The Gradual Acceptance of the Copernican Theory of the Universe/Part 1/Chapter 2

by Dorothy Stimson

 

CHAPTER II.

Copernicus and His Times.

DURING these centuries, one notable scholar at least stood forth in open hostility to the slavish devotion to Aristotle's writings and with hearty appreciation for the greater scientific accuracy of "infidel philosophers among the Arabians, Hebrews and Greeks."^[1] In his Opus Tertium (1267), Roger Bacon also pointed out how inaccurate were the astronomical tables used by the Church, for in 1267, according to these tables "Christians will fast the whole week following the true Easter, and will eat flesh instead of fasting at Quadragesima for a week—which is absurd," and thus Christians are made foolish in the eyes of the heathen.^[2] Even the rustic, he added, can observe the phases of the moon occurring a week ahead of the date set by the calendar.^[3] Bacon's protests were unheeded, however, and the Church continued using the old tables which grew increasingly inaccurate with each year. Pope Sixtus IV sought to reform the calendar two centuries later with the aid of Regiomontanus, then the greatest astronomer in Europe (1475);^[4] the Lateran Council appealed to Copernicus for help (1514), but little could be done, as Copernicus replied, till the sun's and the moon's positions had been observed far more precisely;^[5] and the modern scientific calendar was not adopted until 1582 under Pope Gregory XIII.

What was the state of astronomy in the century of Copernicus's birth? Regiomontanus—to use Johann Müller's Latin name—his teacher Pürbach, and the great cardinal Nicolas of Cues were the leading astronomers of this fifteenth century. Pürbach^[6] (1432-1462) died before he had fulfilled the promise of his youth, leaving his Epitome of Ptolemy's Almagest to be completed by his greater pupil. In his Theorica Planetarum (1460) Pürbach sought to explain the motions of the planets by placing each planet between the walls of two curved surfaces with just sufficient space in which the planet could move. As M. Delambre remarked:^[7] "These walls might aid the understanding, but one must suppose them transparent; and even if they guided the planet as was their purpose, they hindered the movement of the comets. Therefore they had to be abandoned, and in our own modern physics they are absolutely superfluous; they have even been rather harmful, since they interfered with the slight irregularities caused by the force of attraction in planetary movements which observations have disclosed." This scheme gives some indication of the elaborate devices scholars evolved in order to cope with the increasing number of seeming irregularities observed in "the heavens," and perhaps it makes clearer why Copernicus was so dissatisfied with the astronomical hypothesis of his day, and longed for some simpler, more harmonious explanation.

Regiomontanus^[8] (1436-1476) after Pürbach's death, continued his work, and his astronomical tables (pub. 1475) were in general use throughout Europe till superseded by the vastly more accurate Copernican Tables a century later. It has been said^[9] that his fame inspired Copernicus (born three years before the other's death in 1476) to become as great an astronomer. M. Delambre hails him as the wisest astronomer Europe had yet produced^[10] and certainly his renown was approached only by that of the great Cardinal.

Both Janssen,^[11] the Catholic historian, and Father Hagen^[12] of the Vatican Observatory, together with many other Catholic writers, claim that a hundred years before Copernicus, Cardinal Nicolas Cusanus^[13] (c. 1400-1464) had the courage and independence to uphold the theory of the earth's motion and its rotation on its axis. As Father Hagen remarked: "Had Copernicus been aware of these assertions he would probably have been encouraged by them to publish his own monumental work." But the Cardinal stated these views of the earth's motions in a mystical, hypothetical way which seems to justify the marginal heading "Paradox" (in the edition of 1565).^[14] And unfortunately for these writers, the Jesuit father, Riccioli, the official spokesman of that order in the 17th century after Galileo's condemnation, speaking of this paradox, called attention, also, to a passage in one of the Cardinal's sermons as indicating that the latter had perhaps "forgotten himself" in the De Docta Ignorantia, or that this paradox "was repugnant to him, or that he had thought better of it."^[15] The passage he referred to is as follows: "Prayer is more powerful than all created things. Although angels, or some kind of beings, move the spheres, the Sun and the stars; prayer is more powerful than they are, since it impedes motion, as when the prayer of Joshua made the Sun stand still."^[16] This may explain why Copernicus apparently disregarded the Cardinal's paradox, for he made no reference to it in his book; and the statement itself, to judge by the absence of contemporary comment, aroused no interest at the time. But of late years, the Cardinal's position as stated in the De Docta Ignorantia has been repeatedly cited as an instance of the Church's friendly attitude toward scientific thought,^[17] to show that Galileo's condemnation was due chiefly to his "contumacy and disobedience."

Copernicus^[18] himself was born in Thorn on February 19, 1473,^[19] seven years after that Hansa town founded by the Teutonic Order in 1231 had come under the sway of the king of Poland by the Second Peace of Thorn.^[20] His father,^[21] Niklas Koppernigk, was a wholesale merchant of Cracow who had removed to Thorn before 1458, married Barbara Watzelrode of an old patrician Thorn family, and there had served as town councillor for nineteen years until his death in 1483.^[22] Thereupon his mother's brother, Lucas Watzelrode, later bishop of Ermeland, became his guardian, benefactor and close friend.^[23]

After the elementary training in the Thorn school,^[24] the lad entered the university at Cracow, his father's former home, where he studied under the faculty of arts from 1491-1494.^[25] Nowhere else north of the Alps at this time were mathematics and astronomy in better standing than at this university.^[26] Sixteen teachers taught these subjects there during the years of Copernicus's stay, but no record exists of his work under any of them.^[27] That he must have studied these two sciences there, however, is proved by Rheticus's remark in the Narratio Prima^[28] that Copernicus, after leaving Cracow, went to Bologna to work with Dominicus Maria di Novara "non tam discipulus quam adjutor." He left Cracow without receiving a degree,^[29] returned to Thorn in 1494 when he and his family decided he should enter the Church after first studying in Italy.^[30] Consequently he crossed the Alps in 1496 and was that winter matriculated at Bologna in the "German nation."^[31] The following summer he received word of his appointment to fill a vacancy among the canons of the cathedral chapter at Ermeland where his uncle had been bishop since 1489.^[32] He remained in Italy, however, about ten years altogether, studying civil law at Bologna, and canon law and medicine at Padua,^[33] yet receiving his degree as doctor of canon law from the university of Ferrara in 1503.^[34] He was also in Rome for several months during the Jubilee year, 1500.

At this period the professor of astronomy at Bologna was the famous teacher Dominicus Maria di Novara (1454-1504), a man "ingenio et animo liber" who dared to attack the immutability of the Ptolemiac system, since his own observations, especially of the Pole Star, differed by a degree and more from the traditional ones.^[35] He dared to criticise the long accepted system and to emphasize the Pythagorean notion of the underlying harmony and simplicity in nature^[36]; and from him Copernicus may have acquired these ideas, for whether they lived together or not in Bologna, they were closely associated. It was here, too, that Copernicus began his study of Greek which later was to be the means^[37] of encouraging him in his own theorizing by acquainting him with the ancients who had thought along similar lines.

In the spring of the year (1501) following his visit to Rome,^[38] Copernicus returned to the Chapter at Frauenburg to get further leave of absence to study medicine at the University of Padua.^[39] Whether he received a degree at Padua or not and how long he stayed there are uncertain points.^[40] He was back in Ermeland early in 1506.

His student days were ended. And now for many years he led a very active life, first as companion and assistant to his uncle the Bishop, with whom he stayed at Schloss Heilsberg till after the Bishop's death in 1512; then as one of the leading canons of the chapter at Frauenburg, where he lived most of the rest of his life.^[41] As the chapter representative for five years (at intervals) he had oversight of the spiritual and temporal affairs of two large districts in the care of the chapter.^[42] He went on various diplomatic and other missions to the King of Poland,^[43] to Duke Albrecht of the Teutonic Order,^[44] and to the councils of the German states.^[45] He wrote a paper of considerable weight upon the much needed reform of the Prussian currency.^[46] His skill as a physician was in demand not only in his immediate circle^[47] but in adjoining countries, Duke Albrecht once summoning him to Königsberg to attend one of his courtiers.^[48] He was a humanist as well as a Catholic Churchman, and though he did not approve of the Protestant Revolt, he favored reform and toleration.^[49] Gassendi claims that he was also a painter, at least in his student days, and that he painted portraits well received by his contemporaries.^[50] But his interest and skill in astronomy must have been recognized early in his life for in 1514 the committee of the Lateran Council in charge of the reform of the calendar summoned him to their aid.^[51]

He was no cloistered monk devoting all his time to the study of the heavens, but a cultivated man of affairs, of recognized ability in business and statesmanship, and a leader among his fellow canons. His mathematical and astronomical pursuits were the occupations of his somewhat rare leisure moments, except perhaps during the six years with his uncle in the comparative freedom of the bishop's castle, and during the last ten or twelve years of his life, after his request for a coadjutor had resulted in lightening his duties. In his masterwork De Revolutionibus^[52] there are recorded only 27 of his own astronomical observations, and these extend over the years from 1497 to 1529. The first was made at Bologna, the second at Rome in 1500, and seven of the others at Frauenburg, where the rest were also probably made. It is believed the greater part of the De Revolutionibus was written at Heilsburg^[53] where Copernicus was free from his chapter duties, for as he himself says^[54] in the Dedication to the Pope (dated 1543) his work had been formulated not merely nine years but for "more than three nines of years." It had not been neglected all this time, however, as the original MS. (now in the Prague Library) with its innumerable changes and corrections shows how continually he worked over it, altering and correcting the tables and verifying his statements.^[55]

Copernicus was a philosopher.^[56] He thought out a new explanation of the world machine with relatively little practical work of his own,^[57] though we know he controlled his results by the accumulated observations of the ages.^[58] His instruments were inadequate, inaccurate and out of date even in his time, for much better ones were then being made at Nürnberg^[59]; and the cloudy climate of Ermeland as well as his own active career prevented him from the long-continued, painstaking observing, which men like Tycho Brahe were to carry on later. Despite such handicaps, because of his dissatisfaction with the complexities and intricacies of the Ptolemaic system and because of his conviction that the laws of nature were simple and harmonious. Copernicus searched the writings of the classic philosophers, as he himself tells us,^[60] to see what other explanation of the universe had been suggested. "And I found first in Cicero that a certain Nicetas had thought the earth moved. Later in Plutarch I found certain others had been of the same opinion." He quoted the Greek referring to Philolaus the Pythagorean, Heraclides of Pontus, and Ecphantes the Pythagorean.^[61] As a result he began to consider the mobility of the earth and found that such an explanation seemingly solved many astronomical problems with a simplicity and a harmony utterly lacking in the old traditional scheme. Unaided by a telescope, he worked out in part the right theory of the universe and for the first time in history placed all the then known planets in their true positions with the sun at the center. He claimed that the earth turns on its axis as it travels around the sun, and careens slowly as it goes, thus by these three motions explaining many of the apparent movements of the sun and the planets. He retained,^[62] however, the immobile heaven of the fixed stars (though vastly farther off in order to account for the non-observance of any stellar parallax^[63]), the "perfect" and therefore circular orbits of the planets, certain of the old eccentrics, and 34 new epicycles in place of all the old ones which he had cast aside.^[64] He accepted the false notion of trepidation enunciated by the Arabs in the 9th century and later overthrown by Tycho Brahe.^[65] His calculations were weak.^[66] But his great book is a sane and modern work in an age of astrology and superstition.^[67] His theory is a triumph of reason and imagination and with its almost complete independence of authority is perhaps as original a work as an human being may be expected to produce.

Copernicus was extremely reluctant to publish his book because of the misunderstandings and malicious attacks it would unquestionably arouse.^[68] Possibly, too, he was thinking of the hostility already existing between himself and his Bishop, Dantiscus,^[69] whim he did not wish to antagonize further. But his devoted pupil and friend, Rheticus, aided by Tiedeman Giese, Bishop of Culm and a lifelong friend, at length (1542) persuaded him.^[70] So he entrusted the matter to Giese who passed it on to Rheticus, then connected with the University at Wittenberg as professor of mathematics.^[71] Rheticus, securing leave of absence from Melancthon his superior, went to Nürnberg to supervise the printing.^[72] This was done by Petrejus. Upon his return to Wittenberg, Rheticus left in charge Johann Schöner, a famous mathematician and astronomer, and Andreas Osiander, a Lutheran preacher interested in astronomy. The printed book^[73] was placed in Copernicus's hands at Frauenburg on May 24th, 1543, as he lay dying of paralysis.^[74]

Copernicus passed away that day in ignorance that his life's work appeared before the world not as a truth but as an hypothesis; for there had been inserted an anonymous preface "ad lectorem de hypothesibus huius opera" stating this was but another hypothesis for the greater convenience of astronomers.^[75] "Neque enim necesse est eas hypotheses esse veras, imo ne verisimiles quidem, sed sufficit hoc unum, si calculum observationibus congruentem exhibeant."^[76]—For years Copernicus was thought to have written this preface to disarm criticism. Kepler sixty years later (1601) called attention to this error,^[77] and quoted Osiander's letters to Copernicus and to Rheticus of May, 1541, suggesting that the system be called an hypothesis to avert attacks by theologians and Aristotelians. He claimed that Osiander had written the preface; but Kepler's article never was finished and remained unpublished till 1858.^[78] Giese and Rheticus of course knew that the preface falsified Copernicus's work, and Giese, highly indignant at the "impiety" of the printer (who he thought had written it to save himself from blame) wrote Rheticus urging him to write another "præfatiunculus" purging the book of this falsehood.^[79] This letter is dated July 26, 1543, and the book had appeared in April. Apparently nothing was done and the preface was accepted without further challenge.

It remains to ask whether people other than Copernicus's intimates had known of his theory before 1543. Peucer, Melancthon's nephew, declared Copernicus was famous by 1525,^[80] and the invitation from the Lateran Council committee indicates his renown as early as 1514. In Vienna in 1873^[81] there was found a Commentariolus, or summary of his great work,^[82] written by Copernicus for the scholars friendly to him. It was probably written soon after 1530, and gives a full statement of his views following a series of seven axioms or theses summing up the new theory. This little book probably occasioned the order from Pope Clement VII in 1533 to Widmanstadt to report to him on the new scheme.^[83] This Widmanstadt did in the papal gardens before the Pope with several of the cardinals and bishops, and was presented with a book as his reward.

In 1536, the Cardinal Bishop of Capua, Nicolas con Schönberg, apparently with the intent to pave the way for the theory at Rome, wrote for a report of it.^[84] It is not known whether the report was sent, and the cardinal died the following year. But that Copernicus was pleased by this recognition is evident from the prominence he gave to the cardinal's letter, as he printed it in his book at the beginning, even before the dedication to the Pope.

The most widely circulated account at this time, however, was the Narratio Prima, a letter from Georg Joachim of Rhaetia (better known as Rheticus), written in October, 1539, from Frauenburg to Johann Schöner at Nürnberg.^[85] Rheticus,^[86] at twenty-five years of age professor of mathematics at Wittenberg, had gone uninvited to Frauenburg early that summer to visit Copernicus and learn for himself more in detail about this new system. This was rather a daring undertaking, for not only were Luther and Melancthon outspoken in their condemnation of Copernicus, but Rheticus was going from Wittenberg, the headquarters of the Lutheran heresy, into the bishopric of Ermeland where to the Bishop and the King his overlord, the very name of Luther was anathema. Nothing daunted, Rheticus departed for Frauenberg and could not speak too highly of the cordial welcome he received from the old astronomer. He came for a few weeks, and remained two years to return to Wittenberg as an avowed believer in the system and its first teacher and promulgator. Not only did he write the Narratio Prima and an Encomium Borussæ, both extolling Copernicus, but what is more important, he succeeded in persuading him to allow the publication of the De Revolutionibus. Rheticus returned to his post in 1541, to resign it the next year and become Dean of the Faculty of Arts. In all probability the conflict was too intense between his new scientific beliefs and the statements required of him as professor of the old mathematics and astronomy.

His colleague, Erasmus Reinhold, continued to teach astronomy there, though he, too, accepted the Copernican system.^[87] He published a series of tables (Tabulæ Prutenicæ, 1551) based on the Copernican calculations to supersede the inaccurate ones by Regiomontanus; and these were in general use throughout Europe for the next seventy-odd years. As he himself declared, the series was based in its principles and fundamentals upon the observations of the famous Nicolaus Copernicus. The almanacs deduced from these calculations probably did more to bring the new system into general recognition and gradual acceptance than did the theoretical works.^[88]

Opposition to the theory had not yet gathered serious headway. There is record^[89] of a play poking fun at the system and its originator, written by the Elbing schoolmaster (a Dutch refugee from the Inquisition) and given in 1531 by the villagers at Elbing (3 miles from Frauenburg). Elbing and Ermeland were hostile to each other, Copernicus was well known in Elbing though probably from afar, for there seems to have been almost no personal intercourse between canons and people, and the spread of Luther's teachings had intensified the hostility of the villagers towards the Church and its representatives. But not until Giordano Bruno made the Copernican system the starting-point of his philosophy was the Roman Catholic Church seriously aroused to combat it. Possibly Osiander's preface turned opposition aside, and certainly the non-acceptance of the system as a whole by Tycho Brahe, the leading astronomer of Europe at that time, made people slow to consider it.

1. Roger Bacon: Opus Tertium, 295, 30-31.
2. Ibid: 289.
3. Ibid: 282.
4. Delambre: Moyen Age, 365.
5. Prowe: II, 67-70.
6. Delambre: Moyen Age, 262-272.
7. Delambre: Moyen Age, 272.
8. It has been claimed that Regimontanus knew of the earth's motion around the sun a hundred years before Copernicus; but a German writer has definitely disproved this claim by tracing it to its source in Schöner's Opusculum Geographicum (1553) which states only that he believed in the earth's axial rotation. Ziegler: 62.
9. Ibid: 62.
10. Delambre: Op. cit.; 365.
11. Janssen: Hist. of Ger., I, 5.
12. Cath. Ency.: "Cusanus."
13. From Cues near Treves.
14. Cusanus: De Docta Ignorantia, Bk. II, c. 11-12: "Centrum igitur mundi, coincideret cum circumferentiam, nam si centrum haberet et circumferentiam, et sic intra se haberet suum initium et finem et esset ad aliquid aliud ipse mundus terminatus, et extra mundum esset aluid et locus, quæ omnia veritate carent. Cum igitur non sit possibile, mundum claudi intra centrum corporale et circumferentiam, non intelligitur mundus, cuius centrum et circumferentia sunt Deus: et cum hic non sit mundus infinitus, tamen non potest concipi finitus, cum terminis careat, intra quos claudatur. Terra igitur, quae centrum esse nequit, motu omni carere non potest, nam eam moveri taliter etiam necesse est, quod per infinitum minus moveri posset. Sicut igitur terra non est centram mundi.… Unde licet terra quasi stella sit, propinquior polo centrali, tamen movetur, et non describit minimum circulum in motu, ut est ostensum.… Terrae igitur figura est mobilis et sphærica et eius motus circularis, sed perfectior esse posset. Et quia maximum in perfectionibus motibus, et figuris in mundo non est, ut ex iam dictis patent: tunc non est verum quod terra ista sit vilissima et infima, nam quamvis videatur centralior, quo'ad mundum, est tamen etiam, eadem ratione polo propinquior, ut est dictum." (pp. 38-39).
15. Riccioli: Alm. Nov., II, 292.
16. Cusanus: Opera, 549: Excitationum, Lib. VII, ex sermone: Debitores sumus: "Est enim oratio, omnibus creaturis potentior. Nam angeli seu intelligentiæ, movent orbes, Solem et Stellas: sed oratio potentior, quia impedit motum, sicut oratio Josuae, fecit sistere Solem."
17. Di Bruno. 284, 286a; Walsh: An Early Allusion, 2-3.
18. Nicolaus Coppernicus (Berlin, 1883-4; 3 vol.; Pt. I, Biography, Pt. II, Sources), by Dr. Leopold Prowe gives an exhaustive account of all the known details in regard to Copernicus collected from earlier biographers and tested most painstakingly by the documentary evidence Dr. Prowe and his fellow-workers unearthed during a lifetime devoted to this subject. (Allgemeine Deutsche Biographie.) The manuscript authority Dr. Prowe cites (Prowe: I, 19-27 and foot-notes), requires the double p in Copernicus's name, as Copernicus himself invariably used the two p's in the Latinized form Coppernic without the termination us, and usually when this termination was added. Also official records and the letters from his friends usually give the double p; though the name is found in many variants—Koppernig, Copperinck, etc. His signatures in his books, his name in the letter he published in 1509, and the Latin form of it used by his friends all bear testimony to his use of the double p. But custom has for so many centuries sanctioned the simpler spelling, that it seems unwise not to conform in this instance to the time-honored usage.
19. Prowe: I, 85.
20. Ency. Brit.: "Thorn."
21. Prowe: I, 47-53.
22. These facts would seem to justify the Poles today in claiming Copernicus as their fellow-countryman by right of his father's nationality and that of his native city. Dr. Prowe, however, claims him as a "Prussian" both because of his long residence in the Prussian-Polish bishopric of Ermeland, and because of Copernicus's own reference to Prussia as "unser lieber Vaterland." (Prowe: II, 197.)
23. Prowe: I, 73-82.
24. Ibid: I, 111.
25. Ibid: I, 124-129.
26. Ibid: I, 137.
27. Ibid: I, 141-143.
28. Rheticus: Narratio Prima, 448 (Thorn edit.).
29. Prowe: 1, 154.
30. Ibid: I, 169.
31. Ibid: I, 174.
32. Ibid: I, 175. This insured him an annual income which amounted to a sum equalling about $2250 today. Later he received a sinecure appointment besides at Breslau. (Holden in Pop. Sci., 111.)
33. Prowe: I, 224.
34. Ibid: I, 308.
35. Ibid: I, 240 and note. Little is known about him today, except that he was primarily an observer, and was highly esteemed by his immediate successors; see Gilbert: De Magnete.
36. Clerke in Ency. Brit., "Novara."
37. Prowe: I, 249.
38. Prowe: I, 279.
39. Ibid, 294.
40. Ibid: I, 319.
41. Prowe: I, 335-380.
42. Ibid: II, 75-110, 116, 124.
43. Ibid: II, 204-8.
44. Ibid: II, 110.
45. Ibid: II, 144.
46. Ibid: II, 146.
47. Ibid: II, 293-319.
48. Ibid: II, 464-472.
49. Ibid: II, 170-187.
50. Holden in Pop. Sci., 109.
51. Prowe: II, 67-70.
52. Copernicus: De Revolutionibus, Thorn edit, 444. The last two words of the full title: De Revolutionibus Orbium Coelestium are not on the original MS. and are believed to have been added by Osiander. Prowe: II, 541, note.
53. Ibid: II, 490-1.
54. Copernicus: Dedication, 4. (Thorn edit.)
55. Prowe: II, 503-508.
56. Ibid: II, 64.
57. Ibid: II, 58-9.
58. Rheticus: Narratio Prima.
59. Prowe: II, 56.
60. Copernicus: Dedication, 5-6. See Appendix B.
61. For a translation of this dedication in full, see Appendix B. In the original MS. occurs a reference (struck out) to Aristarchus of Samos as holding the theory of the earth's motion. (Prowe: II, 507, note.) The finding of this passage proves that Copernicus had at least heard of Aristarchus, but his apparent indifference is the more strange since an account of his teaching occurs in the same book of Plutarch from which Copernicus learned about Philolaus. But the chief source of our knowledge about Aristarchus is through Archimedes, and the editio princeps of his works did not appear till 1544, a year after the death of Copernicus. C. R. Eastman in Pop. Sci. 68:325.
62. Delambre: Astr. Mod. pp. xi-xii.
63. As the earth moves, the position in the heavens of a fixed star seen from the earth should differ slightly from its position observed six months later when the earth is on the opposite side of its orbit. The distance to the fixed stars is so vast, however, that this final proof of the earth's motion was not attained till 1838 when Bessel (1784-1846) observed stellar parallax from Königsberg. Berry: 123-24.
64. Commentariolus in Prowe: III, 202.
65. Holden in Pop. Sci., 117.
66. Delambre: Astr. Mod., p. xi.
67. Snyder: 165.
68. Copernicus: Dedication, 3.
69. Prowe: II, 362-7.
70. Ibid: II, 406.
71. Ibid: II, 501.
72. Ibid: II, 517-20.
73. Four other editions have since appeared; at Basel, 1566, Amsterdam 1617, Warsaw 1847, and Thorn 1873. For further details, see Prowe: II, 543-7, and Thorn edition pp. xii-xx. The edition cited in this study is the Thorn one of 1873.
74. Prowe: II, 553-4.
75. Copernicus: De Revolutionibus, I. "To the reader on the hypotheses of this book."
76. "For it is not necessary that these hypotheses be true, nor even probable, but this alone is sufficient, if they show reasoning fitting the observations."
77. Kepler: Apologia Tychonis contra Ursum in Op. Om.: I, 244-246.
78. Prowe: II, 251, note.
79. Ibid: II, 537-9.
80. Ibid: II, 273.
81. Ibid: II, 286-7.
82. A second copy was found at Upsala shortly afterwards, though for centuries its existence was unknown save for two slight references to such a book, one by Gemma Frisius, the other by Tycho Brahe. Prowe: II, 284.
83. Ibid: II, 273-4.
84. Prowe: II, 274, note.
85. Prowe: II, 426-440.
86. Ibid: II, 387-405.
87. Ibid: II, 391.
88. Holden in Pop. Sci., 119.
89. Prowe: II, 233-244.