Tycho Brahe: a picture of scientific life and work in the sixteenth century/Chapter 11
TYCHO BRAHE IN BOHEMIA—HIS DEATH.
The German Emperor, Rudolph the Second, whose service Tycho Brahe was now about to enter, was a man deeply interested in science and art, personally of a most amiable disposition, but most singularly unfit for the exalted and difficult position he had to fill. Totally devoid of energy and taking no interest in political matters, he let public affairs drift in whatever direction they liked, ignorant or careless of the fact that his apathy was hastening the catastrophe which a few years after his death plunged Central Europe into the war which turned Germany into a desert and almost annihilated the Imperial power. The times were certainly most serious, and the difficulty of settling the religious question almost overwhelming, but a monarch of spirit and determination might have done much to counteract the intrigues of the Spanish and Jesuitical party, who blindly pursued their narrow-minded policy, and finally brought on the Thirty Years' War. But, regardless of the duties imposed on him by his station, the Emperor reluctantly devoted a moment to business of any kind, while he willingly gave his time and the limited pecuniary means of his impoverished dominions to collecting art treasures and promoting science—the real science represented by Tycho and Kepler, as well as the imaginary ones taught by the disciples of Cornelius Agrippa and Cardanus. Prague, where he usually resided, was not a very favourable place for the growth of science and art, as Bohemia had never settled down since the Hussite disturbances. The Germans and the Czechs were sharply separated by race and language; Catholics were opposed to Lutherans, Moravians, and Utraquists, the last-mentioned differing from the Catholics only by partaking both of bread and wine in the Eucharist. But notwithstanding this state of things and the miserable condition of the University, Rudolph succeeded in bringing together a number of men of culture in Prague, and for a short time he made the city one of the centres of civilisation—a distinction which was unfortunately destined to be but very short-lived. Long before his death, the Emperor's mind had been so persistently influenced by the intrigues of the Spanish party, that he had no feeling but distrust and suspicion for his surroundings, and scarcely felt relieved from the burden of government in the circle of his scientific friends. But while Tycho Brahe lived, Rudolph was still comparatively free from political anxiety, and ready to do his utmost to befriend the distinguished foreigner who had sought shelter under his roof.
When Tycho arrived at Prague in June 1599, the Emperor sent the Secretary Barvitz to conduct him to the house of the late Vice-Chancellor Curtz, where the widow was still residing. He had only a few instruments with him, as most of those he had brought away from Hveen were still at Magdeburg. He was shortly afterwards received in audience by the Emperor, who welcomed him to Prague, begged him to let his family come from Dresden, and con- versed with him for a long time in Latin. Tycho presented the Emperor with three volumes of his works, and was afterwards told by Barwitz that the Emperor often read in them till very late at night. As Tycho left it to the Emperor to fix the amount of his salary, it was settled that this was to be 3000 florins a year, in addition to some "uncertain income which might amount to some thousands." Tycho tells all this in a long letter to his old friend Vedel, which he wrote on the 18th September following, in which he adds that some councillors were against these arrangements, pointing out that there was nobody at court, not even among counts and barons of long service, who enjoyed so large an income; but as the Emperor insisted on it, and neither the Secretary of State, Rumph, nor the Chamberlain, Trautson, spoke against it, it was settled, and 2000 florins were at once paid to Tycho. The Emperor even ordered that the salary should date from the time when Tycho had been invited to Prague, as he had not accepted service else- where since then. The Emperor also of his own accord promised him an hereditary estate whenever one should fall to the Crown, in order that he and his family might feel secure. It was afterwards ordered that 2000 florins a year were to be paid to Tycho from the Treasury, and 1000from the estates of Benatky or Brandeis, both dating from the 1st May 1599.
In the meantime Tycho had unpacked the few instruments he had brought with him, which were examined with great interest by Corraduc, Hagecius, and other men of learning, as well as by the Emperor, who desired him to send for the remainder as soon as possible. Wishing to display the same taste and elegance in his arrangements as formerly at Uraniborg, Tycho had a pedestal made on which instruments might be placed, and the four sides of this pedestal were adorned with pictures of King Alphonso, with Ptolemy and Al Battani sitting below him; Charles the Fifth with Copernicus and Apianus; Rudolph the Second, and below him Tycho, seated at a table looking towards the Emperor; and lastly, Frederick the Second with Uraniborg. Under the last picture was an epigram by the Imperial poet-laureate.
In his as yet unsettled state Tycho was not able to commence observations with the vigour of former days, the only observation of any interest made at this time being one of the end of a small solar eclipse at sunrise on the 22nd July (new style, which Tycho used from henceforth). One of his pupils, Johannes from Hamburg, observed this eclipse with the little gilt quadrant, from the tower of a neighbouring college.
But Tycho did not wish to settle within the city of Prague. In his letters he states that he did not like that the widow of Curtius should leave her house for his sake, and he feared to be too much disturbed by visitors. Tradition speaks of his being annoyed by the constant ringing of bells at night in the neighbouring Capuchin monastery, but this may more probably refer to his stay in the city during the last year of his life, or it may never have happened; at any rate, it is not mentioned by Tycho himself. But he was accustomed to a country residence, with plenty of fresh air, and he probably longed to get away from the city, which was not very clean, if we may believe Fynes Moryson, who had visited it only seven years before Tycho's arrival, and who gives the following description of it:—"On the west side of Molda is the Emperour's castle, seated on a most high mountaine, in the fall whereof is the suburbe called Kleinseit or little side. From this suburbe to go into the city, a long stone bridge is to be passed over Molda, which runnes from the south to the north and diuides the suburbe from the city, to which as you goe, on the left side is a little city of Jewes, com- passed with wals, and before your eies towards the east is the city called new Prague, both which cities are compassed about with a third, called old Prague. So as Prague consists of three cities, all compassed with wals, yet is nothing less than strong, and except the stinch of the streetes driue backe the Turks or they meet them in open field, there is small hope in the fortifications thereof. The streets are filthy, there be diuers large market places, the building of some houses is of free stone, but the most part are of timber and clay, and are built with little beauty or art, the walles being all of whole trees as they come out of the wood, the which with the barke are laid so rudely as they may on both sides be seen."When the Emperor learned that Tycho Brahe wished to reside outside Prague, he gave him his choice between the three castles of Lyssa, Brandeis, and Benatky, "zur Exercirung seines Studii." Having seen them all, and having learned that Brandeis (which was situated rather low) was the Emperor's favourite hunting-lodge, Tycho selected Benatky on the River Iser (a tributary to the Elbe), about twenty-two miles north-east of Prague. The Castle of Benatky, which the Emperor had recently purchased from Count Dohnin, had been erected in 1522 in the place of an older castle which had been destroyed during the Hussite wars. It has since Tycho's time been considerably enlarged, so that the building inhabited by him now only forms the western wing. The present church tower is also a later addition. The castle is situated close to the town of Nové Benatky (in German, Neu Benatek) on the right bank of the Iser, on a hill raised about two hundred feet over the river. The castle commands a fine view of the vineyards and orchards on the hilly northern (right) bank and tilled fields and pasture-lands on the southern, which latter are not seldom flooded by the Iser, so that the inhabitants on such occasions are surrounded by a lake. This may account for the name of Venetiæ Bohemorum by which Benatky has frequently been called, though Tycho believes that the general beauty of the surroundings has also contributed to the use of this name. On the way to Benatky, Tycho sent from Brandeis a letter to Longomontanus at Kostock, dated the 20th August, in which he mentioned that the road was level, and that the journey took about six hours; an official from Brandeis was that day or the next to conduct him and his belongings to Benatky, where he expected to remain until he got the estate which the Emperor intended to confer on him in fief. As soon as Tycho arrived at Benatky he set about altering the building and constructing an observatory and a laboratory. As usual, he expressed his pleasure at having at last found a resting-place in various Latin poems, two of which were inscribed over the entrances to the observatory and the laboratory. The principal instruments were to be placed in separate rooms, as at Hveen, all connected with each other, and with the laboratory and residence, and a separate entrance was to be
In the meantime the family had arrived from Dresden, and as everything now appeared to promise Tycho that he had found a haven for the remainder of his days, he sent about the end of September his eldest son, together with a certain Claus Mule, to Denmark, to remove the four large instruments which were still at Hveen, and took this opportunity of sending a number of letters to his family and friends. Among these letters was one to Valkendorf, asking him to facilitate the transport of the instruments, one to his own brother, Axel, to the same purport, another to Longomontanus, and a very long one to his old friend Vedel. In this he gave a very full account of his doings since he left Hveen, which he asked Vedel to incorporate in his Danish history, so that it might be handed down to posterity, whether printed or not. Tycho's daughter Magdalene sent a letter to Glaus Mule's mother, in which, she also described the travels of the family. To his kinsman Eske Bille, who seems to have done his best for Tycho in the way of executing commissions and looking after his affairs at Hveen and elsewhere in Denmark, Tycho also wrote on this occasion. Bille had some months before sent him 700 daler, which however did not reach Prague till a short time before Christmas, and he was to receive some money which Tycho's cousin, Axel Gyldenstjerne (Governor of Norway), owed him; and on the other hand, he was to pay 5000 daler which Tycho owed to the widow of Heinrich Rantzov, which he did in the course of the year 1600. Tycho's son got the instruments at Hveen dismounted and sent by sea to Lübeck, after which he returned to Bohemia, where he arrived in January 1600 with a supply of salt fish from Hveen, which island Tycho continued to hold in fee till his death. He was also the bearer of a great many letters from relatives and friends—among others, of one from Tycho Brahe's aged mother.
At that time the instruments were still at Lübeck, probably because Tycho's agent there was unable to get them sent on to Hamburg, where they did not arrive till the following April. On the 8th September 1599 the Emperor had written to the Burgomaster and Senate of Hamburg, desiring them to forward the instruments by ship on the Elbe, and Tycho himself had written to them on the 29th September, requesting them to get the instruments under way before the Elbe froze over, but these letters were
not read in the Senate till the 21st April following, when the agent at Lübeck had at last forwarded the instruments to Hamburg, A similar delay occurred with the bulk of the instruments, books, &c., which Tycho had himself brought from Denmark as far as Magdeburg. About the transport of these to Prague by the Elbe the Emperor had also written in September 1599 to the civic authorities at Magdeburg, and he wrote a reminder to them some time after; but the Town Council coolly replied that they were unable to do anything, and, among other excuses, they mentioned the great damage done to the town when the celebrated Elector Maurice of Saxony, as commander of the Catholic forces, had besieged it some fifty years before. Having, to the disgust of his Austrian councillors, swallowed this affront, which showed how little the Imperial authority was respected in the North of Germany, Rudolph addressed himself to the Chapter of Magdeburg, and Tycho forwarding this letter by a servant of his in April 1600, also wrote to the Chapter begging them to help him in the matter. It appears from a letter which Tycho wrote in September 1600 to Duke Otto of Brunswick (who wanted his horoscope prepared) that the instruments and books had then only got as far as Leitmerits, in Bohemia, and in November 1600 Tycho wrote to Landgrave Maurice that he had at last got all his twenty-eight instruments at Prague. But he had then long ago left Benatky.
While the instruments were on their way to Bohemia, Tycho was endeavouring to push forward the alteration of and addition to the Castle of Benatky; but he had a good many obstacles to contend with, which must often have made him think with bitter regret of the easy times he had had in Denmark, where an order on the Exchequer was at once exchanged for cash without any trouble. At Benatky everything had to be done through Kaspar von Mühlstein, manager of the crown estates of Brandeis and Benatky; and as the estates were in a sad condition, and the Bohemian Exchequer was always empty, the manager was in a bad plight, as Tycho wanted money, and thought the Emperor's orders should produce the money immediately. On the 2nd December 1599, Mühlstein wrote to the President of the Bohemian Treasury, announcing that the building operations were in progress, but that Tycho continued to make new plans, so that the cost would very far exceed the estimate. As Mühlstein could not consent to this without orders from the Treasury, Tycho had threatened him with the Emperor's displeasure, and said that he would leave Bohemia again, and let the world know the reason why. Mühlstein had now received a letter from Barwitz, in which the latter informed him that his Majesty had taken Tycho into special favour, and ordered to let him, in addition to the buildings commenced, erect a wooden dwelling-room and a furnace, for which eighty florins were granted. Mühlstein wrote back that he could not do this without an order from the Treasury. Tycho had also shown him a communication from Barwitz to the effect that the Emperor granted him a thousand florins from the estate of Benatky, and Tycho now demanded the money. Mühlstein answered that he had neither got instructions from the Emperor nor from the Treasury, and even if he had, he did not know where to get so much money from, and it would be much better to spend it on improving ponds, stocking the land, &c. He had also to mention that he had every week to supply Tycho with wood from the Imperial forest, and with charcoal for distilling water. Mühlstein therefore requested the President to consider all this; he would soon send a specification of the outlay already incurred.
The matter was referred by the Treasury to the Emperor, who from Pilsen on the 10th December issued a decree, countersigned by Barwitz, in which he informed the Treasury that he had taken the mathematician Tycho Brahe into his service, and granted him the Castle of Benatky for his use until further orders, and directed that he was to be paid one thousand florins annually from the 1st May 1599 from Benatky or Brandeis, and the cost of building some small rooms (but not more than already granted, as was known to the manager at Benatky). This decree having pacified the conscience of Mühlstein, the building operations were proceeded with, and Tycho and he seem to have got on better afterwards; at least Tycho went to Prague in the following spring to attend Mühlstein's wedding.
While the new observing rooms were being prepared, Tycho kept up his correspondence with scientific men, and endeavoured to enlist assistants for the new observatory. In the above-mentioned letter to Longomontanus, Tycho wrote (after requesting him to help in packing the instruments) that he hoped his old pupil would come back to him; he was expecting Johann Müller from Brandenburg, and he had got the Emperor to write to the Elector to permit Müller to go to Prague, as they had agreed at Wittenberg. He also hoped that David Fabricius, from Ostfriesland, whom Longomontanus had met at Wandsbeck, would come to act both as domestic chaplain and as observer; and he was getting two students from Wittenberg, who had offered themselves through Jostelius, as he hoped to start again an astronomical school for the benefit of posterity and for the glory of God and the credit of the Emperor. Possibly Christopher Rothmann would also come, as he had recently written to Rollenhagen of Magdeburg (a well- known writer on astrology and many other things), so that he was not dead, as Tycho had for some time believed; but that bear-like and Dithmarsian brute (ursina ista et Dithmarsica bestia) had told a double lie when he had spread the rumours that Tycho had fled from Denmark for some great act of villainy, and that Rothmann had died from debauchery. The same Reymers had secretly absconded lately from Prague, but he would yet meet the punishment he deserved. The sheets which were still wanting in the first volume of the Progymnasmata, and which the Hamburg printer had done so badly, were soon to be printed, and when Longomontanus came, all might be settled, so that the book might be issued together with the second volume (on the comet of 1577), while the third volume on the other comets might follow.
Several of the collaborators whom Tycho in this letter hoped to secure did not put in an appearance. Longomontanus arrived in January 1600 with Tycho's son, but Rothmann never came; Fabricius only came in June 1601 for a couple of weeks, and Müller did not arrive till after March 1600, and left again in the spring of 1601, after which he disappears from the history of science altogether. But in the meantime negotiations had been entered into with a far greater man than any of these, which terminated in the removal of Kepler from Gratz to Prague, an event which produced the happiest results.
Johann Kepler was born on the 27th December 1571, at Weilderstadt, in Würtemberg, and studied from 1589 at the University of Tübingen under the talented mathematician Michael Mästlin, through whom he became acquainted with the Copernican system, and convinced himself of its being the only true representation of the planetary system. He completed his studies in the faculty of Arts, and took the Master's degree in 1591, after which he entered the theological faculty, and spent the next two years in studying the intensely narrow-minded dogmas which then prevailed in the Lutheran Church, and which were so distasteful to him that he was soon known among theologians as one unfit for a clerical career. When, therefore, in 1594 the post of "provincial mathematician" of Styria was offered to him, he was urged by his friends to accept it; and though he hesitated somewhat, as he had not particularly devoted himself to the study of mathematics, he yielded in the end, as it might not be easy for him to find suitable employment in Würtemberg, while the lively intercourse between the numerous Protestants in Styria and their co-religionists at Tübingen helped to bridge over the distance of Gratz from his home. In Gratz the young professor lectured less on mathematics than on classics and rhetoric, while from 1594 he prepared annual calendars, with the usual meteorological predictions and hints on the political events of the coming year. In 1596 his first great work appeared, Prodromus Dissertationum Cosmographicarum continens Mysterium Cosmographicum in which he set forth a relation between the five regular polyhedra and the distances which then were assumed between the planets and the sun in the Copernican system. The genius of the writer was conspicuously displayed in this book and at once attracted attention. Kepler had already in November 1595 addressed a letter to Reymers, in which he explained the ideas contained in his forthcoming work, but the "Cæsarean mathematician" took no notice of the letter of the unknown young man until June 1597, when he had probably heard the book well spoken of, and wrote to Kepler to ask for a copy. In the mad book which he published in the same year, Reymers inserted Kepler's letter of 1595, at which Tycho did not feel particularly pleased, though he had sense enough to acknowledge that Kepler had merely been civil to a man whom he only knew through his scientific writings. In a letter which Tycho wrote from Wandsbeck on the 1st April 1598, to thank him for a copy of the Prodromus (which Kepler had recently sent with a respectful letter), he expressed himself to that effect. At the same time he gave due praise to the ingenious speculations of Kepler, though he had some doubts as to the numerical data employed, and of course he could not help regretting that the Copernican system was the foundation on which Kepler had built. He expressed, however, the hope that Kepler would yet adopt something similar to the Tychonic system, which made Kepler (who throughout furnished the letter with marginal notes) remark:"Quilibet se amat" Shortly afterwards Tycho also wrote to Mästlin (to whom he had ten years previously sent his book on the comet of 1577 without hearing from Mästlin since then), and repeated some of the doubts he had already expressed to Kepler. The latter was, however, not discouraged by these doubts, and wrote to Mästlin that he could in no way accept the Tychonic system, and that Tycho had abundance of riches which he did not use properly, as was generally the way with rich people, and it would be well to extort his riches from him by getting him to publish all his observations. To Tycho himself Kepler addressed a letter in which he, with manly and unaffected eloquence, protested against the crafty use which Reymers had made of his complimentary letter, which he had written simply because he had read Reymers' Fundamentum astronomicum with much profit, had been advised by some Styrian noblemen to make a friend of this man on account of his influential position (though they called him a new Diogenes), and had felt a desire of communing with a mathematician, since there were none in his own neighbourhood. The whole letter evidently made a good impression on Tycho, as Kepler's open and noble mind is reflected in every line, and Tycho wrote in reply that he had not required so elaborate an apology.
The literary intercourse which had thus been opened between Tycho Brahe and Kepler was soon to become a personal one. The very numerous Protestants in Styria had hitherto been perfectly unmolested by their Catholic rulers, but during a pilgrimage to Loretto which Archduke Ferdinand (afterwards the Emperor Ferdinand II.) undertook in 1598, he vowed to root out the heretics from his dominions, and on the 28th September all preachers and the teachers at the Gymnasium of Gratz were ordered to leave the town before sunset. Kepler had to leave his family (he had eighteen months before married a young widow, who was the mother of a girl seven years old) and depart for Hungary. He was, however, recalled within a month, as some of the Jesuits were much interested in his scientific work, and hoped that he might be persuaded to change his faith. He soon saw that he could not hope to be left in peace very long, and he made vain attempts to obtain some employment at Tübingen. Mästlin was, however, unable to help his former pupil, and Kepler saw no other opening elsewhere. Meanwhile Tycho had been invited to Prague, and Kepler, who had already been anxious to meet him, was now more than ever desirous of doing so, and thought of undertaking a journey to Wittenberg for the purpose of conferring with Tycho. In August 1599 he learned from Herwart von Hohenburg, Chancellor to the Duke of Bavaria, who was a correspondent of Kepler's, and had frequently consulted the rising astronomer on matters connected with chronology, that Tycho had arrived at Prague and was to have a salary of 3000 florins. Herwart ended the letter by saying, "I wish you had such a chance, and who knows what fate may have in store for you." Kepler now consulted a number of friends and some men of influence at Prague, among whom was Baron Hoffman, a privy councillor who was well acquainted with Tycho, but who would at first give only an evasive answer. The most sensible advice was given by Papius, a physician, who had been obliged to leave Gratz as a Protestant, and was then practising his art at Tübingen. He suggested that Kepler should make all possible inquiries at Prague about the conditions on which he might become associated with Tycho, and that he should let his literary productions be shown at Prague in order to pave the way for him there. The latter part of the advice was certainly superfluous, and Tycho himself was more than willing to accept Kepler's services. In a long letter which Tycho wrote from Benatky on the 9th December 1599, he expressed his hope of soon meeting Kepler, though he did not wish that the latter should be driven to him by misfortune, but by his own free will and his love of science, and he assured Kepler that he would find in him a friend who would always stand by him with help and counsel.
Tycho's letter did not find Kepler at Gratz. He had at last made up his mind to examine the state of things at Prague with his own eyes, and, encouraged by Baron Hoffmann, he started with this nobleman from Gratz on the 6th January 1600, and arrived at Prague about a fort- night later. On the 26th Tycho wrote to Hoffmann that he had with great pleasure heard of their arrival, and thanked Hoffmann for being the means of introducing Kepler to him. Tengnagel (who had just returned from his home in Westphalia) and Tycho's eldest son were the bearers of this letter, as well as of another for Kepler, in which Tycho apologised for not welcoming him in person, but he rarely went to Prague except when called by the Emperor; the oppositions of Mars and Jupiter were now to be observed, and the other three planets and a lunar eclipse likewise, so that he did not like to interrupt his work, but he would receive Kepler, not as a guest, but as a dear friend and colleague. On the 3rd February Kepler arrived at Benatky with a civil answer from Hoffmann, warmly recommending him to Tycho. Within a few days some preliminary arrangements were made with regard to the distribution of work between the various assistants. Tycho's younger son, Jörgen, was to have charge of the laboratory; Longomontanus had the theory of Mars in hand; Kepler at first had to put up with the promise of the next planet which was taken up, but afterwards Mars was intrusted to him, as he was particularly eager to attack this most difficult planet, while Longomontanus undertook the lunar theory. But though Tycho was most cordial to Kepler, he did not enter very much into learned discourses, so that Kepler had often to coax him into answering some question while they were at table. He had a feeling that he was not looked upon as a man of recognised scientific standing, but merely as an ordinary assistant to the world-famed Tycho Brahe, and yet he felt that he ought to have full access to the great treasure of observations which Tycho possessed. In a document which Kepler drew up for the information of his friends, he remarks that Tycho had hitherto, by the magnitude of his undertakings, been prevented from discussing his observations, and now that old age was approaching and soon would enervate him, he would hardly be able to undertake that great work himself. If the journey from Gratz was not to have been made in vain, either Tycho should allow him to copy the observations, which he doubtless would refuse, since they were his treasure to which he had devoted all his life, or he should admit Kepler to a share in the working out of the results from them. And the Emperor should do as King Alphonso had done, and associate others with Tycho. He himself ran the risk of losing his post at Gratz, for if Tycho took offence at something in Bohemia and went away, or if something happened to him, what would then become of himself (Kepler), and perhaps the observations would be lost or become inaccessible.
Influenced by these considerations as well as by the possible difficulty of getting the consent of his wife's relations to her removal from Gratz, where she had a small property near the town, to Benatky, where she would have to live among foreigners, Kepler drew up several different proposals for a formal agreement with Tycho Brahe, in which he most carefully tried to secure his future position, both as regards the lodging of his family at Prague, or at least in an upper storey at Benatky, with separate kitchen, supply of fuel and victuals, &c., as also with regard to his scientific work. He added that he would not be content with general promises, which was a rather superfluous remark, since the minuteness with which he had specified his demands made this very evident. On the 5th of April the matter was discussed verbally between Tycho and Kepler in the presence of Jessenius of Wittenberg, and in answer to Kepler's written demands, Tycho partly read himself, partly let Jessenius read, a written answer which followed Kepler's demands point for point. Tycho took the whole matter far more quietly than might have been expected from a man of his hot temper and imperious ways, but though he offered to bear part of Kepler's travelling expenses, and to do his utmost to get him settled at Prague (if he absolutely wanted to live there), or in a separate house in or near Benatky, he was unable to guarantee anything about salary or the keeping open of Kepler's Styrian post, until he could communicate with the Emperor and with Corraduc and Barwitz. Though Tycho begged Kepler to wait until his servant Daniel came back from Pilsen with replies to letters which Tycho had written to Corraduc, Kepler refused to listen to reason, and left Benatky the following day with Jessenius to return to Baron Hoffmann at Prague.
There had evidently for several weeks been some misunderstanding between the two astronomers, as Tycho already, on the 6th March, had written to Hoffmann that as soon as he could find time from other occupations, they would both drive to Prague to discuss with Hoffmann the question as to Kepler's position. It cannot, however, have been Kepler's uncertain prospects alone which brought about the crisis on the 5th April, for it appears that Kepler on the following day wrote a very violent letter to Tycho, of which the latter took no notice beyond sending it to Jessenius. It seems, therefore, probable that Kepler, as we hinted above, felt himself treated too much as an inferior and a mere beginner, while he, conscious of his genius, expected to be regarded as an independent investigator. Tycho, however, always expressed himself most kindly of Kepler in his letters, and it probably never occurred to him that he ought not to place Kepler on the same footing as his assistants. He now, on the 6th April, wrote a short letter to Hoffmann, in which he referred him to Jessenius for information as to the difference between Kepler and himself, and expressed the hope that Hoffmann, with his prudent advice, would endeavour to settle the matter. He was not disappointed, for the remonstrances of Hoffmann, who was anxious to see Tycho and Kepler co-operate in the service of science, succeeded in softening Kepler, to which Jessenius, as a friend of both parties, also contributed. About three weeks after his departure from Benatky, Kepler therefore wrote a repentant letter to Tycho, in which he acknowledged that he had met with nothing but kindness from Tycho, and begged to be forgiven for his conduct, which was the result of a youthful and choleric temper and his shaken health. The two astronomers met at Prague, were reconciled, and went back to Benatky together, where Kepler now stayed four weeks, until at the beginning of June he left Bohemia for a while to settle his affairs at Gratz. At parting, Tycho gave him a most flattering testimonial, in which he spoke in the highest terms of the manner in which Kepler had devoted himself to scientific work at Benatky.
Kepler had hoped to be able to retain his appointment at Gratz and get leave for a year or two to work with Tycho. To settle permanently with him he was not inclined, but he soon had very little choice in the matter. Early in August an Ecclesiastical Commission arrived at Gratz, and every official had to appear before it and to state whether he would become a Roman Catholic or not. Those who refused were ordered to dispose of their goods and to leave the Austrian provinces within forty-five days. Among these was Kepler, who again applied to Mästlin and Her wartfor advice. But at Tübingen there was no opening, and Herwart strongly advised him to go to Prague. There seemed to be no help for it now, and no matter what doubts Kepler might have as to the feasibility of living in the same house with Tycho and his family, or of preparing planetary tables in concert with a man from whom he differed on the most fundamental questions, he had no choice but to go to Prague.In the meantime the Emperor had returned from Pilsen to Prague in July 1600, and about the same time, or shortly afterwards, Barwitz advised Tycho to leave Benatky and move to Prague, as the Emperor would like to have his astronomer near him. Probably Tycho was not sorry to leave Benatky, where he and Mühlstein still kept up a running fight about money matters and building operations. He therefore left Benatky and took up his quarters temporarily in the hotel Beim goldenen Greif, on the Hradschin, while his instruments were placed in Ferdinand I.'s villa, not far from the castle. A few days after his arrival, Tycho was received in audience by the Emperor, who conversed with him for an hour and a half. The Emperor inquired about Tycho's work, upon which Tycho remarked that he necessarily required more help, and suggested that Kepler might be attached to the observatory for a year or two. The Emperor nodded his consent to this, and desired Tycho to mention this proposal in a memorial about his requirements, which was to be sent to Barwitz. Tycho afterwards spoke to Corraduc, and asked that the Styrian authorities might be requested officially to give Kepler leave of absence for two years, and let him retain his salary, to which the Emperor would add a hundred florins on account of the expense of living at Prague. Tycho wrote to Kepler
Tycho was much pleased to see Kepler return to Prague, the more so as he had lost his most experienced assistant, Longomontanus, who had wished to return to Denmark, and had received his discharge on the 4th August, when Tycho at parting gave him a very kind letter of recommendation. It took a long time to get the question about Kepler's salary settled by the Government, but he and his family soon removed from Hoffmann's to Tycho's house, and he began work. This was probably not until the Emperor had purchased Curtius' house from the widow for 10,000 thaler, and Tycho had taken possession of it, which he did on the 25th February 1601. Kepler still could learn nothing about his salary, and continued, though in vain, to look out for an appointment in Germany, while Tycho now and then helped him with money. His health also gave him cause for anxiety, as he could not get rid of the intermittent fever, and early in 1601 he was troubled with a bad cough, which even made him fear that he was consumptive. In April he was obliged to go to Gratz to arrange some affairs connected with his wife's property, whence he did not return until August, having failed to accomplish his object, but having recovered his health. A curious letter has been preserved which Kepler's wife wrote to him on the 31st May, in which she tells him that Johann Müller had left again; that Tengnagel had not yet given her any money, but that he and Tycho were friends again, and that his wedding (with Tycho's second daughter, Elisabeth) was to take place a week after Whitsuntide. This cannot have been the first complaint Kepler received from his wife about her getting no money, for he had already on the 30th May written an indignant letter to Tycho, blaming him for not having given her the twenty thaler which had been promised. Tycho did not trouble himself to answer this, but let one of his pupils, Johannes Eriksen, write to Kepler that he had unasked, through his daughter, promised her ten thaler soon after Kepler's departure, which she also got on asking for them, and when she a fortnight later again requested ten more, Tycho sent to her by Eriksen six thaler and promised her more, though he had not much cash at the time. All this he had done without grumbling, and both he and his family had been kind and obliging to Kepler's wife and her daughter. Tycho therefore desired Eriksen to beg of Kepler to have more confidence in him, and to conduct himself in future with more prudence and moderation towards his benefactor, who had been very patient with him, and wished him and his well. This letter had probably the desired effect, and Kepler, who at heart was most generous and noble, but whose weak point it was always to complain to everybody about money matters, no doubt acknowledged having been too hasty. When he returned to Prague in August, Tycho brought him to the Emperor, who congratulated him on his recovery, and promised him the office of Imperial mathematician on condition that he should work jointly with Tycho on the new planetary tables, which Tycho begged the Emperor's permission to call the Rudolphean or Rudolphine tables.
It was mentioned above that Tengnagel was engaged to be married to Tycho Brahe's second daughter, Elisabeth. On the 5th April 1601, Tycho wrote a letter (in Danish) to his friend Holger Rosenkrands, inviting him to the wedding, which was to take place between Easter and Whitsuntide, and the following day he wrote another letter (in Latin), in which he mentioned that he expected his sister Sophia. Neither she nor Rosenkrands came, however, to the wedding, which was celebrated on the 17th June, after which the married couple set out for Westphalia, the home of the bridegroom, accompanied by Eriksen.
Tengnagel does not seem to have occupied himself much with astronomy, and probably did not take an active part in the scientific work in Tycho's house. At Prague, Tycho had not as many assistants as at Hveen. In addition to Longomontanus, Müller, and Eriksen, he was assisted for some time by Melchior Joestelius, Professor of Mathematics at Wittenberg; by Ambrosius Rhodius, who left Prague shortly before Tycho's death, and likewise became Professor at Wittenberg; by a certain Matthias Seiffart, who afterwards for some years assisted Kepler in computing and observing; and from June 1601 by a young Dane, Poul Jensen Colding. It appears also that Simon Marius (Mayer), who afterwards obtained some notoriety by laying claim to various discoveries and inventions long after they had been published by others, spent some time at Prague with Tycho and Kepler in the summer of 1601. The Imperial physician, Hagecius, with whom Tycho had corresponded for so many years, died on the 1st September 1600, after a prolonged illness, but Tycho found other scientific friends at Prague, among whom were Martin Bachazek, Rector of the University, Peter Wok Ursinus of Rosenberg, Baron Johan von Hasenburg (who was an ardent alchemist), and the Jewish chronologist, David Ganz.
As Tycho at Benatky or at Prague had never more than a few assistants at a time, and most of his instruments did not reach him till October or November 1600, the observations made in Bohemia cannot compare in fulness and extent with those made during an equal period of time at Hveen, to which disparity the interruptions caused by Tycho's various removals also contributed. In December 1600, and the first week of January 1601, observations were made in the Emperor Ferdinand's villa, and on the 3rd March the work was resumed in Curtius' house, where Tycho had just become settled. Kepler hardly took an active part in the observations, but he began preparing for the great work to which he afterwards devoted his life. When he arrived at Benatky in February 1600, Mars had just been in opposition to the sun, and a table of the oppositions observed since 1580 had been prepared, and a theory worked out which represented the motion in longitude very well, the remaining errors being only about 2'. On this a table of the mean motion of Mars and the mean motions of the apogee and node for 400 years had been founded (as was done for the sun and moon in the Progymnasmata). But the latitudes and annual parallax at opposition (or the difference between the heliocentric and geocentric longitude) gave trouble, and Longomontanus was just then occupied with this matter. Kepler therefore began to consider whether the theory might not after all be wrong, though it represented the longitudes so well; but during the short time he was at Benatky he was unable to make any progress in this problem, which it eventually took him four years to solve.
During Kepler's residence with Tycho at Prague between October 1600 and April 1601, he seems to have been mainly occupied with a piece of work which cannot have been congenial to him—a refutation of the book of Reymers Bär. Shortly after his arrival in Bohemia, Tycho began to take legal proceedings for libel against this person, who had fled to Silesia, from whence he, however, secretly came back some time afterwards. In the summer of 1600 Tycho learned that there was periculum in mora, as Reymers was very ill; but even this did not soften Tycho's heart, and he persisted in having the poor wretch punished, and persuaded the Emperor to appoint a commission of four members, two barons and two Doctors of Law, to try the libeller. But just as the trial was about to commence, Reymers died, on the 15th August 1600. The Emperor directed the Archbishop of Prague to have every obtainable copy of the book confiscated and burned, while Tycho, who was rather unduly proud of his system of the world, wished to publish a book which was to contain all the documents on the subject of the alleged plagiarism, as well as a scientific refutation of Reymers' book. The preparation of the latter had to be undertaken by Kepler, who, while battling with intermittent fever in 1601, wrote his Apologia Tychonis contra Ursum, in which he showed that neither Apollonius of Perga nor
any one else before Tycho had proposed the Tychonic system. Tycho's death made this memoir superfluous, and Kepler laid it aside, so that it has only recently been published in the complete edition of his works. The same was the case with an unfinished reply to the attack of Craig on Tycho's book on the comet of 1577.
In 1601 Kepler also occupied himself with the theories of Mercury, Venus, and Mars, and noticed that it was not possible to represent the apparent motion of the planets by assuming for the orbit of the sun (or the earth) a simple excentric circle with uniform motion, as had always hitherto been done, but that it would be necessary to have recourse to an equant as in the planetary theories of Ptolemy. When Kepler asked Tycho if he would not mention this in the Progymnasmata, he declined to do so, as it would take time to investigate the equal motion, and he wanted the book published at once. The subject was therefore merely alluded to by Kepler in the Appendix with which he wound up the book after Tycho's death.
While Kepler was thus reconnoitring the ground for his future work on the planets, Longomontanus had before his departure finished the lunar theory and tables, the incomplete state of which had so long delayed the publication of the Progymnasmata. It is much to be regretted that the account of Tycho's lunar theory is very short, and gives no account of the successive steps which led Tycho to his great discoveries in this branch of astronomy. When he wrote the report on his labours at Hveen for his Mechanica, he was already in possession of the discovery of the third inequality in longitude (variation), and of the periodical change of the inclination and of the motion of the node. During his stay at Wittenberg (if not before) he had from observations of eclipses perceived the necessity of introducing an equation in longitude with a period of a year, but the theory had already required so many circles and epicycles that Longomontanus thought it simplest to allow for this equation by using a different equation of time for the moon; and when Tycho did not appear very delighted with this makeshift, the pupil answered his master somewhat rudely, that he might try to find another method himself, which would agree better with the observations.
It must have been a great satisfaction to Tycho to see his researches on the moon reach at least a temporary conclusion, as his mind had of late years been so full of anxiety for the future that he could doubly enjoy a ray of sunshine. The Emperor appears always to have been most friendly to him, and Tycho wrote in March 1600 to his sister Sophia that Rudolph had not only been very kind to him while the plague was raging during the previous winter, and had offered to send him and his family to Vienna while it lasted, but that the Emperor also took the greatest interest in his work, had read the unfinished Progymnasmata, and had consented to let it be dedicated to him. But however pleasant his relations with the Emperor were, Tycho had often practical experience of the scarcity of money in Bohemia, and he could not be blind to the shaky condition of the Imperial Government, caused by the religious and political flames which, though as yet only smouldering, were certain ere long to burst out in their fury, and for the quenching of which the weakness of the Emperor did not promise well. Perhaps he may sometimes have wondered in his own mind whether it might not have been wiser to have remained in peaceful Denmark, even without an endowment for his observatory, instead of coming to the stormy Bohemia, where he had no guarantee for the continuance of his salary but the life of his patron, just as in the old days at Hveen. His health would also seem to have become shaken, if we may judge from Kepler's remark that the feebleness of old age was approaching, since he would hardly have said so of a healthy man only fifty-three years of age.
But the die was cast, and Tycho Brahe could only try to make himself as much at home in Bohemia as possible. On the 9th February 1601 the Emperor wrote to the Bohemian Estates that Tycho Brahe and his sons desired to be naturalised, and to have their names entered on the roll of the nobility. It is not known whether this matter was considered by the Estates, but the name of Brahe does not occur in their proceedings, so that Tycho must have died before he could get his wish fulfilled. In several of his letters Tycho alludes to his intention of buying landed property in Bohemia, and in order to do so he took steps to get back the money which he had lent in 1597 to the Dukes of Mecklenburg. In accordance with the terms of the bond, he had, about Michaelmas 1600, through his kinsman Eske Bille, given notice to the agent of the Dukes to repay the capital sum of 10,000 thaler at Easter 1601; and for fear of his letter to Bille having been lost, he took the further precaution of giving notice himself to the "Landrentmeister," Andreas Mayer, to pay the money at Michaelmas 1601, if Bille had not already carried out his instructions. He stated expressly that he required the money for buying property in Bohemia, and wrote to this effect to Duke Ulrich in April 1601, as he had been informed that Mayer had stated that he could not get the money together so soon. At Easter the money was not forthcoming, as Mayer "at the last moment" was disappointed about some money which should have been paid to him, but Tycho's money was promised for St. John's Day. Bille now sent his own servant to Doberan, where Duke Ulrich was then staying, to receive the money, but he was again disappointed, and Tycho had on the 18th July to send off another reminder, to which the Duke answered that the money had been ready, but that Bille's servant had not called again. Before the 9th August Bille had himself arrived at Rostock to receive the money, which the Duke on that day ordered to be paid to him "before his departure on Tuesday morning." This must have been done, as the cancelled bond is still in the archives at Schwerin.
There appears to be nothing known as to whether Tycho actually purchased land in Bohemia after receiving back his money from Mecklenburg, but it is not likely that he did so, as his life terminated very suddenly soon after. On the 13th October 1601 (new style) he was invited to supper at the house of the Baron of Rosenberg, and went there in company with the Imperial Councillor, Ernfried Minkawitz. During supper he was seized with illness, which was aggravated by his remaining at table. On returning home, he suffered greatly for five days, when he became somewhat relieved, although sleeplessness and fever continued to harass him. He was frequently delirious, and at other times refused to keep the prescribed diet, but demanded to be given to eat anything he fancied. Five more days elapsed in this manner. During the night before the 24th October he was frequently heard to exclaim that he hoped he should not appear to have lived in vain ("ne frustra vixisse videar"). When the morning came, the delirium had left him, but his strength was exhausted and he felt the approach of death. His eldest son was absent, and his second daughter and her husband also; but he now charged his younger son and the pupils to continue their studies, and he begged Kepler to finish the Rudolphine tables as soon as possible, adding the hope that he would demonstrate their theory according to the Tychonic system and not by that of Copernicus. Among those present at his bedside was a namesake of Tycho's, Erik Brahe, Count Visingsborg, a Swede by birth, but in the service of the King of Poland, whom Tycho thanked for all the kindness he had shown to him during his illness, asking him to carry his last remembrances to his relations in Denmark. Soon afterwards he peacefully drew his last breath, amidst the tearful prayers of his family and pupils. He had only reached the age of fifty-four years and ten months; a short span of time (as Gassendi remarks) if we look to the age which he might have attained, but a lengthy one if we consider the magnitude of his works, which will live in the recollection of mankind as long as the love of astronomy remains among us.On the 4th November the body of the renowned astronomer was with great pomp brought to its last resting-place in the Teynkirche (Týnskýkostel), in which a semi-Protestant (utraquistic) service was still tolerated. The funeral procession was headed by persons carrying candles embellished with the arms of the Brahe family; next was carried a banner of black damask with the arms and name of the deceased embroidered in gold; then came his favourite horse, succeeded by another banner and a second horse, after which came persons bearing a helmet with feathers in the colours of his family, a pair of gilt spurs, and a shield with the Brahe coat of arms. Then followed the coffin, covered with a velvet cloth, and carried by twelve Imperial gentlemen- at-arms. Next after the coffin came the younger son of the deceased, walking between Count Erik Brahe and the Imperial Councillor, Ernfried Minkawitz, and followed by councillors and nobles, and Tycho's pupils. Then came the
It is scarcely worth mentioning that a silly rumour very soon began to spread that Tycho Brahe had died from poison, administered by some envious courtier at Prague, or, as others thought, by his old enemy Reymers Bär. As the latter died fourteen months before his supposed victim, it would indeed have been a remarkably slow poison.
The most important inheritance which Tycho left to Kepler and to posterity was the vast mass of observations, of which Kepler justly said that they deserved to be kept among the royal treasures, as the reform of astronomy could not be accomplished without them. He even added that there was no hope of any one ever making more accurate observations, for it was a most tedious and lengthy business! This would have been perfectly true if the telescope had not afterwards been invented. It is not here the place to set forth how Kepler, when Tengnagel had given up pretending that he was going to work out the theory of the planets, took up the work, and how his mighty genius mastered it and gave to the world the great laws of Kepler, at one breath blowing away the epicycles and other musty appendages which disfigured the Copernican system. But Kepler was not only a great genius, he was also a pure and noble character, and he never forgot in his writings to do honour to the man without whose labours he never could have found out the secrets of the planetary motions. On the title-page of his Astronomia nova de motibus stellæ Martis, he states that it is founded on Tycho's observations, and on that of the Tabulæ Rudolphinæ he mentions Tycho as a phœnix among astronomers. And it was no exaggeration. Archimedes of old had said, "Give me a place to stand on, and I shall move the world." Tycho Brahe had given Kepler the place to stand on, and Kepler did move the world! And so it was with Kepler's labours in other fields, as we may see in that wonderfully interesting book, Ad Vitellionem Paralipomena, sive Astronomiæ Pars Optica, where Tycho's name is quoted so constantly as having supplied the materials. Kepler and Tycho had squabbled often enough while the latter was alive, but after his death this was forgotten, and Kepler's mind had only room for gratitude for having become heir to the great treasures left by Tycho. But on the other hand, it must be conceded that it was fortunate for Tycho's glory that his observations fell into the hands of Kepler. Longomontanus would doubtless have hoarded them carefully as a great treasure, but he would most certainly not have discovered the laws of planetary motion, and Tycho's exile thus turned out to be of vast advantage to science.
- In addition to Gassendi and Tycho's letters to Vedel and Longomontanus, the sources for this period are: Frisch's Vita Kepleri, in vol. viii. of Joh. Kepleri Opera Omnia, and Joseph v. Hasner, Tycho Brahe und J. Kepler in Prag. Eine Studie, Prag, 1872.
- Bang's Samlinger, ii. p. 511; Weistritz, i. p. 175.
- One florin (schock meissn.) = 5 mark 81 pf.; 1000 florins therefore about £300; but the value of money in Bohemia appears at that time to have been about four times as great as now.
- Gassendi, p. 161, where another poem composed on the same occasion is also given.
- Ibid., p. 162; Barrettus, p. 844. The quadrant is described above, p. 102.
- Mädler, Pop. Astronomie, 1st edit., 1841, p. 561 (not in the latest editions), and Heiberg, Urania, Aarbog for 1846, p. 131. According to another tradition, the monks did not like the neighbourhood of the heretic, and got up an apparition of a ghost to persuade the Emperor to turn him out.
- Hradschin, where the house of Curtius was situated, west of the castle.
- Description of Benatky by David. See Zach's Monatliche Correspondenz, vi. p. 475 (1802). On the appended plate the wing in the centre and the church-spire were added after Tycho's time.
- Letter to Pinelli, Aus Tycho Brahe's Briefwechsel, p. 12. Tycho always calls the place Benach.
- Gassendi, p. 163; Bang's Samlinger, ii. p. 501 (Weistritz, i. p. 164).
- Gassendi, p. 164.
- Letter to Sophia Brahe in Breve og Aktstykker, pp. 85–86.
- Barrettus, pp. 850 and 856; Breve og Aktstykker, pp. 98 and 108.
- See above, p. 130.
- The letter is not extant, but Tycho alludes to it in the letter to Longomontanus (Gassendi, p. 167 ; Weistritz, i. p. 186). The Emperor had directed Barwitz to write to the Danish Privy Councillor, Henrik Ramel, on the same matter.
- This letter was published at Jena in 1730 (23 pp. 4to) by G. B. Casseburg, Tychonis Brahe Relatio de statu suo post discessum ex patria, and more accurately in the Dänische Bibliothek, iii. 1740, p. 180 et seq. Translated in Weistritz, i. p. 169 et seq.
- Danske Magazin, ii. p. 359; Weistritz, ii. p. 365. Glaus Mule was a son of the Burgomaster of Odense in Denmark. A letter from Tycho to him parently written while Mule was abroad, perhaps at Rostock, as it alludes to Professor Caselius) is quoted above p. 240, footnote.
- Breve og Aktstykker, pp. 50, 57, 93, 101, 117, 148.
- The two letters (in the city archives of Hamburg), printed in Friis, Tyge Brahe, pp. 320 and 324. Letter from Tycho to Vincent Müller, Burgomaster of Hamburg, of April 24, 1600, in Breve og Aktstykker, p. 125.
- Tycho's letter to the Chapter, Aus Tycho Brahe's Briefwechsel, p. 21; compare Breve og Aktstykker, p. 114.
- Breve og Aktstykker, pp. 141 and 143. Tycho wrote to Eske Bille on November 16, that on looking over his things, he noticed that some articles were missing which might still be at Copenhagen or at Lübeck. Ibid., p. 149.
- Hasner, p. 7 et seq.
- Where these were situated is not known, and there are no remains of Tycho's buildings or inscriptions, &c., as the Castle of Benatky has changed owners many times since then. In March 1801 Professor Aloys David determined the latitude of Benatky and found 50° 17' 24" (Tycho gives 50° 18' 15") and longitude 50m. 0s. east of Paris. Monatl. Correspondenz, vi. (1802), p. 477. Tradition attributes a still existing sundial at Benatky to Tycho, but there is no proof of its having been constructed by him.
- In the letter to Vedel, Tycho also mentions this, and adds that Reymers had left his wife behind, who (of course) enjoyed an evil reputation.
- In January 1600 Tycho inquired from Scultetus whether the printing could not be done at Görlitz (Aus Tycho Brahe's Briefwechsel, p. 16).
- Kepleri Opera, viii. p. 715.
- Apelt, Die Reformation der Sternkunde, p. 271. Fabricius went with a message from the Count of Ostfriesland to his envoy at Prague. A letter which he wrote to Kepler from Prague is printed, Opera, i. p. 305.
- Breve og Akstykker, p. 110.
- Ursus had just published a work on chronology, Chronotheatrum sive Theatrum temporis annorum 4000, of which he sent Kepler a copy with the letter (the full title is given by Hanisch, Epist. ad I. Keplerum, p. 90; it must be an extremely scarce book). Kepler was so little aware of the enmity between Tycho and Ursus that he even asked Ursus to forward a copy of the Prodromus to Tycho (Opera, i. p. 233).
- Epist. Kepleri, p. 102; Opera, i. p. 43 and p. 219; Kepler's marginal notes, p. 189.
- Opera, i. p. 45 et seq.
- Ibid., p. 48 et seq.
- Ibid., p. 220 et seq.; Epist. ed. Hanschius, p. 106.
- Tycho had also for some time corresponded with Herwart, to whom he, on the 31st August, wrote a letter explaining his lunar theory, and particularly the calculation of eclipses. About this letter and Herwart's answer, see Gassendi, p. 165.
- Kepleri Opera, viii. p. 709.
- Epist. ed. Hanschius, p. 108 et seq.; Opera, i. p. 223 and p. 47.
- Kepleri Opera, viii. p. 716; Aus Tycho Brahe's Briefwechsel, p. 18.
- Opera, pp. 716, 717; Briefwechsel, p. 19.
- Kepler, De Stella Martis, chap. vii. (Opera, iii. p. 210).
- Opera, viii. p. 718 et seq.
- Opera, viii. pp. 721–724.
- Ibid., p. 725.
- Among the Kepler MSS. in the Hofbibliothek at Vienna is a declaration written and signed by Kepler on the 5th April 1600, in which he, having been hospitably received by Tycho Brahe, "auch diese gantze zeit vber aller müg- licheit nach also tractirt worden, das ich mich hingegen iederzeit, zue aller Vnderthaniger Danckbarkheit schuldig erkhennen" pledges himself to keep secret all observations or inventions which Tycho Brahe had communicated or might communicate to him. (Friis, Tyge Brahe, p. 327). This MS. is not mentioned by Frisch. If the date is correctly given, this document may have been an attempt on Kepler's part to conciliate Tycho, in order that the latter might make some concession as to the scientific work.
- Kepler's letter is only known from Tycho's letter to Jessenius. Opera, viii. p. 728. In this letter Tycho asks Jessenius to find out whether Kepler had now taken up with Reymers Bär, who had returned to Prague.
- Opera, viii. p. 729.
- Ibid., p. 730.
- Hasner, p. 10. The house "Zum goldenen Greif" is still in existence (Neuweltgasse, No. 76), but is no longer an inn or a hotel. This quarter of Prague was then the most aristocratic one, being close to the castle. It was thoroughly devastated by the Prussians in 1757 by bombardment, and has since been the poorest part of the city.
- Now called the Imperial Belvedere. On January 24, 1601, Tycho wrote to Magini that he had now all his twenty-eight instruments "non longe ab Arce, in Cæsaris quadam magnifice extructa domo." Carteggio, p. 241. The observations at Benatky had been stopped at the end of June 1600, and they were not resumed till the 2nd December, "in domo Cæsaris horto vicina ubi instrumenta mea adhuc disponebantur." Barrettus, p. 860.
- Opera, viii. p. 732.
- Ibid., pp. 734–737.
- Printed by Gassendi, p. 174. In 1603 Longomontanus became head- master of Viborg school, in Jutland (where he had been educated himself); in 1605 Professor at the University of Copenhagen; in 1607 Professor mathematum superiorum. He died in 1647, before the University Observatory on the Round Tower (which existed till 1861) was finished.
- Gassendi, p. 176. The site of Curtius' house on the Loretto Place is now occupied by the Černin Palace. Canon David determined the geographical position, lat. +50° 5' 28", 3°2 3' 37" east of Ferro. In 1804–5 an old tower was pulled down, which probably had been part of Tycho's observatory.
- Opera, iii. pp. 739–741.
- "Der hanss Miller ist den 29 Mai mit seiner frau darvon vnd haim, der diho Prei (Tycho Brahe) hat jra abgeförtigt vnd hat jm göben was er jm hat zuegesagt, aber vom khaiser ist jm khain heler nit worten. Der Diho hat jm sein hantl verdörbt beim khaiser er het sonst woll ein guette Verehrung bekhumen so hat ehr des Diho müessen engelten. Der franz (Tengnagel) vnd der Diho sint witer einss sie rihten ietz zu der hochzeit zue, der franz hat mier noh khein gelt göben." . . . Müller left on the 26th, according to a letter from Eriksen to Kepler (Epistolæ, ed. Hanschius, p. 176).
- This name occurs here for the first time. Perhaps he had come to Tycho on the 15th August 1596, as we read in the diary: "Rediit Tycho Hafnia, cum eo duo studiosi, alter Germanus commendatus a Landtgravio, alter Danus, Joannes nomine."
- Opera, viii. p. 741.
- Gassendi, p. 177.
- The Danish letter is printed in Danske Magazin, ii, p. 360 (translated in Weistritz, ii. p. 366); the Latin one is only alluded to ibid, and iii. p. 23.
- Epist. ed. Hanschius, p. 179, and Opera, viii. p. 741.
- Joestelius must have returned to Wittenberg before June 1600, when he observed the solar eclipse there (Kepler, i. p. 56).
- Son of a wealthy citizen at Kolding, in Jutland; born 1581, died 1640 as a clergyman in Seeland. Came to Tycho in June 1600, and was with him till his death; wrote an elegy on him, which is printed by Gassendi, p. 241. About him see Norsk Historisk Tidskrift, ii. p. 338 (1872).
- On the 27th May 1601 Eriksen wrote to Kepler that Marggravii Anspachensis Mathematicus, Simon Marius, was expected in a day or two, and would, the writer hoped, relieve him of some of the observing (Epist. ed. Hanschius, p. 176), but I cannot find any evidence that Mayer really came. He had already in 1596 published a small pamphlet of the ordinary type on the comet of that year.
- Kepler, De Stella Martis, cap. viii.; Opera, iii. p. 210. Apelt (Reformation der Sternkunde, p. 276), quoting Gassendi, believes his "duo ininuta" to be a misprint for "duodecim;" but Kepler distinctly says "intra duorum scrupulorum propinquitatem."
- The greatest drawback of the Tychonic system was the difficulty of distinguishing between the real and apparent orbit of a planet; the greatest observed latitude at opposition was naturally assumed to be the inclination of the orbit, and this turned out to have a different value at different times, as if the Ptolemean oscillations of the orbit really existed.
- Kepler spoke to him at Prague in January 1600, without revealing his own name (Opera, i. p. 237).
- Opera, i. pp. 236–276. It is curious that Gassendi should have fallen into the same error with regard to Apollonius (Vita Copernici, p. 297). Kepler had already, in March 1600, at Benatky, written a short refutation, which is printed i. p. 281 et seq.
- Opera, i. pp. 279–281.
- In a letter to Longomontanus, Kepler wrote in 1605:—"Ab Octobri 1600 in Augustum 1601 quartana me tenuit. Interim scripsi contra Ursum jubente Tychone, & alia ipsius studia pro ipsius arbitrio & meis viribus adjuvi. Speculatus sum, indignante Tychone, in Venere, Mercurio, Luna, in illis utiliter, in Luna plane frustra: Speculatus sum et in Marte, correxi inæqualitatem primam, . . . A Septembri, inquam, coepi laboriosissime inquirere excentricitatem solis, in quo labore Tycho mortuus est." Epist. ed. Hanschius, p. 171. About the solar excentricity, see below, Chapter xii.
- "Tu ergo ipse aliud inveni, quod cum tuis consentiat observatis" (see a letter from Kepler to Odontius on Tycho's lunar theory, Opera, viii. p. 627). That Longomontanus had enjoyed the advice of Kepler on many points in the lunar theory appears from the letters exchanged between them in 1604 and 1605, in one of which Longomontanus counts up the various steps in the work, while Kepler after each item put a mark, and wrote in the margin, "Vide etiam atqve etiam, hæc me svadente et præeunte exemplo." Epist. ed. Hanschius, p. 165. We shall consider the lunar theory in more detail in Chapter xii.
- Breve og Aktstykker, p. 85.
- F. Dvorsky, Nové zpravy o Tychonu Brahovi a jeho rodine (New particulars about Tycho Brahe and his family), Časopis Musea Královstvi Českeho, vol. lvii., 1883, pp. 60–77.
- Breve og Aktstykker, p. 145. It appears from this letter that an annual interest of 6 per cent, was paid on the capital to Tycho's friend, Professor Backmeister, in Rostock (in whose house the quarrel with Parsbjerg had begun in 1566 which led to the loss of part of Tycho's nose).
- Lisch, T. Brahe u. seine Verh. zu Meklenburg, pp. 11, 18. In the letter of 10th April 1601, Tycho mentions that all his instruments are now conveniently placed in Curtius' house.
- Kepler dedicated his little book De Fundamentis Astrologiæ to "Petro Wok Ursino, Domus Rosembergicae Gubernatori."
- The younger Tycho Brahe had in January 1601 started for Italy in company with Robert Sherley, ambassador from the Shah of Persia to various European courts. Carteggio di Magini, p. 237.
- "Ego in sequentibus demonstrationibus omnes tres auctorum formas conjungam. Nam et Tycho, me hoc quandoque suadente id se ultro vel me tacente facturum fuisse respondit (fecissetque si supervixisset) et moriens a me, quern in Copernici sententia esse sciebat, petiit, uti in sua hypothesi omnia demonstrarem." Kepler, De Stella Martis, cap. vi.; Opera, iii. p. 193. Gassendi (p. 179) gives it in these words:—"Quæso te, mi Joannes, ut quando quod tu Soli pellicienti, ego ipsis Planetis ultro affectantibus et quasi adulantibus tribuo, velis eadem omnia in mea demonstrare hypothesi, quæ in Copernicana declarare tibi est cordi."
- Kepler wrote in the observing ledger a short account of Tycho's last illness, which was printed by Snellius in his Observations Hassiacæ, Lugduni Bat., 1618, pp. 83–84, and in this volume, Note D. Kepler also wrote an elegy over Tycho Brahe, which is printed by Gassendi, p. 235 et seq., and in Kepler's Opera, viii. p. 138 et seq.
- "De vita et morte D. Tychonis Brahe Oratio Funebris D. Johannis Jessenii, Pragæ, 1601, 4to, Hamburgi, 1610, and reprinted by Gassendi, pp. 224–235. In May 1602 the King of Denmark wrote to the Elector of Saxony to com- plain of the unfair way in which Jessenius had alluded to the broken nose ("facies decora et aperta, quam ante annos triginta Rostochii quidam noctu ausu prorsus sicario læsit, vestigio ad mortem usque semper conspicuo"). The duel, he added, had been a fair fight, and the two adversaries had always afterwards been good friends, and though Parsbjerg's name had not been mentioned, the story was so well known, that the remarks of the orator were most insulting, and ought publicly to be retracted. Danske Magazin, 4th Series, ii. p. 325.
- Anno Domini MDCI die 24 Octobris obiit illustris et generosus Dñus Tycho Brahe, Dñus in Knudstrup et Præses Uraniburgi, & Sacræ Cæsareæ Maiestatis Consiliarius, cujus ossa hic requiescunt.
- Sometimes he wrote it "Non haberi sed esse."
- The inscription is printed in Danske Magazin, ii. p. 357; Weistritz, ii. p. 362, where the tombstone is also figured.
- Andreas Foss, Bishop of Bergen, who had visited Tycho in 1596, wrote to Longomontanus in February 1602 to inquire if the rumour had any foundation (Bang's Samlinger, ii. p. 529; Weistritz, i. p. 195). The astrologer Rollenhagen wrote at the same time to Kepler that Tycho evidently died "per Ursianum quoddam venenum" (Epist. Kepleri, ed. Hanschius, p. 193).
- "Tabulæ Rudolphinæ, quibus astronomicae scientiae, temporum longinquitate collapsæ, restauratio continetur, a Phoenice illo Astronomorum TYCHONE ex illustri et generosa Braheorum in Regno Daniae familia oriundo equite, primum animo concepta et destinata anno Christi mdlxiv., exinde observationibus siderum accuratissimis, post annum praecipue mdlxxii., quo sidus in Cassiopeiae constellatione novum effulsit, serio affectata, variisque operibus, cum mechanicis, turn librariis, impenso patrimonio amplissimo, accedentibus etiam subsidies Friderici II. Daniæ Regis, regali magnificentia dignis, tracta per annos xxv. potissimum in insula freti Sundici Huenna et arce Uraniburgo, in hos usus a fundamentis exstructa, tandem traducta in Germaniam inque aulam et nomen Rudolphi Imp. anno mdiic. Tabulas ipsas, jam et nuncupatas et affectas, sed morte auctoris sui anno mdci. desertas, . . . perfecit, absolvit adque causarum et calculi perennis formulam traduxit Johannes Kepplerus." (Ulm, 1627.)
- Delambre has made this remark in a somewhat exaggerated form, Hist. de l'Astr. moderne, ii. p. xiv.: "Si Tycho fut resté dans son ile, jamais Kepler ne se fut rendu à ses invitations; nous n'aurions certainement pas la Théorie de Mars, et nous ignorerions peut-être encore le véritable système du Monde."