CHAPTER IV. Dr. Gilbert of Colchester

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:--

“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.

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.

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.

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.

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.

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.