_Is there any connection between magnetism and electricity?_
There is every reason to believe that magnetism and electricity are but
_modifications of one force_.
_What is a loadstone or a natural magnet?_
It is an _ore of iron_, known as the “_protoxide of iron_,” or
“_magnetic oxide of iron_,” which is capable of attracting other pieces
of iron to itself; and if suspended freely by a thread, and left to take
its own position, it will arrange itself so that its extremities will
point towards the north and south poles of the earth.
_Are natural magnets rare?_
They are _not_; they are found in many places in the _United States_. In
_Arkansas_, especially, an ore of iron possessing remarkably strong
attractive powers is very abundant.
The magnetic ore is usually of a dark gray hue, and possesses but little
metallic luster. If a piece of this ore be dipped in iron filings, or a
number of small needles, they will generally be found collected and
clinging together in great quantities at two opposite extremities,
whilst the middle portion is nearly destitute. The magnetic property,
whatever it may be, seems therefore to be collected and act with the
greatest energy at two opposite extremes; these have been termed
_poles_.
_What is the origin of the terms “magnet” and “magnetism”?_
The loadstone or natural magnet was first found at _Magnesia_, in Lydia,
Asia, whence were derived the names.
_Can a natural magnet communicate its attractive properties to other
bodies by contact?_
It _can_, and that too without any _apparent loss_ of attractive
strength.
_What bodies are capable of being magnetized by contact with natural
magnets?_
_Iron_ and _steel_ are the substances most susceptible of this
influence, but brass, nickel, and cobalt can also become magnets.
_Does the magnetism imparted to a piece of soft iron, or steel, by
contact with a natural magnet, remain permanent in their
substances?_
In the _steel_ it _does_, but the soft iron _loses its power_ as soon as
it is removed from the magnet.
_Is it necessary that absolute contact should take place between a
magnet and a piece of soft iron to render the latter a magnet?_
No, every piece of soft iron brought _near_ a magnet becomes by
induction itself a magnet.
_What do you mean by induction?_
It is the production of _like effects_ in _contiguous bodies_. In
electricity or magnetism, it is the influence exerted by an electrified
or magnetized body through a non-conducting medium without any apparent
communication of a current.
_What is meant by the directive power of the magnet?_
It is that power which will cause a magnet, when suspended freely, to
constantly _turn the same part_ towards the north pole and the opposite
part towards the south pole of the earth.
_What are the poles of a magnet?_
They are the _ends_ of the magnet, and are denominated north and south,
according as they point to the north or south poles of the earth.
_What are the poles of the earth?_
The _extremities of the earth’s axis_, or the points on the surface of
the globe through which the axis passes.
_What is a magnetic needle?_
Simply a _bar of steel_ which is a _magnet_, suspended in such a way
that it can _freely turn_ to the north or south.
[Illustration: =DIAGRAM SHOWING THE VARIATION OF THE MAGNETIC AND
GEOGRAPHICAL POLES=]
_What is a mariner’s compass?_
It is a _delicate steel bar or needle_ balanced upon a pivot placed
beneath its center of gravity in such a way that it can turn
horizontally without obstruction. This needle is usually inclosed in a
box, upon the bottom of which is a card, with the various points--north,
south, east, west, etc., etc., marked upon it.
Such a needle, if the box containing it be placed on a level surface,
will generally be observed to vibrate more or less, till it settles in
such a direction that one of its extremities or poles will point towards
the north, and the other consequently towards the south. If the position
of the box be altered or reversed, the needle will always turn and
vibrate again, till its poles have attained the same direction as
before.
_Does the compass needle always point exactly north and south?_
It does _not_; its natural direction is towards the north and south
poles, but it seldom points due north or south.
_Who first discovered the fact that a magnet would invariably point
to the north and the south, and made use of this knowledge in
constructing a compass?_
It is claimed to have been discovered by the _Chinese_: it was known in
Europe, and used in the Mediterranean, in the thirteenth century.
_How were the compasses of that time constructed?_
They were merely _pieces of loadstone_ fixed to a _cork_, which floated
on the surface of water.
_Is the earth itself supposed to be a magnet?_
It is undoubtedly a _great_ magnet.
_Is iron under certain circumstances rendered magnetic by the
inductive action of the earth’s magnetism?_
Most _iron bars_ and _rails_, as the vertical bars of windows, that have
stood for a considerable time in a perpendicular position, will be found
to be _magnetic_.
_If we suspend a bar of soft iron sufficiently long in the air, will
it assume magnetic properties?_
It _will_ gradually become magnetic; and although when it is first
suspended it points indifferently in any direction, it will at last
point _north and south_.
_How may a bar of iron, such as a kitchen poker, be made immediately
magnetic, without resorting to the use of other magnets?_
If the bar devoid of magnetism is placed with _one end on the ground_,
slightly inclined towards the north, and then struck one _smart blow_
with a _hammer_ upon the upper end, it will immediately acquire
_polarity_, and exhibit the attractive and repellant properties of a
magnet.
_What is a horseshoe magnet?_
It is a _magnetic bar_ bent into the _form of a horseshoe_.
When a piece of iron not magnetic is brought in contact with a common
magnet, it will be attracted by either pole; but the most powerful
attraction takes place when both poles can be applied to the surface of
the piece of iron at once. The magnetic bars are for this purpose bent
into the shape of the letter U, and are termed _horseshoe magnets_.
Several of these are frequently joined together with their similar poles
in contact; they then constitute a _magnetic battery_, and are very
powerful, either for lifting weights, or charging other magnets.
_If we break a magnet across the middle, what happens?_
Each fragment becomes converted into a _perfect magnet_; the part which
originally had a north pole acquires a south pole at the fractured end,
and the part which originally had a south pole, gets a north pole.
_If we divide a magnet to the extreme degree of mechanical fineness
possible, will the pieces possess magnetic powers?_
Each fragment, however small, will be a _perfect magnet_.