The Magnetic CompassMariner's compass, possibly Italian,circa1570. The earliest compass in the Museum's collection. The case, lid and compass bowl are made of turned ivory.Repro ID: D9602 National Maritime Museum, Greenwich, LondonWhen people think of instruments that help with direction finding, the first one that springs to mind is probably the magnetic compass. It is the oldest instrument for navigation and has been a vital tool for navigators at sea for centuries. The compass allows ships to steer a selected course. By taking bearings of visible objects with a compass, the navigator is also able to fix a ship's position on a chart.Where was the compass first used?Geomanticcompass by Zhou Hua Ji,circa1850. Repro ID: D6192 National Maritime Museum, Greenwich, London, Gabb collectionThe origin of the compass is shrouded in mystery. Certainly the Greeks knew about the attractive properties of magnetism in ancient times. Similarly, the Chinese were probably aware that an iron bar stroked with a lodestone acquired a directional north-south property as long as 2000 years ago. However, the precise date at which this knowledge was used to create the first magnetic compass is unknown. By the 10th century, the idea had been brought to Europe, probably from China, by Arab traders. Magnetic compasses of a very simple kind were certainly in use in the Mediterranean as early as the 12th century. However, early compasses were not very reliable. Although the magnetic compass was in general use in the Middle Ages, little was known about precisely how it worked.How does a magnetic compass work?A magnetic compass works because the Earth is like a giant magnet, surrounded by a huge magnetic field. The Earth has two magnetic poles which lie near the North and South poles. The magnetic field of the Earth causes a magnetized 'needle' of iron or steel to swing into a north-south position if it is hung from a thread, or if it is stuck through a straw or piece of wood floating in a bowl of water.How were needles magnetized?Needles were magnetized by stroking them with a lodestone, a lump of magnetic rock called magnetite. The needle did not keep its magnetism permanently, so a lodestone was carried on the ship so that the needle could be stroked whenever the magnetism wore off.How accurate is the magnetic compass?As long ago as the 15th century, mariners noticed that the needle of a magnetic compass does not point accurately to Earth's true north. Columbus, for instance was aware of this on his voyages across the Atlantic in the 1490s. Instead, the needle makes an angle with true north, and that angle varies from place to place on the Earth's surface. This means that there is a different magnetic variation for different places on Earth. These variations were investigated on a famous 17th century voyage by the great scientist and astronomer Edmond Halley. It was thought at this time that the longitude of a ship could be found by the compass variation, but this proved to be untrue.How were the simplest compasses improved?A great improvement came when the needle was mounted under a card on a sharp pin, and placed in a little turned wooden or ivory box.How were these cards marked out?At first, compass cards were marked out not in degrees, but in points. There were 32 points, matching the directions of winds which sailors would be familiar with at sea. The four main points North, South, East and West are called the cardinal points.Old compass cards are very ornamental, often covered with decoration and painted figures. All cards have the North point decorated with what is often called a fleur de lys, like the old royal symbol of France. In fact, the sign comes from a very decorated 'T' for Tramontana, the Latin word for the North wind.There is a lot of movement on board a ship at sea. What happens to the compass then?To stop the needle and card from swinging wildly on board ship, even early compasses were gimbal mounted in a square box by an attachment with swivelling rings. This means that the compass is hung in a way that makes it unaffected by the movement of the ship on the sea. The remains of one such compass, housed in a special stand called a binnacle, was found in the wreck of King Henry VIII's flagship, theMary Rose, which sank in 1546. At that time, the compass would have been lit at night by a candle.By the 19th century, the ships compass had become the familiar large, gimbal mounted instrument, enclosed in a binnacle with its own light.Do iron ships pose particular problems for magnetic compasses?Yes. The magnetic field of the iron body of the ship itself affects the reading on the compass.When iron and steel ships became common, many scientists studied the problem. One of the earliest was the Astronomer Royal, Sir G.B. Airy, who in 1838 used the iron steamerRainbowfor his experiments. Airy thought of a method of neutralizing a ship's magnetism by placing magnets and pieces of unmagnetized iron near the compass.Which other scientists successfully improved the compass?Another problem was solved by a Scottish scientist of the 19th century, Sir William Thomson, who later became Lord Kelvin. He introduced a compass design with the needle system slung on fine silk threads through a very light skeleton card. The card was made of fine rice paper so that there was very little friction on the pivot. Jewels, such as agate and ruby, were used to reduce friction on the pivot itself.It was also realised that compass movement could be dampened by filling the bowl with liquid. Alcohol is ideal for this since it only freezes at a very low temperature. Liquid compasses, because of their greater steadiness, are used in most ships, especially small boats and lifecraft.How was the problem of magnetic variation solved?Variations do not worry navigators now because of the introduction of the gyroscopic compass. It was invented in 1908. This uses a spinning gyroscope which keeps the compass pointing not to the magnetic north, but to Earth's true North. A rapidly spinning gyroscope is at the heart of the gyrocompass. Once the gyroscope is set spinning, it remains pointing in the same direction, regardless of the ship's heaving motion.Today, a ship anywhere in the world can check its exact position by means of a signal from a satellite in orbit. However, all navigators still have a compass on board as well. Tracy Edwards, who captained the yachtMaidenin the 198990 Whitbread Round-the-World Yacht Race, used Navsat (satellite navigation) and found it had so many technical problems that she often used a magnetic compass instead.Magnetic compasses, the most simple and common type of compass, are aligned to the earth's magnetic field. These compasses point to the earth's magnetic North Pole. (The magnetic North Pole is located in northern Canada but is continually moving, albeit slowly.) Magnetic compasses are very simple, easily built devices, but must be laid completely flat on a platform, require some time to adjust to a turned platform, and may suffer interference from local magnetic fields.In order to adjust a magnetic compass to due or true north and toward thegeographic North Pole, one must know the amount ofmagnetic declinationor variation that exists in a specific region. There are online maps and calculators available that provide the difference in declination between true north and magnetic north for every point on the globe. By adjusting one's magnetic compass based on the local magnetic declination, it is possible to ensure that one's directions are accurate.The Gyroscopic CompassGyroscopic compassesare aligned to the true North Pole and have a needle that spins in relation to the rotation of the earth. They are often used by ships or aircraft so that any local magnetic equipment doesn't interfere with navigation. Thus, they can quickly adjust to movements. This type of compass is usually set to point at true north, based on the direction of a magnetic compass, and then periodically checked with a magnetic compass to assure accuracy.The History of the CompassTheearliest compasseswere most likely invented by the Chinese in around 1050 BCE. They were created first for the purposes of spiritual life or developing a feng shui environment and then later used for navigation. It is disputed whether other cultures, such as some Mesoamerican societies, may have developed the idea for the magnetized compass first, also in accordance for spiritual aligning and not navigation.Compasses were originally developed when lodestones, a mineral that has naturally magnetized iron ore, were suspended above a board with the ability to pivot and turn. It was discovered that the stones would always point in the same direction, and align themselves with the north/south axis of the earth.The Compass RoseThe compass rose is a depiction of orientation and direction that is placed on compasses, maps, and charts. Thirty-two points are depicted around a circle in equal intervals, marking the four cardinal directions (N, E, S, W), the four intercardinal directions (NE, SE, SW, NW), and the other sixteen secondary intercardinal directions (NE by N, N by E, etc.).The 32 points were originally drawn to indicate winds and were used by sailors in navigation. The 32 points represented the eight major winds, the eight half-winds, and the 16 quarter-winds. All 32 points, their degrees, and their names can be foundonline.On early compass roses, the eight major winds can be seen with a letter initial above the line marking its name, as we do with N (north), E (east), S (south), and W (west) today. Later compass roses, around the time of Portuguese exploration and Christopher Columbus, show a fleur-de-lys replacing the initial letter T (for tramontana, the name of the north wind) that marked north, and a cross replacing the initial letter L (for levante) that marked east, showing the direction of the Holy Land.We still commonly see the fleur-de-lys and cross symbols on compass roses today, if not just the simple letter initials for the cardinal directions. Every cartographer designs a compass rose a little differently, using different colors, graphics, and even symbols. Multiple colors are often used simply as a means of easily distinguishing the many points and lines on a compass rose.360 DegreesMost modern compasses utilize the 360-degree system of indicating direction on the compass with zero and 360 degrees representing north, 90 degrees representing due east, 180 degrees representing due south, and 270 degrees representing due west. Through the use of degrees, navigation is more accurate than through the use of the compass rose.Uses of the CompassMost people use a compass casually, for instance with hiking or camping. In those situations, basic compasses like the thumb compass or other orienteering compasses that are clear and can be read over a map are suitable. Many casual uses where travel is over a short distance require basic markings for cardinal directions and a basic level of understanding compasses. For more advanced navigation, where large distances are covered and a slight variation of degrees would offset your course, a deeper understanding of compass reading is required. Understanding declination, the angle between true north and magnetic north, the 360 degree markings on the compass face, and your course-of-direction arrow combined with individual compass instructions requires more advanced study. Inhospitable as it can be, the sea has played an essential role in human history, and so did that indispensible navigation tool, the magnetic compass. The sea provided the cheapest way to move goods over great distances, generating wealth through trade. Navigating the oceans successfully also played a pivotal role for many countries in gaining political and military power. Along the way, the compass contributed to innovations in physics and electrical engineering.Far from the sight of land, the sea is a seemingly endless, undifferentiated expanse. For most of history, getting lost at sea was a very real danger, often with disastrous consequences. Even when close to land, seafarers can become disoriented in bad weather. For ancient Greek and Roman sailors, weather conditions even limited visibility enough to shorten the sailing season in the Mediterranean Sea. The Roman military writer Publius Flavius Vegetius wrote in the fourth century that travel from June to mid-September was safe, but that sailing any other time was risky. He called the period between mid-November and mid-Marchmare clausum, or the time when the seas are closed.Seafarers adhered to these guidelines until the early 14th century, when the magnetic compass made its first appearance in the Mediterranean. No longer completely dependent on landmarks, the mariner could now find his position relative to Earths magnetic field. With the Mediterranean now open for most of the year, trade increased substantially, which contributed to the rise of the Italian city-states.In 1701, Edmund Halley produced the worlds first isogonic chart, which shows how the angle between magnetic north and true north varies at different points in the Atlantic Ocean.Photo: IEEEFIRST APPEARANCESThough the behavior of lodestone, a naturally magnetized piece of the mineral magnetite, was observed by the ancient Greek philosophers Thales of Miletus and Socrates, the evidence is clear that the idea for using it in a compass first appeared in China. There are allusions in the manuscriptWu Ching Tsung Yao, written in 1040, to an iron fish suspended in water that pointed to the south. And the earliest reference to a magneticdirection-findingdevice for land navigation is recorded in aSong Dynasty book dated to 1040-44.In 1088, Song Dynasty scholar Shen Kuo wrote that when magicians rub the point of a needle with lodestone, then it is able to point to the southIt may be made to float on the surface of water, but it is then rather unsteadyIt is best to suspend it by a single cocoon fiber of new silk attached to the center of the needle by a piece of wax. Then, hanging in a windless place, it will always point to the south.In Europe, the magnetic compass first appeared in Amalfi, Italy, around the turn of the 14th century. But it is not known if the magnetic compass was also invented in the West or if it migrated to Europe along trade routes from China. However, it is clear that because sea trade and military advantage were of far more strategic importance to Western nations, they pushed the technology of the magnetic compass far more intensely than did the Chinese. With the successive rise of the Portuguese, Spanish, Dutch, and English empires, development of the compass shifted to the European nations facing the Atlantic Ocean.The biggest challenge raised by the compass was what we now call magnetic variation: the angular difference between geographic or true north and the magnetic north, or the direction in which a magnetized needle points. Under clear skies, one could find the geographic north-south axis for comparison with where the compass pointed by either referring to the polestar or looking at the sun at noon.Across the Mediterranean, the difference between geographic north and magnetic north was relatively small. However, in the Atlantic, particularly in the northern latitudes, the difference was considerable. If this difference had been constant, there would be no problem, but it varied greatly as one traveled east to west. During his first voyage to North America from Spain in 1492, Christopher Columbus observed this mysterious behavior, but he kept it from his crew, fearing it would spook them.FURTHER DISCOVERIESBeginning in 1698, with the support of Englands Royal Society and the Admiralty, Edmund Halley, who would later be named the countrys Astronomer Royal, set out on several long expeditions to measure Earths magnetic variations across the northern and southern regions of the Atlantic Ocean. This data offered great advantage to the English Navy. In 1701, Halley produced the worlds first isogonic chart, which shows how the angle between magnetic north and true north varies at different points in the Atlantic Ocean [see photo].The study of magnetism set the stage for work in electrostatics. And the compass also served as a scientific instrument. With it, Danish physicist Hans Christian rsted observed in 1820 that an electric current from a battery flowing through a wire produced a magnetic field. This important discovery in electromagnetism paved the way for telegraphy.In 1831, English scientist Michael Faraday showed that moving a conductor in a magnetic field produced an electric current, leading to advances in electric power generation.James Maxwellcombined the electric and magnetic phenomena in a set of elegant field equations. Heinrich Hertzs discovery of radio waves, a type of electromagnetic radiation, set the stage for wireless telecommunications. This great chain of discoveries and inventions was set in motion by the seafarers compass, the tool that made it possible to voyage across Earths inhospitable seas.

THE DISCOVERY OF THE MAGNETIC COMPASS AND ITS USE IN NAVIGATIONH.H. Ricker IIIEmail: kc3mx@yahoo.comThis chapter is concerned with the magnetic compass, its use in maritime navigation, and itstheory of operation. First, it attempts to determine the origin of the discovery that a slender ironrod or needle has the property of alignment with the geometric poles of the earth; ie, it has thepower of giving direction. Then its technical development by exploiting its directional propertyas an instrument in navigation or scientific research is discussed. Finally, the later discoveries ofnavigation are described within the context of the great European explorations. The mainpurpose is to show how the discovery of the directive property of a magnetic needle led to thetechnical development of the compass and the discovery of new magnetic phenomena.Today, it is an accepted fact that the Chinese invented the magnetic compass. But, the evidencethat supports this claim is slim and controversial. Although there is good evidence, that is nowaccepted to conclusively prove the claim that the Chinese knew of the directive property of amagnetized iron needle, there is very little evidence that proves the directive property of themagnetic needle was extensively used by them in maritime or terrestrial navigation. Additionalfragmentary evidence suggests that knowledge of the directive property was transmitted to theEuropean west during the crusades as a result of contact with the Arabs. Here the controversyregarding the origin of the compass in Europe will not be addressed, because it is really a finepoint for scholars. The important point is to realize that by the 13th century the directive propertyis widely recognized and used in navigation.In this chapter the history of the magnetic compass will be addressed beginning with its origin inChina. But, this is really a relatively unimportant part of the story. The true significance of themagnetic compass is its technical development as a navigational instrument, coupled with thetechnologies of navigation, seamanship, shipbuilding, and map making, combined with thesciences of mathematics and geography. This collaboration of scholarly sciences combined withthe skills of the artisan classes, which stressed the economic applications of the directiveproperty of the magnetized needle, was the crucial development that led to the widespreadscientific interest in magnetism as a science. This collaboration was a development thatprofoundly changed western civilization. It led to European economic dominance of the worldand then later to the scientific revolution.Our story is primarily concerned with the period of the later middle ages when the compassappears. Unfortunately its origin is shrouded in mystery. Its discovery and technical developmentis crucial to the development of magnetic science. The high point in our story are thedescriptions for the construction of two types of magnetic compasses by Peter Peregrinus in aletter written in 1269. This letter contains the first technically detailed description of thecompass. It is significant because it includes both a theoretical discussion of magnetism and atechnical description of two different types of compass. Following this there was a furtherdevelopment of terrestrial magnetism, which occurred during the age of ocean navigation and thediscovery and exploitation of the new world that was facilitated by the navigational compass.Here the important point is that the new magnetic science derived its economic importance andsupport from the economic gains of the Portuguese and Spanish worldwide trade empires: whichthe English of the 16th century envied and sought to emulate.The development of navigational technology using the compass, is probably the greatestachievement of the middle ages. It gave birth to the renaissance of European civilization. Itfacilitated a tremendous increase in wealth, which further encouraged the investigation ofscience and its technical innovations. By the time of the publication of On the Magnet byWilliam Gilbert in 1600, a renaissance in western science and technology was well under way.Francis Bacon attributed this to three major technical developments in his book Novum organumpublished in 1620:it is well to observe the force and virtue and consequences of discoveries; and these areto be seen nowhere more conspicuously than in those three which were unknown to theancients...; namely, printing, gunpowder and the magnet. For these three have changed thewhole face and state of things throughout the world; the first in literature, the second in warfare,the third in navigation; whence have followed innumerable changes; insomuch that no empire,no sect, no star seems to have exerted greater power and influence in human affairs that thesemechanical discoveries.1The development of the compass and its use in navigation is therefore a major technicaldevelopment of the first magnitude. This will take the place which it deserves in this history ofthe science of electricity and magnetism.Historians of Chinese civilization have noticed that all three of these technological developmentscan be traced to China. Joseph Needham, who has written the most complete history of scienceand technology in China, advocates the origin of the compass in China in the following manner:Medieval Europe had done something in dynamics, but knew nothing of magnetism tillthe end of the twelfth century. All the work on that had been done in China, where people wereworrying about the cause of declination before Europeans even knew of the existence ofpolarity...Here and again with the magnetic compass that China knew as the South-PointingNeedle, there is clear evidence that something happens in the East, and a little later somethinghappens in the West.2This chapter will not address the impact that its development had on the theoretical interpretationof magnetism. This will be considered in detail in the following chapter. Here the developmentwill be considered primarily as a prelude to the work of Peter Peregrinus. This is a majorlandmark in science history and concerns us for two reasons. It is considered by many experts asthe first scientific work that has survived, and second it is a model of the experimental approachin the scientific method. As such it appears to be the first scientific work that utilizes theexperimental approach to knowledge. But, his most important contribution was a magnetictheory which explained the origin of the directive property of the magnetic needle.The Chinese Discovery of The Mariners CompassThe mariners magnetic compass is the first technological application of magnetism and, one ofthe oldest scientific instruments. The invention or discovery of the mariners compass is acontroversial historical problem, which remains unsolved. The inventors and discovers of theprinciple of the compass are lost to history. The facts are complicated in historical controversy.The origins of this significant scientific development are therefore unknown to us. Here areconstruction of what is known is attempted as unclear as it is.In The Bibliographical History of Electricity and Magnetism Mottelay presents evidence that theprinciple of the compass was in active use in China as early as 2637 B.C. :This date has been conclusively shown to be the earliest one at which history notesanything resembling the application of the magnetic influence....Hoang- ti constructed achariot upon which stood erect a prominent female figure which indicated the four cardinalpoints, and which always turned to the south whatever might be the direction taken by thechariot. 3This opinion derives from a treatise on the history of China published in 1736 by Jean BaptisteDu Halde, who was a missionary in China. In it, Du Halde writes:about the year 2643 B.C., the Emperor Hoang-te, being at war, an instrument wasinvented, which being placed in a car, it pointed to the south and enabled the imperial army todirect its march and surprise the enemy during a thick fog.4Du Halde further observes that the chariot story would indicate the use of the compass, orsomething similar to it ... and it is unfortunate that the device has not been explained more fully.Indeed the conclusion has not been accepted by historians as a conclusive use of magnetism toindicate direction.In the encylopeadic work Cosmos published in 1849, Alexander von Humboldt cites anotherexample of the apparent use of a magnetic compass in China in the year 1110 B.C.:As the ambassadors sent from Cochin China and Tonquin were about to take theirdeparture, Tcheou-Koung gave them an instrument which upon one side always turned towardthe north and on the opposite side to the south, the better to direct them upon their homewardvoyage. This instrument was called tchi-nan (chariot of the south), and it is still the name givento the compass which leads to the belief that Tcheou-Koung invented the latter.5These opinions are controversial. There are those who object and claim that the directional cartswere unknown prior to the fifth century A.D. The modern opinion is that the south pointingcarriages were mechanical devices. ...once erroneously believed to represent a step in the development of the magnetcompass. A two-wheeled horse-drawn chariot on which a figure was mounted with its arm presetto point due south, the vehicle had gears so arranged that whichever way it turned, the figurepivoted to hold its south-pointing posture....The magnet compass, however did originate in Chinain the early middle ages. Both European and Chinese antiquity were aware of the ability of theloadstone (a variety of magnetite) to attract and repel iron, and of its inductive property-thepower to magnetize iron, to impart the same attraction and repulsion to it. Discovery of thedirective possibilities of the magnet, however, belonged to China, as did the invention of themagnetic needle, to make readings more accurate.6Lyons in a technical book on the compass reports that in a Chinese dictionary dated to about 121A.D. there is a description of the loadstone which describes it as:A stone with which an attraction can be given to the needle.4In quoting from a work published about 400 A.D. Lyons tells us regarding the Chinese:They had ships which directed their course to the south by the magnetized needle.. thefortune tellers rub the points of the needle with the stone of love for rendering it proper toindicate the south.4Mottelay reports that about 265 A.D.: What by many is believed to be the earliest, reliable, distinct mention or actuallyprinted record of the use of the magnet for navigation, appears in the justly prominent Chinesedictionary or encyclopedia, Poei-wen-yun-fou, wherein it is mentioned that there were duringthis period ships directed to the south by the ching or needle.7In 419 A.D. Mottelay reports, that a much more detailed description of the magnetic needle isgiven in a Chinese work titled Mung-khi-py-than:The soothsayers rub a needle with the magnet stone, so that it may mark the south;however it declines constantly a little to the east. It does not indicate the south exactly. When theneedle floats on water it is much agitated...It is preferable...to suspend it as follows: Take a singlefilament from a piece of new cotton and attach it exactly to the middle of the needle by a bit ofwax as large as a mustard seed. Hang it up in a place where there is no wind. Then the needlealways shows the south; but among such needles there are some which, being rubbed, indicatethe north. Our soothsayers have some which show the south and some which show the north. Ofthis property of the magnet to indicate the south, like that of the cypress to show the west, no onecan tell the origin.8These passages clearly show that the Chinese had knowledge that the magnetic needle wasinfluenced to indicate either the north or south, but had no conception of the role of the magneticpoles. Further, they understood that the direction indicated was not to the true north or south, aphenomenon we call the magnetic declination. The passages also show why the magnetic needlehad a slow development as an instrument of navigation. It needed to be used in a stableenvironment free from the disturbances of wind and waves. In this form is possessed a crude butlimited utility for navigation. But, a further difficulty was that there was no proof that it indicatedthe actual north or south. There was no theory to account for its action. Finally, there isdisagreement regarding the dates. Lyons states that this passage was written in the eleventhcentury A.D. in disagreement with Mollelay who gives 419 A.D. and also states that: There isno statement, however that the needle thus prepared, was used for any guiding purpose.4 Thispoints out the problem of accurately establishing the dates. A problem which has not beencompletely resolved.The modern belief that the magnetic compass originated in China is based on the descriptions ofprimitive devices used in a form of divination. Lodestones formed into the shape of a primitiveladle or spoon were observed to have a wonderfully mysterious directive property when placedon a cooper plate and spun around. The spoon was balanced so that it could be spun around in acircle, pivoting on the smooth concave surface of the spoon. When the spinning stopped, thehandle was seen to point towards the south. In a book, apparently written about 83 AD, we aretold: But when the south-controlling spoon is thrown upon the ground, it comes to rest pointingat the south. But, was this device a compass? Probably not, even though it was used to mark thecardinal directions, because it didnt have a direct application to direction finding in navigation.In the Chinese book called the Wu Ching Tsung Yao (The Gist of Military Experiences), writtenabout 1040 AD there is a description of a primitive compass made into the shape of a fish, anddesigned to float on the surface in a bowl of water. The fish was made from a thin iron sheet,which was magnetized by heating and then cooling while oriented in a north-south direction.When cooled in the presence of the earths magnetic field, the fish became magnetized, andwhen placed in a bowl of water the fish floated on the surface and turned to point with its headtowards the south. Although clearly a primitive form of magnetic compass, which indicates aknowledge of the directive property of magnetized iron, the device could not be used innavigation. It was too unstable. Being subject to disturbances of the wind and external motions, itcertainly had only a limited use in navigation.Although the Chinese are thought to have had a knowledge of the directional properties oflodestone from around the first century AD, the first mention of the use of a compass innavigation doesnt appear until the 12th century. The reference reads The ships pilots areacquainted with the configuration of the coasts; at night they steer by the stars, and in thedaytime by the sun. In dark weather they look at the south-pointing needle. This passage, whichis from the book Phing-Chou Kho Tan, written between 1111 to 1117 AD, is not unlike similarreferences found in European records written about the same time.The modern historical opinion is that beginning around 1000 AD the Chinese were users of amagnetized needle in the form of a compass. They knew and understood long before the middleages that the directional property of a piece of iron was acquired when stroked or touched by aloadstone. This property was used in divination, necromancy, and fortune telling. The directionalrelation to the sphere of the heavens was used in these rituals. During the period from 850 to1050 A.D. this property began to be used for navigation aboard ships. Lyons reports that someauthors say that it was only towards the end of the thirteenth century that reliable records indicatethe use of the compass for marine navigation. This agrees with the evidence from Europeanhistory which records the use of magnetic needles sometime prior to the twelfth or thirteenthcentury A.D. The thesis is that the device was transmitted to the Europeans from the Arabs atabout the time of the crusades. However, these devices can not be considered instrumentssuitable for marine navigation. This development occurred in the thirteenth century with thepublication in 1269 A.D. of the earliest known description of a magnetic compass suitable foruse in navigation. This description occurs in the Epistola de Magnete of Petrus Peregrinus deMaricourt.4The European Invention Of The Mariners CompassThe idea that the Europeans derived the use of the compass from the Arabs is derived from aFrenchman Cardinal Jacques de Vitry, who after being engaged in the crusades, published aHistory of the Crusaders and Their Voyages to the Holy Land in 1204 A.D. This historydescribes a primitive compass being in regular use among the saracens on the coast of Syria. Adetailed description of this navigational method was given by an Arabian manuscript written in1240 A.D.:The captains who navigate the Syrian Sea, when the night is so obscure that they cannotperceive any star to direct them according to the determination of the four cardinal points, takea vessel full of water which they place in a sheltered from the wind within the ship. Then theytake a needle, which they enclose in a piece of wood or reed formed in the shape of a cross. Theythrow it in the water contained in the vase, so that it floats. Then they take the magnet stonelarge enough to fill the palm of the hand or smaller. They bring it to the surface of the water, andgive to the hand a movement of rotation toward the right, so that the needle turns on the surfaceof the water. Then they withdraw the hand suddenly, and at once the needle, by its two points,faces to the south and to the north, I have seen them, with my own eyes, do that during myvoyages at sea from Tripoli to Alexandria in the (Arab) year 640 (or 1240 A.D.).4The device is clearly not a navigational instrument, but a method or procedure for directionfinding during unsuitable weather conditions. It lacked these essential features of the moderncompass: a permanent method of suspending the needle, a container to shelter it from the wind, asighting device to align the compass in a specific direction and a graduated circle to allowmeasurement in the sighted direction. These are specific innovations that were provided by thedesign invented by Petrus Peregrinus in 1269 A.D.4There is abundant evidence that the mariners compass was developed in europe around thethirteenth century. Prior to this, there is no description of a mariners compass that would justifythe claim that the Chinese invented it. Further, the Chinese were not a maritime nation.Additionally, the devices described by Petrus Peregrinus are also not instruments suitable for usein navigation. One indication that the device was invented in Italy is the fact that Peregrinusletter was written there in 1259 AD, another is the emergence of the Italian maritime tradingstates of Venice and Amalfi at about this time. The later emergence of Portugal and Spain asoverseas maritime powers demonstrated that it was the combination of the compass with theother navigational arts which was the truly decisive factor.Flavio Goia an italian is credited with inventing the method of suspending the magnetic needleupon a perpendicular pivot so that it would remain horizontal despite the movements of a ship.This is the decisively crucial invention that makes its use as an instrument of maritimenavigation possible. Gilbert tells us: The people of Amalfi, in the kingdom of Naples first, tissaid constructed a mariners compass; and as Flavius Blondus says the townsmen do not withoutreason boast, they were taught by one Johannes Goia.24 This story is sometimes thought to be amyth. There is no evidence that Flavio Goia ever existed. His name is disputed. But, it is likelythat significant technical development of the mariners compass occurred in Amalfi. This is asignificant advancement for two reasons. It improved the ability to perform the observations, andit revealed the pointing of the needle below the horizon. A phenomenon known as the dip.Certainly one of the most important scientific endeavors during the 15th and 16th centuries wasthe theory of the compass and its use in ocean navigation by the great explorers ChristopherColumbus, Sebastian Cabot, and others which revealed that the compass direction varied fromtrue north and south. The explanation of this variation was an important and economicallyvaluable concern. It was a European discovery that the variation of the needle from true, variedwith location on the earths surface. A phenomena which introduced a large error if navigation bycompass alone was used. Hence it became important to understand the deviation of the compassfrom true, a phenomena which is called the declination.The first record of the declination of the compass comes from a Chinese source. A Chinesemedical natural history written between 1111 and 1117 A.D. by Keou-tsoungchy, gives thefollowing description of the Chinese water compass, and proves that the declination from thetrue South was known at this time in China:The magnet is covered over with little bristles slightly red, and its superficies is rough. Itattracts iron and unites itself with it; and for this reason, it is commonly called the stone that licksup iron. When an iron point is rubbed upon the magnet, it acquires the property of pointing to thesouth, yet it declines always to the east, and is not perfectly true to the south...If the needle bepassed through a wick or a small tube of a thin reed , and placed upon water, it will indicate thesouth, but with a continual inclination towards the point ping, that is to say East five-sixthsSouth.(Mottelay p29)The attribution of the discovery of the declination from the north in western europe is unknown.It probably was not known to Petrus Peregrinus in 1269, who does not mention it. A manuscriptof the letter found in Leyden contains a passage which warns about the declination from thenorth:Take note that the magnet, as well as the needle that has been touched by it, does notpoint exactly to the poles, but that part of it which is supposed to point to the South sometimesdeclines a little to the West, and that part which looks towards the North sometimes inclines tothe east. The exact quantity of this declination I have ascertained after numerous experiments tobe five degrees. However, this declination is no obstacle to our guidance, because we make theneedle itself decline from the true south by nearly one point and a half towards the West. A pointcontains five degrees.Mottelay says that this passage is unquestionably a late addition entered at a later date, becausethe entry is in a different handwriting inside a circle of one of the original drawings. (Mottelaypage 54)In 1492 during his first voyage to America, Christopher Columbus is credited with being the firstto determine astronomically the coincidence of a magnetic and geographic meridian. On thismeridian there is no magnetic variation from the true north-south direction. The magneticvariation, the divergence of the compass direction from true north-south, was known before hisvoyage to America. Columbus is credited with discovering that the magnetic variation changedwith geographic location. On September 13, 1492, he was 2.5 degrees east of the island of Corvoin the Azores when he noted in his logbook that the magnetic variation changed from beingnortheast of true north to northwest of it. The variation continued to change as he proceededwestward, so that day by day the error increased. This was a source of alarm for his pilots andcrew when they learned of it. But, Columbus managed to allay their fears by explaining that theerror was due to a change in position of the north star, and not to a fault of the compass.25In 1497 after returning from his voyage of discovery to Labrador, Sebastion Cabot...represented to the King of England that the variation of the compass was different in manyplaces, and was not absolutely regulated by distance from any particular meridian; that he couldpoint to a spot of no variation...26Later the idea occurred to him and Jean Rotz that thisphenomena might be useful in the determination of a ships longitude at sea. Measurement oflongitude via the variation of the compass is known as mecometry. This idea was notsuccessfully applied, because the variation in the deviation from true was found to be vary tooirregularly from place to place to be useful for determining longitude. Later in 1635 an Englishmathematican, Henry Gellibrand published a book, which proved that the variation from truevaried with time as well as place. Gellibrand was able to compare his contempory measurementswith ones obtained 12 and 50 years earlier. The results put an end to attempts to use the variationas a method of determining longitude.In 1544, Greog Hartmann discovered the magnetic dip. He describes the phenomenon in a letterwritten March 4th of that year. Besides, I find also this in the magnet, that it not only turns fromthe north and deflects to the east about nine degrees, more or less, as I have reported, but it pointsdownward. Hartmann found that the north pole of the compass deviated about 9 degrees fromthe horizontal so that it dipped below the horizontal plane.27The discovery of the dip is often attributed the Robert Norman who manufactured compassneedles. In 1576 he designed an instrument and measured the magnetic dip in London. In 1581he published a pamphlet titled The Newe Attractive in which he announced his discovery. Thetitle reads:The Newe Attractive, containing a short discourse of the Magnes or Loadstone, andamongst other his virtues, of a newe discoured secret, and subtil propertie concerning theDeclinyng Needle, touched therewith, under the plaine of the Horizon...In this pamphlet, Norman describes the design of his instrument and the results of hismeasurement of the dip which for this citie of London, I finde, by exact obseruations to beabout 71 degrees 50 mynutes. The charming description of his discovery is described as:Hauing made many and diurs compasses and using alwaies to finish and end thembefore I touched the needle, I found continuallie that after I had touched the irons with the stone,that presentlie the north point thereof woulde bend or decline downwards under the horizon insome quantitie so much that to the flie of the compass, which was before levell, I was stillconstrained to put some small piece of ware on the south point and make it equall againe...28William Gilbert believed that there was a correlation between dip and latitude as a result of hismeasurements on spherical loadstones. He suggested that this method could be used to determinelatitude under cloudy conditions. Gilberts theory assumed that the dip would be vertical orninety degrees at the north pole. Henry Hudson attempted to verify the utility of this methodduring one of his northern voyages in 1608. He obtained the surprising result that the dip wasnearly vertical at a latitude of 75 degrees. A result which indicated that Gilberts method couldnot be applied to determine latitude.We can examine the problem in two ways. The first is theoretical while the second practical. Thetheoretical issue was concerned with the theory of magnetism. If it could be definitelyestablished the nature of the magnetic movement towards north and south, then the reason for thedeviations could be explained. But the primary theory was that established by Peregrinus, thatthe directional power was drawn from the celestial poles. Since these were astronomically knownto be fixed, the cause of the variation was sought elsewhere.Summary and ConclusionsThe discovery that a steel needle rubbed by the loadstone acquired the power to point north andsouth was profound. The evidence does indicate that the Chinese were the first to recognize thisfact, but in connection with ritual magic. The decisive invention was the suspension of the needleon a pivot in combination with a compass card indicating the wind directions. This inventionopened up an entirely new field of magnetic inquiry through the discovery of the declination andits variation. The discovery of the dip was also decisive. It argued against the idea that thecompass needle pointed towards the north pole as the source of magnetic influence. Hence thestage is set for the decisive theory, presented by William Gilbert, that the origin of the magneticforce is within the earth.Finally, it is very important to realize that the invention of the compass and its technical andscientific investigation is one of the unrecognized roots of modern science. Traditionally, thedevelopment of modern science has been claimed to arise from the old science of Ptolemaicastronomy with the publication of Copernicus heliocentric theory. But equally important wasthe technical development of the compass and the practical navigational arts based on themagnetic compass. This opened the age of exploration, and the discovery of the new world.These changes shook the authoritarian foundations of the academic world of the renaissance;because the new world, discovered by Columbus, was unknown to the ancients. Hence theirauthority in matters of geography and geometry was undermined. Opening the door to thepossibility that other new discoveries would lead to new knowledge about the natural world.Because the compass was unknown in antiquity, along with the printing press and gunpowder,the huge success of these inventions led to the modern movement that aspired to obtain newknowledge. The acquisition of this knowledge was identified with the rejection of ancientknowledge and the application of the new procedures of experimental science which would leadin the same way to the discoveries brought about by the technical and scientific development ofthe compass. The two main ingredients of this new method were the combination of theexperimental arts of the artisan and the new idea of a science based on an inductive orexperimental method of proof.Next Chapter Exit REFERENCES1.Debus, Allen,G., Man and Nature in the Renaissance, Cambridge Science Series, CambridgeUniversity Press, London,1978, page 1.2.Needham, Joseph, Explorations of an Ancient Tradition, MIT Press, 1973, pages 3-19.3. Mottelay, The Biblographical History of Electricity and Magnetism, page 1.4. Lyons, T.A., A Treatise on Electromagnetic Phenomena and on the Compass and ItsDeviations Aboard Ship, Vol. II, John Wiley, 1903, Page 560-567.5.Mottelay, The Biblographical History of Electricity and Magnetism, page 3.6. Gies, Frances and Joseph, Cathedral, Forge ,and Waterwheel, Technology and Invention in theMiddle Ages, Harper Collins, 1994, page 93.7.Mottelay, The Biblographical History of Electricity and Magnetism, page 22.8.Mottelay, The Biblographical History of Electricity and Magnetism, page 23.9.Lucretius, On the Nature of the Universe,Penguin Books,1951.10.Mottelay, The Biblographical History of Electricity and Magnetism, page 21.11. Cohen and Grant, Source Book in Mideval Science.