,,the ,,letter ,,of ,,petrus ,,peregrinus ,,on ,,the ,,magnet1 ,a4,d4 #abfi ,,translated ,,by ,,brother ,,arnold1 ,m4,sc4 ,,principal ,,of ,,la ,,salle ,,institute1 ,,troy ,,with ,,introductory ,,notice ,,by ,,brother ,,potamian1 ,d4,sc4 ,,professor ,,of ,,physics ,,in ,,manhattan ,,college1 ,,new ,,york ,,new ,,york ,mc,g,r,a,w ,,publishing ,,company ,,mcmiv ,copyright1 #aijd1 by ,mc,graw ,publishing ,company ,,introductory ,the magnetic lore of classic antiquity was scanty indeed1 being limited to the attraction which the lodestone manifests for iron4 ,lucretius 7#ii-ee ,b4 ,c471 however1 in his poetical dissertation on the magnet1 contained in ,de ,rerum ,natura1 ,book ,,vi4#a recognizes magnetic repulsion1 magnetic induction1 and to some extent the magnetic field with its lines of force1 for in verse #ajdj he writes3 ,oft from the magnet1 too1 the steel recedes1 ,repelled by turns and re-attracted close4 ,and in verse #ajhe3 ,its viewless1 potent virtues men surprise2 ,its strange effects1 they view with wond'ring eyes ,when without aid of hinges1 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 force3 ,those held above1 the ones below maintain1 ,circle 'neath circle downward draws in vain ,whilst free in air disports the oscillating chain4 ,the poet ,claudian 7#cfe-djh ,a4 ,d47 wrote a short idyll on the attractive virtue of the lodestone and its symbolism2 ,st4 ,augustine 7#ced-dcj71 in his work ,de ,civitate ,dei1 records the fact that a lodestone1 held under a silver plate1 draws after it a scrap of iron lying on the plate4 ,abbot ,neckam1 the ,augustinian 7#aaeg-abag71 distinguishes between the properties of the two ends of the lodestone1 and gives in his ,de ,utensilibus1 what is perhaps the earliest reference to the mariner's compass that we have4 ,albertus ,magnus1 the ,dominican 7#aaic-abhj71 in his treatise1 ,de ,mineralibus1 enumerates different kinds of natural magnets and states some of the properties commonly attributed to them2 the minstrel1 ,guyot de ,provins1 in a famous satirical poem1 written about #abjh1 refers to the directive quality of the lodestone and its use in navigation1 as do also ,cardinal de ,vitry in his ,historia ,orientalis 7#abae-abbj72 ,brunetto ,latini1 poet1 orator and philosopher1 in his ,trsor des ,sciences1 a veritable library1 written in ,paris in #abfj2 ,raymond ,lully1 the ,enlightened ,doctor1 in his treatise1 ,de ,contemplatione1 begun in #abgb1 and ,guido ,guinicelli1 the poet-priest of ,bologna1 who died in #abgf4 ,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 discovery1 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 it4 ,but this was not the case with such contemporaries of theirs as ,roger ,bacon1 the ,franciscan1 and his ,gallic friend1 ,pierre de ,maricourt1 commonly called ,petrus ,peregrinus1 the subject of the present notice1 a man of academic culture and of a practical rather than speculative turn of mind4 ,of the early years of ,peregrinus nothing is known save that he studied probably at the ,university of ,paris1 and that he graduated with the highest scholastic honors4 ,he owes his surname to the village of ,maricourt1 in ,picardy1 and the appellation ,peregrinus1 or ,pilgrim1 to his having visited the ,holy ,land as a member of one of the crusading expeditions of the time4 ,in #abfi we find him in the engineering corps of the ,french army then besieging ,lucera1 in ,southern ,italy1 which had revolted from the authority of its ,french master1 ,charles of ,anjou4 ,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 city4 ,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 time4 ,in the course of his work over the new motor1 ,peregrinus was gradually led to consider the more fascinating problem of perpetual motion itself with the result that he showed1 at least diagrammatically1 and to his own evident satisfaction1 how a wheel might be driven round forever by the power of magnetic attraction4 ,elated over his imaginary success1 ,peregrinus hastened to inform a friend of his at home2 and that his friend might the more readily comprehend the mechanism of the motor and the functions of its parts1 he proceeds to set forth in a methodical manner all the properties of the lodestone1 most of which he himself had discovered4 ,it is a fortunate circumstance that this ,picard friend of his was not a man learned in the sciences1 otherwise we would probably never have had the remarkable exposition which ,peregrinus gives of the phenomena and laws of magnetism4 ,this letter of #c1ejj words is the first great landmark in the domain of magnetic philosophy1 the next being ,gilbert's ,de ,magnete1 in #afjj4 ,the letter was addressed from the trenches at ,lucera1 ,southern ,italy1 in ,august1 #abfi1 to ,sigerus de ,foucaucourt1 his 8amicorum intimus10 the dearest of friends4 ,a more enlightened friend1 however1 than the knight of ,foucaucourt was ,roger ,bacon1 who held ,peregrinus in the very highest esteem1 as the following glowing testimony shows3 8,there are but two perfect mathematicians10 wrote the ,english monk1 8,john of ,london and ,petrus de ,maharne-,curia1 a ,picard40 ,further on in his ,opus ,tertium1 ,bacon thus appraises the merits of the ,picard3 8,i know of only one person who deserves praise for his work in experimental philosophy1 for he does not care for the discourses of men and their wordy warfare1 but quietly and diligently pursues the works of wisdom4 ,therefore1 what others grope after blindly1 as bats in the evening twilight1 this man contemplates in all their brilliancy because he is a master of experiment4 ,hence1 he knows all natural science whether pertaining to medicine and alchemy1 or to matters celestial and terrestrial4 ,he has worked diligently in the smelting of ores as also in the working of minerals2 he is thoroughly acquainted with all sorts of arms and implements used in military service and in hunting1 besides which he is skilled in agriculture and in the measurement of lands4 ,it is impossible to write a useful or correct treatise in experimental philosophy without mentioning this man's name4 ,moreover1 he pursues knowledge for its own sake2 for if he wished to obtain royal favor1 he could easily find sovereigns who would honor and enrich him40 ,this last statement is worthy of the best utterances of the twentieth century4 ,say what they will1 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 research1 while in ,peregrinus1 the medivalist1 they have ,bacon's impersonation of what a student of science ought to be4 ,peregrinus was a hard worker1 nor a mere theorizer1 preferring1 ,procrustean-like1 to make theory fit the facts rather than facts the theory2 he was a brilliant discoverer who knew at the same time how to use his discoveries for the benefit of mankind2 he was a pioneer of science and a leader in the progress of the world4 ,an analysis of the 8,epistola0 shows that 7a7 ,peregrinus was the first to assign a definite position to the poles of a lodestone1 and to give directions for determining which is north and which south2 7b7 ,he proved that unlike poles attract each other1 and that similar ones repel2 7c7 ,he established by experiment that every fragment of a lodestone1 however small1 is a complete magnet1 thus anticipating one of our fundamental laboratory illustrations of the molecular theory2 7d7 ,he recognized that a pole of a magnet may neutralize a weaker one of the same name1 and even reverse its polarity2 7e7 ,he was the first to pivot a magnetized needle and surround it with a graduated circle1 ,figs4 #b and #c4b 7f7 ,he determined the position of an object by its magnetic bearing as done to-day in compass surveying2 and 7g7 ,he introduced into his perpetual motion machine1 ,fig4 #d1 the idea of a magnetic motor1 a clever idea1 indeed1 for a thirteenth century engineer4 ,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 geodesy4 ,for nearly three centuries1 it lay unnoticed among the libraries of ,europe1 but it did not escape ,gilbert1 who makes frequent mention of it in his ,de ,magnete1 #afjj2 nor the illustrious ,jesuit writers1 ,cabus1 who refers to it in his ,philosophia ,magnetica1 #afbi1 and ,kircher1 who quotes from it in his ,de ,arte ,magnetica1 #afda2 it was well known to ,jean ,taisnier1 the ,belgian plagiarist1 who transferred a great part of it verbatim to the pages of his ,de ,natura ,magnetis1 #aefb1 without a word of acknowledgment4 ,by this piece of fraud1 ,taisnier acquired considerable celebrity1 a fact that goes to show the meritorious character of the work which he unscrupulously copied4 ,this memorable letter is divided into two parts3 the first contains ten chapters on the general properties of the lodestone2 the second has but three chapters1 and shows how the author proposed to use a lodestone for the purpose of producing continuous rotation4 ,there are many manuscript copies of the letter in ,european libraries3 the ,bodleian has six2 the ,vatican1 two2 ,trinity ,college1 ,dublin1 one2 the ,bibliothque ,nationale1 ,paris1 one2 ,leyden1 ,geneva and ,turin1 one each4 ,the ,leyden ,,ms4 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 given3 but ,prof4 ,w4 ,wenckebach1 of ,the ,hague1 has shown#c that the lines are spurious1 having been interpolated in the manuscript in the early part of the sixteenth century4 ,the ,leyden manuscript has also led some writers to believe in a fictitious author of the letter1 one ,peter ,adsiger1 or ,petrus ,adsigerus4 ,as said above1 ,sigerus was the name of his countryman1 to whom ,peregrinus addressed his letter1 the ,epistola ad ,sigerum1 from the trenches at ,lucera1 in ,august1 #abfi4 ,magnetic declination was unknown to ,peregrinus1 else he would not have written the following words3 8,wherever a man may be1 he finds the lodestone pointing to the heavens in accordance with the position of the meridian0 7,chapter ,x74 ,of course1 the geographical meridian is the one here meant1 as the necessity of a distinct magnetic meridian had not yet occurred to any one4 ,nor was this important magnetic element known to ,columbus when he sailed from the shores of the ,old ,world in #adib as appears from the surprise with which he noticed the deviation of the needle from ,north as well as from the consternation of his pilots4 ,columbus has the unquestionable merit of being the first to observe and record the change of declination with change of place4 ,the first printed edition of the ,epistola1 now very rare1 was prepared by ,achilles ,gasser1 a physician of ,lindau1 a man well versed in mathematics1 astronomy1 history and philosophy4 ,the work was printed in ,augsburg in #aeeh4 ,a copy of this early print is among the treasures of the ,wheeler collection in the library of the ,american ,institute of ,electrical ,engineers1 ,new ,york4 ,it was from this text that the translation which follows was made4 ,besides the ,latin edition of ,gasser1 #aeeh1 there is also that of ,libri in his ,histoire des ,sciences ,mathmatiques1 #ahch2 of ,bertelli1 #ahfh1 and ,hellmann1 #ahih4 ,bertelli's is a learned and exhaustive work in which the ,barnabite monk1 sometimes called by mistake1 ,barnabita1 instead of ,bertelli1 collates and compares the readings of the two ,vatican codices with other texts1 adding copious references and explanatory notes4 ,it appeared in the ,bulletino di ,bibliografia e di ,storia delle ,scienze ,matematiche e ,fisiche for #ahfh4 ,of translations1 we have that which ,richard ,eden made from ,taisnier's pirated extracts1 the first dated edition appearing in #aegi4 ,cavallo's ,treatise on ,magnetism1 #ahjj1 also contains some of the more remarkable passages4 ,the only complete ,english translation that we have1 appeared in #aijb from the scholarly pen of ,prof4 ,silvanus ,p4 ,thompson1 of ,london4 ,it is an dition de luxe beautifully rubricated1 but limited to #bej copies4 ,the translation was based on the texts of ,gasser and ,hellmann1 amended by reference to a manuscript in the author's possession1 dated #acia4 ,we are informed that ,mr4 ,fleury ,p4 ,mottelay1 of ,new ,york1 the learned translator of ,gilbert's ,de ,magnete1 possesses a manuscript version by ,prof4 ,peirce1 of ,harvard1 of the ,paris codex1 of which he made a careful study in an endeavor to decipher the illegible parts4 ,,part ,i ,,the ,,letter ,,of ,,peregrinus ,,part ,i ,,chapter ,i ,,purpose ,,of ,,this ,,work ,dearest of ,friends3 ,at your earnest request1 ,i will now make known to you1 in an unpolished narrative1 the undoubted though hidden virtue of the lodestone1 concerning which philosophers up to the present time give us no information1 because it is characteristic of good things to be hidden in darkness until they are brought to light by application to public utility4 ,out of affection for you1 ,i will write in a simple style about things entirely unknown to the ordinary individual4 ,nevertheless ,i will speak only of the manifest properties of the lodestone1 because this tract will form part of a work on the construction of philosophical instruments4 ,the disclosing of the hidden properties of this stone is like the art of the sculptor by which he brings figures and seals into existence4 ,although ,i may call the matters about which you inquire evident and of inestimable value1 they are considered by common folk to be illusions and mere creations of the imagination4 ,but the things that are hidden from the multitude will become clear to astrologers and students of nature1 and will constitute their delight1 as they will also be of great help to those that are old and more learned4 ,,chapter ,,ii ,,qualifications ,,of ,,the ,,experimenter ,you must know1 my dear friend1 that whoever wishes to experiment1 should be acquainted with the nature of things1 and should not be ignorant of the motion of the celestial bodies4 ,he must also be skilful in manipulation in order that1 by means of this stone1 he may produce these marvelous effects4 ,through his own industry he can1 to some extent1 indeed1 correct the errors that a mathematician would inevitably make if he were lacking in dexterity4 ,besides1 in such occult experimentation1 great skill is required1 for very frequently without it the desired result cannot be obtained1 because there are many things in the domain of reason which demand this manual dexterity4 ,,chapter ,,iii ,,characteristics ,,of ,a ,,good ,,lodestone ,the lodestone selected must be distinguished by four marks--its color1 homogeneity1 weight and strength4 ,its color should be iron-like1 pale1 slightly bluish or indigo1 just as polished iron becomes when exposed to the corroding atmosphere4 ,i have never yet seen a stone of such description which did not produce wonderful effects4 ,such stones are found most frequently in northern countries1 as is attested by sailors who frequent places on the northern seas1 notably in ,normandy1 ,flanders and ,picardy4 ,this stone should also be of homogeneous material2 one having reddish spots and small holes in it should not be chosen2 yet a lodestone is hardly ever found entirely free from such blemishes4 ,on account of uniformity in its composition and the compactness of its innermost parts1 such a stone is heavy and therefore more valuable4 ,its strength is known by its vigorous attraction for a large mass of iron2 further on ,i will explain the nature of this attraction4 ,if you chance to see a stone with all these characteristics1 secure it if you can4 ,,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 heavens1 as ,i will now clearly demonstrate4 ,there are in the heavens two points more important than all others1 because on them1 as on pivots1 the celestial sphere revolves3 these points are called1 one the arctic or north pole1 the other the antarctic or south pole4 ,similarly you must fully realize that in this stone there are two points styled respectively the north pole and the south pole4 ,if you are very careful1 you can discover these two points in a general way4 ,one method for doing so is the following3 ,with an instrument with which crystals and other stones are rounded let a lodestone be made into a globe and then polished4 ,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 iron1 thus dividing the stone into two equal parts4 ,the needle is next placed on another part of the stone and a second median line drawn4 ,if desired1 this operation may be performed on many different parts1 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 globe4 ,one of these is the north pole1 the other the south pole4 ,proof of this will be found in a subsequent chapter of this tract4 ,a second method for determining these important points is this3 ,note the place on the above-mentioned spherical lodestone where the point of the needle clings most frequently and most strongly2 for this will be one of the poles as discovered by the previous method4 ,in order to determine this point exactly1 break off a small piece of the needle or iron so as to obtain a fragment about the length of two fingernails2 then put it on the spot which was found to be the pole by the former operation4 ,if the fragment stands perpendicular to the stone1 then that is1 unquestionably1 the pole sought2 if not1 then move the iron fragment about until it becomes so2 mark this point carefully2 on the opposite end another point may be found in a similar manner4 ,if all this has been done rightly1 and if the stone is homogeneous throughout and a choice specimen1 these two points will be diametrically opposite1 like the poles of a sphere4 ,,chapter ,v ,,how ,,to ,,discover ,,the ,,poles ,,of ,a ,,lodestone ,,and ,,how ,,to ,,tell ,,which ,,is ,,north ,,and ,,which ,,south ,the poles of a lodestone having been located in a general way1 you will determine which is north and which south in the following manner3 ,take a wooden vessel rounded like a platter or dish1 and in it place the stone in such a way that the two poles will be equidistant from the edge of the vessel2 then place the dish in another and larger vessel full of water1 so that the stone in the first-mentioned dish may be like a sailor in a boat4 ,the second vessel should be of considerable size so that the first may resemble a ship floating in a river or on the sea4 ,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 other4 ,when the stone has been thus placed1 it will turn the dish round until the north pole lies in the direction of the north pole of the heavens1 and the south pole of the stone points to the south pole of the heavens4 ,even if the stone be moved a thousand times away from its position1 it will return thereto a thousand times1 as by natural instinct4 ,since the north and south parts of the heavens are known1 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 heavens4 ,,chapter ,,vi ,,how ,,one ,,lodestone ,,attracts ,,another ,when you have discovered the north and the south pole in your lodestone1 mark them both carefully1 so that by means of these indentations they may be distinguished whenever necessary4 ,should you wish to see how one lodestone attracts another1 then1 with two lodestones selected and prepared as mentioned in the preceding chapter1 proceed as follows3 ,place one in its dish that it may float about as a sailor in a skiff1 and let its poles which have already been determined be equidistant from the horizon1 i4 e41 from the edge of the vessel4 ,taking the other stone in your hand1 approach its north pole to the south pole of the lodestone floating in the vessel2 the latter will follow the stone in your hand as if longing to cling to it4 ,if1 conversely1 you bring the south end of the lodestone in your hand toward the north end of the floating lodestone1 the same phenomenon will occur2 namely1 the floating lodestone will follow the one in your hand4 ,know then that this is the law3 the north pole of one lodestone attracts the south pole of another1 while the south pole attracts the north4 ,should you proceed otherwise and bring the north pole of one near the north pole of another1 the one you hold in your hand will seem to put the floating one to flight4 ,if the south pole of one is brought near the south pole of another1 the same will happen4 ,this is because the north pole of one seeks the south pole of the other1 and therefore repels the north pole4 ,a proof of this is that finally the north pole becomes united with the south pole4 ,likewise if the south pole is stretched out towards the south pole of the floating lodestone1 you will observe the latter to be repelled1 which does not occur1 as said before1 when the north pole is extended towards the south4 ,hence the silliness of certain persons is manifest1 who claim that just as scammony attracts jaundice on account of a similarity between them1 so one lodestone attracts another even more strongly than it does iron1 a fact which they suppose to be false although really true as shown by experiment4 ,,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 experiment1 that when an elongated piece of iron has touched a lodestone and is then fastened to a light block of wood or to a straw and made float on water1 one end will turn to the star which has been called the ,sailor's star because it is near the pole2 the truth is1 however1 that it does not point to the star but to the pole itself4 ,a proof of this will be furnished in a following chapter4 ,the other end of the iron will point in an opposite direction4 ,but as to which end of the iron will turn towards the north and which to the south1 you will observe that that part of the iron which has touched the south pole of the lodestone will point to the north and conversely1 that part which had been in contact with the north pole will turn to the south4 ,though this appears marvelous to the uninitiated1 yet it is known with certainty to those who have tried the experiment4 ,,chapter ,,viii ,,how ,a ,,lodestone ,,attracts ,,iron ,if you wish the stone1 according to its natural desire1 to attract iron1 proceed as follows3 ,mark the north end of the iron and towards this end approach the south pole of the stone1 when it will be found to follow the latter4 ,or1 on the contrary1 to the south part of the iron present the north pole of the stone and the latter will attract it without any difficulty4 ,should you1 however1 do the opposite1 namely1 if you bring the north end of the stone towards the north pole of the iron1 you will notice the iron turn round until its south pole unites with the north end of the lodestone4 ,the same thing will occur when the south end of the lodestone is brought near the south pole of the iron4 ,should force be exerted at either pole1 so that when the south pole of the iron is made touch the south end of the stone1 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 conversely4 ,the cause is that the last impression acts1 confounds1 or counteracts and alters the force of the original movement4 ,,chapter ,,ix ,,why ,,the ,,north ,,pole ,,of ,,one ,,lodestone ,,attracts ,,the ,,south ,,pole ,,of ,,another ,,and ,,vice ,,versa ,as already stated1 the north pole of one lodestone attracts the south pole of another and conversely2 in this case the virtue of the stronger becomes active1 whilst that of the weaker becomes obedient or passive4 ,i consider the following to be the cause of this phenomenon3 the active agent requires a passive subject1 not merely to be joined to it1 but also to be united with it1 so that the two make but one by nature4 ,in the case of this wonderful lodestone this may be shown in the following manner3 ,take a lodestone which you may call ,a ,d1 in which ,a is the north pole and ,d the south2 cut this stone into two parts1 so that you may have two distinct stones2 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 before2 the breaking did not destroy the properties of the parts of the stone1 since it is homogeneous2 hence it follows that the part of the stone at the point of fracture1 which may be marked ,b1 must be a south pole2 this broken part of which we are now speaking may be called ,a ,b4 ,the other1 which contains ,d1 should then be placed so as to float on water1 when you will see ,d point towards the south because it is a south pole2 but the other end at the point of fracture1 lettered ,c1 will be a north pole2 this stone may now be named ,c ,d4 ,if we consider the first stone as the active agent1 then the second1 or ,c ,d1 will be the passive subject4 ,you will also notice that the ends of the two stones which before their separation were together1 after breaking will become one a north pole and the other a south pole4 ,if now these same broken portions are brought near each other1 one will attract the other1 so that they will again be joined at the points ,b and ,c1 where the fracture occurred4 ,thus1 by natural instinct1 one single stone will be formed as before4 ,this may be demonstrated fully by cementing the parts together1 when the same effects will be produced as before the stone was broken4 ,as you will perceive from this experiment1 the active agent desires to become one with the passive subject because of the similarity that exists between them4 ,hence ,c1 being a north pole1 must be brought close to ,b1 so that the agent and its subject may form one and the same straight line in the order ,a ,b1 ,c ,d and ,b and ,c being at the same point4 ,in this union the identity of the extreme parts is retained and preserved just as they were at first2 for ,a is the north pole in the entire line as it was in the divided one2 so also ,d is the south pole as it was in the divided passive subject1 but ,b and ,c have been made effectually into one4 ,in the same way it happens that if ,a be joined to ,d so as to make the two lines one1 in virtue of this union due to attraction in the order ,c ,d ,a ,b1 then ,a and ,d will constitute but one point1 the identity of the extreme parts will remain unchanged just as they were before being brought together1 for ,c is a north pole and ,b a south1 as during their separation4 ,if you proceed in a different fashion1 this identity or similarity of parts will not be preserved2 for you will perceive that if ,c1 a north pole1 be joined to ,a1 a north pole1 contrary to the demonstrated truth1 and from these two lines a single one1 ,b ,a ,c ,d1 is formed1 as ,d was a south pole before the parts were united1 it is then necessary that the other extremity should be a north pole1 and as ,b is a south pole1 the identity of the parts of the former similarity is destroyed4 ,if you make ,b the south pole as it was before they united1 then ,d must become north1 though it was south in the original stone2 in this way neither the identity nor similarity of parts is preserved4 ,it is becoming that when the two are united into one1 they should bear the same likeness as the agent1 otherwise nature would be called upon to do what is impossible4 ,the same incongruity would occur if you were to join ,b with ,d so as to make the line ,a ,b ,d ,c1 as is plain to any person who reflects a moment4 ,nature1 therefore1 aims at being and also at acting in the best manner possible2 it selects the former motion and order rather than the second because the identity is better preserved4 ,from all this it is evident why the north pole attracts the south and conversely1 and also why the south pole does not attract the south pole and the north pole does not attract the north4 ,,chapter ,x ,,an ,,inquiry ,,into ,,the ,,cause ,,of ,,the ,,natural ,,virtue ,,of ,,the ,,lodestone ,certain persons who were but poor investigators of nature held the opinion that the force with which a lodestone draws iron1 is found in the mineral veins themselves from which the stone is obtained2 whence they claim that the iron turns towards the poles of the earth1 only because of the numerous iron mines found there4 ,but such persons are ignorant of the fact that in many different parts of the globe the lodestone is found2 from which it would follow that the iron needle should turn in different directions according to the locality2 but this is contrary to experience4 ,secondly1 these individuals do not seem to know that the places under the poles are uninhabitable because there one-half the year is day and the other half night4 ,hence it is most silly to imagine that the lodestone should come to us from such places4 ,since the lodestone points to the south as well as to the north1 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 lodestone4 ,this follows from the consideration that wherever a man may be1 he finds the stone pointing to the heavens in accordance with the position of the meridian2 but all meridians meet in the poles of the world2 hence it is manifest that from the poles of the world1 the poles of the lodestone receive their virtue4 ,another necessary consequence of this is that the needle does not point to the pole star1 since the meridians do not intersect in that star but in the poles of the world4 ,in every region1 the pole star is always found outside the meridian except twice in each complete revolution of the heavens4 ,from all these considerations1 it is clear that the poles of the lodestone derive their virtue from the poles of the heavens4 ,as regards the other parts of the stone1 the right conclusion is1 that they obtain their virtue from the other parts of the heavens1 so that we may infer that not only the poles of the stone receive their virtue and influence from the poles of the world1 but likewise also the other parts1 or the entire stone from the entire heavens4 ,you may test this in the following manner3 ,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 pivots4 ,having done this1 make sure that it is equally balanced and that it turns smoothly on the pivots4 ,repeat this several times at different hours of the day and always with the utmost care4 ,then place the stone with its axis in the meridian1 the poles resting on the pivots4 ,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 experimenting4 ,if now the stone be moved according to the motion of the heavens1 you will be delighted in having discovered such a wonderful secret2 but if not1 ascribe the failure to your own lack of skill rather than to a defect in nature4 ,moreover1 in this position ,i consider the strength of the lodestone to be best preserved4 ,when it is placed differently1 i4 e41 not in the meridian1 ,i think its virtue is weakened or obscured rather than maintained4 ,with such an instrument you will need no timepiece1 for by it you can know the ascendant at any hour you please1 as well as all other dispositions of the heavens which are sought for by astrologers4 ,,part ,,ii ,,part ,,ii ,,chapter ,i ,,the ,,construction ,,of ,,an ,,instrument ,,for ,,measuring ,,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 connected therewith1 let us now come to those instruments which depend for their operation on the knowledge of those facts4 ,take a rounded lodestone1#d and after determining its poles in the manner already mentioned1 file its two sides so that it becomes elongated at its poles and occupies less space4 ,the lodestone prepared in this wise is then enclosed within two capsules after the fashion of a mirror4 ,let these capsules be so joined together that they cannot be separated and that water cannot enter2 they should be made of light wood and fastened with cement suited to the purpose4 ,having done this1 place them in a large vessel of water on the edges of which the two parts of the world1 i4 e41 the north and south points1 have been found and marked4 ,these points may be united by a thread stretched across from north to south4 ,then float the capsules and place a smooth strip of wood over them in the manner of a diameter4 ,move the strip until it is equally distant from the meridian-line1 previously determined and marked by a thread1 or else until it coincides therewith4 ,then mark a line on the capsules according to the position of the strip1 and this will indicate forever the meridian of that place4 ,let this line be divided at its middle by another cutting it at right angles1 which will give the east and west line2 thus the four cardinal points will be determined and indicated on the edge of the capsules4 ,each quarter is to be subdivided into #ij parts1 making #cfj in the circumference of the capsules4 ,engrave these divisions on them as usually done on the back of an astrolabe4 ,on the top or edge of the capsules thus marked place a thin ruler like the pointer on the back of the astrolabe2 instead of the sights attach two perpendicular pins1 one at each end4 ,if1 therefore1 you desire to take the azimuth of the sun1 place the capsules in water and let them move freely until they come to rest in their natural position4 ,hold them firmly in one hand1 while with the other you move the ruler until the shadow of the pins falls along the length of the ruler2 then the end of the ruler which is towards the sun will indicate the azimuth of the sun4 ,should it be windy1 let the capsules be covered with a suitable vessel until they have taken their position north and south4 ,the same method1 namely1 by sighting1 may be followed at night for determining the azimuth of the moon and stars2 move the ruler until the ends of the pins are in the same line with the moon or star2 the end of the ruler will then indicate the azimuth just as in the case of the sun4 ,by means of the azimuth may then be determined the hour of the day1 the ascendant1 and all those other things usually determined by the astrolabe4 ,a form of the instrument is shown in the following figure4 ,illustration3 ,,fig4 #a4--;,,azimuth ,,compass ,,chapter ,,ii ,,the ,,construction ,,of ,a ,,better ,,instrument ,,for ,,the ,,same ,,purpose ,in this chapter ,i will describe the construction of a better and more efficient instrument4 ,select a vessel of wood1 brass or any solid material you like1 circular in shape1 moderate in size1 shallow but of sufficient width1 with a cover of some transparent substance1 such as glass or crystal2 it would be even better to have both the vessel and the cover transparent4 ,at the centre of this vessel fasten a thin axis of brass or silver1 having its extremities in the cover above and the vessel below4 ,at the middle of this axis let there be two apertures at right angles to each other2 through one of them pass an iron stylus or needle1 through the other a silver or brass needle crossing the iron one at right angles4 ,divide the cover first into four parts and subdivide these into #ij parts1 as was mentioned in describing the former instrument4 ,mark the parts north1 south1 east and west4 ,add thereto a ruler of transparent material with pins at each end4 ,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 lodestone4 ,then turn the vessel until the needle stands in the north and south line already marked on the instrument2 after which turn the ruler towards the sun if day-time1 and towards the moon and stars at night1 as described in the preceding chapter4 ,by means of this instrument you can direct your course towards cities and islands and any other place wherever you may wish to go by land or sea1 provided the latitude and longitude of the places are known to you4 ,how iron remains suspended in air by virtue of the lodestone1 ,i will explain in my book on the action of mirrors4 ,such1 then1 is the description of the instrument illustrated below4 7,see ,figs4 #b and #c47 ,illustration3 ,,fig4 #b4--;,,double-,,pivoted ,,needle ,illustration3 ,,fig4 #c4--,,pivoted ,,compass ,,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 remarkable manner moves continuously4 ,i have seen many persons vainly busy themselves and even becoming exhausted with much labor in their endeavors to invent such a wheel4 ,but these invariably failed to notice that by means of the virtue or power of the lodestone all difficulty can be overcome4 ,for the construction of such a wheel1 take a silver capsule like that of a concave mirror1 and worked on the outside with fine carving and perforations1 not only for the sake of beauty1 but also for the purpose of diminishing its weight4 ,you should manage also that the eye of the unskilled may not perceive what is cunningly placed inside4 ,within let there be iron nails or teeth of equal weight fastened to the periphery of the wheel in a slanting direction1 close to one another so that their distance apart may not be more than the thickness of a bean or a pea2 the wheel itself must be of uniform weight throughout4 ,fasten the middle of the axis about which the wheel revolves so that the said axis may always remain immovable4 ,add thereto a silver bar1 and at its extremity affix a lodestone placed between two capsules and prepared in the following way3 ,when it has been rounded and its poles marked as said before1 let it be shaped like an egg2 leaving the poles untouched1 file down the intervening parts so that thus flattened and occupying less space1 it may not touch the sides of the capsules when the wheel revolves4 ,thus prepared1 let it be attached to the silver rod just as a precious stone is placed in a ring2 let the north pole be then turned towards the teeth or cogs of the wheel somewhat slantingly so that the virtue of the stone may not flow diametrically into the iron teeth1 but at a certain angle2 consequently when one of the teeth comes near the north pole and owing to the impetus of the wheel passes it1 it then approaches the south pole from which it is rather driven away than attracted1 as is evident from the law given in a preceding chapter4 ,therefore such a tooth would be constantly attracted and constantly repelled4 ,illustration3 ,,fig4 #d4--,,perpetual ,,motion ,,wheel ,in order that the wheel may do its work more speedily1 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 teeth2 consequently as the movement of the wheel is continuous in one direction1 so the fall of the weight will be continuous in the other4 ,being caught between the teeth of a wheel which is continuously revolving1 it seeks the centre of the earth in virtue of its own weight1 thereby aiding the motion of the teeth and preventing them from coming to rest in a direct line with the lodestone4 ,let the places between the teeth be suitably hollowed out so that they may easily catch the body in its fall1 as shown in the diagram above4 7,fig4 #d47 ,farewell3 finished in camp at the siege of ,lucera on the eighth day of ,august1 ,anno ,domini ,,mcclxix4 ,,notes ,,early ,,references ,,to ,,the ,,mariner',s ,,compass ,the following are the passages referred to in the introductory notice3 ,abbot ,neckam 7#aaeg-abag71 in his ,de ,naturis ,rerum1 writes3 8,the sailors1 moreover1 as they sail over the sea1 when in cloudy weather they can no longer profit by the light of the sun1 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 directed1 these mariners touch the lodestone with a needle1 which 7the needle7 is whirled round in a circle until when its motion ceases1 its point looks direct to the north4 7,cuspis ipsius septentrionalem plagam respiciat470 ,in his ,de ,utensilibus1 we read3 8,among other stores of a ship1 there must be a needle mounted on a dart 7habeat etiam acum jaculo superpositam7 which will oscillate and turn until the point looks to the north1 and the sailors will thus know how to direct their course when the pole star is concealed through the troubled state of the atmosphere40#e ,alexander ,neckam was born at ,st4 ,albans in #aaeg1 joined the ,augustinian ,order and taught in the ,university of ,paris from #aahj to #aahg1 after which he returned to ,england to take charge of a ,college of his ,order at ,dunstable4 ,he was elected ,abbot of ,cirencester in #abac and died at ,kemsey1 near ,worcester1 in #abag4 ,the satirical poem of ,guyot de ,provins1 written about #abjh1 contains the following passage3 ,the mariners employ an art which cannot deceive1 ,by the property of the lodestone1 ,an ugly stone and brown1 ,to which iron joints itself willingly ,they have2 they attend to where it points ,after they have applied a needle to it2 ,and they lay the latter on a straw ,and put it simply in the water ,where the straw makes it float4 ,then the point turns direct ,to the star with such certainty ,that no man will ever doubt it1 ,nor will it ever go wrong4 ,when the sea is dark and hazy1 ,that one sees neither star nor moon1 ,then they put a light by the needle ,and have no fear of losing their way4 ,the point turns towards the star2 ,and the mariners are taught ,to follow the right way4 ,it is an art which cannot fail4 ,provins1 from which ,guyot took his surname1 was a small town in the vicinity of ,paris4 ,cardinal ,jacques de ,vitry1 in his ,historia ,orientalis1 ,cap4 #hi1 writes3 8,an iron needle1 after having been in contact with the lodestone1 turns towards the north star1 so that it is very necessary for those who navigate the seas40 ,jacques de ,vitry was born at ,argenteuil1 near ,paris1 joined the fourth crusade1 became ,bishop of ,ptolemais1 and died in ,rome in #abdd4 ,he wrote his 8,description of ,palestine10 which forms the first book of his ,historia ,orientalis1 in the ,east1 between #abae and #abbj4 ,albertus ,magnus 7#aaic-abhj7 in his ,de ,mineralibus1 ,lib4 ,,ii41 ,tract #c1 ,cap4 #f1 writes3 8,it is the end of the lodestone which makes the iron that touched it turn to the north 7ad zoron7 and which is of use to mariners2 but the other end of the needle turns toward the south 7ad aphron740 ,this illustrious ,bavarian schoolman joined the ,dominican ,order in his youth1 lectured to great audiences in ,cologne1 became bishop of ,ratisbonne in #abfj1 and died in #abhj4 ,thomas ,aquinas the greatest of schoolmen1 was among his pupils4 ,in the ,spanish code of laws1 begun in #abef1 during the reign of ,alfonso el ,sabio1 and known as ,las ,siete ,partidas1 we read3 8,just as mariners are guided during the night by the needle1 which replaces for them the shores and pole star alike1 by showing them the course to pursue both in fair weather and foul1 so those who are called upon to advise the ,king must always be guided by a spirit of justice40 ,brunetto ,latini1 in his ,trsor des ,sciences1 #abfj1 writes3 8,the sailors navigate the seas guided by the two stars called the tramontanes1 and each of the two parts of the lodestone directs the end of the needle to the star to which that part itself turns40 ,brunetto ,latini 7#abcj-abid7 was a man of great eminence in the thirteenth century2 ,dante was among his pupils at ,florence4 ,for political reasons1 he removed to ,paris1 where he wrote his ,trsor and also his ,tesoretto4 ,he visited ,roger ,bacon at ,oxford about #abfj4 ,in his treatise ,de ,contemplatione1 begun in #abgb1 ,raymond ,lully writes3 8,as the needle1 after having touched the lodestone1 turns to the north1 so the mariner's needle 7acus nautica7 directs them over the sea40 ,lully was born at ,palma in the ,island of ,majorca in #abcf2 he joined the ,third ,order of ,st4 ,francis1 dying in #acae4 ,ristoro d',arezzo1 in his ,libro della ,composizione del ,mundo1 written in #abhb1 has the following3 8,besides this1 there is the needle which guides the mariner1 and which is itself directed by the star called the tramontane40#f ,the following metrical translation of a poem by ,guido ,guinicelli1 an ,italian priest1 #abgf1 is from the pen of ,dr4 ,park ,benjamin1 of ,new ,york3 ,in what strange regions 'neath the polar star ,may the great hills of massy lodestone rise1 ,virtue imparting to the ambient air ,to draw the stubborn iron2 while afar ,from that same stone1 the hidden virtue flies ,to turn the quivering needle to the ,bear ,in splendor blazing in the ,northern skies4 ,the above extracts show that the directive property of the magnetic needle was well known in ,england1 ,france1 ,germany1 ,spain and ,italy in the thirteenth century4 ,in the passage from ,neckam1 the acum jaculo superpositam has been construed by some to mean a form of pivoted needle1 while in the letter of ,peregrinus1 #abfi1 the double pivoted form is clearly described4 ,footnotes #a,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 ,institute of ,electrical ,engineers1 ,new ,york4 #b;,it is probable that ,flavio ,gioja1 an ,italian pilot1 some fifty years later1 added the compass-card and attached it to the magnet4 #c;,annali di ,matematica ,pura ed ,applicata1 #ahfe4 #d;,a terrella1 or earthkin4 #e,the ,chronicles and ,memoirs of ,great ,britain and ,ireland during the ,middle ,ages1 by ,thomas ,wright 7#ahfc74 #f,the pole-star was thus named in the south of ,france and the north of ,italy because seen beyond the mountains 7the ,alps74 ,transcriber's ,notes --,retained publication and copyright information from the original2 this e,book is public-domain in the ,u4,s4 --,silently corrected a few palpable typographical errors4 --,in the text versions1 enclosed italicized text in underscore4