HISTORY OF MAGNETISM.
It is said that the word magnetism
is derived from the name of a Greek shepherd, called
Magnes, who once observed on Mount Ida the attractive
properties of loadstone when applied to his iron shepherd’s
crook. It is more likely that the name came from
Magnesia, a country in Lydia, where it was first discovered.
It was also called Lapis Heracleus. Heraclea
was the capital of Magnesia. Loadstone is a magnetic
ore or oxide of iron found in the natural state, and
has at some time by natural processes been rendered
magnetic that is, given the power of attracting
iron, and, when suspended, of pointing to the North
and South Poles. The power of the natural magnet
was known at a very early age in the history of man.
It was referred to by Homer, Pythagoras, and Aristotle.
Pliny also speaks of it, and refers to one Dinocares,
who recommended to Ptolemy Philadelphus to build a
temple at Alexandria and suspend in its vault a statue
of the queen by the attractive power of “loadstones.”
There is also mention of a statue being suspended in
like manner in the temple of Serapis, Alexandria.
It is claimed that the Chinese knew
of and used the magnetic needle in the earliest times
and that travelers by land employed this needle suspended
by a string to guide them in their journeys across
the country a thousand years before Christ. Notwithstanding
the claims of the Chinese and Arabians to the discovery
of the use of the magnetic needle, modern authors
question whether the ancients were familiar with any
artificial construction of a magnetic needle, however
much they may have studied and used the loadstones.
No doubt the loadstone in its natural state was used
by mariners to steer their ships by, long before its
artificial counterpart was invented. In a history
of the discovery of Iceland, by Are Frode, who
was born in 1068, it is stated that a mariner by name
of Folke Gadenhalen sailed from Norway in search of
Iceland in the year 868, and that he carried with
him three ravens as guides, for he says, “in
those times seamen had no loadstones in the northern
countries.” The magnetic needle as applied
to the mariner’s compass was known in the eleventh
century, as proved by various authors. In an old
French poem, the manuscript of which still exists,
the mariner’s compass is clearly mentioned.
The author was Guyot, of Provence, who was alive in
1181.
Like electricity, magnetism has had
a long history, but little use was made of it till
modern times beyond that of the mariner’s compass.
It can readily be seen what an important factor it
was in the science of navigation. Long after
the discovery of the compass needle there were many
perplexing problems arising, and all sorts of theories
were advanced to account for the various phenomena.
The variation of the needle was one of these problems.
It is said that Columbus was the first to discover
the variation of the needle, as well as America.
This is disputed, however, as every man’s pretensions
usually are. However this may be, Columbus had
to invent some plausible theory to account for this
variation to prevent a mutiny among his crew.
They were very superstitious and thought that they
were sailing into a new world where the laws of nature
were different from those of Spain. One phenomenon
that disturbed Columbus was the dip of the needle.
As we move in a northerly direction a magnetic needle
dips, and it was the observation of this phenomenon
in different latitudes that finally resulted in the
invention of the dipping needle. It is well known
that one pole of a magnetic needle points to the north
and the other to the south. In other words, what
is called the north pole of a needle points to one
of the magnetic poles of the earth which is in the
direction of the north pole, though not the same as
the geographical pole. A dipping needle revolves
on an axis so that it can point to any declination.
If we should construct one that is perfectly balanced,
so as to lie in a perfectly horizontal direction before
it is magnetized, it will dip in this latitude downward
toward the north after magnetization. If we keep
moving northward it will continue to dip downward till
we come to the true magnetic pole, when what is called
the north pole of the needle will point directly downward.
If we go back to the equator the needle will lie horizontally
again. We call the end of the needle that points
to the north the north pole. It is really the
south pole, because unlike poles attract each other.
If the magnetic poles of the earth are at the north
and south geographical poles, the south pole of the
needle will point north. But it is less confusing
to call the end of the needle that points north the
north pole. The nomenclature is purely arbitrary.
It was not until it was learned that
magnets could be made by electricity that they became
commercially important outside of their use in navigation.
The advent of electricity has brought magnetism to
the front as one of the great factors in our modern
civilization. And we might say with equal force
that the discovery of magnetism has brought electricity
to the front. The truth is that they depend upon
each other. Electricity would be robbed of a
large part of its importance as a factor in modern
life if it were not for its relation to magnetism.
Even electric lighting would be impossible, commercially,
if it were not for the part magnetism plays in the
production of electricity for this purpose. It
could not be successfully carried on with any battery
but the storage-battery, and the storage-battery is
dependent upon the dynamo, and the dynamo is a magneto-electric
machine. When we come to analyze the relation
between magnetism and electricity we cannot separate
them without robbing each of a large part of its usefulness.
They are interdependent forces.
As in the case of electricity there
have been many theories regarding magnetism.
One philosopher in the old days accounts for the variation
of the compass-needle on the theory that there are
two globes, one revolving within the other, and that
any derangement of their normal movements in relation
to each other affects the needle. Evidently there
were cranks in those days as well as now. Another
theory of magnetism was that there were two fluids a
boreal and an austral one developing north
polarity and the other south polarity. In the
next chapter the nature of magnetism in the light
of modern investigation will be discussed.