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Full text of "The letter of Petrus Peregrinus on the magnet, A.D. 1269"

THE LETTER OF 
P E T R U S 

PEREGRINUS 

ON THE MAGNET, A,D. I2,6p 



LETTER OF 

PETRUS PEREGRINUS 

ON THE MAGNET 

A.D. 1269 



THE LETTER OF 
P E T R U S 

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 



5KLr 
URL 

5140247 



THE magnetic lore of classic antiquity was 
scanty indeed, being limited to the at- 
traction 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 mag- 
netic repulsion, magnetic induction, and to some 
extent the magnetic field with its lines of force, 
for in verse 1 040 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 



1 With very few exceptions all the works referred to in this notice will 
be found in the Wheeler Collection in the Library of the American In- 
stitute of Electrical Engineers, New York. 



THE LETTER OF PEREGRINUS 

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 lode- 
stone 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 Uten- 
silibus, 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 prop- 
erties commonly attributed to them; the min- 
strel, Guyot de Provins, in a famous satirical poem, 
written about 1 208, refers to the directive qual- 
viii 



INTRODUCTORY 

ity of the lodestone and its use in navigation, as 
do also Cardinal de Vitry in his Historia Orien- 
talis (1215-1220); Brunetto Latini, poet, orator 
and philosopher, in his Tresor des Sciences, a veri- 
table library, written in Paris in 1 260 ; Ray- 
mond Lully, the Enlightened Doctor, in his 
treatise, De Contemplation, begun in 1272, and 
Guido Guinicelli, the poet-priest of Bologna, 
who died in i 276. 

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 con- 
tent 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 contem- 
poraries of theirs as Roger Bacon, the Francis- 
can, 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 



THE LETTER OF PEREGRINUS 

is known save that he studied probably at the Uni- 
versity of Paris, and that hegraduated with the high- 
est scholastic honors. He owes his surname to 
the village of Maricourt, in Picardy, and the ap- 
pellation 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 auth- 
ority of its French master, Charles of Anjou. To 
Peregrinus was assigned the work of fortifying 
the camp and laying mines as well as of con- 
structing engines for projecting 1 stones and fire- 
balls into the beleaguered city. 

It was in the midst of such warlike preoccu- 
pations that the idea seems to have occurred to 
him of devising a piece of mechanism to keep 
the astronomical sphere of Archimedes in uni- 
form 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 



INTRODUCTORY 

that he showed, at least diagrammatically, and to 
his own evident satisfaction, how a wheel might 
be driven round forever by the power of mag- 
netic attraction. 

Elated over his imaginary success, Peregrinus 
hastened to inform a friend of his at home ; and 
that his friend might the more readily compre- 
hend the mechanism of the motor and the func- 
tions of its parts, he proceeds to set forth in a 
methodical manner all the properties of the lode- 
stone, 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 sci- 
ences, 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 land- 
mark in the domain of magnetic philosophy, the 
next being Gilbert's De Magnete,\n 1600. 

The letter was addressed from the trenches 
at Lucera, Southern Italy, in August, i 269,10 Sige- 
rus de Foucaucourt, his "amicorum intimus," 
the dearest of friends. A more enlightened friend, 



THE LETTER OF PEREGRINUS 

however, than the knight of Foucaucourt was 
Roger Bacon, who held Peregrinus in the very 
highest esteem, as the following glowing testi- 
mony shows : " There are but two perfect math- 
ematicians," wrote the English monk, " John of 
London and Petrus de Maharne-Curia, a Picard." 
Further on in his Opus Tertium, Bacon thus ap- 
praises 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 war- 
fare, 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 terres- 
trial. 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 hunt- 
ing, besides which he is skilled in agriculture and 



INTRODUCTORY 

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 en- 
rich him." 

This last statement is worthy of the best ut- 
terances of the twentieth century. Say what they 
will, the most ardent pleaders of our day for or- 
iginal work and laboratory methods cannot sur- 
pass the Franciscan monk of the thirteenth cen- 
tury in his denunciation of mere book learning 
or in his advocacy of experiment and research, 
while in Peregrinus, the mediaevalist, they have 
Bacon's impersonation of what a student of sci- 
ence 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. 



THE LETTER OF PEREGRINUS 

An analysis of the " Epistola " shows that 

(tf) Peregrinus was the first to assign a defi- 
nite position to the poles of a lodestone, and to 
give directions for determining which is north and 
which south; 

(^) He proved that unlike poles attract each 
other, and that similar ones repel ; 

(r) He established by experiment that every 
fragment of a lodestone, however small, is a com- 
plete magnet, thus anticipating one of our fun- 
damental laboratory illustrations of the molecu- 
lar 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.' 

(f ] He determined the position of an object 
by its magnetic bearing as done to-day in com- 
pass surveying ; and 

1 It is probable that Flavio Gioja, an Italian pilot, some fifty years 
later, added the compass-card and attached it to the magnet. 



INTRODUCTORY 

(g) He introduced into his perpetual motion 
machine, Fig. 4, the idea of a magnetic motor, 
a clever idea, indeed, for a thirteenth century en- 
gineer. 

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 Gil- 
bert, who makes frequent mention of it in his 
De Magnete, 1 600 ; nor the illustrious Jesuit writ- 
ers, Cabasus, who refers to it in his Philosophia 
Magnetic a, 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 char- 
acter of the work which he unscrupulously 
copied. 

This memorable letter is divided into two 



THE LETTER OF PEREGRINUS 

parts : the first contains ten chapters on the gen- 
eral properties of the lodestone ; the second has 
but three chapters, and shows how the author pro- 
posed to use a lodestone for the purpose of pro- 
ducing continuous rotation. 

There are many manuscript copies of the let- 
ter in European libraries : the Bodleian has six ; 
the Vatican, two ; Trinity College, Dublin, one; 
the Bibliotheque 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' that the lines are spurious, having been in- 
terpolated 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 let- 
ter, one Peter Adsiger, or Petrus Adsigerus. As 
said above, Sigerus was the name of his country- 
man, to whom Peregrinus addressed his letter, 

1 Annali di Matematica Pura ed Applicata, 1865. 



INTRODUCTORY 

the Epistola ad Sigerum, from the trenches at Luc- 
era, in August, 1269. 

Magnetic declination was unknown to Pere- 
grinus, else he would not have written the follow- 
ing words : " Wherever a man may be, he finds 
the lodestone pointing to the heavens in accord- 
ance 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 Epislola, now 
very rare, was prepared by Achilles Gasser, a phy- 
sician of Lindau, a man well versed in mathe- 



THE LETTER OF PEREGRINUS 

matics, 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 Ameri- 
can 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 Sci- 
ences Mathematiques, 1838 ; of Bertelli, 1868, and 
Hellmann, 1898. Bertelli's is a learned and ex- 
haustive work in which the Barnabite monk, some- 
times called by mistake, Barnabita, instead of Ber- 
telli, collates and compares the readings of the 
two Vatican codices with other texts, adding copi- 
ous references and explanatory notes. It appeared 
in the Bulletino di Eibliografia e di Storia delle Science 
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 com- 



INTRODUCTORY 

plete English translation that we have, appeared 
in 1902 from the scholarly pen of Prof. Silvanus 
P. Thompson, of London. It is an edition deluxe 
beautifully rubricated, but limited to 250 copies. 
The translation was based on the texts of Gasser 
and Hellmann, amended by reference to a man- 
uscript 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: 
T your earnest request, I will now make 



A 



known to you, in an unpolished narrative, 
the undoubted though hidden virtue of the lode- 
stone, 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 ap- 
plication 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 phil- 
osophical instruments. The disclosing of the 



THE LETTER OF PEREGRINUS 

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 inesti- 
mable value, they are considered by common 
folk to be illusions and mere creations of the im- 
agination. 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. 



Y 



CHAPTER II 
QUALIFICATIONS OF THE EXPERIMENTER 

OU must know, my dear friend, that who- 



ever wishes to experiment, should be ac- 
quainted with the nature of things, and should 
not be ignorant of the motion of the celestial 
bodies. He must also be skilful in manipulation 
in order that, by means of this stone, he may pro- 
duce these marvelous effects. Through his own 
industry he can, to some extent, indeed, correct 



THE LETTER OF PEREGRINUS 

the errors that a mathematician would inevitably 
make if he were lacking in dexterity. Besides, 
in such occult experimentation, great skill is re- 
quired, for very frequently without it the desired 
result cannot be obtained, because there are many 
things in the domain of reason which demand 
this manual dexterity. 

CHAPTER III 
CHARACTERISTICS OF A GOOD LODESTONE 



lodestone selected must be distinguished 
by four marks its color, homogeneity, 
weight and strength. Its color should be iron- 
like, pale, slightly bluish or indigo, just as pol- 
ished iron becomes when exposed to the corrod- 
ing atmosphere. I have never yet seen a stone 
of such description which did not produce won- 
derful effects. Such stones are found most fre- 
quently in northern countries, as is attested by 
sailors who frequent places on the northern seas, 
notably in Normandy, Flanders and Picardy. 
This stone should also be of homogeneous ma- 



THE LETTER OF PEREGRINUS 

terial ; one having reddish spots and small holes 
in it should not be chosen; yet a lodestone is 
hardly ever found entirely free from such blem- 
ishes. On account of uniformity in its compo- 
sition and the compactness of its innermost parts, 
such a stone is heavy and therefore more valua- 
ble. Its strength is known by its vigorous at- 
traction for a large mass of iron ; further on I 
will explain the nature of this attraction. If you 
chance to see a stone with all these characteris- 
tics, secure it if you can. 

CHAPTER IV 

HOW TO DISTINGUISH THE POLES OF A 
LODESTONE 

I WISH to inform you that this stone bears in 
itself the likeness of the heavens, as I will 
now clearly demonstrate. There are in the heav- 
ens two points more important than all others, 
because on them, as on pivots, the celestial sphere 
revolves : these points are called, one the arctic 
or north pole, the other the antarctic or south 
pole. Similarly you must fully realize that in 
6 



THE LETTER OF PEREGRINUS 

this stone there are two points styled respect- 
ively the north pole and the south pole. If you 
are very careful, you can discover these two 
points in a general way. One method for doing 
so is the following : With an instrument with 
which crystals and other stones are rounded let 
a lodestone be made into a globe and then pol- 
ished. A needle or an elongated piece of iron 
is then placed on top of the lodestone and a line 
is drawn in the direction of the needle or iron, 
thus dividing the stone into two equal parts. 
The needle is next placed on another part of the 
stone and a second median line drawn. If de- 
sired, this operation may be performed on many 
different parts, and undoubtedly all these lines 
will meet in two points just as all meridian or 
azimuth circles meet in the two opposite poles 
of the globe. One of these is the north pole, 
the other the south pole. Proof of this will be 
found in a subsequent chapter of this tract. 

A second method for determining these im- 
portant points is this : Note the place on the 
above-mentioned spherical lodestone where the 
point of the needle clings most frequently and 



THE LETTER OF PEREGRINUS 

most strongly ; for this will be one of the poles 
as discovered by the previous method. In order 
to determine this point exactly, break off a small 
piece of the needle or iron so as to obtain a frag- 
ment about the length of two fingernails ; then 
put it on the spot which was found to be the 
pole by the former operation. If the fragment 
stands perpendicular to the stone, then that is, 
unquestionably, the pole sought ; if not, then 
move the iron fragment about until it becomes 
so ; mark this point carefully ; on the opposite 
end another point may be found in a similar man- 
ner. If all this has been done rightly, and if 
the stone is homogeneous throughout and a 
choice specimen, these two points will be dia- 
metrically opposite, like the poles of a sphere. 

CHAPTER v 

HOW TO DISCOVER THE POLES OF A LODESTONE AND 
HOW TO TELL WHICH IS NORTH AND WHICH SOUTH 



poles of a lodestone having been located 
in a general way, you will determine which 
is north and which south in the following man- 
8 



THE LETTER OF PEREGRINUS 

ner : Take a wooden vessel rounded like a plat- 
ter or dish, and in it place the stone in such a 
way that the two poles will be equidistant from 
the edge of the vessel ; then place the dish in 
another and larger vessel full of water, so that 
the stone in the first-mentioned dish may be like 
a sailor in a boat. The second vessel should be 
of considerable size so that the first may resemble 
a ship floating in a river or on the sea. I insist 
upon the larger size of the second vessel in order 
that the natural tendency of the lodestone may 
not be impeded by contact of one vessel against 
the sides of the other. When the stone has been 
thus placed, it will turn the dish round until the 
north pole lies in the direction of the north pole 
of the heavens, and the south pole of the stone 
points to the south pole of the heavens. Even 
if the stone be moved a thousand times away from 
its position, it will return thereto a thousand 
times, as by natural instinct. Since the north 
and south parts of the heavens are known, these 
same points will then be easily recognized in 
the stone because each part of the lodestone will 
turn to the corresponding one of the heavens. 



THE LETTER OF PEREGRINUS 

CHAPTER VI 
HOW ONE LODESTONE ATTRACTS ANOTHER 

T717HEN you have discovered the north and 
the south pole in your lodestone, mark 
them both carefully, so that by means of these 
indentations they may be distinguished whenever 
necessary. Should you wish to see how one lode- 
stone attracts another, then, with two lodestones 
selected and prepared as mentioned in the pre- 
ceding chapter, proceed as follows : Place one 
in its dish that it may float about as a sailor in 
a skiff, and let its poles which have already been 
determined be equidistant from the horizon, i. e., 
from the edge of the vessel. Taking the other 
stone in your hand, approach its north pole to 
the south pole of the lodestone floating in the 
vessel ; the latter will follow the stone in your 
hand as if longing to cling to it. If, conversely, 
you bring the south end of the lodestone in your 
hand toward the north end of the floating lode- 
stone, the same phenomenon will occur ; namely, 
the floating lodestone will follow the one in your 
hand. Know then that this is the law : the north 

10 



THE LETTER OF PEREGRINUS 

pole of one lodestone attracts the south pole of 
another, while the south pole attracts the north. 
Should you proceed otherwise and bring the north 
pole of one near the north pole of another, the 
one you hold in your hand will seem to put the 
floating one to flight. If the south pole of one 
is brought near the south pole of another, the 
same will happen. This is because the north 
pole of one seeks the south pole of the other, 
and therefore repels the north pole. A proof of 
this is that finally the north pole becomes united 
with the south pole. Likewise if the south pole 
is stretched out towards the south pole of the 
floating lodestone, you will observe the latter to 
be repelled, which does not occur, as said before, 
when the north pole is extended towards the 
south. Hence the silliness of certain persons is 
manifest, who claim that just as scammony at- 
tracts jaundice on account of a similarity between 
them, so one lodestone attracts another even more 
strongly than it does iron, a fact which they sup- 
pose to be false although really true as shown by 
experiment. 

ii 



THE LETTER OF PEREGRINUS 

CHAPTER VII 

HOW IRON TOUCHED BY A LODESTONE TURNS 
TOWARDS THE POLES OF THE WORLD 

IT is well known to all who have made the 
experiment, that when an elongated piece 
of iron has touched a lodestone and is then fas- 
tened to a light block of wood or to a straw and 
made float on water, one end will turn to the 
star which has been called the Sailor's star be- 
cause it is near the pole; the truth is, however, 
that it does not point to the star but to the pole 
itself. A proof of this will be furnished in a 
following chapter. The other end of the iron 
will point in an opposite direction. But as to 
which end of the iron will turn towards the 
north and which to the south, you will observe 
that that part of the iron which has touched the 
south pole of the lodestone will point to the north 
and conversely, that part which had been in con- 
tact with the north pole will turn to the south. 
Though this appears marvelous to the uniniti- 
ated, yet it is known with certainty to those who 
have tried the experiment. 

12 



THE LETTER OF PEREGRINUS 

CHAPTER VIII 
HOW A LODESTONE ATTRACTS IRON 

IF you wish the stone, according to its 'natural 
desire, to attract iron, proceed as follows: 
Mark the north end of the iron and towards 
this end approach the south pole of the stone, 
when it will be found to follow the latter. Or, 
on the contrary, to the south part of the iron 
present the north pole of the stone and the lat- 
ter will attract it without any difficulty. Should 
you, however, do the opposite, namely, if you 
bring the north end of the stone towards the 
north pole of the iron, you will notice the iron 
turn round until its south pole unites with the 
north end of the lodestone. The same thing 
will occur when the south end of the lodestone 
is brought near the south pole of the iron. 
Should force be exerted at either pole, so that 
when the south pole of the iron is made touch 
the south end of the stone, then the virtue in 
the iron will be easily altered in such a manner 
that what was before the south end will now 
become the north and conversely. The cause is 

13 



THE LETTER OF PEREGRINUS 

that the last impression acts, confounds, or count- 
eracts and alters the force of the original move- 
ment. 



CHAPTER IX 

WHY THE NORTH POLE OF ONE LODESTONE 
ATTRACTS THE SOUTH POLE OF AN- 
OTHER AND VICE VERSA 

\ S already stated, the north pole of one lode- 
* ^ stone attracts the south pole of another 
and conversely; in this case the virtue of the 
stronger becomes active, whilst that of the weaker 
becomes obedient or passive. I consider the fol- 
lowing to be the cause of this phenomenon : the 
active agent requires a passive subject, not merely 
to be joined to it, but also to be united with it, 
so that the two make but one by nature. In the 
case of this wonderful lodestone this may be 
shown in the following manner: Take a lode- 
stone which you may call A Z), in which A is 
the north pole and D the south ; cut this stone 
into two parts, so that you may have two distinct 

H 



THE LETTER OF PEREGRINUS 

stones; place the stone having the pole A so 
that it may float on water and you will observe 
that A turns towards the north as before; the 
breaking did not destroy the properties of the 
parts of the stone, since it is homogeneous; 
hence it follows that the part of the stone at 
the point of fracture, which may be marked B, 
must be a south pole; this broken part of which 
we are now speaking may be called A B. The 
other, which contains Z), should then be placed 
so as to float on water, when you will see D 
point towards the south because it is a south 
pole ; but the other end at the point of fracture, 
lettered C, will be a north pole ; this stone may 
now be named C D. If we consider the first 
stone as the active agent, then the second, or 
C Z), will be the passive subject. You will also 
notice that the ends of the two stones which 
before their separation were together, after 
breaking will become one a north pole and the 
other a south pole. If now these same broken 
portions are brought near each other, one will 
attract the other, so that they will again be 

15 



THE LETTER OF PEREGRINUS 

joined at the points B and C, where the fracture 
occurred. Thus, by natural instinct, one single 
stone will be formed as before. This may be 
demonstrated fully by cementing the parts to- 
gether, when the same effects will be produced 
as before the stone was broken. As you will 
perceive from this experiment, the active agent 
desires to become one with the passive subject 
because of the similarity that exists between 
them. Hence C, being a north pole, must be 
brought close to B, so that the agent and its 
subject may form one and the same straight line 
in the order A B, C D and B and C being at 
the same point. In this union the identity 
of the extreme parts is retained and preserved 
just as they were at first; for A is the north pole 
in the entire line as it was in the divided one; 
so also D is the south pole as it was in the di- 
vided passive subject, but B and C have been 
made effectually into one. In the same way it 
happens that if A be joined to D so as to make 
the two lines one, in virtue of this union due to 
attraction in the order C D A B, then A and D 
16 



THE LETTER OF PEREGRINUS 

will constitute but one point, the identity of the 
extreme parts will remain unchanged just as they 
were before being brought together, for C is a 
north pole and B a south, as during their sepa- 
ration. If you proceed in a different fashion, 
this identity or similarity of parts will not be 
preserved ; for you will perceive that if C, a 
north pole, be joined to A, a north pole, con- 
trary to the demonstrated truth, and from these 
two lines a single one, B A C D, is formed, as 
D was a south pole before the parts were united, 
it is then necessary that the other extremity 
should be a north pole, and as B is a south pole, 
the identity of the parts of the former similarity 
is destroyed. If you make B the south pole as 
it was before they united, then D must become 
north, though it was south in the original stone ; 
in this way neither the identity nor similarity 
of parts is preserved. It is becoming that when 
the two are united into one, they should bear 
the same likeness as the agent, otherwise nature 
would be called upon to do what is impossible. 
The same incongruity would occur if you were 

I 7 



THE LETTER OF PEREGRINUS 

to join B with D so as to make the line A B D C, 
as is plain to any person who reflects a moment. 
Nature, therefore, aims at being and also at act- 
ing in the best manner possible ; it selects the 
former motion and order rather than the second 
because the identity is better preserved. From 
all this it is evident why the north pole attracts 
the south and conversely, and also why the south 
pole does not attract the south pole and the 
north pole does not attract the north. 

CHAPTER x 

AN INQUIRY INTO THE CAUSE OF THE NATURAL 
VIRTUE OF THE LODESTONE 

/CERTAIN persons who were but poor in- 
^^ vestigators of nature held the opinion that 
the force with which a lodestone draws iron, is 
found in the mineral veins themselves from which 
the stone is obtained ; whence they claim that 
the iron turns towards the poles of the earth, only 
because of the numerous iron mines found there. 
But such persons are ignorant of the fact that in 
18 



THE LETTER OF PEREGRINUS 

many different parts of the globe the lodestone 
is found; from which it would follow that the iron 
needle should turn in different directions accord- 
ing to the locality ; but this is contrary to expe- 
rience. Secondly, these individuals do not seem to 
know that the places under the poles are unin- 
habitable because there one-half the year is day 
and the other half night. Hence it is most silly 
to imagine that the lodestone should come to us 
from such places. Since the lodestone points to the 
south as well as to the north, it is evident from 
the foregoing chapters that we must conclude 
that not only from the north pole but also from 
the south pole rather than from the veins of the 
mines virtue flows into the poles of the lodestone. 
This follows from the consideration that wher- 
ever a man may be, he finds the stone pointing 
to the heavens in accordance with the position 
of the meridian; but all meridians meet in the 
poles of the world ; hence it is manifest that 
from the poles of the world, the poles of the 
lodestone receive their virtue. Another neces- 
sary consequence of this is that the needle does 

19 



THE LETTER OF PEREGRINUS 

not point to the pole star, since the meridians 
do not intersect in that star but in the poles of 
the world. In every region, the pole star is al- 
ways found outside the meridian except twice in 
each complete revolution of the heavens. From 
all these considerations, it is clear that the poles 
of the lodestone derive their virtue from the 
poles of the heavens. As regards the other parts 
of the stone, the right conclusion is, that they 
obtain their virtue from the other parts of the 
heavens, so that we may infer that not only 
the poles of the stone receive their virtue and 
influence from the poles of the world, but like- 
wise also the other parts, or the entire stone from 
the entire heavens. You may test this in the 
following manner : A round lodestone on which 
the poles are marked is placed on two sharp styles 
as pivots having one pivot under each pole so 
that the lodestone may easily revolve on these 
pivots. Having done this, make sure that it is 
equally balanced and that it turns smoothly on 
the pivots. Repeat this several times at different 
hours of the day and always with the utmost 

20 



THE LETTER OF PEREGRINUS 

care. Then place the stone with its axis in 
the meridian, the poles resting on the pivots. 
Let it be moved after the manner of bracelets so 
that the elevation and depression of the poles may 
equal the elevation and depressions of the poles 
of the heavens of the place in which you are ex- 
perimenting. If now the stone be moved ac- 
cording to the motion of the heavens, you will 
be delighted in having discovered such a won- 
derful secret ; but if not, ascribe the failure to 
your own lack of skill rather than to a defect in 
nature. Moreover, in this position I consider 
the strength of the lodestone to be best preserved. 
When it is placed differently, i. e., not in the mer- 
idian, I think its virtue is weakened or obscured 
rather than maintained. With such an instrument 
you will need no timepiece, for by it you can know 
the ascendant at any hour you please, as well as 
all other dispositions of the heavens which are 
sought for by astrologers. 



21 



PART II 



THE LETTER OF 
PEREGRINUS 



PART II 

CHAPTER I 

THE CONSTRUCTION OF AN INSTRUMENT FOR MEAS- 
URING THE AZIMUTH OF THE SUN 
THE MOON OR ANY STAR 
ON THE HORIZON 

HAVING fully examined all the properties 
of the lodestone and the phenomena con- 
nected therewith, let us now come to those in- 
struments which depend for their operation on 
the knowledge of those facts. Take a rounded 
lodestone, 1 and after determining its poles in the 
manner already mentioned, file its two sides so 
that it becomes elongated at its poles and occu- 
pies less space. The lodestone prepared in this 
wise is then enclosed within two capsules after 
the fashion of a mirror. Let these capsules be 
so joined together that they cannot be sepa- 

1 A tcrrella, or earthkin. 

2 5 



THE LETTER OF PEREGRINUS 

rated and that water cannot enter ; they should 
be made of light wood and fastened with cement 
suited to the purpose. Having done this, place 
them in a large vessel of water on the edges of 
which the two parts of the world, i. e., the 
north and south points, have been found and 
marked. These points may be united by a 
thread stretched across from north to south. 
Then float the capsules and place a smooth strip 
of wood over them in the manner of a diam- 
eter. Move the strip until it is equally distant 
from the meridian-line, previously determined 
and marked by a thread, or else until it coin- 
cides therewith. Then mark a line on the cap- 
sules according to the position of the strip, and 
this will indicate forever the meridian of that 
place. Let this line be divided at its middle by 
another cutting it at right angles, which will 
give the east and west line ; thus the four cardi- 
nal points will be determined and indicated on 
the edge of the capsules. Each quarter is to be 
subdivided into 90 parts, making 360 in the cir- 
cumference of the capsules. Engrave these divi- 
26 



THE LETTER OF PEREGRINUS 

sions on them as usually done on the back of 
an astrolabe. On the top or edge of the cap- 
sules thus marked place a thin ruler like the 
pointer on the back of the astrolabe ; instead of 
the sights attach two perpendicular pins, one at 
each end. If, therefore, you desire to take the 
azimuth of the sun, place the capsules in water 
and let them move freely until they come to 
rest in their natural position. Hold them firmly 
in one hand, while with the other you move the 
ruler until the shadow of the pins falls along the 
length of the ruler ; then the end of the ruler 
which is towards the sun will indicate the azi- 
muth of the sun. Should it be windy, let the 
capsules be covered with a suitable vessel until 
they have taken their position north and south. 
The same method, namely, by sighting, may be 
followed at night for determining the azimuth 
of the moon and stars ; move the ruler until the 
ends of the pins are in the same line with the 
moon or star ; the end of the ruler will then in- 
dicate the azimuth just as in the case of the sun. 
By means of the azimuth may then be deter- 
27 



THE LETTER OF PEREGRINUS 

mined the hour of the day, the ascendant, and 
all those other things usually determined by the 
astrolabe. A form of the instrument is shown 
in the following figure. 




FIG. I. AZIMUTH COMPASS 

CHAPTER II 

THE CONSTRUCTION OF A BETTER INSTRUMENT 
FOR THE SAME PURPOSE 

TN this chapter I will describe the construc- 
- tion of a better and more efficient instrument. 
Select a vessel of wood, brass or any solid ma- 
terial you like, circular in shape, moderate in 
28 



THE LETTER OF PEREGRINUS 

size, shallow but of sufficient width, with a cover 
of some transparent substance, such as glass or 
crystal; it would be even better to have both 
the vessel and the cover transparent. At the 
centre of this vessel fasten a thin axis of brass 
or silver, having its extremities in the cover 
above and the vessel below. At the middle of 
this axis let there be two apertures at right an- 
gles to each other ; through one of them pass 
an iron stylus or needle, through the other a sil- 
ver or brass needle crossing the iron one at right 
angles. Divide the cover first into four parts 
and subdivide these into 90 parts, as was men- 
tioned in describing the former instrument. 
Mark the parts north, south, east and west. Add 
thereto a ruler of transparent material with pins 
at each end. After this bring either the north 
or the south pole of a lodestone near the cover 
so that the needle may be attracted and receive 
its virtue from -the lodestone. Then turn the 
vessel until the needle stands in the north and 
south line already marked on the instrument ; 
after which turn the ruler towards the sun if 
29 



THE LETTER OF PEREGRINUS 

day-time, and towards the moon and stars at 
night, as described in the preceding chapter. 
By means of this instrument you can direct your 
course towards cities and islands and any other 




TIC. 2. DOUBLE -PIVOTED NEEDLE 




FIG. 3. PIVOTED COMPASS 



place wherever you may wish to go by land or 
sea, provided the latitude and longitude of the 
places are known to you. How iron remains 
suspended in air by virtue of the lodestone, I 
will explain in my book on the action of mir- 

3 



THE LETTER OF PEREGRINUS 

rors. Such, then, is the description of the instru- 
ment illustrated below. (See Figs. 2 and 3.) 



CHAPTER III 

THE ART OF MAKING A WHEEL OF 
PERPETUAL MOTION 

IN this chapter I will make known to you the 
construction of a wheel which in a remark- 
able manner moves continuously. I have seen 
many persons vainly busy themselves and even 
becoming exhausted with much labor in their 
endeavors to invent such a wheel. But these in- 
variably failed to notice that by means of the vir- 
tue or power of the lodestone all difficulty can be 
overcome. For the construction of such a wheel, 
take a silver capsule like that of a concave mir- 
ror, and worked on the outside with fine carv- 
ing and perforations, not only for the sake of 
beauty, but also for the purpose of diminishing 
its weight. You should manage also that the 
eye of the unskilled may not perceive what is 
cunningly placed inside. Within let there be 



THE LETTER OF PEREGRINUS 

iron nails or teeth of equal weight fastened to 
the periphery of the wheel in a slanting direc- 
tion, close to one another so that their distance 
apart may not be more than the thickness of a 
bean or a pea ; the wheel itself must be of uni- 
form weight throughout. Fasten the middle of 
the axis about which the wheel revolves so that 
the said axis may always remain immovable. Add 
thereto a silver bar, and at its extremity affix a 
lodestone placed between two capsules and pre- 
pared in the following way : When it has been 
rounded and its poles marked as said before, let 
it be shaped like an egg ; leaving the poles un- 
touched, file down the intervening parts so that 
thus flattened and occupying less space, it may 
not touch the sides of the capsules when the 
wheel revolves. Thus prepared, let it be attached 
to the silver rod just as a precious stone is placed 
in a ring ; let the north pole be then turned to- 
wards the teeth or cogs of the wheel somewhat 
slantingly so that the virtue of the stone may not 
flow diametrically into the iron teeth, but at a 
certain angle ; consequently when one of the 

32 



THE LETTER OF PEREGRINUS 

teeth comes near the north pole and owing to 
the impetus of the wheel passes it, it then ap- 
proaches the south pole from which it is rather 
driven away than attracted, as is evident from the 
law given in a preceding chapter. Therefore such 
a tooth would be constantly attracted and con- 




. 4. PERPETUAL MOTION WHEEL 



stantly repelled. In order that the wheel may 
do its work more speedily, place within the box a 
small rounded weight made of brass or silver of 
such a size that it may be caught between each 
pair of teeth ; consequently as the movement of 

33 



THE LETTER OF PEREGRINUS 

the wheel is continuous in one direction, so the 
fall of the weight will be continuous in the other. 
Being caught between the teeth of a wheel which 
is continuously revolving, it seeks the centre of the 
earth in virtue of its own weight, thereby aiding 
the motion of the teeth and preventing them from 
coming to rest in a direct line with the lode- 
stone. Let the places between the teeth be suit- 
ably hollowed out so that they may easily catch 
the body in its fall, as shown in the diagram 
above. (Fig. 4.) 

Farewell : finished in camp at the siege of 
Lucera on the eighth day of August, Anno Dom- 
ini MCCLXIX. 



34 



NOTES 



35 



EARLY REFERENCES TO 
THE MARINER'S COMPASS 



THE following are the passages referred to in the intro- 
ductory notice: 

Abbot Neckam (1157-1217), in his De Naturis Rerum, 
writes : 

"The sailors, moreover, as they sail over the sea, when in 
cloudy weather they can no longer profit by the light of the sun, 
or when the world is wrapped up in the darkness of the shades 
of night and they are ignorant to what point their ship's course 
is directed, these mariners touch the lodestone with a needle, 
which (the needle) is whirled round in a circle until when its 
motion ceases, its point looks direct to the north. (Cuspis 
ipsius septentrionalem plagam respiciat.)" 

In his De Utensilibus, we read : 

"Among other stores of a ship, there must be a needle 
mounted on a dart (habeat etlam acum jaculo superpositam) 
which will oscillate and turn until the point looks to the north, 
and the sailors will thus know how to direct their course when 

37 



THE LETTER OF PEREGRINUS 

the pole star is concealed through the troubled state of the at- 
mosphere." l 

Alexander Neckam was born at St. Albans in 1157, joined 
the Augustinian Order and taught in the University of Paris 
from 1180 to 1187, after which he returned to England to take 
charge of a College of his Order at Dunstable. He was elected 
Abbot of Cirencester in 1213 and died at Kemsey, near Wor- 
cester, in 1217. 

The satirical poem of Guyot de Provins, written about 
1208, contains the following passage: 

The mariners employ an art which cannot deceive, 

By the property of the lodestone, 

An ugly stone and brown, 

To which iron joints itself willingly 

They have; they attend to where it points 

After they have applied a needle to it j 

And 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 ; 

1 The Chronicles and Memoirs of Great Britain and Ireland during 
the Middle Ages, by Thomas Wright (1863). 

38 



NOTES 

And the mariners are taught 
To follow the right way. 
It is an art which cannot fail. 



Provins, from which Guyot took his surname, was a small 
town in the vicinity of Paris. 

Cardinal Jacques de Vitry, in his Htstoria Orientalis, Cap. 
89, writes: 

"An iron needle, after having been in contact with the 
lodestone, turns towards the north star, so that it is very neces- 
sary for those who navigate the seas." 

Jacques de Vitry was born at Argenteuil, near Paris, joined 
the fourth crusade, became Bishop of Ptolemais, and died in 
Rome in 1244. He wrote his "Description of Palestine," 
which forms the first book of his Htstoria Orientalis, in the 
East, between 1215 and 1220. 

Albertus Magnus (1193-1280) in his De Mineralibus, Lib. 
II., Tract 3, Cap. 6, writes: 

"It is the end of the lodestone which makes the iron that 
touched it turn to the north (ad zoron) and which is of use to 
mariners; but the other end of the needle turns toward the 
south (ad aphron)." 

This illustrious Bavarian schoolman joined the Dominican 
Order in his youth, lectured to great audiences in Cologne, be- 
came bishop of Ratisbonne in 1260, and died in 1280. Thomas 
Aquinas the greatest of schoolmen, was among his pupils. 

39 



THE LETTER OF PEREGRINUS 

In the Spanish code of laws, begun in 1256, during the 
reign of Alfonso el Sabio, and known as Las Siete Partidas, we 
read: 

"Just as mariners are guided during the night by the 
needle, which replaces for them the shores and pole star alike, 
by showing them the course to pursue both in fair weather and 
foul, so those who are called upon to advise the King must al- 
ways be guided by a spirit of justice." 

Brunette Latini, in his Tresor des Sciences, 1260, writes: 

"The sailors navigate the seas guided by the two stars 
called the tramontanes, and each of the two parts of the lode- 
stone directs the end of the needle to the star to which that part 
itself turns." 

Brunette Latini (1230-1294) was a man of great eminence 
in the thirteenth century; Dante was among his pupils at Flor- 
ence. For political reasons, he removed to Paris, where he 
wrote his Tresor and also his Tesoretto. He visited Roger 
Bacon at Oxford about 1260. 

In his treatise De Contemplatione, begun in 1272, Ray- 
mond Lully writes : 

"As the needle, after having touched the lodestone, turns 
to the north, so the mariner's needle (acus nautica) directs them 
over the sea." 

Lully was born at Palma in the Island of Majorca in 
1236; he joined the Third Order of St. Francis, dying in 1315. 

40 



NOTES 

Ristoro d'Arezzo, in his Libra della Composizione del 
Mundo, written in 1282, has the following: 

" Besides this, there is the needle which guides the mariner, 
and which is itself directed by the star called the tramontane." ' 

The following metrical translation of a poem by Guido 
Guinicelli, an Italian priest, 1276, is from the pen of Dr. Park 
Benjamin, of New York: 

In what strange regions ' neath the polar star 
May the great hills of massy lodestone rise, 
Virtue imparting to the ambient air 
To draw the stubborn iron ; while afar 
From that same stone, the hidden virtue flies 
To turn the quivering needle to the Bear 
In splendor blazing in the Northern skies. 

The above extracts show that the directive property of the 
magnetic needle was well known in England, France, Germany, 
Spain and Italy in the thirteenth century. In the passage from 
Neckam, the acum jaculo superpositam has been construed by 
some to mean a form of pivoted needle, while in the letter of 
Peregrinus, 1269, the double pivoted form is clearly described. 



1 The pole-star was thus named in the south of France and the north 
of Italy because seen beyond the mountains (the Alps). 



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