IT WAS DUMB luck that Miriam and I missed the flight out of Oklahoma City on a Sunday in February 1993. The airline counter was suspiciously empty, and we should have had an instant foreboding that something was wrong. "You're quite early for the flight," the attendant cheerfully informed us. But then she examined our tickets. "Woops—your plane left half an hour ago! But don't worry. You can get to Boston via Chicago instead of Dallas, and neither segment is full."
The nature of my blunder dawned on me after a few moments. At that hour our connection in Dallas was boarding, not the link from Oklahoma City, which had long since departed. We had showed up at the right time, but in the wrong state! But if I hadn't made that stupid mistake, I might never have learned where Jofrancus Offusius was born nor unscrambled his connection with De revolutionibus, and I might even still think that his name was an erudite Greek pseudonym based on the celestial constellation Ophiuchus, the Serpent Bearer.
We had come to Oklahoma to attend a conference at the university in Norman, and while there I intended to take advantage of its outstanding collection of rare books in the history of science. I had inspected its copy of Copernicus' book early on in my search, in fact, so near the beginning that I hadn't been very savvy about what to look for in the annotations.
My colleague Bob Westman had come to the conference too, and when I learned that after the conference the library was being opened specially for him Sunday morning, I decided to come along to have a fresh look at the De revolutionibus. Had I remembered when our plane was really scheduled to leave, I never would have taken the extra time to sit with the Copernicus book again, and to copy out some of the more interesting notes. And then I would have overlooked an important clue to a puzzle about the Copernicus books that had been baffling me for nearly a decade.
Unfortunately, not every owner of De revolutionibus bothered to put his name in it, and in particular I had a cluster of copies with very similar annotations but no clearly defined original annotator. One potentially useful feature of Copernicus' book, for those readers who actually wished to calculate the position of a planet, was the so-called mean motion tables, the first step in locating a planet. But to use the tables, it was necessary to have a starting position, or radix, something that Copernicus unfortunately buried in the text where it was a nuisance to find, so this group of annotators had written in a starting position for 1550 at the bottom of each relevant table. Thus I called whoever started the sequence the "Master of the 1550 Radices," but his mysterious identity had eluded me.
As I sat with the first-edition De revolutionibus at the University of Oklahoma that Sunday morning, one unusual detail caught my eye: three marginal references that attributed the original annotations to someone named Vesalius. Westman allowed that he had noticed the name earlier, but like me, the only Vesalius he had ever heard of was the famous medical doctor whose De humani corporis fabrica, published in 1543, the same year as De revolutionibus, had revolutionized the study of human anatomy. Did Andreas Vesalius also have a secret life as an astronomer? Strange things had turned up in the census, but nothing quite as astonishing as that.
Thanks to the helpful clerk at American Airlines, we made it back to Cambridge only an hour after our originally scheduled plane. A few days later, in reviewing my notes, I suddenly noticed that the longest note I had transcribed, on folio 127, matched an annotation that had previously turned up in seven other copies of the book. What was really maddening was that each of the notes was written in the first person—"Ego reperi . . . (I have found . . .)—and yet they were written in eight different hands.
A seemingly valuable clue to the elusive original annotator had come not from one of the books in the Master of the 1550 Radices series but from a quite different copy of De revolutionibus. It was in Yale's Beinecke Library, the copy that had exhilarated me so much years before when I had identified it as a long-lost one that had been owned by someone with at least an indirect connection to Paul Wittich. At the back of the Yale book an early owner had written that Thaddeus Hagecius—the personal physician to Emperor Rudolf II and a sometime astronomical author himself—had found out from Paul Wittich about three errors in Copernicus' book. These he listed in their stark triviality. The last two, minor arithmetic mistakes in the great cosmological chapter in Book I of De revolutionibus, were pretty inconsequential. But the first related to folio 127, the very place where the Master of the 1550 Radices copies had such a huge annotation.
In at least one of the eight copies, in a De revolutionibus in Debrecen, Hungary, the same three errors were marked, in so precise a way that it couldn't be coincidence.* A slender clue indeed, but to me, it smelled of Central Europe and in particular of Georg Joachim Rheticus, the rebellious young man who had been Copernicus' only disciple and who had taken De revolutionibus to the press. Subsequently, he had been persuaded by a particularly high salary offer to leave Wittenberg for Leipzig, and had eventually settled in Cracow, from where he had later connections with both Hagecius and Paul Wittich's family.
But why Rheticus? He had been the professor of mathematics at Wittenberg when Erasmus Reinhold was the professor of astronomy there. The census had turned up more than a dozen books with partial copies of Reinhold's annotations, but from Rheticus there were only a couple of presentation copies without any significant annotations. Surely the young man who made the trip to Poland, who first learned of the heliocentric system, and who brought the manuscript back to Germany for publication would have taught the details to a generation of students. Where was his teaching tradition? It was curiously absent from the annotated copies.
Since finding Rheticus' annotations would be a major coup, I had a secret hope that these eight books might hold a precious record of his own master notes. Rheticus had carefully computed an ephemeris for 1551, that is, an almanac giving planetary positions for every day of the year, of course based on the tables in De revolutionibus. If anyone aimed to embark on such a task, probably the first step would be to calculate the mean position of each planet for some suitable starting date, such as 1 January 1550, and write that in a convenient place. And that is precisely what I had found in the tables of seven of these eight books, which helped me recognize their affiliation in the first place. Only the Oklahoma copy lacked these numbers, and that is why I hadn't caught on right away that it belonged to the set.
Was the mysterious Master of the 1550 Radices, in fact, Rheticus? In 1992 my Polish colleague Jerzy Dobrzycki came to Cambridge for a research visit, and I put the suggestion to him. He lost little time in shooting it down. Though I had been collecting the materials and worrying about the problem for some years, I had not yet made a definitive transcription and translation of the longest marginalium, the one on folio 127. Jerzy set to work on my preliminary notes and microfilms. "This is heavy criticism of what the annotator thinks are errors in this very technical passage," he pointed out, "but look here at the end. He says maybe Copernicus didn't do it but entrusted this part to a student. Since Rheticus was Copernicus' only student, he would hardly have written that."
So it was back to the drawing board to find another candidate for the Master of the 1550 Radices. One of the eight copies, in the Bibliotheque Nationale in Paris, actually had inscribed on its title page the name of the student who had copied the notes: Jean Pierre de Mesmes, sometime astronomer of Paris, about whom very little is known except that he put out an elegant but rather derivative book entitled Les institutions astronomiques. In one marginal note, not found in any of the other copies of this family of annotations, he had added a value for the precessional motion "from my teacher Jofrancus for this current year 1557." And, near the end of the book, he wrote "Johannes Franciscus,* not your ordinary astronomer, made a wonderful Copernican instrument for Master Rousseau."
Jofrancus, not a very common name, clearly referred to one Jofrancus Offusius, who in 1557 published in Paris an ephemeris for that year. Therein he referred to himself as a German, but he gave very little hint as to his origins, position, or patrons (if any). Not only did de Mesmes add to his own book those few notes about Offusius, but he also changed a few of the first-person "ego" notes to refer to Jofrancus. However, he left others as "ego," which made the situation very murky. And the fact that the Oklahoma copy changed three of the other "ego" notes to "Vesalius" muddied the waters still further. Added to this was yet another curious detail: A close copy of the de Mesmes version, a book also now in Paris, bore a note on its title page saying "from the hand of C. Peucer." (Caspar Peucer was Reinhold's successor in Wittenberg.) We could trace its route from Germany to present-day Paris, but it did seem preposterous to suppose that it had been annotated in Catholic Paris, found its way to Lutheran Wittenberg, and then back to prerevolutionary France.
Gradually, despite the confusion, it became obvious that Jofrancus Offusius had to be a principal in the case, but it wasn't clear whether he alone had written the basic set of notes. Was a colleague named Vesalius also in on the study?
To crack this aspect of the case required a map of the lower Rhine Valley and two more pieces of information: a letter that Offusius wrote in 1553 to the Elizabethan mathematician and spiritualist John Dee, in which he signed his name as J. F. van Offhuysen, and a reference to him as Johannes Franciscus Geldrensis by the Italian mathematician, astrologer, and medical doctor Girolamo Cardano. Geldrensis was Offusius' toponymn, that is, his geographic name, meaning that he came from the town of Geldern.† Today the town of Geldern sits near the Rhine just across the Dutch border in Germany. Nearby, on the Rhine itself, is Wesel, whence the toponymn Vesalius. And not far upstream is Ober-hausen (or Overhausen, as it is spelled on the map of Westphalia in Ger-ardus Mercator's atlas of 1568), which conceivably relates to the dialect family name Offhuysen or Offusius. Dobrzycki had come back again in the summer of 1993 to work with me on the census, and there was great glee on his countenance when he held the National Geographic Atlas in his hands and convinced me that Vesalius and Offusius had to be one and the same. The Master of the 1550 Radices was surely Jofrancus Offusius.
We easily learned that Offusius had published one book in his lifetime, Ephemerides for 1557.1 was a little proud of myself for having judged correctly the significance of those radices, for he surely added those base positions for 1550 to the tables of his De revolutionibus to simplify his calculation of the ephemerides. In our sleuthing we also discovered that Offusius had spent 1552 in England, with John Dee as his patron. Much later, in 1570, Offusius' widow issued a posthumous astrological publication by her late husband, De divina astrorum facultate (On the Prophetic Power of the Stars). This latter volume greatly annoyed the aging, crotchety Dee, who cried plagiarism for some of his astrological aphorisms, but modern commentators have given Offusius the benefit of the doubt.
One final but important point still had to be sorted out. Was the original Offusius copy of De revolutionibus extant? As the evidence began to point ever more strongly to Offusius as the perpetrator, I argued that the copy now in Debrecen, Hungary, was the likeliest candidate. This copy had an interesting pedigree, having been owned by the Hungarian humanist Johannes Sambucus, who had made a book-buying trip to Paris in 1559 and another in 1561—62. Since this is around the time when Offusius mysteriously disappeared from the Parisian scene (as mysteriously as he had suddenly emerged there several years earlier), the book could have been sold from his estate around that time. Besides, the marginalia had the kind of cross-outs that might be expected from the annotator himself.
All the other seven copies of the Master of the 1550 Radices series were demonstrably derivative, except for the one at the National Library of Scotland. How the Edinburgh copy got there isn't known. But what distinguished it from all the others was the presence of about fifty pages of astronomical notes bound at the end of the volume. These notes were in the same hand as the annotations in the margins, and by their nature they were clearly holographs—that is, written in the hand of the author himself. Recognizing that they were, in fact, Offusius' originals was not like a bolt from the blue, a sudden denouement when the detective assembles all the suspects and announces the inescapable line of logic that led to the inevitable solution. This conclusion was gradual, increasingly convincing, but ultimately irresistible, and very, very satisfying. For years the unresolved issue—who was the mysterious annotator of this major cluster of copies?—had stood as an obstacle in the path of publication of the Copernican census. Many misleading clues and false pathways had prolonged the research, but at last a definitive solution was in hand. The Edinburgh copy, not the one in Debrecen, had to be Jofrancus Offusius' original working text.
Owen Gingerich reading microfilms with Jerzy Dobrzycki, in Gingerich's Harvard-Smithsonian office in 1979.
WITH THE mysterious annotator unmasked, Dobrzycki and I sat back and considered whether we had merely solved another New York Times Sunday crossword puzzle, or if we had really learned anything interesting about Renaissance astronomy.
One fascinating insight from the Offusius case came from the opportunity to see his reaction to the heliocentric cosmology, as documented in the astronomical notes at the end of his copy of Copernicus' book, now in Edinburgh. There he cautiously praised Copernicus' accomplishment and criticized the timid instrumentalist position of the anonymous advice to the reader (Ad lectorem) that had been surreptitiously added by Andreas Osiander, but Offusius stopped short of a thorough endorsement of heliocentrism. Such matters, "when the arguments from geometry and physics are inadequate," must finally be settled by the Bible, he declared (as Osiander had demanded), and he went on to cite a series of Old Testament texts in favor of a fixed Earth. There was Psalm 19, "He set the tabernacle for the Sun, which is as a bridegroom coming out of his chamber, and rejoiceth as a strong man to run a race. His going forth is from the end of the heaven, and his circuit unto the ends of it," and Psalm 93, "Thou hast fixed the Earth immovable and firm, thy throne firm from of old," and the beginning of Ecclesiastes, "But the Earth abideth forever. The Sun also ariseth, and the Sun goes down, and hastens to his place where he arose."
In sixteenth-century Europe the Bible had a unique status among books. It was universally accepted that the Bible had literally been dictated by God. Though Offusius was to some extent open-minded about the Copernican cosmology, in the end he fell back on the Bible, which makes all the more remarkable the positions of Copernicus and Kepler and Galileo, each of whom was deeply religious.
BEFORE WE zeroed in on Offusius and his group, no one had any notion about a serious technical study of Copernicus' book in Paris in the sixteenth century, or for that matter, in any primarily Catholic setting. Yet here was an astrologer and mathematical astronomer, not a professor at the university but nevertheless with his own atelier of students eagerly copying out his insights into Copernicus' text. Curiously enough, none of Offusius' copyists had discovered that their master stumbled in his long critique on folio 127. He erred in his recalculation of the initial position of the Sun and Moon. But it was, after all, the most complex spot in Copernicus' entire book, a passage dealing with the parallax of the Moon, that is, the change in the Moon's position because it is relatively close to the Earth. And it would not be the first time in history that students had swallowed a lecture hook, line, and sinker without scrutinizing their teacher's claims. Despite his starting errors, however, Offusius did manage to calculate some of the later numbers slightly more accurately than Copernicus had done.
The astronomer who eventually discovered that Offusius' criticism was wrong turned out to be none other than Paul Wittich. Tracing the tenuous connection from Offusius to Wittich is a curious but informative story in itself. In the back of the Beinecke Library copy of De revolutionibus at Yale, a note describes Wittich passing on to Hagecius a terse list of three errors in Copernicus' text. These three errors exactly match three errors noted in some detail in the margins of Offusius' own De revolutionibus. Wittich must therefore have seen that copy (or possibly the one now in Debrecen, the only other one to note all three supposed errors), but he himself did not transcribe the long critique of folio 127 into any of his own four copies of the book. Nevertheless, on folio 127 in his copy (now in the Vatican Library) he made a careful analysis of Offusius' starting claim and showed it wanting, and he also cited the other two rather trivial errors in its margins, adding secundum Jofrantium (according to Jofrancus)."*
Finding this convoluted connection to Wittich was totally unexpected fallout from the Offusius case, a stunning confirmation of the "invisible college," that network of sixteenth-century astronomical communications outside formal university instruction. The invisible college comprised tutorial and mentor relationships that transcended institutional boundaries. The evidence for such connections is of course now made visible by scholarly sleuthing, but those sociological structures were neither formally codified nor rooted in the universities.
While the Offusius linkages present some of the best evidence for this communication network, it is by no means unique. Another example is a De revolutionibus I found in the Ossolineum in Wroclaw, Poland. This second edition contains annotations from two different traditions, from Michael Maestlin in Tubingen and from Paul Wittich somewhere in Central Europe (or from the copy of Wittich's notes made by the Scot John Craig). Like all too many of the copies, it doesn't record who made the annotations or where the copying took place; nevertheless, the notes show that, despite the challenges of travel and communications, somehow the messages made the rounds.
WHILE THE identification of Jofrancus Offusius as the Master of the 1550 Radices cleared up a major mystery relating to the copies of De revolutionibus that I had examined, there remained a serious puzzlement. Copernicus' only disciple, Georg Joachim Rheticus, who had persuaded the aging Polish cosmologist to authorize the publication of his book, was surely a member of the invisible college, inspiring students and communicating with his contemporaries, yet where was any trace of a family of annotations stemming from his own copy of De revolutionibus?
Although Rheticus had been appointed both professor and dean when he returned to Wittenberg after his Polish sojourn, he taught there only briefly before he headed south to Nuremberg with the manuscript of De revolutionibus. Perhaps he was still not entirely comfortable at Wittenberg. But his influential friend Philipp Melanchthon busily pulled strings on his behalf. Joachim Camerarius, a distinguished humanist and Greek scholar, was in the process of transferring from Tubingen to become the leading professor at Leipzig. Rheticus must have impressed Camerarius several years earlier when he visited Tubingen before setting out to see Copernicus in Frauenburg. By then a particularly well-informed astronomer, Rheticus soon received an offer to become the number two professor in Leipzig, and at a particularly tempting salary, 140 florins per annum. (The standard rate was 100 florins.) So Rheticus took the manuscript to Nuremberg in the spring of 1542, got the printing started, and then in the fall left for Leipzig. Camerarius had made something of a cottage industry of writing Greek prefatory poems, and Rheticus asked him to compose an appropriate Greek poem to introduce Copernicus' book.
In April 1543 Rheticus received his first complete copies of De revolutionibus. He must have been shocked. Not only was Camerarius' poem omitted, but there was no acknowledgment of his own role in publishing the book. Instead, the book opened with Osiander's anonymous apologia, the infamous Ad lectorem.
Rheticus was incensed. With a red crayon he struck out the unexpected Ad lectorem. Then he asked Camerarius to pen onto the flyleaf the Greek poem he had composed for the book. The iambic pentameters carried a Platonic dialogue between a philosopher and a stranger, who was ultimately advised not to criticize as the ignorant might do, but to study and then try to do better. Finally, he signed the book as a gift to Andreas Aurifaber, then the dean at Wittenberg. Taking another copy, Rheticus again applied the red-crayon deletion. Without the poem, he inscribed it for George Donner, a canon at the cathedral in Frauenburg (plate 7d). Another similar copy he dedicated to Tiedemann Giese, Copernicus' best friend and the bishop of Chelmno; in fact, he sent two copies to Giese. Camerarius penned his Greek poem into another copy. Was it his own copy, or was it one that Rheticus decided to keep for himself? Three of these copies survive today, and another is attested in the historical record, though it has vanished. Yet none of them could qualify as Rheticus' working copy, one to compare with the magnificent, thoroughly marked-up copy from Reinhold preserved at the Royal Observatory, Edinburgh.
Copernicus himself did not see a completed book for another month after Rheticus received his copies, on account of the extra transit time required to send it to his far-off outpost in northern Poland. The final pages to be sent were of course the unnumbered opening pages, the so-called front matter. Copernicus had by then suffered a stroke and was partially paralyzed. Perhaps he, too, was distressed by the anonymous introduction that Osiander had added. Or, more likely, he might simply have been holding out against the dark angel of death until he could at last see his work completed, and thus satisfied, he died.
Tiedemann Giese described the end in a heartfelt letter to Rheticus. He apologized for the lack of recognition for Rheticus, saying that in the final days Copernicus was forgetful, and he urged Rheticus to demand that the front matter be reprinted without the Osiander piece. Nothing came of his suggestion.
Rheticus carried on as both the astronomy and the mathematics professor at Leipzig. His reputation was such that some of his students from Wittenberg transferred to Leipzig. But once again his wanderlust caught hold of him, and he yearned to visit Italy—perhaps remembering what Copernicus had told him of his own graduate student days there. So in the summer semester of 1545 Rheticus took a leave and journeyed south. And once again what presumably started as a brief trip took on a life of its own, and for nearly three years he was absent.
Among the people he visited was the Italian mathematician Girolamo Cardano. In 1545 Cardano had published with Petreius in Nuremberg the greatest mathematical text of the sixteenth century, his major work, Ars magna, wherein he had praised Andreas Osiander for his skill as a proofreader. "He not only knows Latin and Greek," Cardano wrote, "but even mathematics." No doubt Rheticus and Cardano discussed Copernicus during their visit, but could that conversation have led to the aphorism that Cardano included in his Aphorismata astronomica that he published with Petreius in 1547? There, under aphorism 69, he wrote, "Indeed, the opinions of Copernicus are not yet well understood, for he barely seems to say what he wants."
Returning from Milan, Rheticus visited Lindau, where he lay seriously ill for five months, then Constance, Zurich, and Basel. Finally, after three years, he was back lecturing again in Leipzig. Did he teach any of his students about the new cosmology? Presumably he continued to be familiar with the technical details, because in 1550 he published an ephemeris for 1551 based onDe revolutionibus. In the previous year he edited an edition of the first six books of Euclid's geometry. This time was the high-water mark for Rheticus' professorial career.
Then, in the spring of 1551, Rheticus' world came crashing down. He had fallen deeply in debt, to the tune of twice his annual salary, and soon in scandal. There were dark rumors of a drunken homosexual episode involving a student half his age. The irate father of the young man involved brought a lawsuit. In disgrace, Rheticus fled from Leipzig.
Rheticus moved eastward, first to Prague, where he took up the study of medicine (just as his mentor, Copernicus, had done), then to the University of Vienna, and finally to yet another university city, Cracow, which became his residence for nearly twenty years until the last year of his life, when he moved to Hungary. He took with him his work on a massive trigonometric table, sines and cosines to ten decimal places, an accuracy unsurpassed until the modern computer age. The project lagged as his interest in medicine grew, a career shift of a number of upwardly mobile professors. Ever the rebel, he took up the new medicine advocated by Theophrastus von Paracelsus (using chemical drugs rather than the traditional herbs), the radical medical equivalent of heliocentrism.
Only toward the end of his life, especially with the arrival of a young collaborator, Valentin Otto, in 1573, did his enthusiasm for the calculations revive. Rheticus was moved by the obvious parallel: Just as Rheticus, as an eager young researcher, had worked with and encouraged the elderly Copernicus to publish De revolutionibus, so, too, did the young Otto play midwife to Rheticus' Opus Palatinum, the ten-place table of sines, cosines, and secants.
Clearly, the destiny of Rheticus' personal copy of De revolutionibus was one of the mysteries of the entire Copernicus chase. Even if his own working copy didn't survive, surely some students would have made copies.
Though Rheticus served as dean and professor in Wittenberg only for one semester, his students included seven men who later became mathematics professors either at Wittenberg or elsewhere in the Lutheran university system. Copies of De revolutionibus from four of them survive, and for a fifth we have evidence of the annotations in his book. None of these show evidence of a standard pattern of annotations that could have been copied from Rheticus. Making an ephemeris from Copernicus' work, as Rheticus did in 1550, was not a particularly easy task, because some of the essential numbers were well buried in the text. Highlighting these numbers seems like an obvious teaching aid, and while the copies from Jofrancus Offusius' students show precisely this kind of marginal additions, for example, no copy attests to such activity on Rheticus' part.
This is where the matter stood until 1998, almost three decades into my census research. Then, unexpectedly, a rather interesting second-edition De revolutionibus appeared in London. Paul Quarrie, who was aware of my investigations ever since I had turned up at Eton to inspect its two first editions while he was librarian there, had in the meantime become Sotheby's rare book expert. He alerted me to the volume, which had been consigned to Sotheby's, and when I inspected it, I was able to point to a special feature of that copy. When Petreius finished printing the book proper, he immediately printed an errata leaf with the errors on the first 280 pages of the 400-page book. There is a logical explanation why Petreius printed only the first part of the errata. I am guessing that when the last pages went through the press, the corrections for the final part hadn't yet been returned from Copernicus, so on the errata leaf he printed what he had and that was that. Later the remaining corrections came to hand but were never printed, although a few insiders in Wittenberg got access to them. In the course of compiling the census I had found seven copies in which the errors were hand-corrected all the way to the end of the book, not just on the first 280 pages given on the printed errata leaf. The De revolutionibus at Sotheby's was an eighth copy with the errata marked all the way to the end.
Paul Quarrie carefully described the book in the auction catalog. He mentioned a characteristic comment on folio 96 that I had recorded in several of the other copies. This was a rather interesting marginalium alongside the place where Copernicus raised the question whether it was the Sun that was the center of the universe or the center of the Earth's orbit, the place in the text that Kepler and Maestlin must have specifically discussed.
I coveted the copy coming up in the auction, but I didn't have the cash to back up a winning bid. It went to a French collector who wasn't particularly interested in annotations, so by and by I offered him my own copy of the second edition plus a cash premium in order to make an exchange. We rendezvoused at a modest French restaurant near Place Den-fert Rochereau in Paris, had a pleasant conversation about book collecting, and consummated the swap. I carried my acquisition over to the nearby Observatoire de Paris and showed it to Alain Segonds, a colleague who had been unusually helpful with the census. Then I took a closer look at the annotation on folio 96, and I was stunned.
An annotation copied from Rheticus' original note, possibly by his assistant Valentin Otto, author's collection.
In my previous inspection of the book and in glancing at the transcription in the Sotheby's auction catalog, I had simply assumed that the annotation matched several in the other, related copies. What I hadn't noticed was that the annotation was in the first person. It read, "We touched on this in our Narratio but my teacher skipped over it," and the note was specifically attributed to Georg Joachim Rheticus. It was not in Rheticus' hand, but it was surely a verbatim copy from Rheticus' own De revolutionibus. I hadn't found Rheticus' own book, but here was a transcription of his sparse notes and his list of corrections, including a few not found in the other copies with the extended errata list. The second edition had been published in 1566, and several years later Valentin Otto had gone to Hungary to work with Rheticus, so quite possibly what I now have is a copy Otto made at that time. Alas, Rheticus' annotations, at least those transcribed into my copy, scarcely offer intriguing insights, at least not the way Maestlin's or Kepler's marginalia do. Rheticus clearly understood the astronomy at a deep level, but it seems he lost interest in following up on the technical details, and the copy of his annotations shows that only too vividly.
Did Rheticus dust off his interest in heliocentric astronomy when his young visitor arrived? Who can guess what stories the sixty-year-old Joachim told the thirty-year-old Valentin about his own apprenticeship a quarter century earlier with the master cosmologist? In those bygone days Copernicus and Rheticus must have discussed astronomy, medicine, student days in Italy—and possibly even astrology.
* Whether any of the other copies included these three errors was hard ro know, since I didn't have microfilms of all of rhem, and in the first instance of examining the books these errors would have escaped notice as being so seemingly innocuous. As in most good mystery stories, minor details assume great importance only in rerrospect. It turned out that a copy in Edinburgh also had these errors marked—even more thoroughly than the copy in Debrecen.
* Johannes Franciscus is simply a longer form of Jofrancus.
† The use of a geographic identifier was very popular in sixteenth-century central Europe, and nearly all the srudents matricularing at Wittenberg or Leipzig signed in with one.
* The note in the Yale copy connecting Hagecius and Wittich is in the hand of Johannes Praetorius, who in 1576 had become professor of mathemarics at Altdorf, a town just east of Nuremberg. In some way he had gotten the information from Thaddeus Hagecius, a man with broad asrronomical interests and connections in the courtly circles of Prague. No De revolutionibus with a Hagecius provenance has turned up, but it is tempting to think that at some point he might have owned the Edinburgh copy with the Offusius notes and that he showed it to Wittich.