Gerardus Mercator
Gerardus Mercator was born in the small Flemish village of Rupelmonde on the 5th of March 1512, the seventh child of a poor shoemaker named Hubert. He would die on the 2nd of December 1594 having never left Europe, having travelled remarkably little for a man who spent his entire life describing the whole of the world. He read geography from a library of over a thousand books. He learned about distant coastlines from merchants, seamen, and statesmen who visited him or wrote to him in any of six languages. He produced the world map that still underlies every nautical chart on the planet. And he spent decades trying to reconcile the Bible with the shape of the Earth, a tension that landed him in prison and shaped nearly every decision of his adult life. What drove a shoemaker's son to produce the first use of the word Atlas as a title for a book of maps? Why did the Catholic Inquisition put his name on a list of heretics alongside architects, priests, and monks? And what exactly did he do to a map that mariners had been struggling with for a century?
After Hubert Kremer died in 1526, his brother Gisbert, a priest and a man of standing in Rupelmonde, became guardian to the fifteen-year-old Geert. Gisbert sent him to the school of the Brethren of the Common Life at 's-Hertogenbosch in the Duchy of Brabant, one of the most famous schools in the Low Countries. The school had been founded by Geert Groote, a figure who emphasised direct Bible study and expressed open scepticism of church dogma. The headmaster during Mercator's years there was Georgius Macropedius, and under him Geert studied the Bible, Latin, logic, rhetoric, Aristotle, Pliny, and the geography of Ptolemy. It was also here that he encountered the italic script, practised by the Brethren in their scriptorium, which he would later apply to every map and globe he made. The school's previous alumni included Erasmus, who had attended forty years before Mercator. It was at 's-Hertogenbosch that Geert Kremer gave himself a new identity: Gerardus Mercator Rupelmundanus, Mercator being the Latin word for Kremer, which means merchant.
From 's-Hertogenbosch, Mercator entered the University of Leuven in 1530. Though classified as a pauper, he studied alongside students who would become famous: the anatomist Andreas Vesalius, the statesman Antoine Perrenot, and the theologian George Cassander. He earned his Magister degree in 1532. The degree centred on philosophy and theology under conservative Scholasticism, with mathematics and astronomy largely neglected, gaps that Mercator would spend years filling on his own. The philosophical tension at the university was already present for him: the authority of Aristotle sat uncomfortably against his own reading of the Bible and his observations of the natural world. He left Leuven rather than commit any of his doubts to paper, spending time in Antwerp in philosophical contemplation, and meeting a Franciscan friar named Franciscus Monachus whose humanist geography, based on observation rather than Aristotelian doctrine, left a deep impression on him.
Towards the end of 1534, the twenty-two-year-old Mercator returned to Leuven and placed himself under the guidance of the mathematician Gemma Frisius, only four years his senior. Gemma was already designing mathematical instruments and had completed a terrestrial globe in 1529 with the goldsmith Gaspar Van der Heyden. Within two years, Mercator had mastered enough mathematics to tutor private students, and he also learned the practical skills of working in brass and engraving. When Gemma and Van der Heyden planned a new globe in 1535, Mercator engraved the text including the cartouche, which carried his own name in public for the first time. The globe was finished in 1536; its celestial counterpart followed one year later. Their sales gave Mercator enough income to marry Barbara Schellekens in September 1536, and their first child, Arnold, arrived one year after that.
In 1537, aged only twenty-five, Mercator established his reputation with a map of the Holy Land, which he researched, engraved, printed, and partly published himself. A year later came his first world map, the Orbis Imago. In 1539-40 he produced a map of Flanders, and in 1541 a terrestrial globe. All four were received with acclaim and sold in large numbers. The dedications of three of these works reveal the circles he had already entered: the Holy Land was dedicated to Franciscus van Cranevelt of the Great Council of Mechelen, the map of Flanders to the emperor Charles V himself, and the globe to Nicholas Perrenot, the emperor's chief advisor. In between this burst of output, he found time to write Literarum latinarum, a small instruction manual on the italic script, which he had been the first to apply to maps and globes. In 1541, the terrestrial globe offered mariners something no previous globe had: rhumb lines drawn from compass roses, marking the lines of constant sailing direction that seafarers actually used.
In 1543, a list of fifty-two Lutheran heretics circulated in Leuven. It included an architect, a sculptor, a former rector of the university, a monk, three priests, and many others. Mercator's name was on it. He had never declared himself a Lutheran, but the signals of sympathy were there for those looking. His closest friends included Philip Melanchthon, one of the principal Lutheran reformers. His family had connections to Molanus, a religious reformer who would later flee Leuven. The school he had attended as a boy was founded on values that overlapped sharply with Luther's emphasis on direct Bible study. His visits to the free-thinking Franciscans in Mechelen had apparently attracted the notice of two senior Inquisitors at the university, Jacobus Latomus and Ruard Tapper. The words of Tapper on the death of heretics, preserved in the source, convey the atmosphere: "It is no great matter whether those that die on this account be guilty or innocent, provided we terrify the people by these examples; which generally succeeds best, when persons eminent for learning, riches, nobility or high stations, are thus sacrificed."
All fifty-two were arrested except Mercator, who happened to be away in Rupelmonde on business concerning the estate of Gisbert, who had just died. That absence only made matters worse: he was now classed as a fugitive whose flight proved his own guilt. He was apprehended in Rupelmonde and imprisoned in the castle. No incriminating writings were found in his home or at the Mechelen friary. Well-placed friends petitioned on his behalf. After seven months, he was released for lack of evidence. Others on the list did not escape: two men were burnt at the stake, another was beheaded, and two women were entombed alive. Mercator never committed any of his prison experiences to paper. All he would say, in later life, was that he had suffered an "unjust persecution."
In 1552, Mercator, now forty years old, left Leuven for Duisburg in the Duchy of Cleves, a city in the Holy Roman Empire in what is now Germany. He never gave his reasons in writing, but several factors converged: he had not been born in Brabant and could never be a full citizen of Leuven; a man once suspected of heresy would never fully be trusted by Catholic authorities; and the Erasmian constitution of Cleves offered genuine religious tolerance. The proposed university in Duisburg, which had attracted him, failed to materialise because the papal licence was delayed twelve years and Duke Wilhelm had lost interest by then. It was another ninety years before the city got its university.
Duke Wilhelm welcomed Mercator and appointed him court cosmographer, a title that encompassed geography, astronomy, astrology, and the history of the world from the creation. His first practical assignment was the unglamorous task of surveying the disputed boundary between the County of Mark and the Duchy of Westphalia. He also carried out a special commission for the Holy Roman Emperor Charles V: a pair of small globes in which the inner Earth was made of wood and the outer celestial sphere was blown crystal glass engraved with diamond and inlaid with gold. Mercator described these in a letter to Philip Melanchthon, noting that the globes were designed to rotate atop an astronomical clock made by Juanelo Turriano for Charles V, a clock with eight dials showing the positions of the moon, stars, and planets. The emperor awarded Mercator the title Imperatoris domesticus, a member of the Imperial household.
In 1554, Mercator published the long-awaited wall map of Europe, dedicating it to Antoine Perrenot, now a Cardinal. He had been collecting and collating data for more than twelve years. Scholars everywhere praised it more than any similar work that had come before, and it sold steadily for much of the rest of the century. The young English scholar John Dee had visited Mercator in Leuven in 1547 and returned as a student in 1548, spending three years constantly in Mercator's company. Forty years later the two men were still exchanging letters, with Dee using Mercator's maps to convince the English court to fund Martin Frobisher's expeditions.
As the age of ocean exploration deepened, navigators faced a problem that cost lives. A course of constant direction at sea, a rhumb line, did not correspond to a straight line on any chart then available. After a long voyage, a ship's estimated position could be a hundred miles off. In 1569, Mercator published Nova et Aucta Orbis Terrae Descriptio ad Usum Navigantium Emendate Accommodata, which translates as "A new and more complete representation of the terrestrial globe properly adapted for use in navigation." On this wall map, he made the scale increase with latitude in a precisely calculated way, so that rhumb lines became straight lines. Sailors could now draw a straight line between two points, read off the compass bearing, and hold that bearing across the entire voyage. Exactly how Mercator worked out the mathematics is not recorded in any of his own papers. Modern scholars suggest he used tables of rhumbs devised by the Portuguese mathematician Pedro Nunes.
The map itself was physically too large to be used aboard ship. It did not immediately transform navigation. But within a hundred years of its creation, the projection had become the world standard for marine charts, and it remains so today. The map was inscribed with over five thousand words in fifteen legends. It also carried Mercator's ongoing speculations on the Arctic and a southern continent, speculations that new discoveries quickly showed to be wrong. Although the projection has since been rejected for general depictions of the world's land masses because of its severe distortions at high latitudes, it continues to underpin nautical charts everywhere. Edward Wright was the first to clarify the mathematical method in his 1599 book Certaine Errors. A full analytical formula for the projection was not derived until roughly seventy years after Wright.
In 1569, as his great world map was going to press, Mercator also began work on the Chronologia, a table of every significant event since the beginning of the world. He drew on his literal reading of the Bible and on no fewer than 123 other authors of genealogies and histories. He was the first person to link historical dates of solar and lunar eclipses to Julian dates calculated mathematically from the motions of the sun, moon, and Earth, then to use those eclipses to fix the dates of events recorded in Babylonian, Greek, Hebrew, and Roman calendars. The time origin he fixed at 3,965 years before the birth of Christ. The finished work ran to some four hundred pages. Scholars across Europe greeted it with acclaim. The Catholic Church placed it on the Index Librorum Prohibitorum, the list of prohibited books, because Mercator had included the deeds of Martin Luther.
The Chronologia was only one piece of an even larger ambition, the Cosmographia, a description of the whole universe. Mercator's plan covered the creation of the world, the heavens, modern geography, the geography of Ptolemy, the geography of the ancients, genealogy, history, and chronology. Of these, only the chronology and the modern maps were fully completed before his death. His edition of Ptolemy's twenty-eight maps appeared in 1578, accepted by scholars as the final word on a chapter of geography that was now definitively closed. In 1585, Mercator issued fifty-one maps of France, the Low Countries, and Germany. In 1589, at the age of seventy-seven, he married a second time, to Gertrude Vierlings, the wealthy widow of a former mayor of Duisburg, and published a second collection of twenty-two maps covering Italy, Greece, and the Balkans. In the preface to that volume, he first mentioned Atlas as a mythical king of Mauretania, writing: "I have set this man Atlas, so notable for his erudition, humaneness, and wisdom as a model for my imitation."
Mercator had a stroke around 1590 and struggled with his family's assistance to complete the remaining maps and a new treatise on the Creation of the World. He considered this last theological work to surpass all his other endeavours. He died after two further strokes in 1594. His son Rumold published the Atlas posthumously in 1595. The full title, Atlas Sive Cosmographicae Meditationes de Fabrica Mundi et Fabricati Figura, translates as "Atlas or cosmographical meditations upon the creation of the universe, and the universe as created." The 1595 atlas is the first time the word Atlas appeared as the title of a book of maps, though Mercator himself understood the term as a neologism for a much larger cosmological treatise. He chose the word to honour the Titan Atlas, King of Mauretania, whom he considered the first great geographer.
In 1604, ten years after Mercator's death, his family sold the copper plates for his maps to the publisher Jodocus Hondius. Hondius added almost forty new maps, including maps of Spain and Portugal that the original atlas had omitted, and published a new edition in 1606 with full acknowledgement that most maps were Mercator's work. The title page showed portraits of Hondius and Mercator together, even though the two men had never met. Hondius was a skilled businessman. He and his successors, including his son Henricus and son-in-law Johannes Janssonius, produced twenty-nine editions between 1609 and 1641, including one in English. They also published a compact version called the Atlas Minor, which brought the work to a wider market. Over successive editions, Mercator's theological commentaries disappeared and the image of the mythical King Atlas on the cover was gradually replaced by the Titan Atlas. By the final edition, fewer than half the maps in the atlas were still Mercator's originals, and by the middle of the seventeenth century, publishers such as Joan Blaeu and Frederik de Wit had taken over.
Mercator was buried in the church of St. Salvatore in Duisburg. A memorial erected about fifty years after his death describes him as "the foremost mathematician of his time who crafted artistic and accurate globes showing the heaven from the inside and the Earth from the outside." His library of some one thousand books was sold at public auction in Leiden in 1604. The only known copy of the sale catalogue perished in the Second World War, but a manuscript copy made by Van Raemdonck in 1891 was rediscovered in 1987. The mathematics section alone covered arithmetic, geometry, trigonometry, surveying, architecture, fortification, astronomy, astrology, time measurement, and cartography. Only one of Mercator's own annotated copies has been found: a first edition of Copernicus's De revolutionibus orbium coelestium, held by Glasgow University. Walter Ghim, the twelve-times mayor of Duisburg and Mercator's closest friend, described him in his biography as sober in behaviour, yet cheerful and witty in company, and never more happy than in debate with other scholars.
Common questions
What is the Mercator projection and why is it still used today?
The Mercator projection is a method of drawing nautical charts, first published by Gerardus Mercator in 1569, in which the map scale increases with latitude so that lines of constant compass bearing appear as straight lines. Mariners could draw a straight line between two points, read off a bearing, and hold it across an entire voyage. The projection remains the world standard for nautical charts to this day, even though it is now rejected for general maps of the world because of its severe distortions at high latitudes.
Why was Gerardus Mercator accused of heresy by the Inquisition?
In 1543, Mercator's name appeared on a list of fifty-two Lutheran heretics drawn up by Inquisitors at the University of Leuven. He was accused of suspicious correspondence with Franciscan friars in Mechelen. His close friendship with Philip Melanchthon, a principal Lutheran reformer, his attendance at a school founded on proto-Lutheran ideals, and his visits to humanist Franciscans all contributed to suspicion. After seven months in prison in Rupelmonde castle, he was released because no incriminating writings were found.
What was the first book of maps to use the word Atlas as its title?
The 1595 Atlas Sive Cosmographicae Meditationes de Fabrica Mundi et Fabricati Figura, published posthumously by Mercator's son Rumold, was the first book of maps to carry the word Atlas as its title. Mercator chose the word to honour the Titan Atlas, King of Mauretania, whom he considered the first great geographer, and he intended it as a neologism for a cosmological treatise rather than simply a collection of maps.
Where did Gerardus Mercator spend the last thirty years of his life and why did he move there?
Mercator moved to Duisburg in the Duchy of Cleves, in what is now Germany, in 1552 and lived there until his death in 1594. He left Leuven because Catholic intolerance of religious dissent was intensifying in the Low Countries, and a man once accused of heresy could never fully be trusted there. Duisburg offered religious tolerance under an Erasmian constitution, and Duke Wilhelm welcomed Mercator, appointing him court cosmographer.
What did Gerardus Mercator do besides make maps?
Mercator was a maker of scientific instruments and globes, an accomplished engraver and calligrapher, and a scholar of theology, philosophy, mathematics, history, and geomagnetism. He wrote the Chronologia, a four-hundred-page table of world events from the creation, and produced a definitive edition of Ptolemy's twenty-eight maps. He also wrote on the gospels, the Old Testament, and the Harmonisation of the Gospels, and completed a treatise on the Creation of the World shortly before his death.
How did Jodocus Hondius transform the Mercator Atlas after Mercator's death?
Jodocus Hondius purchased the copper plates from Mercator's family in 1604 and added almost forty new maps, including maps of Spain and Portugal that the original atlas had omitted. He published a new edition in 1606 under his own name while fully acknowledging Mercator's authorship. Hondius and his successors produced twenty-nine editions between 1609 and 1641, including an English edition and a compact Atlas Minor, turning what had been a commercial disappointment into an enormous success.