The cover image was created by the transcriber and is placed in the public domain.

Makers of Electricity

BY
BROTHER POTAMIAN, F.S.C., D.Sc., Lond.
PROFESSOR OF PHYSICS IN MANHATTAN COLLEGE, N. Y.
AND
JAMES J. WALSH, M. D., Ph.D., LL.D.
DEAN AND PROFESSOR OF NERVOUS DISEASES AND OF THE HISTORY OF MEDICINE AT FORDHAM UNIVERSITY SCHOOL OF MEDICINE; PROFESSOR OF PHYSIOLOGICAL PSYCHOLOGY AT THE CATHEDRAL COLLEGE, NEW YORK

FORDHAM UNIVERSITY PRESS
NEW YORK
1909

Copyright, 1909,
Fordham University Press,
New York.

[PREFACE]

This volume represents an effort in the direction of what may be called the biographical history of electricity. The controlling idea in its preparation was to provide brief yet reasonably complete sketches of the lives of the great pioneer workers in electricity, the ground-breaking investigators who went distinctly beyond the bounds of what was known before their time, not merely to add a fringe of information to previous knowledge, but to make it easy for succeeding generations to reach conclusions in electrical science that would have been quite impossible until their revealing work was done. The lives of these men are not only interesting as scientific history, but especially as human documents, showing the sort of men who are likely to make great advances in science and, above all, demonstrating what the outlook of such original thinkers was on all the great problems of the world around us.

In recent times, many people have come to accept the impression that modern science leads to such an exclusive occupation with things material, that scientists almost inevitably lose sight of the deeper significance of the world of mystery in which humanity finds itself placed on this planet. The lives of these great pioneers in electricity, however, do not lend the slightest evidence in confirmation of any such impression. They were all of them firm believers in the existence of Providence, of a Creator, of man's responsibility for his acts to that Creator, and of a hereafter of reward and punishment where the sanction of responsibility shall be fulfilled. Besides, they were men characterized by some of the best qualities in human nature. Their fellows liked them for their unselfishness, for their readiness to help others, for their devotedness to their work and to their duties as teachers, citizens and patriots. Almost without exception, they were as far above the average of mankind in their personal ethics as they were in their intellectual qualities.

The lives of such men, who were inspiring forces in their day, are as illuminating as they are instructive and encouraging. Perhaps never more than now do we need such inspiration and illumination to lift life to a higher plane of purpose and accomplishment, than that to which it is so prone to sink when material interests attract almost exclusive attention.

[CONTENTS]

[ILLUSTRATIONS]

[MAKERS OF ELECTRICITY.]

[CHAPTER I.]
Peregrinus and Columbus.

The ancients laid down the laws of literary form in prose as well as in verse, and bequeathed to posterity works which still serve as models of excellence. Their poets and historians continue to be read for the sake of the narrative and beauty of the style; their philosophers for breadth and depth of thought; and their orators for judicious analysis and impassioned eloquence.

In the exact sciences, too, the ancients were conspicuous leaders by reason of the number and magnitude of the discoveries which they made. You have only to think of Euclid and his "Elements," of Apollonius and his Conics, of Eratosthenes and his determination of the earth's circumference, of Archimedes and his mensuration of the sphere, and of the inscription on Plato's Academy, Let none ignorant of geometry enter my door, to realize the fondness of the Greek mind for abstract truth and its suppleness and ingenuity in mathematical investigation.

But the sciences of observation did not advance with equal pace; nor was this to be expected, as time is an essential element in experimentation and in the collection of data, both of which are necessary for the framing of theories in explanation of natural phenomena.

The slowness of advance is well seen in the development of the twin subjects of electricity and magnetism. As to the lodestone, with which we are concerned at present, the attractive property was the only one known to ancient philosophy for a period of six hundred years, from the time of Thales to the age of the Cæsars, when Lucretius wrote on the nature of things in Latin verse.

Lucretius records the scant magnetic knowledge of his predecessors and then proceeds to unfold a theory of his own to account for the phenomena of the wonder-working stone. Book VI. of "De Natura Rerum" contains his speculations anent the magnet, together with certain observations which show that the poet was not only a thinker, but somewhat of an experimenter as well. Thus he recognizes magnetic repulsion when he says: "It happens, too, at times that the substance of the iron recedes from the stone as if accustomed to start back from it, and by turns to follow it."

This recognition of the repelling property of the lodestone is immediately followed by the description of an experiment which is frequently referred to in works on magnetic philosophy. It reads: "Thus have I seen raspings of iron, lying in brazen vessels, thrown into agitation and start up when the magnet was moved beneath"; or metrically,

And oft in brazen vessels may we mark
Ringlets of Samothrace, or fragments fine
Struck from the valid iron bounding high
When close below, the magnet points its powers.

This experiment, seen and recorded by Lucretius, is of special interest to the student of magnetic history because of the use which is made of iron filings and also because it has led certain writers to credit the poet with a knowledge of what is known to-day by the various names of magnetic figures, magnetic curves, magnetic spectrum. We do not, however, share this view, because we see no adequate resemblance between the positions assumed by the bristling particles of iron in the one case, as described by the Roman poet, and the continuous symmetrical curves of our laboratories in the other. If Lucretius noticed such curves in his brazen vessels, he does not say so; nor does the meagre description of magnetic phenomena given in Book VI. warrant us in assuming that he did.

The use of iron filings to map out the entire field of force that surrounds a magnet was unknown to classical antiquity; it was not known to Peregrinus or Roger Bacon in the thirteenth century or even to Gilbert in the sixteenth. The credit for reviving the use of filings and employing them to show the direction of the resultant force at any point in the neighborhood of a magnet, belongs to Cabeo, an Italian Jesuit, who described and illustrated it in his "Philosophia Magnetica," published at Ferrara in the year 1629. On page 316 of that celebrated work will be found a figure, the first of the kind, showing the position taken by the filings when plentifully sifted over a lodestone: thick tufts at the polar ends with curved lines in the other parts of the field.

The Samothracian rings mentioned in the passage quoted above were light, hollow rings of iron which, for the amusement of the crowd, the jugglers of the times held suspended one from the other by the power of a lodestone.

Writing of the lodestone, Lucretius says:

Its viewless, potent virtues men surprise,
Its strange effects, they view with wond'ring eyes,
When without aid of hinges, links or springs
A pendent chain we hold of steely rings.
Dropt from the stone—the stone the binding source—
Ring cleaves to ring and owns magnetic force;
Those held above, the ones below maintain;
Circle 'neath circle downward draws in vain
Whilst free in air disports the oscillating chain.

Though the Roman poet was acquainted with two of the leading properties of the lodestone, viz., attraction and repulsion, there is nothing in the lines quoted above or in any other lines of his great didactic poem to indicate that he was aware of the remarkable difference which there is between one end of a lodestone and the other. The polarity of the magnet, as we term it, was unknown to him and remained unknown for a period of 1200 years.

During that long period nothing of importance was added to the magnetic lore of the world. True, a few fables were dug out of the tomes of ancient writers which gained credence and popularity, partly by reason of the fondness of the human mind for the marvelous, and partly also by reason of the reputation of the authors who stood sponsors for them.

Pliny (23-79 A. D.) devotes several pages of his "Natural History" to the nature and geographical distribution of various kinds of lodestones, one of which was said to repel iron just as the normal lodestone attracts it. Needless to say that the mineral kingdom does not hold such a stone, although Pliny calls it theamedes and says that it was found in Ethiopia.

Pliny is responsible for another myth which found favor with subsequent writers for a long time, when he says that a certain architect intended to place a mass of magnetite in the vault of an Alexandrian temple for the purpose of holding an iron statue of Queen Arsinoe suspended in mid-air. Of like fabulous character is the oft-repeated story about Mahomet, that an iron sarcophagus containing his remains was suspended by means of the lodestone between the roof of the temple at Mecca and the ground.

As a matter of fact, Mahomet died at Medina and was buried there in the ordinary manner, so that the story as currently told of the suspension of his coffin in the "Holy City" of Mecca, contains a twofold error, one of place and the other of position. By a recent (1908) imperial irade of the Sultan of Turkey, the tomb is lit up by electric light in a manner that is considered worthy of the "Prophet of Islam."

Four centuries after Pliny, Claudian, the last of the Latin poets as he is styled, wrote an idyl of fifty-seven lines on the magnet, which contains nothing but poetic generalities. St. Ambrose (340-397) and Palladius (368-430), writing on the Brahmans of India, tell how certain magnetic mountains were said to draw iron nails from passing ships and how wooden pegs were substituted for nails in vessels going to Taprobane, the modern Ceylon. St. Augustine (354-430) records in his "De Civitate Dei" the wonder which he felt in seeing scraps of iron contained in a silver dish follow every movement of a lodestone held underneath.

With time, the legendary literature of the magnet became abundant and in some respects amusing. Thus we read of the "flesh" magnet endowed with the extraordinary power of adhering to the skin and even of drawing the heart out of a man; the "gold" magnet which would attract particles of the precious metal from an admixture of sand; the "white" magnet used as a philter; magnetic unguents of various kinds, one of which, when smeared over a bald head, would make the hair grow; magnetic plasters for the relief of headache; magnetic applications to ease toothaches and dispel melancholy; magnetic nostrums to cure the dropsy, to quell disputes and even reconcile husband and wife. No less fictitious was the pernicious effect on the lodestone attributed in the early days of the mariner's compass to onions and garlic; and yet, so deeply rooted was the belief in this figment that sailors, while steering by the compass, were forbidden the use of these vegetables lest by their breath they might intoxicate the "index of the pole" and turn it away from its true pointing. More reasonable than this prohibition was the maritime legislation of certain northern countries for the protection of the lodestone on shipboard. According to this penal code, a sailor found guilty of tampering with the lodestone used for stroking the needles, was to have the guilty hand held to a mast of the ship by a dagger thrust through it until, by tearing the flesh away, he wrenched himself free.

It was only at the time of the Crusades that people in Europe began to recognize the directive property of the magnet, in virtue of which a freely suspended compass-needle takes up a definite position relatively to the north-and-south line, property which is serviceable to the traveler on land and supremely useful to the navigator on sea.

It is commonly said that the compass was introduced into Europe by the returning Crusaders, who heard of it from their Mussulman foes. These, in turn, derived their knowledge from the Chinese, who are credited with its use on sea as far back as the third century of our era.[1]

Among the earliest references to the sailing compass is that of the trouvère Guyot de Provins,[2] who wrote, about the year 1208, a satirical poem of three thousand lines, in which the following passage occurs:

The mariners employ an art which cannot deceive.
An ugly stone and brown,
To which iron joins itself willingly
They have; after applying a needle to it,
They lay the latter on a straw
And put it simply in the water
Where the straw makes it float.
Then the point turns direct.
To the star with such certainty
That no man will ever doubt it,
Nor will it ever go wrong.
When the sea is dark and hazy,
That one sees neither star nor moon,
Then they put a light by the needle
And have no fear of losing their way.
The point turns towards the star;
And the mariners are taught
To follow the right way.
It is an art which cannot fail.

The author was a caustic and fearless critic, who lashed with equal freedom the clergy and laity, nobles and princes, and even the reigning pontiff himself, all of whom should be for their subjects, according to the satirist, what the pole-star is for mariners—a beacon to guide them over the stormy sea of life.

Guyot traveled extensively in his early years, but later in life retired from a world which he despised, and ended his days in the peaceful seclusion of the Benedictine Abbey of Cluny.

An interesting reference, of a similar nature to that of the minstrel Guyot, is found in the Spanish code of laws known as Las Siete Partidas of Alfonso el Sabio, begun in 1250 and completed in 1257. It says:

"And even as mariners guide themselves in the dark night by the needle, which is their connecting medium between the lodestone and the star, and thus shows them where they go alike in bad seasons as in good; so those who are to give counsel to the king ought always to guide themselves by justice, which is the connecting medium between God and the world, at all times to give their guerdon to the good and their punishment to the Wicked, to each according to his deserts."[3]

It will be necessary to give a few more extracts from writers of the first half of the thirteenth century in order to show how little was known about the magnet and how crude were the early appliances used in navigation when Peregrinus appeared on the scene.

Cardinal Jacques de Vitry, who lived in the East for some years, wrote his "History of the Orient" between the years 1215 and 1220, in which he says:

"An iron needle after touching the lodestone, turns towards the north star, so that such a needle is necessary for those who navigate the seas."

This passage of the celebrated Cardinal seems to indicate that even then the compass was widely known and commonly used in navigation.

Neckam (1157-1217), the Augustinian Abbot of Cirencester, wrote in his "Utensilibus":

"Among the stores of a ship, there must be a needle mounted on a dart which will oscillate and turn until the point looks to the north; the sailors will thus know how to direct their course when the pole-star is concealed through the troubled state of the atmosphere."

This passage is of historical value, as it contains what is probably the earliest known reference to a mounted or pivoted compass. Prior to the introduction of this mode of suspension, the needle was floated on a straw, in a reed, on a piece of cork or a strip of wood, all of which modes of flotation, when taken in conjunction with the unsteadiness of the vessel in troubled waters, must have made observation difficult and unsatisfactory.

Brunetto Latini (1230-1294) makes a passing reference to the new magnetic knowledge in his "Livres dou Tresor," which he wrote in 1260, during his exile in Paris.

"The sailors navigate the seas," he says, "guided by the two stars called tramontanes; and each of the two parts of the lodestone directs the end of the needle that has touched it to the particular star to which that part of the stone itself turns."

Though a statesman, orator and philosopher of ability, the preceptor of Dante in Florence and guest of Friar Bacon in Oxford, Brunetto has not got the philosophy of the needle quite right in this passage; for the part that has been touched by the north end of a lodestone will acquire south polarity and will not, therefore, turn towards the same "tramontane" as the end of the stone by which it was touched.

Dante himself admitted the occult influence on the compass-needle that emanates from the pole-star when he wrote:

"Out of the heart of one of the new lights
There came a voice that, needle to the star,
Made me appear in turning thitherward.
Paradise, XII., 28-30.

The next writer on the compass is Raymond Lully (1236-1315), who was noted for his versatility, voluminous writings and extensive travels as well as for the zeal which he displayed in converting the African Moors. Lully writes in his "De Contemplatione": "As the needle after touching the lodestone, turns to the north, so the mariners' needle directs them over the sea."

This brings us to the last of our ante-Peregrinian writers who make definite allusions to the use of the compass for navigation purposes, viz., Roger Bacon, one of the glories of the thirteenth century as he would be of the twentieth. It was at the request of his patron, Pope Clement IV., that Bacon wrote his "Opus Majus," a work in which he treats of all the sciences and in which he advocates the experimental method as the right one for the study of natural phenomena and the only one that will serve to extend the boundaries of human knowledge. In a section on the magnet, a clear distinction is drawn between the physical properties of the two ends of a lodestone; for "iron which has been touched by a lodestone," he says, "follows the end by which it has been touched and turns away from the other." Besides being a recognition of magnetic polarity, this is equivalent to saying that unlike poles attract while like poles repel each other. Bacon further remarks, by way of corroboration, that if a strip of iron be floated in a basin, the end that was touched by the lodestone will follow the stone, while the other end will flee from it as a lamb from the wolf. There is, however, an earlier recognition known of the polarity of the lodestone; for Abbot Neckam, fifty years before, called attention to the dual nature of the physical action of the lodestone, attracting in one part (say) by sympathy and repelling at the other by antipathy. It was the common belief in Bacon's time and for centuries after, that the compass-needle was directed by the pole-star, often called the sailor's star; but Bacon himself did not think so, preferring to believe with Peregrinus, that it was controlled not by any one star or by any one constellation, but by the entire celestial sphere. Other contemporaries of his sought the cause of the directive property not in the heavens at all, but in the earth itself, attributing it to hypothetical mines of iron which, naturally enough, they located in regions situated near the pole. Peregrinus records this opinion, which he criticises and rejects, saying in Chapter X. that persons who hold such a doctrine "are ignorant of the fact that in many different parts of the globe the lodestone is found; from which it would follow that the needle should turn in different directions, according to the locality, which is contrary to experience." A little further on he gives his own view, saying: "It is evident from the foregoing chapters that we must conclude that not only from the north pole (of the world), but also from the south pole rather than from the veins of mines, virtue flows into the poles of the lodestone."

Observations had to accumulate and much experimentation had to be done before it was finally established that the cause of the directive property of the magnet is not to be sought in the remote star depths at all, but in the earth itself, the whole terrestrial globe acting as a colossal magnet, partly in virtue of magnetic ore lying near the surface and partly also in virtue of electrical currents, due to solar heat, circulating in the crust of the earth.

Of the early years of Pierre le Pélérin (Petrus Peregrinus), nothing is known save that he was born of wealthy parents in Maricourt, a village of Picardy in Northern France. From his academic title of Magister, we infer that he received the best instruction available at the time, probably in the University of Paris, which was then in the height of its fame. His reputation for mathematical learning and mechanical skill crossed the Channel and reached Friar Bacon in the University of Oxford. In his "Opus Tertium," the Franciscan Friar records the esteem in which he held his Picard friend, saying: "I know of only one person who deserves praise for his work in experimental philosophy, because he does not care for the discourses of men or their wordy warfare, but quietly and diligently pursues the works of wisdom. Therefore it is that what others grope after blindly, as bats in the evening twilight, this man contemplates in all their brilliancy because he is master of experiment."

Continuing the appraisal of his Gallic friend's achievements, he says: "He knows all natural sciences, whether pertaining to medicine and alchemy or to matters celestial and terrestrial. He has worked diligently in the smelting of ores and also in the working of minerals; he is thoroughly acquainted with all sorts of arms and implements used in military service and in hunting, besides which he is skilled in agriculture and also in the measurement of lands. It is impossible to write a useful or correct treatise on experimental philosophy without mentioning this man's name. Moreover, he pursues knowledge for its own sake; for if he wished to obtain royal favor, he could easily find sovereigns to honor and enrich him."

This is at once a beautiful tribute to the work and character of Peregrinus and an emphatic recognition of the paramount importance of laboratory methods for the advancement of learning. It is evident from such testimony, coming as it does from an eminent member of the brotherhood of science, that the world had not to wait for the advent of Chancellor Bacon or for the publication of his Novum Organum in 1620, to learn how to undertake and carry out a scientific research to a reliable issue. Call the method what you will, inductive, deductive or both, the method advocated by the Franciscan friar of the thirteenth century was the one followed at all times from Archimedes to Peregrinus and from Peregrinus to Gilbert, none of whom knew anything of Lord Bacon's pompous phrases and lofty commendation of the inductive method of inquiry for the advancement of physical knowledge. Be it said in passing, that Bacon, eminent as he undoubtedly was in the realm of the higher philosophy, was, nevertheless, neither a mathematician nor a man of science; he never put to a practical test the rules which he laid down with such certitude and expectancy for the guidance of physical inquiry. Moreover, there is not a single discovery in science made during the three centuries that have elapsed since the promulgation of the Baconian doctrine that can be ascribed to it; it has been steadily ignored by men renowned in the world for their scientific achievements and has been absolutely barren of results.

Peregrinus, on the other hand, does not stop to enumerate opinions, he does not even quote Aristotle; but he experiments, observes, reasons and draws conclusions which he puts to the further test of experiment before finally accepting them. Then and then only does he rise from the order of the physicist to that of the philosopher, from correlating facts and phenomena to the discovery of the laws which govern them and the causes that produce them. Furthermore, he was in no hurry to let the world know that he was grinding lodestones one day and pivoting compass-needles the next; what he cared for supremely was to discover facts, new phenomena, new methods. Peregrinus was not an essayist, nor was he a man of mere book-learning. He was a clear-headed thinker, a close and resourceful worker, a man who preferred facts to phrases and observation to speculation.

At one period of his life, Master Peter applied his ingenuity to the solution of a problem in practical optics, involving the construction of a burning-mirror of large dimensions somewhat after the manner of Archimedes; but though he spent three years on the enterprise and a correspondingly large sum of money, we are not told by Friar Bacon, who mentions the fact, what measure of success was achieved. Bacon, however, avails himself of the occasion to insinuate a possible cause of failure, for he says that nothing is difficult of accomplishment to his friend unless it be for want of means.

Centuries later, the French naturalist Buffon took up the same optical problem, with a view to showing that the feat attributed to Archimedes during the siege of Syracuse by the Romans was not impossible of accomplishment. For this purpose, he used 168 small mirrors in the construction of a large concave reflector, with which he ignited wood at a distance of 150 feet and succeeded in melting lead at a distance of 140 feet. As this was done in the winter time in Paris, it was concluded that it would have been quite possible to set a Roman trireme on fire from a safe distance by the concentrated energy of a Sicilian sun.

If Peregrinus was alert in mind, he appears to have been very active in body. Prompted, no doubt, by the higher motives of Christian faith and perhaps a little, too, by his fondness for travel and adventure, he took the cross in early life and joined one of the crusading expeditions of the time. That he went to the land of the paynim, we have no direct evidence; but we infer the fact from the title of Peregrinus or Pilgrim, by which he is known, his full name being Pierre le Pélérin de Maricourt, or, in the Latinized form, Petrus Peregrinus de Maricourt.

In 1269, we find him engaged in a military expedition undertaken by Charles Duke of Anjou, for the purpose of bringing back to his allegiance as King of the Two Sicilies the revolted city of Lucera in Southern Italy. He served in what might be called the engineering corps of the army, and was engaged in fortifying the camp and constructing engines of defense and attack. Unlike his companions in arms, Peregrinus does not allow himself to be wholly absorbed with military duties, nor does he waste his leisure hours in frivolous amusements; his mind is on higher things; he is engrossed with a problem in practical mechanics which required him to devise a piece of mechanism that would keep an armillary sphere in motion for a time.

In outlining the necessary mechanism, as he conceived it, he was gradually led to consider the general and more fascinating problem of perpetual motion itself, with the result that he waxed somewhat enthusiastic when he thought that he saw the possibility of constructing an ever-turning wheel in which the motive power would be magnetic attraction, the attraction of a lodestone for a number of iron teeth arranged at equal distances on the periphery of a wheel. The device looked well on paper, beyond which stage it was not carried, perhaps for want of leisure, or more probably for want of the necessary material and tools. Had Peregrinus been able to test his theoretical views on the magnetic motor by actual experiment, the delusive character of perpetual motion would have been recognized at an early epoch in the world's history, and much time and money spared for more profitable investment.

This very wheel, which was designed in the trenches before Lucera in 1269, was probably the cause of the withering rebuke which Justin Huntly McCarthy administers in his "History of the French Revolution," Vol. I., p. 256, where he says: "In the long record of rascaldom from Peregrinus to Bamfylde Moore Carew, no single rascal stands forward with such magnificent effrontery, such majestic impudence, such astonishing success as Cagliostro." To say the least, this is a very serious slip of the pen on the part of the Irish historian of the French Revolution, in which a scientific pioneer of the first rank and a patriot of exalted type is mistaken for a charlatan of the deepest dye.

Although Peregrinus puts the burden of constructing his wheel on others, he does not appear to have considered it a vain conceit; for, in the beginning of the last chapter of the "Epistola" he says: "In this chapter, I will make known to you the construction of a wheel which, in a remarkable manner, moves continuously." He is writing from Southern Italy to his friend Siger (Syger, Sygerus), at home in Picardy; and that this friend may the better comprehend the mechanism of the wheel, he proceeds to describe in a systematic manner the various properties of the lodestone, all of which he had investigated and many of which he had discovered. The "Epistola" of Peregrinus is, therefore, the first treatise on the magnet ever written; it stands as the first great landmark in magnetic philosophy.

The work is divided into two parts—the first contains ten chapters and the latter three. "At your request," he says to his friend, "I will make known to you in an unpolished narrative the undoubted though hidden virtue of the lodestone, concerning which philosophers, up to the present time, give us no information. Out of affection for you, I will write in simple style about things entirely unknown to the ordinary individual."

Fig. 1
The Double Pivoted Needle of Petrus Peregrinus, A.D., 1269

After this declaration as to the original character of his work Peregrinus proceeds: "You must know that whoever wishes to experiment should be acquainted with the nature of things; he must also be skilled in manipulation, in order that by means of this stone, he may produce those marvelous results."

The titles of the chapters will give an idea of the comprehensive character of the magnetic work accomplished by the author and, at the same time, will serve to show how much was known about the lodestone in the thirteenth century.

PART I.
Chap. I. Purpose of this work.
II. Qualifications of the experimenter.
III. Characteristics of a good lodestone.
IV. How to distinguish the poles of a lodestone.
V. How to tell which pole is north and which south.
VI. How one lodestone attracts another.
VII. How iron touched by a lodestone turns towards the
poles of the world.
VIII. How a lodestone attracts iron.
IX. Why the north pole of one lodestone attracts the south
pole of another, and vice versa.
X. An inquiry into the natural virtue of the lodestone.
PART II.
Chap. I. Construction of an instrument for measuring the azimuth
of the sun, the moon or any star when in
the horizon.
II. Construction of a better instrument for the same purpose.
III. The art of making a wheel of perpetual motion.

An attentive reading of the thirteen chapters of this treatise of 3,500 words will show that:

(1) Peregrinus assigns a definite position to what he calls the poles of a lodestone and gives practical directions for determining which is north and which south.

(2) He establishes the two fundamental laws of magnetism, that like poles repel and unlike poles attract each other.

(3) He demonstrates by experiment that every fragment of a lodestone is a complete magnet, and shows how the fragments should be put together in order to reproduce the polarity of the unbroken stone.

(4) He shows how a pole of a lodestone may neutralize a weaker one of the same name and even reverse its polarity.

(5) He pivots a magnetized needle and surrounds it with a circle divided into 360 degrees.

This brief summary shows the great advance made by the author on what was known about the lodestone before his time. Most of the salient facts in magnetism are clearly described and some of their applications pointed out. So thorough and complete was this apprehension and explanation of magnetic phenomena that nothing of importance was added to it for the next three hundred years.

Fig. 2
First Pivoted Compass, Peregrinus, 1269

In the compass which Peregrinus devised for use in navigation, a light magnetic needle was thrust through a slender vertical axis made of wood, which axis also carried a pointer of brass or silver at right angles to the needle. According to the belief of the time, the magnetic needle gave the north and south points of the horizon, while the brass pointer determined the east and west points. This compass, double pivoted be it noticed, was provided with a graduated circle and a movable arm, having a pair of upright pins at its extremities, which movable arm enabled the navigator to determine the magnetic bearing of the sun, moon or any star at the time of rising or setting. "By means of this instrument," the author says in Chap. II., "you can direct your course towards cities and islands and any other place wherever you may wish to go, by land or by sea, provided you know the latitude and longitude of the place which you want to reach."

The invention of the compass has been attributed to one Flavio Gioja, a seafaring man of Amalfi, a flourishing maritime town in Southern Italy. If we admit that Gioja was a real and not a fictitious person, we cannot, however, admit the claim which is made by his countrymen, when they say that he gave to the mariner the use of the compass in the year 1302; for we have seen that Peregrinus distinctly states that his compass, described in 1269, could be relied upon for guidance by the traveler on land as well as by the voyager on sea.

To Gioja may belong the merit of having simplified and improved the compass. It is likely that he suspended the needle on one pivot instead of the two used by Peregrinus, and that he added the compass-card with its thirty-two divisions, attaching it to the needle itself, thereby adding materially to the practical character of the compass as a nautical instrument.

On the other hand, a claim has been made for Peregrinus which cannot be admitted. It was put forward by his itinerant countryman Thévenot, in the seventeenth century, to the effect that the author of the "Epistola" was acquainted with magnetic declination, in virtue of which a freely suspended magnet does not point north and south, but cuts the geographical meridian at a definite angle.

Writing in 1681, Thévenot says in his "Recueil de Voyages" that: "It was a matter of general belief down to the present day, that the declination of the magnetic needle was first observed sometime in the beginning of the last (16th) century. I have found, however, that there was a declination of five degrees in the year 1269, having found it recorded in a manuscript with the title "Epistola Petri Adsigerii," etc.

The title of the manuscript seen by Thévenot is not, however, as he gives it above, but "Epistola Petri ad Sygerium," etc., which is quite a different reading.

There are twenty-eight manuscript copies of the "Epistola" known to exist; and only one of them, that of the University of Leyden, contains the passage alluded to by Thévenot. This manuscript was the object of careful study and critical examination by Wenckebach (1865) and other competent scholars, who pronounced it a spurious addition made some time in the early part of the 16th century.[4]

In the time of Peregrinus, it is probable that the declination did not exceed three degrees in Paris or on the shores of the Mediterranean, a quantity so small that it would have been difficult of detection; and, if detected, would have been attributed either to errors in the construction of the instrument used or to inaccuracy on the part of the observer. This is what happened to Columbus when, on his return to Spain, having reported the many and definite observations on the variation of the compass which he had made on his outward voyage, he was told by the learned ones of the day that he was in error and not the needle, because the latter was everywhere true to the pole.

This oft-stated and widely-believed fidelity of the needle to the pole is not, however, founded on fact; it is the exception, the rare exception, not the rule, despite the couplet of the poet:

Th' obedient steel with living instinct moves
And veers for ever to the pole it loves;

or this other,

So turns the faithful needle to the pole,
Though mountains rise between and oceans roll.

Fig. 3
Magnetic Declination at New York, 1907 (Left) and at San Francisco, 1907 (Right)

That the magnet does not turn to the pole of the world is common knowledge to-day, when the High School tyro will tell you that in New York it points 9° west of north, while in San Francisco it points 15° east of north. If he happens to be well up, he may refer to the position of the agonic line on the globe along which the needle stands true to the pole, while all places to the east of that line in our hemisphere have westerly declination and those to the west have easterly declination. Indeed, magnetic charts show places where the needle points east and west instead of north and south, and others where the north-seeking end points directly south. Such varying and conflicting behavior of the compass-needle serves to show the irregular manner in which the earth's magnetism is distributed and also the intensity of distributing forces which exist at certain places.

It is one of the gems in the crown of Columbus, that he observed, measured and recorded this strange behavior of the magnetic needle in his narrative of the voyage. True, he did not notice it until he was far out on the trackless ocean. A week had elapsed since he left the lordly Teneriffe, and a few days since the mountainous outline of Gomera had disappeared from sight. The memorable night was that of September 13th, 1492. There was no mistaking it; the needle of the Santa Maria pointed a little west of north instead of due north. Some days later, on September 17th, the pilots, having taken the sun's amplitude, reported that the variation had reached a whole point of the compass, the alarming amount of 11 degrees.

The surprise and anxiety which Columbus manifested on those occasions may be taken as indications that the phenomenon was new to him. As a matter of fact, however, his needles were not true even at the outset of the voyage from the port of Palos, where, though no one was aware of it, they pointed about 3° east of north. This angle diminished from day to day as the Admiral kept the prow of his caravel directed to the west, until it vanished altogether, after which the needles veered to the west, and kept moving westward for a time as the flag-ship proceeded on her voyage.

Fig. 4
Magnetic Declination in London in 1580 and in 1907

Columbus thus determined a place on the Atlantic in which the magnetic meridian coincided with the geographical and in which the needle stood true to the pole. Six years later, in 1498, Sebastian Cabot found another place on the same ocean, a little further north, in which the compass lay exactly in the north-and-south line. These two observations, one by Columbus and the other by Cabot, sufficed to determine the position of the agonic line, or line of no variation, for that locality and epoch.

The Columbian line acquired at once considerable importance, in the geographical and the political world, because of the proposal that was made to discard the Island of Ferro and take it for the prime meridian from which longitude would be reckoned east and west, and also because it was selected by Pope Alexander VI. to serve as a line of reference in settling the rival claims of the kingdoms of Portugal and Castile with regard to their respective discoveries. It was decided that all recently discovered lands lying to the east of that line should belong to Portugal; and those to the west, to Castile.

The line of no variation, like all other isomagnetic lines, has shifted its position with time, so that it runs to-day considerably to the west of the place assigned to it by Columbus in 1492 and by the Papal Bull of the following year.

Columbus did not speak of the disquieting observation which he made on the night of the 13th of September; he thought of it, and wondered greatly what might be the cause of such an unexpected and untoward phenomenon. His silence on the matter did not avail, for the keen-eyed sailors noticed the westerly deflection of the needle when, after a few days, it became quite apparent. They grew alarmed, believing that the laws of nature were changing as they advanced farther and farther into the unknown. It was a trying moment for the Admiral, but his ingenuity and tactfulness rose to the occasion. He told his seamen that the needle did not point to the cynosure or last star in the tail of the Little Bear, as commonly supposed, but to a fixed point in the celestial sphere at which there was no star, adding that the "cynosure" itself, the Polaris of our days, was not stationary, but had a rotational movement of its own like all other heavenly bodies.

We do not know what Columbus thought of his explanation, born of the stress of the moment, but the esteem in which he was held by pilots and sailors alike for his knowledge of astronomy and cosmography led them to accept it. Their fears were allayed, a mutiny was averted and a successful termination to their voyage rendered possible.

Captains of ocean-liners would give to-day a different answer to a passenger who might consult them about the splinter of steel which serves to guide their fleet vessels in darkest nights, through howling tempests and over billowy seas. The mysterious influence that controls it, they would say, comes neither from Polaris nor the pole of the world, nor from the heavens above, but from the earth beneath.

Such an explanation was not thought of until it was clearly shown a hundred years later that this globe of ours acts like a colossal lodestone, controlling every magnet in our laboratories and observatories, and every needle on board the merchantmen and fighting-monsters that plough our seas and oceans.

Without any intuition of modern theory, Columbus made two discoveries in terrestrial magnetism, as we have seen, each of fundamental importance, whether considered from the view-point of pure science or that of practical navigation, viz., (a) that the needle is not true to the pole and (b) that the angular displacement of the needle from true orientation, the variation of the compass, as it is called in nautical parlance, differs with the place of the observer. These two discoveries as well as the location of a place of no variation on the Atlantic Ocean entitle Columbus to a prominent place among the founders of the science of terrestrial magnetism.

Later observers discovered that even for a given place this element of magnetic declination has not a constant value, but undergoes changes which complete their cycle, some in a day, others in a year, and others again in centuries. The last or secular change in the direction of the magnetic needle was discovered by Gellibrand, of London, in 1634 (published in 1635); the annual, by Cassini, at Paris, 1782-1791; and the diurnal, by Graham, of London, in 1722.

The first observation of magnetic declination on land appears to have been made about the year 1510 by George Hartmann (1489-1564), Vicar of the Church of St. Sebald in Nuremberg, who found it to be 6° east in Rome, where he was living at the time. Hartmann's observation of the declination in Rome and also in Nuremberg, where the needle pointed 10° east of north, will be found in a letter which he wrote in 1544 to Duke Albert of Prussia and which remained unpublished until the year 1831.

Returning to the treatise of Peregrinus on the magnet, it should be said that for several centuries the twenty-eight manuscript copies lay undisturbed on the dusty shelves of city and university libraries. In 1562, four years after the appearance of the first printed edition (Augsburg, 1558), Taisnier, a Belgian writer on magnetics, who is also described as poet-laureate and Doctor "utriusque juris," was among the earliest to discover the "Epistola," from which he copied extensively in his little quarto on the magnet and its effects, thus showing that there were literary pirates in those days. It was also well known to Gilbert, to Cabeo and Kircher; but despite the references of these writers, the "Epistola" remained practically unknown until Cavallo, of London, called attention to the Leyden manuscript in the third edition of his "Treatise on Magnetism,"[5] 1800, by giving part of the text and accompanying it with a translation.

Later, in 1838, Libri, historian of the mathematical sciences in Italy, gave excerpts from the Paris codex with translation; but the scholar who contributed most of all to make the work of Peregrinus known is the Italian Barnabite, Timoteo Bertelli, who published in 1868 a critical study of the various manuscripts of the letter, principally those which he found in Rome and in Florence, adding copious notes of historic, bibliographic and scientific value. Father Bertelli was Professor of Physics in the Collegio della Quercia, in Florence, where he took an active interest in Italian seismology besides carrying on investigations in meteorology, telegraphy and electricity. Born in Bologna in 1826, he died in Florence in March, 1905.

The following list of manuscript copies of the "Epistola" is taken from a scholarly paper by Professor Silvanus P. Thompson, of London, which appeared in the "Proceedings of the British Academy" for 1906:—

The first printed edition of the "Epistola" was prepared for the press in 1558 by Achilles Gasser, a man well versed in the science and philosophy of his day; another edition, which will probably be considered the textus receptus, is that which was prepared and published by Bertelli in 1868.

No complete translation in any language of this historical work on magnetism was made until 1902, when Prof. Silvanus P. Thompson, of London, published his "Epistle of Peter Peregrinus of Maricourt to Sygerus of Foncaucourt, soldier, concerning the Magnet." Unfortunately, this translation was printed for private circulation and limited to 250 copies. Two years later, 1904, Brother Arnold, F. S. C., presented a memoir on Peregrinus, including a translation of the "Epistola," for the M. Sc. degree of Manhattan College, New York City, which translation was published some months later by the McGraw Publishing Company, New York. These are the only complete translations of the "Letter" of Peregrinus on the Magnet which have yet appeared.

Brother Potamian.

FOOTNOTES:

[1] See Klaproth, "Lettre à M. le Baron A. de Humbolt sur l'Invention de la Boussole." 1834; also Encyc. Brit., article Compass.

[2] Provins, town 57 miles southeast of Paris.

[3] Southey, "Omniana," Vol. I., p. 213, ed. 1812.

[4] Annali di Matematica pura ed applicata. Rome, 1865.

[5] Also in Rees Encyclopedia, article Compass.

[CHAPTER II.]
Norman and Gilbert.

We have seen that in the thirteenth century the directive property of the lodestone was recognized by Peregrinus and used by him in his pivoted compass; and that in the fifteenth, Columbus discovered magnetic declination on sea as well as its variation with place.

The next cardinal fact in terrestrial magnetism, magnetic dip, was discovered in 1576 by Robert Norman, a compass-maker of Limehouse, London. Norman possessed many of the fine qualities of mind, hand and disposition that are indispensable in the make-up of the original investigator. In pivoting his compass-needles, he soon noticed that, however carefully they were balanced before being magnetized, they did not remain horizontal after magnetization, the north-seeking end always going down through a small angle. He next had the happy idea of swinging a needle on a horizontal axis, so that it might be free to move up and down in a vertical plane, with the result that the north-seeking end again went down through a constant but much greater angle.

Fig. 5
The First Dip-Circle, Invented by Norman in 1576

Like declination, the first discovered of the three magnetic elements, the dip was found to vary with place on the earth's surface, being 0° at the magnetic equator and 90° at either pole. It was with a Norman dip-circle, greatly improved, that Ross in 1831 found the north magnetic pole of the earth to be in Boothia Felix in latitude 70° 5'.3 N., and longitude 96° 45'.8 W.; and it was with a similar instrument that Amundsen recently studied the magnetic conditions of that Arctic region, the exact location of the pole itself being finally determined by an earth-inductor or spinning coil of the latest make. Though the results of his observations have not yet been made public, it is generally known that they indicate a spot for the magnetic pole close to that found by Sir James Ross. It is not expected, however, that the location of the pole by the Norwegian Commander shall exactly coincide with that of the English Captain, because the magnetic pole is believed to have nomadic tendencies of its own like our geographical pole, only much more pronounced in magnitude. After moving westward for some time at the rate of a mile per year, it retraced its steps and is now back again in the vicinity of its starting place.

Besides his dip-circle, Norman also devised a simple and very apt illustration of magnetic inclination. Thrusting a steel needle through a round piece of cork, he pared the latter down until the system, consisting of the needle and the cork, sank to a certain depth in a glass vessel containing water, and there took up a horizontal position. The needle was next removed from the water and magnetized with great care, so as not to disturb its position in the cork. When placed again in the water, the needle sank to its former depth and settled down at an angle of 71° to the horizon.

The same illustration shows another experiment which Norman made in order to determine whether the earth exerts a force of translation on a magnet, in virtue of which the magnet would tend to move bodily toward the pole. For this purpose, he floated a magnetized piece of steel wire on the surface of the water and noticed that, wherever placed, it merely swung round into the magnetic meridian without showing any tendency to move northward or southward toward the rim of the vessel. Hartmann, who observed the declination of the needle on land as stated on p. 26, appears also to have been the first to notice magnetic inclination. Having balanced a steel needle with great precision, he found that, after magnetization, it did not remain horizontal, the north-seeking end invariably dipping through an angle of 9°. The smallness of the angle in this experiment was due to the fact that the needle used by the Nuremberg Vicar could move only in a horizontal plane, whereas Norman's was free to move in a vertical circle. Had Hartmann used such a device, he would have obtained more than 60° for the dip instead of the 9° which he records.

Fig. 6
Norman's Illustration of Magnetic Dip

As already remarked, the letter in which Hartmann consigns these capital observations was written in 1544, but was not published until the third decade of the nineteenth century, so that Norman has clearly the full merit of independent discovery.

In the directions which Norman gives for making observations of dip, he states explicitly that the instrument must be adjusted "duley according to the variation of the place," which means that the plane of the circle must be turned into what was called after his time "the magnetic meridian."

The discovery of magnetic dip led Norman to discard the view generally held in his time, which placed the controlling influence of the compass-needle in far-off celestial space; for he says that the poynt respective which the magnet indicates, but to which it is not bodily drawn, is not in the heavens above, but in the earth itself. His words are: "And by the declining of the needle is also proved that the poynt respective is rather in the earth than in the heavens, as some have imagined; and the greatest reason why they so thought, as I judge, was because they were never acquainted with this declining in the needle."

Here we have a radical departure from the scientific creed of the time, a notable advance in scientific theory, an entirely new philosophy founded by Norman, the compass-maker, and greatly developed twenty-four years later by his fellow-citizen, Gilbert, the physician.

Fig. 7
Gilbert's Orb of Virtue, 1600

Norman made another remark of great importance in the new philosophy, the justness of which was appreciated by Gilbert, his contemporary, but more so by Faraday and Clerk Maxwell, two centuries later. It refers to the space surrounding a magnet, natural or artificial, which cubical space Gilbert, following Norman, called an orb of virtue. That the influence or "effluvium" of the magnet extends throughout the entire space may readily be seen by carrying a compass-needle round a magnet from point to point, far away as well as close by. The phrase "orb of virtue," or sphere of magnetic influence, appears to describe the actual magnetic condition of the space in question more pertinently than our modern equivalent of "magnetic field."

The words of Norman are very remarkable: "I am of opinion that if this vertue could by anie means be made visible to the eie of man, it would be found in a sphericall forme, extending round about the stone in great compasse and the dead bodie of the stone in the middle thereof." The lines which immediately follow this statement, pregnant with significance, show the deep religious feeling of the author. They read: "and this I have partly proved and made visible to be seene in some manner, and God sparing mee life, I will herein make further experience and that not curiouslie but in the feare of God as neere as He shall give me grace and meane to annexe the same unto a booke of navigation which I have had long in hand."—Chap. VIII.

It is evident from the pages of the Newe Attractive (1581) that Norman was animated with the right spirit of inquiry, which is calm, deliberate and judicious, which leads to the discovery of facts, to their coordination and experimental illustration before explanations are thought of and long before new theories are propounded. The style in which this little treatise is written has a charm of its own, mainly by reason of its quaintness. At the end of his address to the candid reader, which, after the manner of the times, was somewhat belabored and rhetorical in character, Norman breaks away from common inadequate prose; and, giving wings to his imagination, writes a lyric on the magnet which is the first metrical composition in English that we have on such a subject. It reads:—

THE MAGNES OR LOADSTONE'S CHALLENGE.

Give place ye glittering sparks,
ye glimmering Diamonds bright,
Ye Rubies red, and Saphires brave
wherein ye most delight.

In breefe, yee stones inricht,
and burnisht all with golde,
Set forth in Lapidaries shops,
for Jewells to be sold.

Give place, give place I say,
your beautie, gleame and glee,
Is all the vertue for the which,
accepted so you bee.

Magnes, the Loadstone I,
your painted sheath defie,
Without my help in Indian seas,
the best of you might lie.

I guide the Pilot's course,
his helping hand I am,
The Mariner delights in me,
so doth the Marchant man.

My vertue lies unknowne,
my secrets hidden are,
By me, the Court and Commonweale,
are pleasured very farre.

No ship could sail on Seas,
her course to run aright,
Nor Compass shew the ready way
were Magnes not of might.

Blush then, and blemish all,
bequeath to mee thats due,
Your seats in golde, your price in plate,
which Jewellers do renue.

Its I, its I alone,
whom you usurp upon,
Magnes my name, the Loadstone cal'd,
the prince of stones alone.

If this you can deny,
then seem to make reply,
And let the painfull sea-man judge,
the which of us doth lie.

The Mariner's Judgement.

The Loadstone is the stone,
the onely stone alone,
Deserving praise above the rest
whose vertues are unknown.

The Marchant's Verdict.

The Diamonds bright, the Saphires brave,
Are stones that bear the name,
but flatter not, and tell the troath,
Magnes deserves the same.
(Edition of 1720.)

Norman's Newe Attractive was well known to Gilbert, as were also the Epistola of Peregrinus, the Magiae Naturalis of Porta, and indeed all books treating of the lodestone, the magnet, or the compass-needle. His own work De Magnete, published in the year 1600, is a compendium of the world's knowledge of magnetism and electricity at the time. In its pages, he not only discusses the opinions of others, but describes discoveries of his own made during the twenty years which he ardently devoted to the pursuit of experimental science, crowning his investigations with theories in electricity and magnetism as became a true philosopher.

Impressed by the originality of Gilbert's treatise, the practical ingenuity and philosophic acumen displayed throughout, Hallam wrote in his Introduction to the Literature of Europe: "Gilbert not only collected all the knowledge which others had possessed on the subject, but became at once the father of experimental philosophy in this island; and, by a singular felicity and acuteness of genius, the founder of theories which have been received after the lapse of ages and are almost universally received into the creed of science."

At a period when natural science was taught in the schools of Europe mainly from text-books, we find Gilbert proclaiming by example and advocacy the paramount value of experiment for the advancement of learning. He was unsparing in his denunciation of the superficiality and verbosity of mere bookmen, and had no patience with writers who treated their subjects "esoterically, reconditely and mystically." For him, the laboratory method was the only one that could secure fruitful results and contribute effectively to the advancement of learning.

It is true that men of unusual ability and strong character strove before his time to adjust the claims of authority in matters scientific. While respectful of the teachings of recognized leaders, they were not, however, awed into acquiescence by an academical "magister dixit." On the contrary, they wanted to test with their eyes in order to judge with reason; believing in the importance of experiment, they sought to acquire a knowledge of nature from nature herself.

Such were Albert the Great and Friar Bacon. Albert did not bow obsequiously to the authority of Aristotle or any of his Arabian commentators; he investigated for himself and became, for his age, a distinguished botanist, physiologist and mineralogist.

The Franciscan monk of Ilchester has left us in his Opus Majus a lasting memorial of his practical genius. In the section entitled "Scientia Experimentalis," he affirms that "Without experiment, nothing can be adequately known. An argument proves theoretically, but does not give the certitude necessary to remove all doubt, nor will the mind repose in the clear view of truth, unless it find it by way of experiment." And in his Opus Tertium: "The strongest arguments prove nothing, so long as the conclusions are not verified by experience. Experimental science is the queen of sciences and the goal of all speculation."

No one, even in our own times, wrote more strongly in favor of the practical method than did this follower of St. Francis in the thirteenth century. Being convinced that there can be no conflict between scientific and revealed truths, he became an irrepressible advocate for observation and experiment in the study of the phenomena and forces of nature.

The example of Peregrinus, of Albert and Friar Bacon, not to mention others like Vincent of Beauvais, the Dominican encyclopedist, was, however, not sufficient to wean students from the easy-going routine of book-learning. A few centuries had to elapse before the weaning was effectively begun; and the man who contributed in a marked degree to this result was Gilbert the Philosopher of Colchester (1544-1603).

Having received the elements of his education in the Grammar School of Colchester, his native town, Gilbert entered St. John's College, Cambridge, from which university he took his B. A. degree in 1560, M. A. in 1564 and M. D. in 1569. In all, he appears to have been connected with the University for a period of eleven or twelve years, as student, Fellow, and examiner.

On leaving Cambridge, Gilbert traveled for four years on the Continent, principally in Italy, visiting medical schools and studying methods of treatment under the leading physicians and surgeons of the day as well as discussing scientific theory with the leaders of thought. On his return to England in 1573, he practised medicine in London "with great applause and success." He was elected President of the Royal College of Physicians in 1599, and appointed Physician to Queen Elizabeth in 1601 and to her successor, James I., in 1603.

On one occasion, he hears that Baptista Porta, whom he calls "a philosopher of no ordinary note," said that a piece of iron rubbed with a diamond turns to the north. He suspects this to be heresy. So, forthwith he proceeds to test the statement by experiment. He was not dazzled by the reputation of Baptista Porta; he respected Porta, but respected truth even more. He tells us that he experimented with seventy diamonds in presence of many witnesses, employing a number of iron bars and pieces of wire, manipulating them with the greatest care while they floated on corks; and concludes his long and exhaustive research by plaintively saying: "Yet never was it granted me to see the effect mentioned by Porta."

Though it led to a negative result, this probing inquiry was a masterpiece of experimental work.

Gilbert incidentally regrets that the men of his time "are deplorably ignorant with respect to natural things," and the only way he sees to remedy this is to make them "quit the sort of learning that comes only from books and that rests only on vain arguments and conjectures," for he shrewdly remarks that "even men of acute intelligence without actual knowledge of facts and in the absence of experiment easily fall into error."

Acting on this intimate conviction, he labored for twenty years over the theories and experiments which he sets forth in his great work on the magnet. "There is naught in these books," he tells us, "that has not been investigated, and again and again done and repeated under our eyes." He begs any one that should feel disposed to challenge his results to repeat the experiments for himself "carefully, skilfully and deftly, but not heedlessly and bunglingly."

It has been said that we are indebted to Sir Francis Bacon, Queen Elizabeth's Chancellor, for the inductive method of studying the phenomena of nature. Bacon's merit lies in the fact that he not only minutely analyzed the method, pointing out its uses and abuses, but also that he showed it to be the only one by which we can attain an accurate knowledge of the physical world around us. His sententious eulogy went forth to the world of scholars invested with all the importance, authority and dignity which the high position and worldwide fame of the philosophic Chancellor could give it. But while Bacon thought and wrote in his study, Gilbert labored and toiled in his workshop. By his pen, Bacon made a profound impression on the philosophic mind of his age; by his researches, Gilbert explored two provinces of nature and added them to the domain of science. Bacon was a theorist, Gilbert an investigator. For twenty years he shunned the glare of society and the throbbing excitement of public life; he wrenched himself away from all but the strictest exigencies of his profession, in order to devote himself undistractedly to the pursuit of science. And all this forty years before the appearance of Bacon's Novum Organum, the very work which contains the philosopher's "large thoughts and lofty phrases" on the value of experiment as a means for the advancement of learning. During that long period Gilbert haunted Colchester, where he delved into the secrets of nature and prepared the materials for his great work on the magnet. The publication of this Latin treatise made him known in the universities at home and especially abroad: he was appreciated by all the great physicists and mathematicians of his age; by such men as Sir Kenelm Digby; by William Barlowe, a great "magneticall" man; by Kepler, the astronomer, who adopted and defended his views; by Galileo himself, who said: "I extremely admire and envy the author of De Magnete."

The science of magnetism owes more to Gilbert than to any other man, Peregrinus (1269) excepted. He repeated for himself the numerous and ingenious experiments of the medieval philosopher, and added much of his own which he discovered during the long period of a life devoted to the diligent exploration of this domain in the world of natural knowledge.

The ancients spoke of the lodestone as the Magnesian stone, from its being found in abundance in the vicinity of Magnesia, a city of Asia Minor. In his Latin treatise of 254 (small) folio pages, Gilbert uses the adjective form of the term, but never the noun "Magnetismus" itself. Our English term magnetism appears for the first time on page 2 of Archdeacon Barlowe's "Magneticall Advertisements," published in 1616; while the surprising compound, "electro-magnetismos," is the title of a chapter in Father Kircher's "Magnes, sive de Arte Magnetica," printed in the year 1641.

Gilbert showed that a great number of bodies could be electrified; but maintained that those only could exhibit magnetic properties which contain iron. He satisfies himself of this by rubbing with a lodestone such substances as wood, gold, silver, copper, zinc, lead, glass, etc., and then floating them on corks, quaintly adding that they show "no poles, because the energy of the lodestone has no entrance into their interior."

To-day we know that nickel and cobalt behave like iron, whilst antimony, bismuth, copper, silver and gold are susceptible of being influenced by powerful electro-magnets, showing what has been termed diamagnetic phenomena. Even liquids and gases, in Faraday's classical experiments, yielded to the influence of his great magnet; and Professor Dewar, in the same Royal Institution, exposed some of his liquid air and liquid oxygen to the influence of Faraday's electromagnet and found them to be strongly attracted, thus behaving like the paramagnetic bodies, iron, nickel and cobalt.

Gilbert observes in all his magnets two points, one near each end, in which the force, or, as he terms it, "the supreme attractional power," is concentrated. Like Peregrinus, he calls these points the poles of the magnet, and the line joining them its magnetic axis. With the aid of his steel versorium, he recognizes that similar poles are mutually hostile, whilst opposite poles seize and hold each other in friendly embrace. He also satisfies himself that the energy of magnets resides not only in their extremities, but that it permeates "their inmost parts, being entire in the whole and entire in each part." This is exactly what Peregrinus said in 1269 and what we say to-day; it is nothing else than the molecular theory proposed by Weber, extended by Ewing and universally accepted.

At any rate, Gilbert is quite certain that whatever magnetism may be, it is not, like electricity, a material, ponderable substance. He ascertained this by weighing in the most accurate scales of a goldsmith a rod of iron before and after it had been rubbed with the lodestone, and then observing that the weight is precisely the same in both cases, being "neither less nor more."

Without referring to the prior discovery of Norman, whom he calls "a skilled navigator and ingenious artificer," Gilbert satisfies himself that not only the magnet, but all the space surrounding it, possesses magnetic properties; for the magnet "sends its force abroad in all directions, according to its energy and quality." This region of influence Norman called a sphere of "vertue," and Gilbert an "orbis virtutis," which is the Latin equivalent; we call it a "magnetic field," or field of force, which is less expressive and less appropriate. With wonderful intuition, Gilbert sees this space filled with lines of magnetic virtue passing out radially from his spherical lodestone, which lines he calls "rays of magnetic force."

Clerk Maxwell was so fascinated with this beautiful concept that he made it the work of his life to study the field of force due to electrified bodies, to magnets and to conductors conveying currents; his powerful intellect visualized those lines and gave them accurate mathematical expression in the great treatise on electricity and magnetism which he gave to the world in 1873.

Gilbert observes that the lodestone may be spherical or oblong; "whatever the shape, imperfect or irregular, verticity is present; there are poles," and the lodestones "have the selfsame way of turning to the poles of the world." He knows that a compass-needle is not drawn bodily towards the pole, and does not hesitate in this instance to give credit to his countryman, Robert Norman, for having clearly stated this fact and aptly demonstrated it. Following Norman, he floats a needle in a vessel by means of a piece of cork, and notices that on whatever part of the surface of the water it may be placed, the needle settles down after a few swings invariably in the same direction. His words are: "It revolves on its iron center and is not borne towards the rim of the vessel."

Gilbert knew nothing about the mechanical couple that came into play, but he knew the fact; and, with the instinct of the philosopher, tested it in a variety of ways.

We explain the orientation of the compass-needle by saying that it is acted upon by a pair of equal and opposite forces due to the influence of the terrestrial magnetic poles on each end of the needle and by showing that such a couple can produce rotation, but not translation.

We find Gilbert working not only with steel needles and iron bars, but also with rings of iron. He strokes them with a natural magnet and feels certain that he has magnetized them. He assures us that "one of the poles will be at the point rubbed and the other will be at the opposite side." To show that the ring is really magnetized, he cuts it across, opens it out, and finds that the ends exhibit polar properties.

A favorite piece of apparatus with Gilbert, as with Peregrinus, was a lodestone ground down into globular form. He called it a terrella, a miniature earth, and used it extensively for reproducing the phenomena described by magnetizers, travelers and navigators. He breaks up terrellas, in order to examine the magnetic condition of their inner parts. There is not a doubtful utterance in his description of what he finds; he speaks clearly and emphatically. "If magnetic bodies be divided, or in any way broken up, each several part hath a north and a south end"; i.e., each part will be a complete magnet.

Fig. 8
Begavior of Compas-Needle on a Terrella or Sphrical Lodestone

We find him also comparing magnets by what is known to us as the "magnetometer method." He brings the magnetized bars in turn near a compass-needle and concludes that the magnet or the lodestone which is able to make the needle go round is the best and strongest. He also seeks to compare magnets by a process of weighing, similar to what is called, in laboratory parlance, the "test-nail" method. He also inquires into the effect of heat upon his magnets, and finds that 'a lodestone subjected to any great heat loses some of its energy.' He applies a red-hot iron to a compass-needle and notices that it 'stands still, not turning to the iron.' He thrusts a magnetized bar into the fire until it is red-hot and shows that it has lost all magnetic power. He does not stop at this remarkable discovery, for he proceeds to let his red-hot bars cool while lying in various positions, and finds: (1) that the bar will acquire magnetic properties if it lie in the magnetic meridian; and (2) that it will acquire none if it lie east and west. These effects he rightly attributes to the inductive action of the earth.

Gilbert marks these and other experiments with marginal asterisks; small stars denoting minor and large ones important discoveries of his. There are in all 21 large and 178 small asterisks, as well as 84 illustrations in De Magnete. This implies a vast amount of original work, and forms no small contribution to the foundations of electric and magnetic science.

Gilbert clearly realized the phenomena and laws of magnetic induction. He tells us that "as soon as a bar of iron comes within the lodestone's sphere of influence, though it be at some distance from the lodestone itself, the iron changes instantly and has its form renewed; it was before dormant and inert; but now is quick and active." He hangs a nail from a lodestone; a second nail from the first, a third from the second and so on—a well-known experiment, made every day for elementary classes. Nor is this all, for he interposes between the lodestone and his iron nail, thick boards, walls of pottery and marble, and even metals, and he finds that there is naught so solid as to do away with its force or to check it, save a plate of iron. All that can be added to this pregnant observation is that the plate of iron must be very thick in order to carry all the lines of force due to the magnet, and thus completely screen the space beyond.

But Gilbert is astonishing when he goes on to make thick boxes of gold, glass and marble; and, suspending his needle within them, declares with excusable enthusiasm that, regardless of the box which imprisons the magnet, it turns to its predestined points of north and south. He even constructs a box of iron, places his magnet within, observes its behavior, and concludes that it turns north and south, and would do so were "it shut up in iron vaults sufficiently roomy." In this, he was in error, for experiments show that if the sides of the box are thin, the needle will experience the directive force of the earth; but if they are sufficiently thick—thick as the walls of an ordinary safe—the inside of such a box will be completely screened; none of the earth's magnetic lines will get into it so that the needle will remain indifferently in any position in which it is placed. Some years ago, the physical laboratory of St. John's College, Oxford, was screened from the obtrusive lines of neighboring dynamos by building two brick walls parallel to each other and eight inches apart and filling in the space with scrap iron. A delicate magnetometer showed that such a structure allowed no leakage of lines of force through it, but offered an impenetrable barrier to the magnetic influence of the working dynamos.

Gilbert's greatest discovery is that the earth itself acts as a vast globular magnet having its magnetic poles, axis and equator. The pole which is in our hemisphere, he variously calls north, boreal or arctic. Whilst that in the other hemisphere he calls south, austral or antarctic. He sought to explain the magnetic condition of our globe by the presence, especially in its innermost parts, of what he calls true, terrene matter, homogeneous in structure and endowed with magnetic properties, so that every separate fragment exhibits the whole force of magnetic matter. He is quite aware that his theory is a grand generalization; and admits that it is "a new and till now unheard-of view," and so confident is he in its worth that he is not afraid to say that "it will stand as firm as aught that ever was produced in philosophy, backed by ingenious argumentation or buttressed by mathematical demonstration."

In developing his theory of terrestrial magnetism, Gilbert fell into certain errors, chiefly for want of data, but partly also by reason of his adherence to the view that the earth exactly resembled his terrella in its magnetic action. Accordingly, he believed that the magnetic poles of the earth were diametrically opposite each other and that they coincided with the poles of rotation, whence it followed that the magnetic meridian everywhere coincided with the geographical, and that the magnet, unless influenced by local disturbances, stood true to the pole.

It was, however, well known from the thrilling experience of Columbus and the constant report of travelers that this was not the case. Gilbert himself says that at the time of writing, in the year 1600, the needle pointed 11-1/3° east of north in London; but what he did not know and could not have known was that this easterly deviation was decreasing from year to year, to vanish altogether in 1657, after which the needle began to decline to the west.

This magnetic declination sorely perplexed Gilbert, as it did not fit in with his theory. Yet an explanation was needed; and as the earth must be considered a normal and well-behaved magnet, though of cosmical size, Gilbert turns the difficulty by saying that this variation is nothing else than "a sort of perturbation of the directive force" caused by inequalities in the earth's surface by continents and mountain masses: "Since the earth's surface is diversified by elevations of land and depths of seas, great continental lands, oceans and seas differing in every way while the power that produces all magnetic movements comes from the constant magnetic earth-substance which is strongest in the most massive continent and not where the surface is water or fluid or unsettled, it follows that toward a massive body of land or continent rising to some height in any meridian, there is a measurable magnetic leaning from the true pole toward the east or the west."

So convinced is Gilbert of the true and satisfactory character of his explanation that he goes on to say that, "In northern regions, the compass varies because of the northern eminences; in southern regions, because of southern eminences. On the equator, if the eminences on both sides were equal, there would be no variation." In a later chapter of Book IV., he adds that, "in the heart of great continents there is no variation; so, too, in the midst of great seas."

As continents and mountain-chains are among the permanent features of our planet, Gilbert concluded that the misdirection of the needle was likewise permanent or constant at any given place, a conclusion which observations made after Gilbert's time showed to be incorrect. Gilbert writes: "As the needle hath ever inclined toward the east or toward the west, so even now does the arc of variation continue to be the same in whatever place or region, be it sea or continent; so, too, will it be forever unchanging."

This we know to be untrue, and Gilbert, too, could have known as much had he brought the experimental method, which he used with such consummate skill and fruitful results in other departments of his favorite studies, to bear on this particular element of terrestrial magnetism. He labored with incredible ardor and persistence for twenty years in his workshops at Colchester over the experiments in electricity, magnetism and terrestrial magnetism which he embodies and discusses in his original and epoch-making book, De Magnete, published in the year 1600; a period of twenty years was long enough for such a careful observer as he was to detect the slow change in magnetic declination discovered by his friend Gellibrand in 1634, published by him in 1635, and known to-day as the "secular variation." It is true the quantity to be measured was small; but what is surprising is that such an industrious and resourceful experimenter as Gilbert was does not record in his pages any observations of his own on declination or dip, elements of primary importance in magnetic theory.

Shortly after the voyage of Columbus it was thought that the longitude of a place could be found from its magnetic declination. Gilbert, however, did not think so, and accordingly scores those who championed that view. "Porta," he says, "is deluded by a vain hope and a baseless theory"; Livius Sanutus "sorely tortures himself and his readers with like vanities"; and even the researches of Stevin, the great Flemish mathematician, on the cause of variation in the southern regions of the earth are "utterly vain and absurd."

With regard to dip, Gilbert erroneously held that for any given latitude it had a constant value. He was so charmed with this constancy that he proposed it as a means of determining latitude. There is no diffidence in his mind about the matter; he is sure that with his "inclinatorium" or dip-circle, together with accompanying tables, calculated for him by Briggs, of logarithmic fame, an observer can find his latitude "in any part of the world without the aid of the sun, planets or fixed stars in foggy weather as well as in darkness."

After such a statement, it is no wonder that he waxes warm over the capabilities of his instrument and allows himself to exclaim: "We can see how far from idle is magnetic philosophy; on the contrary, how delightful it is, how beneficial, how divine! Seamen tossed by the waves and vexed with incessant storms while they cannot learn even from the heavenly luminaries aught as to where on earth they are, may with the greatest ease gain comfort from an insignificant instrument and ascertain the latitude of the place where they happen to be."

Gilbert dwells at length on the inductive action of the earth. He hammers heated bars of iron on his anvil and then allows them to cool while lying in the magnetic meridian. He notes that they become magnetized, and does not fail to point out the polarity of each end. He likewise attributes to the influence of the earth the magnetic condition acquired by iron bars that have for a long time lain fixed in the north-and-south position and ingenuously adds: "for great is the effect of long-continued direction of a body towards the poles." To the same cause, he attributes the magnetization of iron crosses attached to steeples, towers, etc., and does not hesitate to say that the foot of the cross always acquires north-seeking polarity.

In a similar manner, every vertical piece of iron, like railings, lamp-posts, and fire-irons, becomes a magnet under the inductive action of the earth. In the case of our modern ships, the magnetization of every plate and vertical post, intensified by the hammering during construction, converts the whole vessel into a magnetic magazine, the resulting complex "field" rendering the adjustment of the compasses somewhat difficult and unreliable. The unreliable character of the adjustment arises mainly from the changing magnetism of the ship with change of place in the earth's magnetic field, the effect increasing slightly from the magnetic equator to the poles.

With luminous insight into the phenomena of terrestrial magnetism, Gilbert observes that in the neighborhood of the poles, a compass-needle, tending as it does to dip greatly, must in consequence experience only a feeble directive power. To which he adds that "at the poles there is no direction," meaning, no doubt, that a compass-needle would remain in any horizontal position in which it might be placed when in the vicinity of the magnetic pole.

This is precisely the experience of all Arctic explorers, who find that their compasses become less and less active as they sail northward, the reason being that the horizontal component of the earth's magnetic force, which alone controls the movements of the compass-needle, decreases as the ship advances and vanishes altogether at the magnetic pole. When once a high latitude is reached, captains do not depend upon their compasses for their bearings, but have recourse to astronomical observations. In his account of magnetic work carried on in the neighborhood of the magnetic pole, Amundsen says: "At Prescott Island the compass, which for some time had been somewhat sluggish, refused entirely to act, and we could as well have used a stick to steer by."

As a physician, Gilbert valued iron for its medicinal properties, but denounced quacks and wandering mountebanks who practised "the vilest imposture for lucre's sake," using powdered lodestone for the cure of wounds and disorders. "Headaches," he said, "are no more cured by application of a lodestone than by putting on an iron helmet or a steel hat"; and again: "To give it in a draught to dropsical persons is either an error of the ancients or an impudent tale of their copyists." Elsewhere he condemns prescriptions of lodestone as "an evil and deadly advice" and as "an abominable imposture."

In the sixth and last book of De Magnete, Gilbert sets forth his views on such astronomical subjects as the figure of the earth, its suspension in space, rotation on its axis and revolution around the sun.

As to the figure of our planet, the primitive view widely credited in early times was that the earth is a flat, uneven mass floating in a boundless ocean. The Hindoos, however, did not accept the flatland doctrine, but taught that the earth was a convex mass which rested on the back of a triad of elephants having for their support the carapace of a gigantic tortoise. Of course, they did not say how the complaisant chelonian contrived to maintain his wonderful state of equilibrium under the superincumbent mass.

Aristotle (384-322, B. C.) taught that the earth, fixed in the center of the universe, is not flat as a disk, but round as an orange, giving as proofs (1) the gradual disappearance of a ship standing out to sea and (2) the form of the shadow cast by the earth in lunar eclipses, to which others added (3) the change in the altitude of circumpolar stars readily noticeable in traveling north or south. Aristarchus of Samos (310-250), one of the great astronomers of antiquity, went further, not fearing to teach that the earth is spherical in form, that it turns on its axis daily and revolves annually around the sun. Such orthodox teaching did not, however, commend itself to people generally, as they did not exactly like the idea of being whisked round with their houses and cities at a dangerous speed, preferring to explain celestial phenomena by the rotation of the vast celestial sphere, with all the starry host, round a flat, immovable earth. For them such a system of cosmography recommended itself by its simplicity and reasonableness as well as by the sense of stability, rest and comfort which it brought along with it.

Ptolemy, who flourished at Alexandria about 150 A. D. and whose name is associated with a system of the world, also held that the earth is spherical in form, giving at the same time some very ingenious proofs of his belief. St. Augustine, in the fourth century, was not opposed to the doctrine of a round earth, though he felt the religious difficulty arising from the existence of the antipodes, which difficulty reached its acute stage four hundred years later.

It is well to remember that the Church did not condemn the existence of an antipodean world; what it did condemn was the teaching of Virgilius, Bishop of Salzburg, to the effect that this world, lying under the equator, was inhabited by a race of men not descended from Adam. Virgilius also taught that the antipodes had a sun and moon different from ours, an astronomical opinion for which he was never molested by ecclesiastical authority.

Boethius, the worthy representative of the natural and the higher philosophy of the sixth century, wrote of the earth as globe-like in form, but small in comparison with the heavens. Isidore of Seville, in the seventh century, "the most learned man of his age," and the encyclopedic Bede, in the eighth, rejected the theory of a flat, discoidal earth and returned to the spherical form of the early Greek astronomers. But again, centuries had to elapse before people could be brought to tolerate views of the world that seemed so directly opposed to the daily testimony of their senses.

The strong, conclusive arguments which alone establish this theory on a firm basis were, however, not known to Copernicus and could not have been known in an age that preceded the invention of the telescope and in which the astronomer had to be the constructor of his own crude wooden instruments. The wonder is that Copernicus did such excellent observational work on the banks of the Vistula with the rough appliances at his disposal. The arguments which he put forward and urged with consummate skill for the acceptance of his revolutionary theory were its general simplicity and probability. Of proofs clear and decisive, he gave none; yet, while he was working on his epoch-making treatise, begun in 1507 and published in 1543 with dedication to Pope Paul III., a direct proof of the earth's spherical form was given by the return (1528) from the Philippines along an eastern route of one of Magellan's ships, which had reached those distant isles after crossing the western ocean, which the Portuguese navigator called the "Pacific," from the tranquility of its waters. For a direct proof of the earth's annual motion, the world had to wait two hundred years more, until Bradley discovered the "aberration of light" in 1729; and for a direct demonstration of its diurnal motion until Foucault made his pendulum experiment in the Panthéon, in 1851.

We cannot let Gilbert's reference to a "weightless earth" pass without a few remarks to justify our approval of the statement.

The idea connoted by the term weight is the pull which the earth exerts on the mass of a body; thus, when we say that an iron ball weighs six pounds, we mean that the earth pulls it downwards with a force equal to the weight of six pounds. That the weight of a given lump of matter is not a constant but a dependent quantity may be seen from a number of considerations. Its weight in vacuo, for instance, is different from its weight in air, and this latter differs considerably from its weight in water or in oil. Again, if we take our experimental ball down the shaft of a mine, the spring-balance used to measure the pull of the earth on it will not record six pounds but something less; and the further we descend, the less will the spring-balance be found to register. At a depth of two thousand miles below the surface, the ball would be found to have lost half its weight; and at a depth of four thousand, all its weight. At the earth's center a "box of weights" would still be called a "box of weights," though neither the box itself nor its enclosed standards singly or collectively would have any weight whatever. It has been shown experimentally that two masses weigh slightly less when placed one above the other than when placed side by side, because in the latter case their common mass-center is measurably nearer to the center of the earth. Every mother knows that when a boy is sent to buy a pound of candy, it is the mass of the sweet stuff that makes him happy, and not its weight, for this acts more like an incumbrance while he is bringing it home. Of course, weight is every day used, and correctly, as a measure of mass, for every student of mechanics writes without the least hesitation,

W=Mg.

by which he simply means that the weight of a body is directly proportional to its mass (M), which is constant wherever the body may be taken, and to the intensity of gravity (g), which varies slightly with geographical position. As both scale-pans of an ordinary balance are equally affected by the local value of g, it follows that equilibrium is established only when the two masses—that of the body and that of the standards—are themselves equal: hence weighing is in reality only a process of comparing masses, i.e., a process of "massing."

If we bring our experimental ball to the top of a hill or to the summit of a mountain or aloft in a balloon, we find the pull on the registering spring growing less and less as we go higher and higher, from which we naturally conclude that if we could go far enough out into circumterrestrial space, say, towards the moon, the ball would lose its weight entirely; it would cease to stretch the spring of the measuring balance, its weight vanishing at a definite, calculable distance from the earth's center. If carried beyond that point the ball would come under the moon's preponderating attraction and would begin to depress anew the index of the balance until at the surface of our satellite it would be found to weigh exactly one pound. If transferred to the planet Mars the ball would weigh two pounds, and if to the surface of the giant planet Jupiter, sixteen pounds. But while its weight thus changes continually, its mass or quantity of matter, the stuff of which it is made, remains constant all the while, being equally unaffected by such variables as motion, position or even temperature.

Returning from celestial space to our more congenial terrestrial surroundings, we find a similar inconstancy in the weight of the ball as we travel from the equator toward either pole, the weight being least at the equator and slightly greater at either end of our axis of rotation. This change is fully accounted for by the spheroidal figure of the earth and its motion of rotation, in virtue of which, while going from the equator toward the pole, our distance from the center of attraction undergoes a slight diminution, as does also the component of the local centrifugal force, which is in opposition to gravity.

From all this, it will be seen that the weight of a body is more of the nature of an accidental rather than an essential property of matter, whereas its mass is a necessary and unvarying property. Hence we speak with propriety of the conservation of mass just as we speak with equal propriety of the conservation of energy; but we may never speak or write of the conservation of weight. The mass of our iron ball is precisely the same away from the surface of the earth as it is anywhere on the surface, whether a thousand miles below the surface or a thousand miles above it; and the same it would be found in any part of the solar system or of the starry universe to which it might be taken.

Since weight is nothing else than the pull which the earth exerts on a body, it follows that, big and massive as our planet is, it must, nevertheless, be weightless; for it cannot with any degree of propriety be said to pull itself. It is incapable of producing even an infinitesimal change in the position of its mass-center, or center of gravity, as this centroid is sometimes called. The earth attracts itself with no force whatever; but is attracted and governed in its annual movement by the sun, the central controlling body of our system, while the moon and planets play only the part of petty disturbers.

It would, however, be right to speak of the weight of the earth relatively to the sun; for the sun attracts the mass of our planet with a certain definite force, readily calculable from the familiar formula for central force, viz., mv²/r., in which m is the mass of the earth, v its orbital velocity and r its distance from the sun. Supplying the numbers, the weight of the earth relatively to the sun, comes out to be

3,000000,000000,000000 or 3×10^{18} tons weight,

or, in words, three million million million tons weight.

It may here be noted that the velocity v of the earth in its orbit is a varying quantity, depending on distance from the sun. As this distance is least in December and greatest in June, it follows that the earth is heavier relatively to the sun in winter than it is in summer.

The mass of the earth, on the other hand, is not a relative and variable quantity, but a constant and independent one, which would not be affected either by the sudden annihilation of all the other members of the solar system or by the instantaneous or successive addition of a thousand orbs. Mass being the product of volume by density, that of the earth is 6000,000000,000000,000000 or 6×10²¹ tons mass, which reads six thousand million million million tons mass.

The number which expresses the mass of the earth is thus very different from that which represents its weight relatively to the sun. It is obvious that the latter would be a much greater quantity if our planet were transferred to the orbit of Venus and very much less if transferred to that of far-off Jupiter, but the number which expresses its mass would remain precisely the same in both cases, viz., the value given above.

In elaborating his theory of magnetism, and especially his magnetic theory of the earth, Gilbert made extensive use of lodestone-globes, which he called "terrellas," i.e., miniature models of the earth. In pursuing his searching inquiry, he was gradually led from these "terrellas" to his great induction that the earth itself is a colossal, globe-like magnet. Following Norman, "the ingenious artificer," of Limehouse, London, he also showed that the entire cubical space which surrounds a lodestone is an "orb of virtue," or region of influence, from which he inferred that the earth itself must have its "orb of virtue," or magnetic field, extending outward to a very great distance.

Gilbert does not, for a moment, think that this theory of terrestrial magnetism, the first ever given to the world, is a wild speculation. Far from it; he is convinced that "it will stand as firm as aught that ever was produced in philosophy, backed by ingenious argumentation or buttressed by mathematical demonstration."

If the earth has a magnetic field, he argued, why not the moon, the planets and the sun itself, "the mover and inciter of the universe"? Given these planetary magnetic fields, Gilbert seems to have no difficulty in finding out the forces necessary to account for the crucial difficulties of the Copernican doctrine. Nor is the medium absent that is needed for the mutual action of magnetic globes, for we are assured that it is none other than the universal ether, which, he says "is without resistance."

Gilbert disposes of the cosmographic puzzle of the "suspension" of the earth in space by saying, and saying justly, that the earth "has no heaviness of its own," and, therefore, "does not stray away into every region of the sky." To emphasize the statement, he continues: "The earth, in its own place, is in no wise heavy, nor does it need any balancing"; and again, "The whole earth itself has no weight." "By the wonderful wisdom of the Creator," he elsewhere says, "forces were implanted in the earth that the globe itself might with steadfastness take direction."

Gilbert holds that the daily rotation of the earth on its axis is also caused, and maintained with strict uniformity, by the same prevalent system of magnetic forces, for "lest the earth should in divers ways perish and be destroyed, she rotates in virtue of her magnetic energy, and such also are the movements of the rest of the planets."

Just how this magnetic energy acts to produce the rotatory motion of a massive globe Gilbert does not say. Nor was he able to solve such a magnetic riddle, for there was nothing in his philosophy to explain how a lodestone-globe in free space should ever become a perpetual magnetic motor. Oddly enough he disagrees with Peregrinus, who maintained in his Epistola, 1269, that a terrella, or spherical lodestone, poised in the meridian, would turn on its axis regularly every 24 hours. He naively says: "We have never chanced to see this; nay, we doubt if there is such a movement." Continuing, he brings out his clinching argument: "This daily rotation seems to some philosophers wonderful and incredible because of the ingrained belief that the mighty mass of earth makes an orbital movement in 24 hours; it were more incredible that the moon should in the space of 24 hours traverse her orbit or complete her course; more incredible that the sun and Mars should do so; still more that Jupiter and Saturn; more than wonderful would be the velocity of the fixed stars and firmament."

Here he finds himself obliged to berate Ptolemy for being "over-timid and scrupulous in apprehending a break up of this nether world were the earth to move in a circle. Why does he not apprehend universal ruin, dissolution, confusion, conflagration and stupendous celestial and super-celestial calamities from a motion (that of the starry sphere) which surpasses all imagination, all dreams and fables and poetic license, a motion ineffable and inconceivable?"

Gilbert is not clear and emphatic on the other doctrine of Copernicus, the revolution of the earth and planets around the sun. He does, however, say that each of the moving globes "has circular motion either in a great circular orbit or on its own axis, or in both ways." Again: "The earth by some great necessity, even by a virtue innate, evident and conspicuous, is turned circularly about the sun." Elsewhere he affirms that the moon circles round the earth "by a magnetic compact of both." He returns to this point in his De Mundo Nostro, saying, "The force which emanates from the moon reaches to the earth; and, in like manner, the magnetic virtue of the earth pervades the region of the moon."

We have here an implied interaction between two magnetic fields, rather a clever idea for a magnetician of the sixteenth century. In one case, the reaction is between the field of the earth and that of the moon, compelling the latter to rotate round its primary once every month; and the second, between the field of the earth and that of the sun, compelling our planet to revolve round the center of our system once every year.

Though an inefficient cause of the annual motion of our planet, this interaction of two magnetic fields had, nevertheless, something in common with the idea of the mutual action of material particles postulated in the Newtonian theory of universal gravitation.

This magnetic assumption by which Gilbert sought to defend the theory of the universe propounded by Copernicus was a very vulnerable point in his astronomical armor which was promptly detected and fiercely assailed by a galaxy of continental writers; all of them churchmen, physicists and astronomers of note. They accepted Gilbert's electric and magnetic discoveries and warmed up to his experimental method; they did not discard his theory of terrestrial magnetism, but rejected and scoffed at the use which he made of it to justify the heliocentric theory. They poked fun at the English philosopher for his magnetic hypothesis of planetary rotation and revolution, and succeeded in discrediting the Copernican doctrine. Error prevailed for a time, but Newton's Principia, published in 1687, gave the Ptolemaic system the coup de grâce. Gilbert's hypothesis of the interaction of planetary magnetic fields gave way to universal gravitation, and Copernicanism was finally triumphant.

Throughout the pages of Gilbert's treatise, he shows himself remarkably chary in bestowing praise, but surprisingly vigorous in denunciation. St. Thomas is an instance of the former, for it is said that he gets at the nature of the lodestone fairly well; and it is admitted that "with his godlike and perspicacious mind, he would have developed many a point had he been acquainted with magnetic experiments." Taisnier, the Belgian, is an example of the latter, whose plagiarism from Peregrinus wrings from our indignant author such withering words as "May the gods damn all such sham, pilfered, distorted works, which so muddle the minds of students!"

Besides his treatise on the magnet, Gilbert is the author of an extensive work entitled, "De Mundo Nostro Sublunari," in which he defends the modern system of the universe propounded by Copernicus and gives his views on important cosmical problems. This work was published after the author's death, first at Stettin in 1628, and again at Amsterdam in 1651.

Chancellor Bacon was well acquainted with this treatise of our philosopher; indeed he had in his collection the only two manuscript copies ever made, one in Latin and the other in English, a very singular and significant fact in view of the Chancellor's attitude toward Gilbert. Putting it crudely, one would like to know how he obtained possession of the manuscripts and what was his motive in keeping them hidden away from the philosophers of the day. "It is considered surprising," writes Prof. Silvanus P. Thompson, "that Bacon, who had the manuscripts in his possession and held them for years unpublished, should have written severe strictures upon their dead author and his methods, while at the very same time posing as the discoverer of the inductive method in science, a method which Gilberd (Gilbert) had practised for years before."[6]

That Bacon was no admirer of Gilbert's physical and cosmical theories the following passages will show. In the "Novum Organum" the Chancellor wrote: "His philosophy is an instance of extravagant speculation founded on insufficient data"; again, "As the alchemists made a philosophy out of a few experiments of the furnace, Gilbert, our countryman, hath made a philosophy out of the lodestone" ("The Advancement of Learning"); lastly, "Gilbert hath attempted a general system on the magnet, endeavoring to build a ship out of materials not sufficient to make the rowing-pins of a boat" ("De Augmentis Scientiarum").

One is tempted to ask how this strange disregard which Bacon entertained for the scientific views of the greatest natural philosopher of his age and country came to exist? Was it due to a feeling of jealousy that could not brook a rival in the domain of the higher philosophy, or was it because Bacon, the anti-Copernican, wanted to write down Gilbert, the defender of the heliocentric theory, in the British Isles?

When reading Bacon's depreciatory remarks we have to remember that his mathematical and physical outfit was very limited even for the age in which he lived; from which it is safe to infer that he was but little qualified to pass judgment on the value of the electric and magnetic work accomplished in the workshops at Colchester or on the theories to which they gave rise.

Bacon deserves praise for denouncing the prevalent system of natural philosophy which was mainly authoritative, speculative and syllogistic instead of experimental, deductive and inductive, but he was inconsistent and forgetful of his own principles when he belittled the greatest living enemy of mere book-learning, and the most earnest advocate, by word and example, of the laboratory methods for the advancement of learning.

To avoid misapprehension, it should be here stated that Bacon was not always censorious in his treatment of his illustrious fellow-citizen, for in several places he writes approvingly of the electric and magnetic experiments contained in De Magnete, which he calls in his Advancement of Learning, "a painfull (i.e., painstaking) experimentall booke." In other places he draws so freely on Gilbert without acknowledgment as to come dangerously near the suspicion of plagiarism.

Gilbert died, probably of the plague, in the sixtieth year of his age, on December 10th, 1603, and was buried in the chancel of Holy Trinity Church, Colchester, where a mural tablet records in Latin the chief facts of his life.

Dr. Fuller in his "Worthies of England" (1662) describes Gilbert as tall of stature and cheerful of "complexion," a happiness, he quaintly remarks, not ordinarily found in so hard a student and retired a person." Concluding his appreciation of the philosopher, Fuller writes: "Mahomet's tomb at Mecha[7] is said strangely to hang up, attracted by some invisible loadstone; but the memory of this Doctor will never fall to the ground, which his incomparable book De Magnete will support to eternity."

Animated by a similar spirit of national pride, Dryden wrote

Gilbert shall live till loadstones cease to draw,
Or British fleets the boundless ocean awe.

We shall close these remarks by Hallam's estimate of Gilbert as a scientific pioneer, contained in his Introduction to the Literature of Europe. "The year 1600," he says, "was the first in which England produced a remarkable work in physical science; but this was one sufficient to raise a lasting reputation for its author. Gilbert, a physician, in his Latin treatise on the magnet, not only collected all the knowledge which others had possessed on the subject, but became at once the father of experimental philosophy in this island; and, by a singular felicity and acuteness of genius, the founder of theories which have been revived after a lapse of ages and are almost universally received into the creed of science."

For well-nigh three hundred years, De Magnete remained untranslated, being read only by the scholarly few. The first translation was made by P. Fleury Mottelay, of New York, and published by Messrs. Wiley and Sons in the year 1893. Mr. Mottelay has given much attention to the bibliography of the twin sciences of electricity and magnetism, as the foot-notes which he has added to the translation abundantly prove.

A second translation appeared in the tercentenary year, 1900, and was the work of the members of the Gilbert Club, London, among whom were Dr. Joseph Larmor and Prof. Silvanus P. Thompson. It is a page-for-page translation with facsimile illustrations, initial letters and tail-pieces.

As one would infer from the numerous references contained in De Magnete, Gilbert had a considerable collection of valuable books, classical and modern, bearing on the subject of his life-work; but these, as well as his terrellas, globes, minerals and instruments, perished in the great fire of London, 1666, with the buildings of the College of Physicians, in which they were located.

A portrait of Gilbert was preserved in the Bodleian Library, Oxford, for many years; but has long since disappeared from its walls. On the occasion of the three hundredth anniversary (1903) of Gilbert's death, a fine painting representing the Doctor in the act of showing some of his electrical experiments to Queen Elizabeth and her court (including Sir Walter Raleigh, Sir Francis Drake and Cecil, Lord Burleigh, famous Secretary of State), was presented to the Mayor of Colchester by the London Institute of Electrical Engineers. A replica of the painting was sent to the St. Louis Exposition, 1904, where it formed one of the attractions of the Electricity Building.

The house in which Gilbert was born (1544) still stands in Holy Trinity Street, Colchester, where it is frequently visited by persons interested in the history of electric and magnetic science.

Brother Potamian.

FOOTNOTES:

[6] "Souvenir of Gilberd's Tercentenary," p. 6.

[7] See magnetic myths, page 5.

[CHAPTER III.]
Franklin and Some Contemporaries.

As already seen, the writers of Greece and Rome knew little about the lodestone; we have now to add that the knowledge of electricity which they possessed was of the same elementary character. They knew that certain resinous substances, such as amber and jet had, when rubbed, the property of attracting straws, feathers, dry leaves and other light bodies; beyond this, their philosophy did not go. The Middle Ages added little to the subject, as the Schoolmen were occupied with questions of a higher order. The Saxon Heptarchy came and went, Alcuin taught in the schools of Charlemagne, Cardinal Langton compelled a landless and worthless king to sign Magna Charta, universities were founded with Papal sanction in Italy, France, Germany, England and Scotland, Copernicus wrote his treatise on the revolution of heavenly bodies and dedicated it to Pope Paul III., Tycho Brahé made his famous astronomical observations at Uranienborg and befriended at Prague the penniless Kepler, and Columbus gave a New World to Castile and Leon—all this before the man appeared who, using amber as guide, discovered a new world of phenomena, of thought and philosophy. This man was no other that Gilbert, whose discoveries in magnetism were described in an earlier chapter. The trunk line of his work was magnetism; electricity was only a siding. One was the main subject of a life-long quest while the other was only a digression. It was a digression in which the qualities of the native-born investigator are seen at their very best: alertness and earnestness, resourcefulness and perseverance, all rewarded by a rich harvest of valuable results. It is refreshing and inspiring to read the Second Book of Gilbert's treatise, De Magnete, in which are recorded in quick succession the twenty important discoveries which he made in his new field of labor.

Fig. 9
Gilvert's "Versorium" or Electroscope

At the very outset, he found it necessary to invent a recording instrument to test the electrification produced by rubbing a great variety of substances. This he appropriately called a versorium; we would call it an electroscope. "Make to yourself," he says, "a rotating needle of any sort of metal three or four fingers long and pretty light and poised on a sharp point." He then briskly rubs and brings near his versorium glass, sulphur, opal, diamond, sapphire, carbuncle, rock-crystal, sealing-wax, alum, resin, etc., and finds that all these attract his suspended needle, and not only the needle, but everything else. His words are remarkable: "All things are drawn to electrics." Here is a great advance on the amber and jet, the only two bodies previously known as having the power to attract "straws, chaff and twigs," the usual test-substances of the ancients. Pursuing his investigations, he finds numerous bodies which perplex him, because when rubbed they do not affect his electroscope. Among these, he enumerates: bone, ivory, marble, flint, silver, copper, gold, iron, even the lodestone itself. The former class he called electrica, electrics; the latter was termed anelectrica, non-electrics.

To Gilbert we, therefore, are indebted for the terms electric and electrical, which he took from the Greek name for amber instead of succinic and succinical, their Latin equivalents. The noun electricity was a coinage of a later period, due probably to Sir Thomas Browne, in whose Pseudodoxia Epidemica, 1646, it occurs in the singular number on page 51 and in the plural on page 79. It may interest the reader to be here retold that we owe the chemical term affinity to Albertus Magnus, barometer to Boyle, gas to van Helmont, magnetism to Barlowe, magnetic inclination to Bond, electric circuit to Watson, electric potential to Green, galvanometer to Cumming, electro-magnetism to Kircher, electromagnet to Sturgeon, and telephone to Wheatstone.

Gilbert was perplexed by the anomalous behavior of his non-electrics. He toiled and labored hard to find out the cause. He undertook a long, abstract, philosophical discussion on the nature of bodies which, from its very subtlety, failed to reveal the cause of his perplexing anomaly. Gilbert failed to discover the distinction between conductors and insulators; and, as a consequence, never found out that similarly electrified bodies repel each other. Had he but suspended an excited stick of sealing-wax, what a promised land of electrical wonders would have unfolded itself to his vision and what a harvest of results such a reaper would have gathered in! From solids, Gilbert proceeds to examine the behavior of liquids, and finds that they, too, are susceptible of electrical influence. He notices that a piece of rubbed amber when brought near a drop of water deforms it, drawing it out into a conical shape. He even experiments with smoke, concluding that the small carbon particles are attracted by an electrified body. Some years ago, Sir Oliver Lodge, extending this observation, proposed to lay the poisonous dust floating about in the atmosphere of lead works by means of large electrostatic machines. He even hinted in his Royal Institution lecture that they might be useful in dissipating mists and fogs, and recommended that a trial be made on some of our ocean-steamers.

Gilbert next tries heat as an agent to produce electrification. He takes a red-hot coal and finds that it has no effect on his electroscope; he heats a mass of iron up to whiteness and finds that it, too, exerts no electrical effect. He tries a flame, a candle, a burning torch, and concludes that all bodies are attracted by electrics save those that are afire or flaming, or extremely rarefied. He then reverses the experiment, bringing near an excited body the flame of a lamp, and ingenuously states that the body no longer attracts the pivoted needle. He thus discovered the neutralizing effect of flames, and supplied us with the readiest means that we have to-day for discharging non-conductors.

He goes a step further; for we find him exposing some of his electrics to the action of the sun's rays in order to see whether they acquired a charge; but all his results were negative. He then concentrates the rays of the sun by means of lenses, evidently expecting some electrical effect; but finding none, concludes with a vein of pathos that the sun imparts no power, but dissipates and spoils the electric effluvium.

Professor Righi has shown that a clean metallic plate acquires a positive charge when exposed to the ultraviolet radiation from any artificial source of light, but that it does not when exposed to solar rays. The absence of electrical effects in the latter case is attributed to the absorptive action of the atmosphere on the shorter waves of the solar beam.

Of course Gilbert permits himself some speculation as to the nature of the agent with which he was dealing. He thought of it, reasoned about it, pursued it in every way; and came to the conclusion that it must be something extremely tenuous indeed, but yet substantial, ponderable, material. "As air is the effluvium of the earth," he says, "so electrified bodies have an effluvium of their own, which they emit when stimulated or excited"; and again: "It is probable that amber exhales something peculiar that attracts the bodies themselves."

These views are quite in line with the electronic theory of electricity in vogue to-day, which invests that elusive entity with an atomic structure. It is held that the tiny particles or electrons that are shot out from the cathode terminal of a vacuum tube with astounding velocity are none other than particles of negative electricity, pure and simple. They have mass and inertia, both of which properties are held to be entirely electrical, though quite analogous to the mass and inertia of ordinary, ponderable matter.

History shows that scientific theories have their periods of infancy, maturity and decay. When they have served their purpose, like the scaffolding of a building, they are removed from sight and stored away, say, in a limbo of discarded philosophy, for use of the historian of science or of the metaphysician writing on the nature of human knowledge. Such was the fate of Gilbert's "effluvium" theory of electricity, of the fluid theories of Dufay and Franklin, and the ether-strain theory of recent years. "Each physical hypothesis," says Prof. Fleming, "serves as a lamp to conduct us a certain stage in the journey. It illumines a limited portion of the path, throwing light before and behind for some distance; but it has to be discarded and exchanged at intervals because it has become exhausted and because its work is done."

It is a little surprising that the phenomenon of electrical repulsion should have escaped the attention of one so skilled in experimentation as Gilbert. Yet such was the case; and Gilbert even went so far as to deny its very existence, saying, "Electrics attract objects of every kind; they never repel." This error reminds one of Gilbert's own saying that "Men of acute intelligence, without actual knowledge of facts, and in the absence of experiment, easily slip and err." Just twenty-nine years after Gilbert had penned this aphorism, there appeared in Ferrara an extensive work on electric and magnetic philosophy, by the Jesuit Cabeo, in which this electrical repulsion was recognized and described. Having rubbed one of his electrics, Cabeo noticed that it attracted grains of dust at first and afterward repelled them suddenly and violently. In the case of threads, hairs or filaments of any kind, he observed that they quivered a little before being flung away like sawdust. This self-repelling property of electricity, described in the year 1629, opened up a new field of inquiry, which was actively explored by a number of brilliant electricians in England and on the Continent.

This was especially the case after the building of the first frictional machine by Otto von Guericke in 1672. The burgomaster of Magdeburg had already acquired European fame by the original and sensational experiments on atmospheric pressure which he made in presence of the Emperor and his nobles in solemn diet assembled (1651). Von Guericke seems to have been of a mind with Gilbert concerning writers on natural science who treat their subjects "esoterically, miracle-mongeringly, abstrusely, reconditely, mystically"; for he affirms that "oratory, elegance of diction or skill in disputation avails nothing in the field of natural science."

Von Guericke's machine consisted of a ball of sulphur, with the hand of the operator or assistant as rubber. Some years later, the sulphur ball was replaced by Newton (some say Hauksbee) by a glass globe, which, in turn, was exchanged for a glass cylinder by Gordon, a Scotch Benedictine, who was Professor of natural philosophy in the University of Erfurt. In 1755, Martin de Planta, of Sus, in Switzerland, constructed a plate-machine which was subsequently improved by Ramsden of London. The frictional machine, as it was rightly called, has been superseded by the influence machine, a type of static generator which is at once efficient, reliable and easy of operation. The best known form for laboratory use is that of Wimshurst (1832-1903), of London.

Andrew Gordon, the Scotch Benedictine to whom reference has just been made, was a man of an inventive turn of mind. Besides, the cylindrical electric machine which he constructed, he devised several ingenious pieces of electrical apparatus, among which are the electric chimes usually ascribed to Franklin. They are fully described in his Versuch einer Erklärung der Electricität, published in 1745. On page 38, he says that he was led to try an electrical method of ringing bells; and then adds: "For this purpose I placed two small wine-glasses near each other, one of which stood on an electrified board, while the other, placed at a distance of an inch from it, was connected with the ground. Between the two, I suspended a little clapper by a silk thread, which clapper was attracted by the electrified glass and then repelled to the grounded one, giving rise to a sound as it struck each glass. As the clapper adhered somewhat to the glasses, the effect on the whole was not agreeable. I, therefore, substituted two small metallic gongs suspended one from an electrified conductor and the other from a grounded rod, the gongs being on the same level and one inch apart. When the clapper was lowered and adjusted, it moved at once to the electrified bell, from which it was driven over to the other, and kept on moving to and fro, striking the bell each time with pleasing effect until the electrified bell lost its charge." In the illustration, a is connected with the electrified conductor; b is the insulated clapper; c the grounded gong.

Fig. 10
Gordon's Electric Chimes, 1745

Gordon's book was published in Erfurt in 1745, while the year 1752 is that in which Franklin applied the chimes to his experimental rod to apprise him of the approach of an electric storm, an application which was original and quite in keeping with the practical turn of mind that characterized our journeyman-printer, philosopher and statesman. Unquestionably, Franklin had all the ingenuity and constructive ability needed to make such an appliance; but there is no evidence that he actually invented it. Though Franklin neither claimed nor disclaimed the chimes as his own, all his admirers would have preferred less reticence on his part when the discoveries and inventions of contemporary workers in the electrical field were concerned. He had attained sufficient eminence to permit him to look appreciatingly and encouragingly on the efforts of others.

Gordon also invented a toy electric motor in which rotation was effected by the reaction of electrified air-particles escaping from a number of sharp points. One of these motors consisted of a star of light rays cut from a sheet of tin and pivoted at the center, with the ends of the rays slightly bent aside and all in the same direction. When electrified, Gordon noticed that the star required no extraneous help to set it in motion. It was a self-starting electric-motor. In the dark, the points were tipped with light, and as they revolved traced out a luminous circle which "could neither be blown out nor decreased."