DR. GILBERT OF COLCHESTER
THE ancients were in the habit of consulting books written
by old masters whenever they were puzzled by an unknown power or
force of nature. Instead of making experiments they went to their
bookshelves, and read what the wise men of long ago had written on the
same or similar subjects. They thought that they could not surpass
the old masters in wisdom, and that what the old masters did not know
was not worth knowing. This habit accounts for the slow progress made
in science in Europe during the Middle Ages, that is, from about the
sixth to the fifteenth centuries. But when Columbus discovered America,
and broke through the traditions of the ancients by his courageous
exploration of the unknown, a new era began to dawn.
One of the heralds of this new era was Dr. William Gilbert. He was
born in Colchester, in Essex, in the year 1540, and was the son of
the Recorder of that city. He was educated at Cambridge, and became a
medical doctor at the age of twenty-nine. He was appointed physician
to Queen Elizabeth, and was elected president of the Royal College of
Physicians in the year 1600.
It was Dr. Gilbert who founded the science of Magnetism and the science
of Electricity, collecting all that was known on these subjects, and
making many new and valuable experiments of his own. All these facts
he expounded in a great book which was published in London in the
year 1600. It is called, _On the Magnet and Magnetic Bodies, and on
the Great Magnet, the Earth_. In his introduction he lays down new
principles to guide scientific work in the future, in words somewhat as
follows:--
[Illustration: Fig. 17.--Dr. William Gilbert, who founded the Sciences
of Magnetism and Electricity.]
“In the discovery of secrets and in the investigation of the hidden
causes of things, clear proofs are afforded by trustworthy experiments
rather than by probable guesses and opinions of ordinary professors and
philosophers. In order, therefore, that the noble substance of that
great magnet, the earth, hitherto quite unknown, and the exalted powers
of this globe of ours may be better understood, I shall first of all
deal with common magnets, stones, and iron materials, and with magnetic
bodies, and with the near parts of the earth, which we can reach with
our hands and perceive with our senses. After that I shall proceed to
show my new magnetic experiments, and so I shall penetrate for the
first time into the innermost parts of the earth.
“After I had seen and thoroughly examined many of those things which
have been obtained from mountain heights and ocean depths, or from
deep caves and hidden mines, I applied much prolonged labour on
investigating magnetic forces, which surpass in wonder all other
things about us. This labour has not been idle or unfruitful, since
daily, during my experimenting, new and unexpected properties came
to light. In this manner my knowledge has increased so much through
actual observation, that I felt able to explore the interior parts of
our globe, and explain its substance upon magnetic principles, and to
reveal to mankind the earth, our common mother, and point it out, as
if with the finger, by real demonstration and by experiments appealing
to the senses.
“As geometry ascends from very small and very easy principles to the
greatest and most difficult, so our magnetic doctrine and science
sets forth in convenient order the things which are less obscure.
From these have come to light others that are more remarkable, and at
length in due order are opened the concealed and most secret things of
the globe of the earth, and the causes are made known of those things
which either through the ignorance of the ancients, or the neglect of
moderns, have remained unrecognised and overlooked.” Dr. Gilbert then
proceeds to ask why he should expose himself to the violent attacks and
criticisms of men, calling themselves learned though unacquainted with
the facts:--
“Why should I, in so vast an ocean of books, by which the minds of men
are troubled and fatigued, by which the world and men, without reason,
are intoxicated and puffed up, books written by people who profess to
be philosophers, physicians, mathematicians, and astrologers, but who
yet despise and neglect men of learning,--why should I, I say, add
anything to this disturbed republic of books and expose this noble
science, which seems new and incredible by reason of so many things
hitherto unknown, to be torn to pieces by those who are either sworn
to the opinions of other men, or are little better than idiots? To
you alone, honest and true men of science, who seek knowledge, not
from books only, but also from things themselves, do I address these
magnetic principles and this new sort of philosophy. If any disagree
with my opinion, let them at least take note of the experiments and
discoveries which have been worked out and demonstrated by me, with
many pains and vigils and expenses. Let them rejoice in these, and
employ them to better use if they are able.”
The remarks by Dr. Gilbert as to the careful way in which experiments
should be made, the plain words in which they should be described, and
the attention that should be paid to the work of others, are as true
to-day as they were in his time. He said:--
“Whoever wishes to try the same experiments let him handle the
substance, not carelessly, but prudently, deftly, and in the proper
way, and when the thing does not succeed let him not in ignorance
denounce my discoveries, for nothing has been set down in these books
which has not been many times performed and repeated. This nature
knowledge is almost entirely new and unheard of, save what a very few
writers have handed down concerning certain common magnetic powers.
Therefore I but seldom quote ancient Greek authors in my support,
because neither by using Greek argument nor Greek words can the truth
be demonstrated more precisely, for our magnetic doctrine is at
variance with most of their principles.
“Nor have I brought to this work any pretence of eloquence or
ornamentation of words, I have only put difficult and unknown things in
such a form of speech, and in such words, as to be clearly understood.
Sometimes I have to use new and strange words, not in order to throw a
veil of mist over the facts, as alchemists are in the habit of doing,
but that hidden things which have no name, never having been observed
before, may be plainly and correctly described. To the early fathers
of philosophy let due honour be paid, for by them wisdom has been
handed down to posterity. But our age has detected and brought to light
very many facts which they, if they were now alive, would gladly have
accepted. I have therefore not hesitated to expound by demonstration
and theory those things which I have discovered by long experience.”
Dr. Gilbert, as announced by himself, began by studying the various
ores of iron, and soon found that it is only the black iron ore which
is naturally magnetic. He made many experiments with the magnetic
needle, which had been used before his time by the Italians and the
Arabs, and long before them again by the Chinese. He was the first to
show that the natural magnet, or lodestone, is not the only possible
form of magnet, and that a bar of iron may be made into a magnet
by simply hanging it in the direction in which the magnetic needle
points, or by heating it, and hammering it while holding it in the same
direction. He considerably increased the power of the natural magnet by
providing it with an iron cap, or armature, at each end.
[Illustration: Fig. 18.--Magnetising a Bar of Iron by hammering.]
Dr. Gilbert disposed of many mistakes made by previous investigators.
One of these was that, in order to preserve its strength, the
lodestone had to be fed on iron filings. They tried to test it by
taking a lodestone of a certain weight and burying it in iron filings,
which they had also weighed carefully. After leaving it for many
months they took out the stone and weighed it, and thought they found
the stone a little heavier, and the filings a little lighter. The
difference, however, was so small that they doubted whether there was
any. Dr. Gilbert said that some of the filings might easily have stuck
to the stone and made it appear heavier. In any case there was no
evidence that the stone had to absorb any nourishment to keep up its
strength.
Another mistake was committed by Paracelsus, who thought that the power
of the magnet could be increased ten times by heating it nearly to
red heat, and slaking it in oil of saffron. In this way, he said, a
lodestone could draw a nail out of a wall, and accomplish many other
wonderful things which are not possible for any ordinary lodestone.
This, however, was just the reverse of the truth. Dr. Gilbert found
that a lodestone treated in that manner does not gain power, but
actually suffers a certain loss of strength.
It was Dr. Gilbert who first proved that the strongest magnetic force
is found at two opposite points of magnetic bodies. These points he
called the Poles. He proved that two poles which point in the same
direction, when the magnet is free to move, repel each other, and those
which point in the opposite directions when suspended attract each
other.
[Illustration: Fig. 19.--The Earth as a Magnet.]
Magnets may be of very different shapes, and whatever shape a
piece of iron may have it can be magnetised, and when fully magnetised
it will show two poles.
Dr. Gilbert asked himself whether a magnet could have the shape of a
sphere. He cut a sphere out of iron, like a cannon ball, and magnetised
it by touching and rubbing it with a lodestone. Having done that he
took a small magnetic needle and brought it near the magnetic sphere of
iron.
He found that the magnetic needle behaved just as if the iron sphere
were the earth itself, pointing to the poles and showing different
directions at different distances from them. The thought flashed into
his mind that the earth itself might be a great magnet. This thought
was entirely new. The ancients had imagined that the attraction of the
magnetic needle was due to some magnetic mountains in the north, or
some star in the tail of the Great Bear, a group of seven stars which
appear to move round the north pole of the sky.
[Illustration: Fig. 20.--A magnetic Compass.]
This supposition could not be maintained as the facts became better
known. In the first place, since the stars appear to be carried round
the north celestial pole, one would naturally expect that the direction
of the magnetic compass would change in the course of every twenty-four
hours, which it did not.
[Illustration: Fig. 21.--Old form of Magnetic Dip. Circle.]
Then, as to the magnetic mountains, if they were situated at the
north pole, the compass would point in a horizontal direction only
in the region near those mountains. In southern lands and seas the
needle would have to point below the horizon, since the pole itself
is at a considerable angle below the horizon. The angle between the
needle and the horizon would have to become less and less as the ship
sailed towards the pole. This is, however, just the reverse of what
actually takes place. When a needle is balanced carefully before it is
magnetised, then on touching it with the magnet, and so magnetising
it, it is found that it balances no longer. The pole which points
to the north points down, and the pole which points to the south is
raised. This might be taken to indicate the existence of magnetic
mountains at the pole of the earth. But on proceeding to the equator,
this so-called “dip” of the needle becomes less, and on sailing towards
the pole it becomes greater and greater, until a point is reached at
which the needle points vertically downwards.
Dr. Gilbert found that a small needle brought near a magnetic sphere
behaves in a similar manner. At a distance midway between the two poles
the needle points in a direction parallel to the axis of the sphere. At
the two poles the needle points vertically downwards towards the centre
of the sphere. If this variation of the “dip” were quite regular,
sailors might discover their latitude on the sea by simply observing
the “dip,” and Dr. Gilbert thought that it was quite possible. In this
he was mistaken, because not only does the “dip” vary in an irregular
manner, but it also varies from century to century, being greater or
less at the same place from time to time.
Another property of the new compass discovered by Dr. Gilbert was the
magnetic “declination,” or the deviation of the compass from the true
north. This deviation he attributed to the irregular distribution of
land and sea. He thought that the mountains attracted the magnetic
needle towards themselves, and so disturbed the action of the earth as
a whole. Here again he was mistaken.
[Illustration: Fig. 22.--The Compass Needle does not point due North
and South except at a few parts of the earth. The deviation from the
true North is shown in the diagram at a few Places in England.]
The observations made since his time have proved that the deviation,
like the “dip,” is not constant, but varies from century to century. It
is, therefore, absurd to suppose that the mountains of the earth, which
keep their outline unchanged for many centuries, should be the cause of
the observed deviation.
Dr. Gilbert, like those who went before him, made mistakes. But his
mistakes we can easily forgive. So far as he was able, he reasoned only
from actual facts. He could not make personal observations extending
over a century, and he had at his hand no records of observations
extending over long periods. So far as the facts known to him extended,
he reasoned wisely and well. New facts observed by others who came
after him would naturally lead in many cases to new conclusions, and
Dr. Gilbert, had he lived in our own time, would have been the first
to acknowledge and welcome any new facts duly proved and established,
even though they contradicted some of his own theories. In the world of
science there can be no absolute master or dictator. Gilbert himself
was the first to overthrow the opinion that any master mind, however
gifted or distinguished, can govern the thoughts and ideas of all
men who come after him, and in this way he established one of the
principles of modern science.
When all the facts known are collected carefully together, it is
right to arrange them all in a certain order, and look at them from a
certain point of view, guided by certain principles. This principle,
or point of view, is called a scientific theory. The establishment of
such a theory enables us to survey the various facts and bewildering
details at a glance. It is useful as a means of lessening the brain
work required to remember a large number of facts. It also indicates
the directions in which new facts may be looked for, and when such new
facts are found it indicates probable explanations for them. But at
that point the usefulness of a scientific theory ends.
There is no such thing in science as absolute truth. A theory is only
true in so far as it covers all the facts. As soon as new facts are
discovered which do agree with it the theory falls to the ground. As
thousands of people are seeking every day to discover new facts, no
theory can be considered absolutely perfect. Actual facts, or results
of accurate observation, remain the same; but the explanation of the
effects observed changes as knowledge of nature grows from more to
more. This is a matter in which we nowadays differ from the ancients.
We want our science to be living and progressive. We do not want to
lose the fruits of the work of our ancestors. We find a place for it in
our theories, and keep those theories unchanged until we are compelled
to change them by the discovery of a new truth. But we insist that the
new truth shall be a real truth proved as carefully and laboriously as
the older truths were proved. And so we advance, step by step, to the
conquest of realms the limits of which no man can see.