It is very common in the history of science, particularly in popular presentations, to describe the life and work of scientists as if they existed in some sort of bubble cut off from the rest of humanity. This type of presentation is also a form of distortion of the history of science; scientists are almost always parts of a network of thinkers, researchers, critics all exchanging information and constantly reviewing, criticising and praising each other work. Sometimes scientists form deep friendships with other researchers that go beyond the scientific level into the personal. As my contribution to this year’s Conrad Gesner Day I would like to sketch one such personal friendship.
Georg Joachim Iserin was born 16 February 1514 in Feldkirch in present day Austria, the son of the town physician Georg Iserin and his wife Thomasina de Porris, a minor Italian aristocrat. In 1528 Georg Iserin was convicted of having stolen money and belonging from his patients and was executed. As part of his punishment the family name was banned and his fourteen year-old son became Georg Joachim de Porris. Following his father’s death the boy was sent to the school of the Fraumünster collegiate church in Zurich in 1528. It was here that he first made the acquaintance of Conrad Gesner.
Conrad Gesner was born on either 16 or 26 March 1516 in Zurich one of the eight children of the furrier Urs Gesner and his wife Agathe Frick. The family was destitute and when he was five years old Conrad went to live with his great-uncle Johannes Frick a chaplain, in whose garden he first developed his love of botany. Frick sent his nephew to the Fraumünster, school in 1526.
In their first mutual year at the cathedral school, Georg Joachim and Conrad both lived in the house of the teacher Oswald Myconius. Myconius (1488–1552), who was born Geißhüsler, was a friend of both Ulrich Zwingli, the Swiss Reformer, and the humanist scholar Erasmus of Rotterdam, who supposedly gave him the humanist name Myconius. Myconius was a significant religious and educational reformer and he exercised a strong influence on both Georg Joachim and Conrad. From Myconius Georg Joachim probably learnt his love of mathematics and Conrad got his grounding in Hebrew, subjects, which both of them would go on to teach as university professors later in life. The two young men only shared their school life for three years, but they would remain close friends for life.
In 1532 Georg Joachim returned to Feldkirch where Achilles Pirmin Gasser, who later became town physician in Feldkirch, took over his education and sent him off to his own alma mater the University of Wittenberg, where he adopted the toponym Rheticus and became a protégé of Philip Melanchthon, who had been Gasser’s teacher. Conrad left for Strasbourg where he was to deepen his knowledge of Hebrew.
Rheticus graduated MA in 1536 and was appointed to the chair of lower mathematics (arithmetic and geometry) at Wittenberg by Melanchthon. As is well known in 1538 Rheticus took a sabbatical, armed with a letter of recommendation from Melanchthon, and visited Nürnberg, Tübingen and possibly Ingolstadt before returning to Feldkirch, from where he set out on his history making journey to Frombork to meet Nicolaus Copernicus. Here Rheticus persuaded Copernicus to finally publish his opus magnum, De revolutionibus, and took the manuscript to the printer-publisher Johannes Petreius in Nürnberg in 1542. Melanchthon now put pressure on Rheticus to take up his new appointment as professor of mathematics in Leipzig, which he duly did.
Conrad Gesner continued his studies at a series of European universities, at times also teaching, before he finally completed his doctorate in medicine at the University of Basel in 1541, when he returned to Zurich and became professor for the natural sciences on the Collegium Carolinum. In 1545 he published his Bibliotheca universalis, an attempt to catalogue all the books published since to invention of book printing. This was the start of his extraordinary career as a true polymath. It is from the Bibliotheca that we know of the shared school experiences of the young Conrad and Georg Joachim.
It can be assumed that the two young friends, who, like most of their contemporaries, where energetic letter writers, wrote to each other over the years, but if they did none of their correspondence has survived. Both went their way and established their academic careers and it was in 1547 that they first met up again but this time not as school comrades but as teacher and pupil.
In 1545 Rheticus set out on another long journey, this time to Italy where he visited the physician, mathematician and astrologer Girolamo Cardano. In 1547 Rheticus on his way back from Italy stopped in Lindau, where he appears to have suffered some sort of mental breakdown. When he finally recovered from his illness, which had lasted several months, instead of returning to Leipzig, where he was long overdue and was neglecting his duties, he decamped to Konstanz having first despatched a letter to Gesner in Zürich, which is no longer extant. After teaching mathematics and astronomy in Konstanz for several months he made his way to his old school friend in Zürich in December 1547.
In Zürich Rheticus took up the study of medicine as Gesner’s student. It was common practice for professors of mathematics to study for a doctorate in medicine parallel to their teaching duties. During the Renaissance astro-medicine was a dominant direction in school medicine and mathematicians were best equipped to cast and interpret the necessary horoscopes used in diagnosis and treatment. However they usually did this at their own universities and not hundreds of miles away at another university. The university in Leipzig demanded that he return but he wrote back in May that he was still suffering from his illness and did not return until September 1548. During the time that Rheticus was studying under Gesner, the latter published his Pandectarum, save Partitionum universalium (Zürich 1548), which contained a work by Rheticus on the division of the scales on a triquetrum an astronomical instrument.
After Rheticus’ departure from Zürich the two friends did not meet again and, as already mentioned, any correspondence between the two of them has not survived. Gesner died in Zürich in 1565. Having fled the university of Leipzig in 1552 following a scandal, Rheticus wandered around Europe completing his medical studies before settling in Kraków, where he made a successful career as a physician and astrologer.
One wonders if those two unfortunate teenage boys, the one having just lost his father under traumatic circumstances and the other from a family so poor that they couldn’t afford to feed him, who became friends in Zürich in 1528 ever dreamed that they would both be famous in the history of science five hundred years into the future; Rheticus as the midwife of Copernicus’ heliocentric astronomy and Gesner as one of the founders of modern zoology.
 There are no known portraits of Georg Joachim Rheticus so out of a sense of fairness I have decided not to include any of Conrad Gesner in this post.