The World of Gerard Mercator: The Mapmaker Who Revolutionised Geography

Gerard also drew some lessons from his great-uncle and from his own earlier life: that the Church had always been a source of support and stability in the confusing world in which he was growing up, and that Gisbert’s prosperity showed the material rewards that could come from not challenging the system openly. The Brethren were always careful to keep the sympathy for the reform movement which they had inherited from their founder within bounds that were acceptable to the Church authorities. In a town where dissent and dangerous opinions were common, Gerard no doubt saw the importance of discretion and the value of security. Inside the walls he had found scholarly disputation and strict discipline, symbolized by the monkish uniform of gray hooded gowns that the boys wore, “after the ancient usage of the Brethren,” but he had also found stability.

The old world of the Catholic Church had given him security, and for all the reformist leanings, the innovative thinking, and the fascination with new skills and techniques that would mark his adult life, he never lost his instinctive sense that stability would be found in the past, in the way things had always been.

Unlike many of the Brethren’s charges, however, Gerard still had no ambition for a prosperous and honorable career in the Church like his great-uncle’s. The small boy remarkable for the dedication with which he closeted himself with his books became a serious and sober eighteen-year-old, with the prospect of a life dedicated to study. University life, just as much as that of the cloister, could offer support and a place to belong. The rich endowments and charitable foundations of the forty-three colleges of the University of Leuven meant that, as an impoverished but talented student, he could be excused payment of any fees there.* Although there were no formal requirements for admission, a prospective student would have to convince the doctors of his college that he was adequately prepared for the demanding course of study that the university would provide.7 Gerard’s record of study at ’s Hertogenbosch, together with the patronage and recommendation of his uncle, would have been enough to do that. He was ready to take a place in the ancient university.

Chapter Five At the College of the Castle

JOINING THE UNIVERSITY of Leuven was a solemn moment, a commitment like joining a monastery. On August 29, 1530, Gerard de Cremer knelt before the rector, Pierre de Corte – a man who would later prove his courage and friendship by standing up to the Inquisition on his former pupil’s behalf – to take the oath of matriculation, the pupil’s hands clasped between the master’s in prayer and supplication. The university was a cosmopolitan place, with more than five thousand students and scholars from France, Germany, England, Scotland, and the farthest reaches of Europe – enough to create their own distinct community. The Faculty of Arts, which Gerard joined, was divided into four colleges scattered through the town. The Colleges of the Pig, the Lily, and the Hawk were all named after ancient houses in Leuven, while the College of the Castle, in the street that led up to the duke’s old residence, was where Mercator received his board and lodging and most of his tuition.

When Duke John IV of Brabant had applied for papal approval to found the university early in the fifteenth Century, Leuven, some twenty-five miles southeast of Rupelmonde, was in decline. Many of the weavers whose labors had made it prosperous had left for England, frightened by the latest spasm of riots and fighting, and attracted by the lure of better profits in the growing English wool trade. Other cities had flourishing universities: Bologna, Paris, and Oxford had been attracting students for two centuries or more, and similar institutions were opening all over northern Europe. France had twenty universities in the fifteenth century, and the German-speaking countries about the same. A new university in Leuven brought not only prestige to the duke but prosperity to the town.

By the early sixteenth century, its reputation was growing. Its former rector, Nicolas Vernulaeus,1 wrote a history of the university that described a peaceful academic town, with quiet fields and vineyards sheltered from the north winds by the hills around, and with well-swept and respectable houses – the very place, he enthused, for students seeking calm to pursue their studies. Even Erasmus had found it more congenial than the grammar school at ’s Hertogenbosch. Its students, he observed, were well taught, courteous, and mature. “No-one could graduate at Leuven without knowledge, manners, and age,” he declared. He had written to assure a friend: “Its agreeable and healthy climate is conducive to quiet and peaceful study; no other university can rival its intellectual life, nor the number and quality of its academic staff.”2

The establishment of the university, by attracting scholars and businesses, had played its part in the rejuvenation of Leuven, and there was clearly much life in the town beyond the college walls. The university authorities took the possibility of youthful high spirits seriously enough to set down formal statutes banning students from bearing arms, dicing and gaming in public taverns, or even walking the streets after eight o’clock at night, and their rules were stricter still inside the college. Gerard apparently reveled in the austere, contemplative life of fasting, abstinence, and strict obedience to the pater of the college. The sole official record of his time at Leuven is his inscription as a “poor student” in the books of the College of the Castle, but his friends and contemporaries all spoke of a dedicated and high-minded academic, concentrating almost obsessively on his work.

In that society, at least, there should have been no shame in his poverty. But even if the somber, monkish gown, which all the university’s pupils wore,3 disguised the differences between rich and poor, there was little fraternization between them. They all ate in the same hall, but the rich took the high table, while the poor sat at the far end of the hall; the rich students lived in private rooms, while the poor shared the dormitory in the College of the Castle. Few friendships crossed such a divide, but Mercator would have known the names of his rich colleagues, and one in particular would resonate for the rest of his life: Antoine Perrenot de Granvelle, the son of Charles V’s trusted chancellor, Nicholas Perrenot de Granvelle, was starting on his rise to power.

It was customary in scholastic circles, even among poor students, to add dignity to one’s name by translating it into Latin. Gerard’s schoolmaster at ’s Hertogenbosch, Georgius Macropedius, had started life as Joris van Lanckvelt. Gerrit Gerritszoon had already become known as the humanist Desiderius Erasmus Roterodamus, and Mercator’s near contemporary Andries van Wesel would win fame as the anatomist and humanist Andreas Vesalius. The sonorous, Latinized Mercator, or merchant, suited Gerard’s own ambitions much better than de Cremer – pedlar in the vulgar Flemish. In choosing his new name as he started on his career at Leuven, he looked back to the place of his birth and the formative years of his childhood: Gerardus Mercator Rupelmundanus was born.

The rigid timetable of his days was punctuated, as it had been in ’s Hertogenbosch, by celebrations of the Mass, and ran from dawn to dusk, with a brief rest period in the afternoon. His course of studies in the university’s Faculty of Arts was essentially the same logic, physics, metaphysics, mathematics, rhetoric, and moral philosophy that students had tackled for centuries, with attention fastened as firmly on the learning of hundreds of years ago as it had been at ’s Hertogenbosch. Observation, measurement, and independent thought were all dangerous steps on the road to heresy. First among the ancient masters was Aristotle, and it was expressly forbidden even to question his teaching.

The eighteen-hundred-year-old writings of the pre-Christian Greek philosopher were used expressly to bolster and justify the position of the Catholic Church as guardian of thought and theology. The statutes of the university were strict and unambiguous about how religion, philosophy, and natural science should be approached: “You will uphold the teaching of Aristotle, except in cases which are contrary to faith. ... No-one will be allowed to reject the opinion of Aristotle as heretical ... unless it has previously been declared heretical by the Faculty of Theology.”

That official position was strictly enforced by the university authorities, with the sinister power of the Inquisition always in the background. The university had done more than bring prestige and prosperity to Leuven; it had given the dukes of Brabant and their heirs – by then, the emperor Charles V – a powerful tool of religious and political repression. Though it had a degree of independence – one condition of the papal bull by which Pope Martin V had originally consented to its establishment had been that the rector should have full criminal and civil jurisdiction over its members – the university authorities nonetheless worked closely with the imperial government. There was no home within their walls for the reformist agitation so popular in ’s Hertogenbosch. In 1522, Charles V had established a state-run Inquisition to work alongside the Church in quashing the reform movement, and the university authorities took an active part in its investigations. Leuven’s Faculty of Theology was given the task of censoring and approving all newly printed books on behalf of Charles V, and various university officials took their places in the ponderous, awe-inspiring public processions in which the Inquisition’s victims were led to punishment or public repentance. At Leuven, Mercator was studying in one of the greatest strongholds of anti-Reformation learning of the sixteenth century.

At the same time, the university boasted some of the finest teachers in Europe, who were making discoveries of their own while avoiding any direct confrontation with the authorities or the Inquisition. Erasmus had been a professor there, helping to found the Collegium Trilingue for the study of Hebrew, Latin, and Greek, and Adrian of Utrecht, one of the tutors of the young Charles V, had held the chair of philosophy, theology, and canon law before being elected pope in 1522.4 The renowned mathematician, astronomer, and physician Gemma Frisius, who taught Mercator about the movement of the planets and helped him as he grappled with classical geometry, was no backward-looking medieval scholar.

Gemma was a sallow, thin-faced, lame, and asthmatic genius, who had taken his name from the windswept plains of Friesland where he came from, alongside the sandbanks and marshes of the Waddenzee. Like Mercator, he came from a poor family, and his parents had died during his childhood. Though only four years older than Mercator, by the time the latter arrived at Leuven, Gemma had already established a reputation across Europe as the leading mathematician and cosmographer of the Low Countries. A contemporary engraving shows him in his academic robe and bonnet, his long face impassive, with sunken cheeks and a slightly hooked nose. His eyes stare fixedly, challengingly from the frame, and his bony fingers, wrapped casually around a globe, are heavily ringed like a nobleman’s – a picture of a man beyond riches, a scholar literally holding the world in the palm of his hand. While still a student and barely out of his teens, he had produced his own corrected edition of the Cosmographia published five years earlier by the German scholar and sometime tutor of Charles V, Petrus Apianus. The book drew on traditional ancient sources but also, through Martin Waldseemüller’s world map of 1507 and the writings of other German scholars, on the transatlantic voyages of Amerigo Vespucci and the explorers of the previous forty years. The new edition had Gemma’s name on the title page alongside that of its author and was widely accepted as the most authoritative account of the known geography of the world, appearing in some thirty different editions over the next eighty years.

Gemma’s own writings on astronomy and cosmography, De principiis astronomiae et cosmographiae, were published in 1530, the same year that Mercator joined the university. He was working on the practical application of mathematics to surveying and mapmaking, while at the same time following his medical studies, which would lead eventually to his appointment to the university’s medical faculty. He was a role model for the young Mercator, not just a scholar and polymath but a man who combined ancient learning with the most up-to-date research. Gemma was dedicated in particular to the practical application of his studies, the union of mathematics and geography. He had already started to produce the mathematical and scientific instruments for which he would become famous, and he was putting the finishing touches on his new technique of triangulation, the art of defining the location of a place by taking two separate sightings. His planimetrum, a flat wooden disk marked in degrees and fitted with a revolving pointer, could be aligned with magnetic north so that its user could take sightings of different towns across the flat Low Countries. The cathedral at Antwerp, he suggested, was an ideal place to start. First he would settle on a second fixed point nearby and walk the distance between it and the cathedral to check its measurement. Then, using his planimetrum, he would establish the angle between imaginary lines drawn from the cathedral to his observation point and from the observation point to a point of reference, such as a tower, in the distant town. He thus knew the size of one side and two angles of an imaginary triangle drawn between the cathedral, his fixed point, and the distant tower; working out the length of the other two sides, and thus the position of the distant tower, was then a matter of simple geometry. This proved the key to accurate surveying for centuries to come, and a technique which Mercator would master for his own mapmaking.

Gemma Frisius

Science Photo Library, London

Gemma had also found time to tackle the problem of calculating longitude, which had troubled mariners for centuries, and particularly since they had started making long journeys across the Ocean Sea and to the Far East. In theory at least, working out a ship’s latitude was relatively easy – instruments could measure the height of the Sun or other heavenly bodies above the horizon, and sets of tables would give a fairly accurate reading of latitude – but sailors had no accepted way of finding how far east or west they were. Gemma suggested in De principiis astronomiae et cosmographiae that it might be done with a combination of astronomical observations and the use of a reliable clock. Since the Earth was a sphere of 360 degrees that revolved once every twenty-four hours, each fifteen degrees of longitude would make one hour’s difference to the time. First, Gemma advised, the navigator should take an accurate reading of the time and a sighting of the Sun when he set off. If, when he was out at sea, he then marked the time when the Sun was in the same position in the sky, the time difference measured on the clock would tell him how many degrees east or west he had traveled.* “By this art can I find the longitude of regions, although I were a thousand miles out of my attempted course and in an unknown distance,” he declared.5 There were no clocks accurate enough for such a technique – it would be more than two centuries before John Harrison’s chronometer solved that problem – but the theory was impeccable. The technique was simply two hundred years ahead of the technology.

Leuven, from Civitates Orbis Terrarum, 1572

Historic Cities Research Project http://historic-cities.huji.ac.il, The Jewish National and University Library of the Hebrew University of Jerusalem

Despite the hard work of his childhood, Mercator found he lacked basic knowledge in his early days at the university. He struggled at first in Gemma’s lectures on astronomy, he admitted later, because he lacked the mathematical knowledge to grasp the arguments, so he went off alone with his geometry textbooks to follow through the logic of the classical mathematicians.

He started by teaching himself elementary geometry from the books of Gemma’s Friesland countryman Johannes Vögelin, which he said he easily mastered. He then tackled the first six books of Euclid, beginning with the simple, basic definitions – that a line has length but no breadth, for instance, or that a surface has only length and breadth – and gradually building up his understanding of Euclid’s theoretical arguments about lines, points, circles, triangles, and the relationships between them. Mercator’s method was to take a complex geometric proposition and follow it logically, stage by stage, continually referring back to earlier theorems as he went. In Book IV, for instance, he worked painstakingly through Euclid’s seventeen-hundred-year-old instructions for fitting a straight line into a circle, and in Book VI, he followed through the proof that a straight line drawn through a triangle parallel to one side will cut the other two sides in equal proportions. Each proposition built upon the ones before it, so that by the time he had finished, he had mastered the technique of theoretical reasoning to the point where he could follow Gemma’s lectures and understand the principles of triangulation. Mercator shrugged off this minor achievement: “In a few days, I got to the point where there was nothing in the six books that I had not diligently studied and learned,” he wrote later.6

He worked alone but turned to Gemma for help and advice whenever he found himself puzzled by Euclid. In a mark of singular favor, he was invited for private tuition in Gemma’s house as one of the familia of students who sat at his feet. Gemma’s scholarship had won him the regard and friendship of Johann Flaxbinder, the ambassador of the king of Poland to the court of Charles V, and Flaxbinder had tried unsuccessfully to persuade him to leave the lowlands for a post as Polish court cosmographer. The books he published, which supported him during his years at Leuven, were dedicated to such figures as Charles’s advisers Maximilian Transylvain and Jean Obernburger, and to Jean Khreutter, a senior councillor to the queen of Hungary. The emperor himself summoned Gemma to his court in Brussels on occasion for discussions on matters of science and geography. Gemma Frisius was Mercator’s first introduction to the eminent circles on whose support his prosperity would be built.

His influence over the young student went farther. Euclid was entirely theoretical – the study of logical argument as much as lines, triangles, and circles – but Mercator’s interest, like that of Gemma, was engaged from the start in its practical use. “In geometry, I only pursued those studies that were to do with measuring, the location of places, the laying out of maps, the dimensions of territories, and finding the distances and sizes of celestial bodies,” he reminisced when he was sixty-nine years old in a letter to a Swiss Protestant pastor, offering advice on how a child might be taught geometry. “In mathematics, I directed my studies to cosmography alone.”7 His aim throughout was to improve his skills as a geographer, surveyor, cartographer, and astronomer.

He had other interests as well – interests that went far beyond the apparently innocent theories of geometry and took him into areas on which Aristotle and the Church had laid down unshakable rules. Ever since his boyhood in Rupelmonde, Mercator had been fascinated by the natural world, but at Leuven his interest was piqued by nature in its widest sense – not just in plants and animals but in the shape of the world and the universe. He built on his studies of Euclid to understand the movements of the stars and planets, as he described years later: “The contemplation of Nature delighted me marvellously, because she teaches us the causes of all things, the sources of all knowledge. But I delighted particularly in the study of the creation of the world, which shows us the beautiful order, the harmonious proportion, and the singular beauty which is there to be admired in all created things.”8 He saw no clash with his religious belief; to study Creation was a way to understand and appreciate its wonder, not a challenge to divine power.

The university authorities, though, were not as confident that such contemplations were free of heresy. For them, the Earth was the focus of the universe, the unequivocal center of everything, and arguments about order, proportion, and beauty were at best irrelevant and at worst a direct challenge to Holy Writ.

Aristotle had also taught that the oikoumene, the habitable world, was limited to the regions of Europe, Asia, and North Africa that lay between the frozen northern zone and the blistering heat of the “torrid zone.” There was, he said, a symmetrical arrangement to the South, although the southern temperate zone remained uninhabited. Since the first centuries of the Christian Church, philosophers and theologians had pointed out that only descendants of the animals in Noah’s Ark – safely in the northern zone – could have survived the Flood. That was a view which the church of Mercator’s day supported, studiously ignoring the fact that sailors over the previous hundred years had encountered both animals and human beings around the equator and farther south.

For several hundred years, the physical reality of Aristotle had been accepted as fitting most closely with the Christian belief in an all-powerful, eternal Creator; experimentation, measurement, and empirical questioning that might throw Aristotle’s conclusions into doubt were not allowed by the Church. The challenge to Aristotle was as much part of the Reformation as were the attacks on corruption in the Church. Luther’s delight when he declared triumphantly, “Aristotle is going downhill, and perhaps he will go all the way down into hell,”9 reflected Aristotle’s position as one of the Catholic Church’s central pillars against reform. Revolution was no less threatening to the authorities because it was in the mind; pull one brick from the towering building of medieval philosophy, faith, and theology, they believed, and the whole structure might come tumbling down.

FOR TWO YEARS Mercator continued quietly with his studies, avoiding any clash with the authorities, until he was awarded his magisterii gradum. The master’s degree would have allowed him to progress from the Faculty of Arts to further studies in medicine, Church law, civil law, or theology, as Gemma had done. Instead, as he stood on the threshold of the academic career he must have dreamed of, he gave the first sign of the inner turmoil he was suffering. He remained a member of the university, subject to its rules and regulations and – crucially, as he would discover – entitled to its protection, but he abandoned his formal course of study. He left Leuven in 1532 for nearby Antwerp.

Many years later, Mercator admitted that as a young man at Leuven, he had begun to have his first doubts about the wisdom of the philosophers, and to believe that the contemplation of nature, science, and the natural world might offer a better insight into God’s will. “When I understood how the world of Genesis and Moses did not agree in many ways with Aristotle and the rest of the philosophers, then I began to doubt the truth of all the philosophers, and to test it against the mysteries of nature.”10 Those words about his youthful doubts, taken from a treatise on Genesis published after his death, seem calm and judicious, but his actions at the time suggested that they hid an agonizing mental struggle.

Almost certainly, it was with these cogitations on the incompatibility of Aristotle and Genesis that the first seeds of Mercator’s lifelong interest in synthesizing the various ancient and medieval accounts of history were sown. Whether his thoughts were written down for eventual publication or not, they were to develop more than thirty years later into his Chronologia and Cosmographia.