle F, through the rubber B B, which diffuses the
excitement over the glass. The points or balls at each side of the plate
carry off a constant stream of positive electricity to the prime conductor
C. Negative electricity is generated by insulating the conductor to which
the cushion is attached, and continuing the prime conductor with the
ground, so as to carry off the fluid collected from the plate.
HOW TO DRAW SPARKS FROM THE TIP OF THE NOSE.
If the person who works the machine be supported on a stool having glass
legs, and connected with the conductor by means of a glass rod, the
electricity will pass from the conductor to him, and as it cannot get
away, owing to the glass on which he stands being a non-conductor, any
person on touching him can draw the electricity from him, which will
exhibit itself in small sparks as it passes to the person who touches him.
If touched on the nose, sparks of fire will issue from it.
HOW TO GET A JAR FULL OF ELECTRICITY.
[Illustration]
A most useful piece of electrical apparatus is called the Leyden jar,
here represented. It is employed for the purpose of obtaining a quantity
of electricity, which may be applied to any substance. It consists of a
glass jar, coated both inside and without, four fifths of the way up,
with tinfoil. A knob rises through a wooden top, communicating with the
inside of the jar. When it is wished to charge the jar, this knob is
applied to the prime conductor of the electrical machine when in action,
and a quantity of electricity being given off, the jar will remain charged
with it till a connection is made, by some good conductor of electricity,
between the knob and the outside tinfoil. A piece of brass chain must hang
from the stem that carries the knob, and connect it with the interior of
the jar.
THE ELECTRICAL BATTERY.
[Illustration]
If several of these jars be united, an enormous quantity of electricity
can be collected; but in arranging them, all the interior coatings must be
made to communicate by metallic rods, and a similar union must be effected
among the exterior coatings. When thus arranged, the whole series may be
charged as if they formed but one jar.
[Illustration]
For the purpose of making a direct communication between the inner or
outer coatings of a jar or battery, by which a discharge is effected, an
instrument called a discharging rod is employed. It consists of two bent
metallic rods, terminating at one end by brass balls, and connected at
another by a joint which is fixed to the end of a glass handle, and which,
acting like a pair of compasses, allows of the balls being separated at
certain distances. When opened to the proper degree, one of the balls is
made to touch the exterior coating, and the other ball is then brought
into contact with the knob of the jar, when a discharge is effected; while
the glass handle secures the person holding it from the effects of the
shock.
DANCING BALLS AND DOLLS.
[Illustration]
[Illustration]
Get two round pieces of wood, A B, and coat them with tin foil, or two
pieces of metal plate; attach one of them to the prime conductor by a
chain, and let it hang about two or three inches from the knob. Place some
pith balls upon the bottom piece of wood B, and bring it under the other.
Immediately this is done, and the upper piece is charged by electricity
from the machine, the pith balls will jump up and down, and from one to
the other with great rapidity. If some of the pith be formed into little
figures, they will also dance and leap about in the most grotesque manner.
The same may be made to dance by merely holding the inside of a dry glass
tumbler to the prime conductor for a few minutes, while the machine is in
action, and then whelming it over them, when they will jump about to the
no small astonishment of the spectators, as the cause of their motion is
not quite so apparent.
THE ELECTRICAL KISS.
This amusing experiment is performed by means of the electrical stool.
Let any lady challenge a gentleman not acquainted with the experiment,
to favor her with a salute. The lady thereupon mounts the glass stool,
and takes hold of a chain connected with the prime conductor. The
machine being then put in motion, the gentleman approaches the lady, and
immediately he attempts to imprint the seal of soft affection upon her
coral lips, a spark will fly in his face, which generally deters him from
his rash and wicked intention.
RINGING BELLS.
[Illustration]
Bells may be made to ring by electricity in the following manner. Let
three small bells be suspended from a brass wire D D, and supported by
a glass pillar A, passing through bell B to the bell E. The electrical
apparatus being attached to the knob F the electricity passes down the
wires D D to the bells, which are then positively electrified, and
attract the clappers C C, that are negatively so, in consequence of being
insulated by the silken strings, which are not conductors. The bells
therefore attract the clappers till they are charged, when they strike
against the center bell to discharge themselves, and thus a peal is rung
on the bells until the electricity is driven off.
WORKING POWER OF ELECTRICITY.
[Illustration]
This may be shown in a variety of ways. The subjoined machine will
exhibit the principle upon which many ingenious toys may be made by the
young philosopher. In the figure A is a wooden board or stand, B B B B,
four pillars having fine wires, C C, stretched above. On these rest the
rotatory wire or wheel F, having its points turned the reverse way. By
means of a chain attached to the conductor, and to the instrument at B,
the electricity passes over the pillar B, up the wire C into the wheel,
and off at the points, which causes it to be turned round on an inclined
plane till it reaches the top.
THE ELECTRIFIED WIG.
While a person is on the electrical stool, if he be charged with much
electricity,
"Each hair will stand on end,
Like quills upon the fretful porcupine."
[Illustration]
A wooden head, not your own, but a real wooden head, with a wig of
streaming hair, and a handsome face to correspond, may be made in the
following form, with a wire in the neck to support it by, and fixed in
the conductor of an electrical machine. When this is put in motion, the
hair will rise up as in figure 2, to astonish even "Whigs," who are seldom
astonished by, or deterred from anything.
IMITATION THUNDERCLOUDS.
To show the manner in which thunderclouds perform their operations in
the air. A A is a wooden stand, on which are erected two uprights, B B;
C C are two small pulleys, over which a silken cord can pull easily; E
is another silken line stretched across from one upright to another; on
these silken cords two pieces of thin cardboard, covered with tin foil,
and cut so as to represent clouds, are to be fixed horizontally, and made
to communicate by means of thin wires, F and G, one with the _inside_, and
the other with the outside of a charged jar, D. Now, by pulling the loop
of the silk line E, the cloud 1 will be brought near the cloud 2; continue
this slowly until the clouds (which are furnished with two small brass
balls) are within an inch of each other, when a beautiful flash, strongly
resembling lightning in miniature, will pass from one cloud to the other,
restoring electrical equilibrium.
[Illustration]
THE LIGHTNING-STROKE IMITATED.