THE LETTER OF
PETRUS
PEREGRINUS
ON THE MAGNET, A.D. 1269
TRANSLATED BY
BROTHER ARNOLD, M.Sc.
PRINCIPAL OF LA SALLE INSTITUTE, TROY
WITH
INTRODUCTORY NOTICE
BY
BROTHER POTAMIAN, D.Sc.
PROFESSOR OF PHYSICS IN MANHATTAN
COLLEGE, NEW YORK
NEW YORK
McGRAW PUBLISHING COMPANY
MCMIV
Copyright, 1904, by
McGraw Publishing Company
INTRODUCTORY
The magnetic lore of classic antiquity was scanty indeed, being limited
to the attraction which the lodestone manifests for iron. Lucretius
(99-55 B. C.), however, in his poetical dissertation on the magnet,
contained in _De Rerum Natura_, Book VI.[1] recognizes magnetic
repulsion, magnetic induction, and to some extent the magnetic field
with its lines of force, for in verse 1040 he writes:
Oft from the magnet, too, the steel recedes,
Repelled by turns and re-attracted close.
And in verse 1085:
Its viewless, potent virtues men surprise;
Its strange effects, they view with wond’ring eyes
When without aid of hinges, links or springs
A pendant 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.
The poet Claudian (365-408 A. D.) wrote a short idyll on the attractive
virtue of the lodestone and its symbolism; St. Augustine (354-430), in
his work _De Civitate Dei_, records the fact that a lodestone, held
under a silver plate, draws after it a scrap of iron lying on the plate.
Abbot Neckam, the Augustinian (1157-1217), distinguishes between the
properties of the two ends of the lodestone, and gives in his _De
Utensilibus_, what is perhaps the earliest reference to the mariner’s
compass that we have. Albertus Magnus, the Dominican (1193-1280), in his
treatise, _De Mineralibus_, enumerates different kinds of natural
magnets and states some of the properties commonly attributed to them;
the minstrel, Guyot de Provins, in a famous satirical poem, written
about 1208, refers to the directive quality of the lodestone and its use
in navigation, as do also Cardinal de Vitry in his _Historia Orientalis_
(1215-1220); Brunetto Latini, poet, orator and philosopher, in his
_Trésor des Sciences_, a veritable library, written in Paris in 1260;
Raymond Lully, the Enlightened Doctor, in his treatise, _De
Contemplatione_, begun in 1272, and Guido Guinicelli, the poet-priest of
Bologna, who died in 1276.
The authors of these learned works were too busy with the pen to find
time to devote to the close and prolonged study of natural phenomena
necessary for fruitful discovery, and so had to content themselves with
recording and discussing in their tomes the scientific knowledge of
their age without making any notable additions to it.
But this was not the case with such contemporaries of theirs as Roger
Bacon, the Franciscan, and his Gallic friend, Pierre de Maricourt,
commonly called Petrus Peregrinus, the subject of the present notice, a
man of academic culture and of a practical rather than speculative turn
of mind. Of the early years of Peregrinus nothing is known save that he
studied probably at the University of Paris, and that he graduated with
the highest scholastic honors. He owes his surname to the village of
Maricourt, in Picardy, and the appellation Peregrinus, or Pilgrim, to
his having visited the Holy Land as a member of one of the crusading
expeditions of the time.
In 1269 we find him in the engineering corps of the French army then
besieging Lucera, in Southern Italy, which had revolted from the
authority of its French master, Charles of Anjou. To Peregrinus was
assigned the work of fortifying the camp and laying mines as well as of
constructing engines for projecting stones and fire-balls into the
beleaguered city.
It was in the midst of such warlike preoccupations that the idea seems
to have occurred to him of devising a piece of mechanism to keep the
astronomical sphere of Archimedes in uniform rotation for a definite
time. In the course of his work over the new motor, Peregrinus was
gradually led to consider the more fascinating problem of perpetual
motion itself with the result that he showed, at least diagrammatically,
and to his own evident satisfaction, how a wheel might be driven round
forever by the power of magnetic attraction.
Elated over his imaginary success, Peregrinus hastened to inform a
friend of his at home; and that his friend might the more readily
comprehend the mechanism of the motor and the functions of its parts, he
proceeds to set forth in a methodical manner all the properties of the
lodestone, most of which he himself had discovered. It is a fortunate
circumstance that this Picard friend of his was not a man learned in the
sciences, otherwise we would probably never have had the remarkable
exposition which Peregrinus gives of the phenomena and laws of
magnetism. This letter of 3,500 words is the first great landmark in the
domain of magnetic philosophy, the next being Gilbert’s _De Magnete_, in
1600.
The letter was addressed from the trenches at Lucera, Southern Italy, in
August, 1269, to Sigerus de Foucaucourt, his “amicorum intimus,” the
dearest of friends. A more enlightened friend, however, than the knight
of Foucaucourt was Roger Bacon, who held Peregrinus in the very highest
esteem, as the following glowing testimony shows: “There are but two
perfect mathematicians,” wrote the English monk, “John of London and
Petrus de Maharne-Curia, a Picard.” Further on in his _Opus Tertium_,
Bacon thus appraises the merits of the Picard: “I know of only one
person who deserves praise for his work in experimental philosophy, for
he does not care for the discourses of men and their wordy warfare, but
quietly and diligently pursues the works of wisdom. Therefore, what
others grope after blindly, as bats in the evening twilight, this man
contemplates in all their brilliancy because he is a master of
experiment. Hence, he knows all natural science whether pertaining to
medicine and alchemy, or to matters celestial and terrestrial. He has
worked diligently in the smelting of ores as 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 in the measurement of lands. It is impossible
to write a useful or correct treatise in 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 who would honor and enrich him.”
This last statement is worthy of the best utterances of the twentieth
century. Say what they will, the most ardent pleaders of our day for
original work and laboratory methods cannot surpass the Franciscan monk
of the thirteenth century in his denunciation of mere book learning or
in his advocacy of experiment and research, while in Peregrinus, the
mediævalist, they have Bacon’s impersonation of what a student of
science ought to be. Peregrinus was a hard worker, nor a mere theorizer,
preferring, Procrustean-like, to make theory fit the facts rather than
facts the theory; he was a brilliant discoverer who knew at the same
time how to use his discoveries for the benefit of mankind; he was a
pioneer of science and a leader in the progress of the world.
An analysis of the “Epistola” shows that
(_a_) Peregrinus was the first to assign a definite position to the
poles of a lodestone, and to give directions for determining which is
north and which south;
(_b_) He proved that unlike poles attract each other, and that similar
ones repel;
(_c_) He established by experiment that every fragment of a lodestone,
however small, is a complete magnet, thus anticipating one of our
fundamental laboratory illustrations of the molecular theory;
(_d_) He recognized that a pole of a magnet may neutralize a weaker one
of the same name, and even reverse its polarity;
(_e_) He was the first to pivot a magnetized needle and surround it with
a graduated circle, Figs. 2 and 3.[2]
(_f_) He determined the position of an object by its magnetic bearing as
done to-day in compass surveying; and
(_g_) He introduced into his perpetual motion machine, Fig. 4, the idea
of a magnetic motor, a clever idea, indeed, for a thirteenth century
engineer.
This rapid summary will serve to show that the letter of Peregrinus is
one of great interest in physics as well as in navigation and geodesy.
For nearly three centuries, it lay unnoticed among the libraries of
Europe, but it did not escape Gilbert, who makes frequent mention of it
in his _De Magnete_, 1600; nor the illustrious Jesuit writers, Cabæus,
who refers to it in his _Philosophia Magnetica_, 1629, and Kircher, who
quotes from it in his _De Arte Magnetica_, 1641; it was well known to
Jean Taisnier, the Belgian plagiarist, who transferred a great part of
it verbatim to the pages of his _De Natura Magnetis_, 1562, without a
word of acknowledgment. By this piece of fraud, Taisnier acquired
considerable celebrity, a fact that goes to show the meritorious
character of the work which he unscrupulously copied.
This memorable letter is divided into two parts: the first contains ten
chapters on the general properties of the lodestone; the second has but
three chapters, and shows how the author proposed to use a lodestone for
the purpose of producing continuous rotation.
There are many manuscript copies of the letter in European libraries:
the Bodleian has six; the Vatican, two; Trinity College, Dublin, one;
the Bibliothèque Nationale, Paris, one; Leyden, Geneva and Turin, one
each. The Leyden MS. has acquired special notoriety from a passage which
appears near the end of it in which reference is made to magnetic
declination and its value given: but Prof. W. Wenckebach, of The Hague,
has shown[3] that the lines are spurious, having been interpolated in
the manuscript in the early part of the sixteenth century.
The Leyden manuscript has also led some writers to believe in a
fictitious author of the letter, one Peter Adsiger, or Petrus Adsigerus.
As said above, Sigerus was the name of his countryman, to whom
Peregrinus addressed his letter, the _Epistola ad Sigerum_, from the
trenches at Lucera, in August, 1269.
Magnetic declination was unknown to Peregrinus, else he would not have
written the following words: “Wherever a man may be, he finds the
lodestone pointing to the heavens in accordance with the position of the
meridian” (Chapter X). Of course, the geographical meridian is the one
here meant, as the necessity of a distinct magnetic meridian had not yet
occurred to any one.
Nor was this important magnetic element known to Columbus when he sailed
from the shores of the Old World in 1492 as appears from the surprise
with which he noticed the deviation of the needle from North as well as
from the consternation of his pilots. Columbus has the unquestionable
merit of being the first to observe and record the change of declination
with change of place.
The first printed edition of the Epistola, now very rare, was prepared
by Achilles Gasser, a physician of Lindau, a man well versed in
mathematics, astronomy, history and philosophy. The work was printed in
Augsburg in 1558. A copy of this early print is among the treasures of
the Wheeler collection in the library of the American Institute of
Electrical Engineers, New York. It was from this text that the
translation which follows was made.
Besides the Latin edition of Gasser, 1558, there is also that of Libri
in his _Histoire des Sciences Mathématiques_, 1838; of Bertelli, 1868,
and Hellmann, 1898. Bertelli’s is a learned and exhaustive work in which
the Barnabite monk, sometimes called by mistake, Barnabita, instead of
Bertelli, collates and compares the readings of the two Vatican codices
with other texts, adding copious references and explanatory notes. It
appeared in the _Bulletino di Bibliografia e di Storia delle Scienze
Matematiche e Fisiche_ for 1868.
Of translations, we have that which Richard Eden made from Taisnier’s
pirated extracts, the first dated edition appearing in 1579. Cavallo’s
_Treatise on Magnetism_, 1800, also contains some of the more remarkable
passages. The only complete English translation that we have, appeared
in 1902 from the scholarly pen of Prof. Silvanus P. Thompson, of London.
It is an _édition de luxe_ beautifully rubricated, but limited to 250
copies. The translation was based on the texts of Gasser and Hellmann,
amended by reference to a manuscript in the author’s possession, dated
1391. We are informed that Mr. Fleury P. Mottelay, of New York, the
learned translator of Gilbert’s _De Magnete_, possesses a manuscript
version by Prof. Peirce, of Harvard, of the Paris codex, of which he
made a careful study in an endeavor to decipher the illegible parts.
PART I
THE LETTER OF
PEREGRINUS
PART I
CHAPTER I
PURPOSE OF THIS WORK
Dearest of Friends:
At your earnest request, I will now 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, because it is characteristic of good things to be hidden in
darkness until they are brought to light by application to public
utility. Out of affection for you, I will write in a simple style about
things entirely unknown to the ordinary individual. Nevertheless I will
speak only of the manifest properties of the lodestone, because this
tract will form part of a work on the construction of philosophical
instruments. The disclosing of the hidden properties of this stone is
like the art of the sculptor by which he brings figures and seals into
existence. Although I may call the matters about which you inquire
evident and of inestimable value, they are considered by common folk to
be illusions and mere creations of the imagination. But the things that
are hidden from the multitude will become clear to astrologers and
students of nature, and will constitute their delight, as they will also
be of great help to those that are old and more learned.