Tycho Brahe: a picture of scientific life and work in the sixteenth century/Chapter 3

by John Louis Emil Dreyer

 

CHAPTER III.

THE NEW STAR OF 1572.

On the evening of the 11th November 1572, Tycho Brahe had spent some time in the laboratory, and was returning to the house for supper, when he happened to throw his eyes up to the sky, and was startled by perceiving an exceedingly bright star in the constellation of Cassiopea, near the zenith, and in a place which he was well aware had not before been occupied by any star. Doubtful whether he was to believe his own eyes, he turned round to some servants who accompanied him and asked whether they saw the star; and though they answered in the affirmative, he called out to some peasants who happened to be driving by, and asked the same question from them. When they also answered that they saw a very bright star in the place he indicated, Tycho could no longer doubt his senses, so he at once prepared to determine the position of the new star. He had just finished the making of a new instrument, a sextant similar to the one he had made for Paul Hainzel, and he was therefore able to measure the distance of the new star from the principal stars in Cassiopea with greater accuracy than the cross-staff would have enabled him to attain.^[1] In order to lessen the weight, the instrument was not made of metal, but of well-seasoned walnut-wood, the arms being joined by a bronze hinge, and the metallic arc only 30° in extent, and graduated to single minutes. The arms were four cubits, or about five and a half feet long,^[2] three inches broad, and two inches thick; and to steady the instrument an undivided arc was attached to the arm which held the graduated arc, about eighteen inches from the centre, and passing loosely through a hole in the other arm, where it could be clamped by a small screw. This undivided arc and the long screw which served to separate the arms steadied the instrument, and kept its various parts in one plane. The graduated arc was not, as in his later instruments, subdivided by transversals, and the two sights were still of the usual kind, which he afterwards discarded, viz., two square metallic plates with a hole in the centre. The error of excentricity, caused by the unavoidable position of the observer's eye slightly behind the centre of the arc, was duly tabulated and taken into account.

With this instrument Tycho measured the distance of the star from the nine principal stars of Cassiopea. We can easily picture to ourselves the impatience with which he must have awaited the next clear night, in order to see whether this most unusual phenomenon would still appear, or whether the star should have vanished again as suddenly as it had revealed itself. But there the star was, and continued to be for about eighteen months, north of the three stars (now called β, α, γ Cassiopeæ) which form the preceding part of the well-known W of this constellation, and forming a parallelogram with them. It was only a degree and a half distant from a star (κ) of the 41/2 magnitude. Tycho continued, while the star was visible, to measure its distance from the other stars of Cassiopea; and in order to find whether it had any parallax, he repeated these measures from time to time during the night, and even left the sextant clamped in the interval between two observations, to make sure that no change had taken place in the instrument in the meantime. The star being circumpolar for his latitude, he was able to follow it right round the pole, and he took advantage of this circumstance to observe its altitude at the lower culmination by the sextant, as he did not at that time possess a quadrant. He placed it in the plane of the meridian with the one arm, which we may call the fixed one, and to which he had now attached an arc of 60°, resting horizontally on a window-sill and a short column inside the room.^[3] To ensure the horizontal position of the arm, it was moved until a plumb-line suspended from the end of the graduated arc touched a mark exactly at the middle of the arm,^[4] and as the instrument might happen to be slightly moved while the observation was being made, a short graduated arc was traced at the middle of the arm, on which the plumb-line would immediately mark the small correction to be applied to the observed altitude. This simple but neat contrivance is highly characteristic of Tycho; we recognise here the modern principle of acknowledging an instrument to be faulty, and applying corrections for its imperfections to the results determined by it, a principle which we shall see he followed in the construction of all his instruments. From repeated observations he found the smallest altitude of the new star to be 27° 45′, and consequently, as he assumed the latitude of Heridsvad to be 55° 58′, the declination of the star was 61° 47′. He remarks that the declination was as constant as the distances from the neighbouring stars, and that the instrument was not perfect enough to show the change of about a third of a minute which the precession of the equinoxes made in the declination while the star was visible, an amount which even his later and more perfect instruments would hardly have been able to point out.^[5]

With the sextant Tycho was not able to observe the upper culmination of the star, at which it was only 6° from the zenith. As a supplement to his own results, he therefore gives in his later work^[6] the observations made with the great quadrant at Augsburg by Paul Hainzel, which give a value of the declination agreeing within, a fraction of a minute with his own.

The observations with the sextant must have occupied Tycho during the winter of 1572-73, during which time the brightness of the new star had already commenced to decline considerably. When he first saw it, on the 11th November, it was as bright as Venus at its maximum brightness, and remained so during the month of November, so that sharp-sighted people could even see it in the middle of the day, and it could be perceived at night through fairly dense clouds. In December it was somewhat fainter, about equal to Jupiter; in January, a little brighter than stars of the first magnitude; and in February and March, equal to them. In April and May it was like a star of the second magnitude; in June, July, and August, equal to one of the third, so that it was very like the principal stars in Cassiopea. It continued to decrease during September, so that it reached the fourth magnitude in October, and was exactly equal to κ Cassiopeæ in November. At the end of the year and in January 1574 it hardly exceeded the fifth magnitude; in February it came down to the sixth magnitude, and about the end of March it ceased to be visible. At the same time the colour gradually changed; at first it was white, and by degrees became yellow, and, in the spring of 1573, reddish, like Betelgeuze or Aldebaran. About May 1573 it became like lead, or somewhat like Saturn, and seemed to remain so while the star was visible.^[7]

About the time when the new star appeared Tycho Brahe had prepared an astrological and meteorological diary for the following year, giving the time of rising and setting of the principal stars, the aspects of the planets, and the phases of the moon, together with their probable influence on the weather. To this diary he added an account of his observations on the new star and its probable astrological signification. Early in 1573 he went to Copenhagen on a visit to his friend Professor Johannes Pratensis, and brought the manuscript with him. Pratensis had not yet heard of the new star, and would scarcely believe Tycho when he told him about it. Equally incredulous was another friend, Charles Dancey, French envoy at the Danish court, who invited Tycho and Pratensis to dinner as soon as he heard of the arrival of the former. During the dinner Tycho happened to mention the star, but Dancey thought he was joking and intending to sneer at the ignorance of Danish savants in astronomy, while Tycho only smiled, and hoped that the evening would be clear, so that they could see the star with their own eyes. The evening was favourable, and Pratensis and Dancey were as surprised as Tycho had been when they saw this new star, so utterly different from a comet (the only class of celestial bodies with which anybody thought of comparing it), and yet, according to Tycho's observations, more distant than the planets, and probably belonging to "the eighth sphere," which had always hitherto been considered the very picture of immutability. Pratensis at once recollected the statement made by Pliny in the second book of his Natural History (on which he happened to be then lecturing at the University), that Hipparchus is said to have observed a new star; and perceiving the importance of the manuscript essay which Tycho had given him to read, he urged him to have it printed. But Tycho declined, on the pretence that the essay had not received the final touches from his hand, but really because he was not quite free from the prejudice of some of his fellow-nobles, that it was not proper for a nobleman to write books.^[8]

Tycho therefore returned to Scania with his manuscript. But when the spring came, and communication with Germany was reopened, he received from thence through Pratensis so many accounts of the star, both written and printed, containing a vast amount of nonsense, that he became inclined to let his own book be published, as it might serve to refute the erroneous statements circulated about the star. During a second visit to Copenhagen he was entreated to publish the book, not only by Pratensis, but also by his kinsman, Peter Oxe, high treasurer of Denmark, whose sister had been the wife of Jörgen Brahe, and consequently had been a second mother to Tycho. Shaken in his resolution by the persuasions of this intelligent man, who even suggested that he might hide his name under an anagram if he did not wish to put it on the title-page, Tycho finally yielded so far as to allow Pratensis to let the account of the star and the plan of the meteorological diary be printed, omitting the details of the latter. The book was therefore printed at Copenhagen in the year 1573, but very few copies appear to have been distributed or sent abroad, so that it afterwards became necessary to reprint the more important parts of it in the greater work, Astronomiæ Instauratæ Progymnasmata, on which Tycho was engaged during the last fourteen years of his life, and which was published after his death. The little book, De Nova Stella, is now extremely scarce, and does not appear to have been seen by any modern writer on the history of astronomy. It will therefore not appear inopportune if I give a somewhat detailed account of its contents in this place.^[9]

On the back of the title-page is a versified address to the author from Professor Joh. Francisci Ripensis, one of his earliest friends. Then follows a letter from Pratensis, dated 3rd May 1573,^[10] begging Tycho to print the book, at least the part relating to the star, the plan of the diary (if he should think the diary itself too long), and the forecast of the lunar eclipse. Tycho's answer comes next, dated "Knusdorp," 5th May. In this he remarks that the intricate diagrams and figures of the diary would be very troublesome to reproduce, and the year is nearly half over, so that it would not be worth while printing the diary. As to the star, he fears that the account of it is a very immature one; still he will let it be published, partly because his friend wishes it, partly because some of the German accounts of the star place it at a distance of only twelve or fifteen semi-diameters of the earth, while his own observations of its distance from Schedir (α Cassiopeae) show that it is situated in ipso cœlo. He has made his observations with a new and exquisite instrument, much better than a radius or any similar instrument, and the horizontal parallax of three or four degrees, which the star would have if it were as close to us as stated by the German writers, would have been easily detected. "O cœcos cœli spectatores!" Somebody had thought that it was a comet with the tail turned away from the earth, but that writer has forgotten what Apianus and Gemma Frisius have taught us, that the tails of comets are turned away from the sun, and not from the earth. Others thought the star was one of the tailless comets which the ancients called Crinitæ; others again that it belonged to the class called Rosæ, with a disc gradually fainter towards the edges. But it looks exactly like other stars, and nothing like it has been seen since the time of Hipparchus. It does not seem likely that it will last beyond September, or at most October (1573), and it would be far more marvellous if it remained, for things which appear in the world after the creation of the universe ought certainly to cease again before the end of the world. As his own conclusions thus differ so much from those of the German writers, he consents to let his book be printed, and sends it herewith,^[11] leaving him to settle the title, and only begging him to suppress the author's name or to hide it in an anagram, as many people are perverse enough to think it an ingens indecus for a nobleman to work in the free and sublime sciences. He has not had time to revise the manuscript owing to domestic affairs,^[12] other studies, and social intercourse with friends. He next proceeds in some poetical lines^[13] to declare his intention of seeing more of the world in order to increase his knowledge, as it will be time enough later on to return to the frigid North, and, like other nobles, waste his time on horses, dogs, and luxury, unless God should reserve him for something better. Having (in prose) assured Pratensis of his lasting friendship wherever they both may be, and reminded him that they shall at all events be contemplating the same sun, moon, and stars, he gives vent to his feelings in the following lines, which may serve as a specimen of Tycho's poetical effusions:—

"Et quia disiunctis, Radios coniungere in unum
    Non licet, et nosmet posse videre simul,
Jungemus radios radiis radiantis Olympi,
    Quando micant claro, sydera clara, Polo.
Tunc ego, quam specto, figens mea lumina cœlo
    Est quoque luminibus, Stella videnda, tuis.
Sic oculos pariter Cœlum coniunget in unum,
    Nostra licet iungi corpora Terra vetet."

Finally, he ends this lengthy introduction by asking Pratensis to urge the workmen who are making him a celestial globe and other instruments, so that they can all be ready when he comes over again.^[14]

Next comes the account of the star, exactly as afterwards reprinted in his greater work, filling a little more than twenty-seven pages (A to second page of D2). As this is more generally accessible than the other parts of the book, a short abstract will suffice here. Having described how he first saw the star, he quotes the words of Pliny relating to the star of Hipparchus, which many had taken to be a comet; but as it would be absurd to fancy that a great astronomer like Hipparchus should not have known the difference between a star of the æthereal region and a fiery meteor of the air which is called a comet,^[15] it must have been a star like the present one which he saw. Since that time no similar star has been seen till now, for the star of the Magi was not a celestial object, but something relating exclusively to them, and only seen and understood by them. How it was created he does not profess to offer an opinion about, but proceeds to treat of its position among the stars. This is illustrated by a diagram of the stars in Cassiopea, and the measured distances of the new star from α, β, and γ Cassiopeæ are given,^[16] after which he shows how the rules of spherical trigonometry of Regiomontanus give the longitude and latitude of the star from these data. He adds that the accuracy of the co-ordinates deduced will, of course, depend on that of the positions of the fixed stars he has used; but as he has not any observations of his own to depend on, he is obliged to use the positions given by Copernicus, trusting that God will spare him and enable him to correct the accepted places of the fixed stars by new observations. In order to find the distance of the star from the earth, he has measured its angular distance from Schedir, which passed the meridian nearly at the same time, both at upper and lower culmination, and found no difference whatever; whereas he shows that there would have been a parallax at lower culmination equal to 581/2′ if the star had been as near to us as the moon is.^[17] Therefore the star could not be situated in the elementary region below the moon, nor could it be attached to any of the planetary spheres, as it would have been moved along with the sphere in question in a direction contrary to that of the daily revolution of the heavens, while his observations show that it has since its first appearance remained immovable. Consequently, it must belong to the eighth sphere, that of the fixed stars; and it cannot be a comet or other fiery meteor, as these are not generated in the heavens, but below the moon, in the upper regions of the air, upon which all philosophers agree, unless we are to believe Albumassar, who is credited with the statement that he had observed a comet farther off than the moon, in the sphere of Venus. Here again Tycho expresses the hope that he will some time get a chance of deciding this matter (as to the distance of comets); but anyhow, he adds, this star cannot have been a comet, as it had neither the appearance of one nor the proper motion which a comet would have been endowed with.

The third paragraph deals with the magnitude and colour of the star. The volume of a star is very considerable; the smallest are eighteen times as great as the earth, those of the first magnitude 105 times as great. Therefore the new star must have been of immense size. He then describes its gradual decline, until it "now, at the beginning of May, does not exceed the second magnitude." It must, therefore, at first have been much more than a hundred times as large as the earth, but it has decreased in size. It twinkles like other stars, while the planets do not twinkle, which is another proof of its belonging to the eighth sphere. Having mentioned the change in colour, he finishes the astronomical part of the treatise on the star by remarking that the change in colour and magnitude does not prove it to be a comet or a similar phenomenon, for if it is possible that a new body can be generated in the æthereal region, as he has proved to be the case in opposition to the opinions of all philosophers, it must be considered far less impossible and absurd that this new star should change in brightness and colour. And if it could ever, beyond the ordinary laws of nature, have been seen in the heavens, it would not be more absurd if it should again cease altogether to be visible, though again in opposition to those laws.

Tycho now proceeds to give his opinion about the astrological effects of the new star.^[18] These cannot be estimated by the usual methods, because the appearance of the star is a most unusual phenomenon. The only known precedent is the star said to have appeared at the time of Hipparchus, about B.C. 125. It was followed by great commotions both among the Jewish people and among the Gentiles, and there is no doubt that similar fatal times may be expected now, particularly as the star in Cassiopea appeared nearly at the conclusion of a complete period of all the Trigoni.^[19] For in about ten years the watery Trigon will end with a conjunction of the outer planets in the end of the sign of Pisces, and a new period will commence with a fiery Trigon. Referred to the pole (i.e., according to right ascension), the new star belongs to the sign of Aries, where the new Trigon will also begin, and there will therefore be great changes in the world, both religious and political. The star was at first like Venus and Jupiter, and its effects will therefore first be pleasant; but as it then became like Mars, there will next come a period of wars, seditions, captivity, and death of princes and destruction of cities, together with dryness and fiery meteors in the air, pestilence, and venomous snakes. Lastly, the star became like Saturn, and there will therefore, finally, come a time of want, death, imprisonment, and all kinds of sad things. As it is not exactly known when the star first appeared, he follows the example of Halus, a commentator of Ptolemy (on the occasion of the appearance of a comet), and assumes that it appeared at the time of new moon, the 5th of November,^[20] at 7h. 55m., for which moment he finds that Mars was the ruling planet. The places most affected by the star will be those in latitude 62° (in the zenith of which the star could be); but as the star belongs to Aries, its influence will be felt nearly over the whole of Europe, and particularly after the great conjunction (of April 1583) has added its great power to that of the star.

It will be seen that this prediction is only expressed in very vague terms, and we shall find, when we come to analyse Tycho's later writings, that he afterwards modified and extended it. When he wrote his preliminary treatise on the new star, he was evidently chiefly inclined to ascribe a direct physical and meteorological influence to the celestial bodies, though he was by no means blind to the difficulty of foretelling the results of this influence, but he became gradually more inclined to disregard the physical effect (dryness, pestilence, &c.), and solely to look to the effect of the stars on the human mind, and through that on the human actions. That an unusual celestial phenomenon occurring at that particular moment should have been considered as indicating troublous times, is extremely natural when we consider the state of Europe in 1573. The tremendous rebellion against the Papal supremacy, which for a long time had seemed destined to end in the complete overthrow of the latter, appeared now to have reached its limit, and many people thought that the tide had already commenced to turn. In the south of Germany and in Austria the altered tactics of the Church of Rome, due to the influence of the fast rising Society of Jesus, were stamping out the feeble attempts of Reformers; in France, the Huguenots were fighting their unequal battle with the fury of despair against an enemy who a year ago had attempted to end the strife by the infamous butchery of St. Bartholomew;^[21] in the Netherlands, hundreds had suffered for their faith, while the country was being devastated with fire and sword in the vain efforts of the Spanish Government to make a free nation submit to their own sanguinary religion; in England, the hopes of Protestants might at any moment be seriously threatened if the dagger of an assassin should find way to the heart of their queen, or if her most formidable and venomous enemy should turn his dreaded power against her. Who could doubt that fearful disturbances were in store for the generation that beheld the new star as well as for the following one? The moderation of Tycho's astrological predictions is therefore remarkable, and becomes more conspicuous if we compare his opinions with the many silly ones expressed by contemporary writers.

Before we say a few words about these, we shall, however, finish the review of the contents of Tycho's book. We have already mentioned that he did not think it worth while to print the astrological calendar for the year 1573, of which the treatise on the new star originally formed a part, but that he contented himself with publishing the introduction, setting forth the principles on which the calendar, or diary, as he calls it, had been constructed. This fills sixteen and a half pages. It begins with a good deal of abuse of the ordinary prognostications, the absurdities of which he intends to expose in a book to be called Contra Astrologos pro Astrologia. This intention he does not seem to have carried into effect, and two other treatises, which he says were already written, seem not to have been preserved.^[22] He remarks that both the Alphonsine and the Prutenic Tables are several hours wrong with regard to the time of the equinoxes and solstices, and it is useless to give the time of entry of the sun into any part of the Zodiac to a minute, as the sun in an hour moves less than 3′, a quantity which cannot be observed with any instrument. Some writers are foolish enough to give minutes and seconds when stating the time of any particular position of a planet, although at the conjunction of Saturn and Jupiter in 1563 the Alphonsine Tables were a whole month in error, while even the Prutenic Tables could hardly fix the day correctly, not to speak of minutes or seconds.^[23] A calendar should contain the usual information as to the aspects, time of sunrise and sunset, time of rising and setting of the moon and planets, and the names of the principal stars rising and setting at the same time. The moon is of particular importance as it is nearest to the elementary world, but even the planets must influence the weather. Lastly, a calendar should give the probable weather for every day, concluded from the configurations of the celestial bodies. He would warn the reader not to expect too much from the weather predictions, partly because much remains yet to be done in exploring the motions of the stars and their effect, partly on account of the fluidity of the inferior matter, which sometimes delays, sometimes hastens the effect produced by the stars. But any blame should rest on him and not on the art. Besides terrestrial influences must act differently in different parts of the earth, so that one configuration of the stars cannot have the same effect in several localities. Therefore he has undertaken this work principally in order by observation to learn the effect of the stars on this part of the earth, so that our posterity may profit thereby, and in order to secure this object he exhorts all meteorologists to take observations of the weather.

The only part of the diary given in the book is that relating to the total eclipse of the moon on December 8, 1573. It fills twenty-four pages, including two full-page woodcuts—one of the progress of the eclipse, the other of the earth, moon, and planets at that time. He gives first the calculation of the eclipse by the Prutenic Tables, with all the details step by step, and for the sake of comparison, the resulting time of the various phases (without details of calculation) by the Alphonsine Tables and Purbach's Tables; also the same data after correcting the places of the sun and moon by his own observations.^[24] He adopts the meridian 35° ab occasu, by which he probably means 35° east of the peak of Teneriffe. He recommends observers to discard clocks of any kind, but to fix the time by observing altitudes of some stars not too far from the east or west horizon, but which, when on the meridian, would have a considerable altitude, and he gives the altitudes of a few stars for the beginning and end of the eclipse and of totality. The astrological significance he computes by the rules given by Ptolemy in the second book of his Tetrabiblion. Mercury, and in the second place Saturn, are the ruling planets. The former means robbery, stealing, and piracy; the latter want, exile, and grief. The regions chiefly affected by the eclipse are those which Ptolemy specially connected with the sign of Gemini, where the moon is. These are Hircania, Armenia, Cyrene, Marmaria, and Lower Egypt, to which later astrologers have added Sardinia, Lombardy, Flanders, Brabant, and Würtemberg. It has been observed that the sign of Gemini has a special significance for Nürnberg whenever an eclipse or a conjunction took place in it, and the Nürnbergers may therefore expect something, possibly pestilence, as Gemini is a "human sign," and also on account of the positions of Mercury and Mars. Countries whose rulers were born when Gemini was culminating may also be on the look-out, and generally speaking kings and princes are more affected by eclipses than private people ("as I have observed myself"), because the sun and the moon are the princes among the planets. The effect will last as many months as the eclipse lasted hours, and the beginning of it depends on the moon's distance from the horizon at the commencement of the eclipse. This eclipse will take effect from March till July 1574 (for latitude 56°). As examples of this kind of prognostications he quotes several recent eclipses. First, the lunar eclipse of April 3, 1558, after which Charles V. died; then the solar eclipse of April 18, 1558, which did not begin to take effect till the end of the year, and then Christian III. of Denmark and Norway died; and shortly afterward the deposed king, Christiern II., a captive for many years, died also; and Tycho shows how beautifully this agreed with their horoscopes. On November 7, 1565, a lunar eclipse took place near the Plejades, a group of stars with a moist and rainy influence, and consequently rainy weather came on, as he had at the time predicted at Leipzig. Similarly a lunar eclipse occurred on the 28th October 1566 close to Orion, and the effect should, according to Ptolemy, begin at once; and so it did, and the whole winter turned out wet, as he predicted himself at Rostock. He does not say a word about the old Sultan!

The book is wound up with In Vraniam Elegia Autoris, filling more than eight pages, and a page of verses by Vedel. In the Elegy, Tycho promises soon to produce something better, as neither the sneers of idle people nor the hardships of study shall deter him; let others boast of their achievements in war or of their ancient family, let others seek the favour of princes or hunt for riches, or waste their time gambling and hunting, he does not envy them, for though sprung from ancient races both on the father's and on the mother's side, he does not value it, and calls nothing his but what has originated with himself.^[25] But his mind is planning great things, and happy above all men is he who thinks more of celestial than of earthly things.

I have given a very full account of the contents of Tycho's little book, not only because it is now extremely scarce, but also because it is very characteristic of him, and presents us with a perfect picture of the young author, his plans and his difficulties. We see him thoroughly aware of the great desideratum of astronomy, a stock of accurate observations, without which it could not possibly advance a single step further, and hoping that life and means might be granted him to supply this deficiency; we see in him at the same time a perfect son of the sixteenth century, believing the universe to be woven together by mysterious connecting threads which the contemplation of the stars or of the elements of nature might unravel, and thereby lift the veil of the future; we see that he is still, like most of his contemporaries, a believer in the solid spheres and the atmospherical origin of comets, to which errors of the Aristotelean physics he was destined a few years later to give the death-blow by his researches on comets; we see him also thoroughly discontented with his surroundings, and looking abroad in the hope of finding somewhere else the place and the means for carrying out his plans. At the same time the book bears witness to the soberness of mind which distinguishes him from most of the other writers on the subject of the star. His account of it is very short, but it says all there could be said about it—that it had no parallax, that it remained immovable in the same place, that it looked like an ordinary star—and it describes the star's place in the heavens accurately, and its variations in light and colour. Even though Tycho made some remarks about the astrological significance of the star, he did so in a way which shows that he did not himself consider this the most valuable portion of his work. To appreciate his little book perfectly, it is desirable to glance at some of the other numerous books and pamphlets which were written about the star, and of most of which Tycho himself has in his later work (Progymnasmata) given a very detailed analysis, devoting nearly 300 pages to the task. It would lead us too far if we were to follow him through them all, but it will not be without interest briefly to describe what some of the more rational of his contemporaries published about the star, and to what absurdities a fervid imagination led some of the common herd of scribblers.

At Cassel the star was observed by Landgrave Wilhelm IV., an ardent lover of astronomy, of whom we shall hear more in the sequel. He did not hear of the star till the 3rd December, and took observations of its altitude in various azimuths from that date and up to the 14th March following. From the greatest and smallest altitude Tycho found afterwards a value of the declination differing less than a minute from that found by himself. From the azimuths and altitudes observed at Cassel Tycho deduced the right ascension and declination: the single results for the latter are in good accordance inter se, while those for right ascension differ considerably, the greatest difference being more than 2°. Tycho justly concludes that this must be caused by the bad quality of the clock employed by the Landgrave, who merely gave the time of observation in true solar time, without furnishing the means of correcting for the error of his clock. In a letter to Caspar Peucer, the Landgrave stated that the star might have a parallax not exceeding 3′, as there was that difference between the polar distances above and below the pole; but his instruments had at that time not reached the degree of accuracy which they did ten years later, and the difference is not surprising. Peucer and Wolfgang Schuler at Wittenberg found a parallax of 19′, which Tycho believed was a consequence of their having used an old wooden quadrant; and, in fact, when he learned that the Landgrave had found little or no parallax, Schuler had a large triquetrum constructed, and also found that the star had no parallax, or at most a very small one.^[26] Many observers measured the distance of the new star from the neighbouring ones, but the results found were generally considerably in error. Thus the Bohemian, Thaddæus Hagecius, physician to the Emperor, in an otherwise sensible book,^[27] gives a number of observed distances, some of which are 7′ to 12′ (one is even 16′) wrong, and even the English mathematician, Thomas Diggs (or Digges), who had made a special study of the cross staff, and had his instrument furnished with transversal divisions, differed 11/2′ to 4′ from Tycho,—possibly, as the latter thinks, because he did not allow sufficiently for the error of excentricity.^[28] Cornelius Gemma, a son of the well-known astronomer, Gemma Frisius, and professor of medicine at Louvain, had a great deal to say about the star, but most of his distance measures are upwards of a degree wrong. On the other hand, Michael Mœstlin, the teacher of Kepler, though he possessed no instruments, determined the place of the star with fair accuracy simply by picking out four stars so placed that the new star was in the point of intersection of two lines drawn through two and two of them. As the star did not move relatively to these four stars during the daily revolution of the heavens (of which he assured himself by holding a thread before the eye, so that it passed through the three stars), Mœstlin concluded that it had no parallax, and that it was situated among the fixed stars, whose distance Copernicus, of whom he was a follower, had shown to be extremely great. Digges tried the same method, using a straight ruler six feet long, which he first suspended vertically until he found two stars which were in the same vertical as the new star; six hours afterwards he tried again, holding the ruler in his hand, whether the three stars were still in a straight line. He found the star to be exactly in the point of intersection of the line joining β Cephei and γ Cassiopeæ, and the line joining ι Cephei and δ Cassiopeæ, and concluded that it could not have a parallax amounting to 2′. Tycho afterwards computed the place of the star from these data, using his own accurate positions of the four stars, and found the longitude only 2′ greater and the latitude 1/2′; greater than what he had deduced from his own observations.^[29] Digges had hoped to test the Copernican theory of the motion of the earth by trying whether the star had an annual parallax, but he could find none. The question of the star's distance from the earth being one of special interest, all observers tried to determine the daily parallax, but the results varied immensely according to the skill of the observer. While several writers, in addition to those already mentioned, state that they could find no perceptible parallax,^[30] others found a large one. Thus Elias Camerarius at Frankfurt on the Oder had at first thought that he had found a parallax of 12′, but in January 1573 he could only find one of 41/2′, from which he concluded that the star had in the meantime receded from us in a straight line (so that its apparent place was not altered), and that this was the cause of its diminished brightness. A German writer of the name of Nolthius tried to find the parallax by a method suggested by Regiomontanus from the hour angle, the azimuth and the latitude of the observing station, comparing the altitude computed from these with the observed one. He chose, however, a bad time for the experiment, when the altitude was very great (77°), and it is not to be wondered at that he found an absurd result—39′ for the parallax—and it does not seem to have struck him that this would correspond to a parallax equal to 2° 42′ at the lowest altitude of the star, which could not have escaped even casual observers, as pointed out by Tycho.^[31]

Of greater interest than these crude attempts are the statements of the various writers as to the time when the star first became visible. Some writers say that the star was already seen early in October, but none of them are entitled to much credit. The above-named Elias Camerarius at Frankfurt on the Oder says that it appeared "in principio Octobris Anni 1572 uesperi circa horam 10 prope anum;" but as he appears to be utterly unknown in the history of science, too much weight ought not to be attached to his unsupported statement.^[32] Annibal Raimundus of Verona (of whom we shall hear more presently) tells us that the star was seen "circa principium Octobris, a plurimis Nobilibus et Ignobilibus, eruditis atque indoctis," but further on he contradicts himself, saying that the star has now been visible three months, and as he wrote at the end of January 1573, this would make the appearance of the star date from the end of October or the beginning of November.^[33] A little French book, published in 1590, states that the star was seen "au mois d'Octobre" in Spain by shepherds keeping watch over their flocks, but this reminds one too much of the words used by St. Luke, and is contradicted by other testimony.^[34] According to Paul Fabricius at Vienna it appeared "sub Octobris finem."^[35] All these statements are contradicted by Munosius, professor in the University of Valencia, who maintained that he was certain the star had not yet appeared on the 2nd November, as he was showing his pupils the constellations on that night, and could not have failed to see it, and Spanish shepherds agreed with him therein. As Munosius took very fair distance measures of the star, and wrote in a sensible strain, there is every reason to believe him.^[36] The first trustworthy observation seems to have been made by Wolfgang Schuler at Wittenberg, who says that he saw it at six o'clock in the morning on the 6th November.^[37] On the 7th at 6 P.M. it was seen by Paul Hainzel,^[38] and the same evening by Bernhard Lindauer, minister at Winterthur in Switzerland.^[39] Maurolycus, the well-known astronomer at Messina, and David Chytræus at Rostock, saw it on the 8th.^[40] Many writers have quoted the words of Cornelius Gemma, stating that the star appeared first on the 9th November, and that it had not been visible on the previous evening in clear weather,^[41] but they have overlooked the fact that Gemma, in his book De Naturæ Divinis Characterismis, seu raris & admirandis Spectaculis, Libri ii. (Antwerp, 1575, 2 vols. 8vo), tells quite a different story, viz., that some people had already seen it before the end of October. He does not say when he first saw it himself, but he did not begin to observe its position till the 26th November, as he thought it idle talk when he first heard of a new star.^[42] Gemma's testimony is therefore worth nothing, and it may safely be assumed that the star became visible between the 2nd and the 6th of November, and was seen by an apparently trustworthy observer on the morning of the 6th.

That many different attempts should be made to explain the nature of the new star and the cause of its sudden appearance is very natural. Most writers contented themselves by saying that it was some sort of a comet, though not of the usual kind, as these, according to Aristotle, were sublunary, while the star was far beyond the moon. That it did not in the least look like a comet was generally not considered an objection to this theory, as instances could be quoted of comets having appeared without tails;^[43] a greater difficulty was the absence of motion relatively to the other stars in Cassiopea, as only very few writers had the hardihood to maintain that it had actually moved before it disappeared.^[44] Gemma sought to explain this by supposing, with Elias Camerarius, that the star was moving in a straight line away from us,^[45] but this could not account for the sudden appearance of the star with its maximum brightness. Others thought it more probable that the star was not a new one, but merely an old and faint star, which had become brighter through some sudden transformation of the air between it and the earth, or a condensation of part of one of the spheres through which its light had to pass. The principal reason why some writers (e.g., Reisacher and Vallesius) adopted this explanation was, that God had ceased creating on the sixth day, and nothing new had been made since then. Reisacher had at first thought that the star was identical with κ Cassiopeæ, which had merely become brighter, but when the light of the star had become less dazzling he perceived that κ was still in the heavens, and that he had merely failed to see it hitherto owing to the overpowering light of the new star. More obstinate was Raimundus of Verona, who in two publications maintained that it was nothing but κ. He seems to have done so with unnecessary heat, and using contemptuous expressions about people who thought differently, as Tycho in reviewing his writings uses stronger language than usual, and Hagecius thought it necessary to publish a refutation full of the most violent invectives and written in a very slashing style.^[46] Another Italian, Frangipani, also took the star to be κ Cassiopeæ, and as its place did not agree with that assigned to the latter by Ptolemy, he calmly assumed that the old star must have moved. He quotes the old story about the seventh star of the Plejades (Electra) having disappeared after the destruction of Troy, and asserts that the pole-star did the same for a while after the taking of Constantinople by the Turks.^[47] All this is, however, very tame compared with the fancies of a German painter, Georg Busch, of Erfurt, who wrote two pamphlets "Von dem Cometen." According to him it was a comet, and these bodies were formed by the ascending from the earth of human sins and wickedness, formed into a kind of gas, and ignited by the anger of God. This poisonous stuff falls down again on people's heads, and causes all kinds of mischief, such as pestilence, Frenchmen (!), sudden death, bad weather, &c. Perhaps it was the night of St. Bartholomew which made Busch think of Frenchmen in this connection.

The question as to whether new stars had ever appeared before was touched on by several writers, who referred to the star of Hipparchus and the star of Bethlehem. Landgrave Wilhelm IV., in his letter to Peucer, also alludes to the star stated by Marcellinus to have appeared A.D. 389.^[48] Cyprianus Leovitius states that similar stars appeared in the same part of the heavens in the years 945 and 1264, the "comet" of the latter year being without a tail and having no motion, and says that this information was taken from an old manuscript.^[49] It is certainly a very suspicious circumstance that real comets appeared both in 945 and in 1264, and the absence of tail and motion might merely be subsequent embellishments by the writer of the manuscript referred to by Leovitius; but, on the other hand, it is quite possible that new stars may have appeared in those years without being noticed by other chroniclers, as science was then at it its lowest ebb in Europe, and a new star of perhaps less than the first magnitude and of short duration (like the stars of 1866 and 1876) could easily escape detection.^[50] The only other contemporary author who alludes to the years 945 and 1264 is Count Hardeck, who in 1573 was Rector of the University of Wittenberg; but as his little book is dated the 1st May 1573, and that of Leovitius the 20th February, he would have had time to copy from Leovitius, and in any case it is certain that he speaks of a real comet of the year 1264, as he mentions its tail, while it is doubtful whether he means a comet or a star when speaking of 945.^[51] It has been repeatedly suggested that the star of Cassiopea might be a variable star, with a period of about three hundred years, in which case it should again become visible about the present time, but it is needless to say that the vague assertions of Leovitius form a very slender foundation on which to build such a theory. All the same, it is desirable that the place where the star of 1572 appeared should be examined from time to time. Argelander has, from a discussion of all Tycho's distance-measures, found the most probable position of the star for the equinox of 1865 to be: RA = 0h. 17m. 20s., Decl. = +63° 23′.9. This position agrees remarkably well with that of a small star of the 10.11 magnitude, No. 129 of D'Arrest's list of stars in the neighbourhood of Tycho's Nova, which is for 1865: 0h. 17m. 19s. +63° 23′.1.

Whether this small star is variable or not must be left for the future to decide. Argelander stated in 1864 (speaking from memory) that he had about forty years previously failed to see any star in the place with the transit instrument at Åbo (of 51/2 inches aperture), and that he had also later—probably in 1849—been unable to see anything with the transit circle at Bonn.^[52] There is thus a possibility that D'Arrest's star may have increased in light of late years, and observations made at Twickenham by Hind and W. E. Plummer in 1872–73, and at Prague by Safarik in 1888–89, seem to indicate that it is subject to very slight fluctuations of light.^[53] The map of all the stars in the neighbourhood, prepared by D'Arrest (which is complete down to the fifteenth or sixteenth magnitude, within a radius of 10′ from the place of the Nova) may in future be compared with photographs of this interesting spot, which deserves to be watched from time to time.

I shall not here enter into a lengthy examination of the various prognostications and more or less wild speculations to which the new star gave rise in 1572. As remarked by Tycho, the usual methods of astrology were of no avail in this exceptional case, and there is therefore little to be gained even to the student of the history of astrology (a subject of considerable interest) by an examination of the literature on the star. I shall only point out a few curious particulars. That the star portended great events, possibly of an evil character, seemed evident to most writers, and the star of Bethlehem was frequently referred to as a phenomenon of a similar nature. As the star seen by the wise men foretold the birth of Christ, the new one was generally supposed to announce His last coming and the end of the world. This was already suggested by Wilhelm IV. in his above-mentioned letter to Peucer, and among others who declared their belief in this idea was the successor of Calvin at Geneva, Theodore Beza, who announced it in a short Latin poem.^[54] He even says that it is the very same star which was seen by the Magi; but, as Tycho remarks, perhaps that was only said "poetica quadam festivitate." Gemma, in his book on the comet of 1577, points out the great disturbances which followed the star seen by Hipparchus, and expects similar ones to occur now; Tycho justly remarks that it looks as if Gemma had copied all this from his own little book.^[55] Catholic authors naturally thought that the star foretold the victory of their Church; among these is Theodore Graminæus, Professor of Mathematics at Cologne, author of a book in which there is nothing astronomical, but a great deal about old prophecies.^[56] According to one of these, dating from 1488 and founded on the conjunction of Jupiter and Saturn in 1484, a false prophet was soon to arise, who, of course, turned out to be Luther, and a picture is given of the prophet dressed like a monk, with a shrivelled little devil sitting astride on his neck, and followed by a small monk or choir-boy. Unluckily Luther was not born in 1484, but in 1483, and not on the 22nd October, as assumed by the mathematician Cardan, who worked out his horoscope (in what spirit may easily be conceived), but nineteen days later. The above-mentioned French pamphlet of 1590, printed at a time when Henry IV. had not yet come to the conclusion that "Paris vaut bien une messe," also declares that the star meant the victory of the Church and the King, but the latter must not be a heretic, but fide plenus. The author also states that the star disappeared the 18th February 1574, "qui fut le propre iour que le feu Roy Henry de Valois feist son entree en Cracouie."^[57] Doubtless the star expired from grief at seeing this charming creature bury himself so far from his admiring country. Strange that it did not light up again with joy when he bolted from his Polish kingdom a few months later!

After this digression we shall now return to Tycho, deferring to a later chapter an account of the researches and speculations on the subject of the new star which he made in after-years, and which it would not be possible to describe in this place without a serious break in the continuity of our narrative.

1. The sextant is figured and described in Astr. Inst. Progymnasmata, p. 337 et seq.
2. One Tychonic cubit is=16.1 English inches (D'Arrest, Astr. Nachr., No. 1718, p. 219).
3. The sextant in this position is figured in Progymnasmata, p. 348; Mechanica, fol. E. 3 verso.
4. Tycho considers it necessary to quote Euclid iv. 15 and i. 12 in explanation of this (Progymn., p. 349). Euclid was apparently still considered an author with whose work but few were familiar (see H. Hankel, Zur Geschichte der Mathematik im Alterthum und Mittelalter, p. 355).
5. Progymn., p. 351. Individual results of observations are not given, and, unluckily, the original observations of Nova are lost; at least they are not in the volume of observations from 1563-81, repeatedly quoted. This only contains the following observations of Nova:—"1573 Die pentecostis 10 Maji inter flexuram Cassiopeæ et novam stellam 5^g8′, 5^g0′. Inter supremam cathedræ et novam stellam 5^g28′, 5^g20′. Inter Schedir et novam stellam 8^g5′, 7^g52′. Confide his observationibus subtracta tamen instrumenti parallaxi (5 gradus habent parallaxin 8 minutorum, 8 gradus habent 13).—Augusti die 14 inter novam stellam et Polarem 25^g9′."
6. Progymn., p. 360.
7. Progymnasmata, pp. 300-302, and p. 591, the latter place being a reprint of the preliminary account printed in 1573.
8. Progymnasmata, p. 579.
9. The title given in Lalande's Bibliographie is erroneous. The complete title is: "Tychonis Brahe, Dani, De Nova et Nullius Aevi Memoria Prius Visa Stella iam pridem Anno a nato Christo 1572 mense Nouembrj primum Conspecta, Contemplatio Mathematica. Cui, præter exactam Eclipsis Lunaris, hujus Anni, pragmatian, Et elegantem in Vraniam Elegiam, Epistola quoque Dedicatoria accessit: in qua, nova et erudita conscribendi Diaria Metheorologica Methodus, utriusque Astrologiæ Studiosis, eodem Autore, proponitur. Cuius, ad hunc labentem annum, Exemplar, singulari industria elaboratum conscripsit, quod tamen, multiplicium Schematum exprimendorum, quo totum ferme constat, difficultate, edi, hac vice, temporis angustia non patiebatur." Hafniæ Impressit Lavrentius Benedictj, 1573. Printed in small 4to, 106 pp.
10. Evidently written expressly for the book, as there is a previous letter from Pratensis in existence dated 16th April (T. B. et ad eum Doct. Vir. Epist., p. 8), in which he says that the figures are being cut, but that there is some difficulty about the paper; also that the word lucubrationes is not a good one for the title. Tycho must therefore have consented to the publication long before the 3rd of May.
11. As mentioned above, the book was actually in the printer's hands when this was written.
12. Perhaps this is an allusion to his having fallen in love about this time, as we shall see farther on.
13. Reprinted in Danske Magazin, ii. p. 186 (Weistritz, ii. p. 59).
14. This globe is mentioned at some length in the above-mentioned letter from Pratensis of April 16, 1573. It must have been a beautiful piece of work, the surface silvered with gilt stars, &c.
15. The expression is remarkable, as it shows that Tycho had not yet shaken himself free from the old Aristotelean opinion of the comets as atmospheric phenomena.
16. Respectively 7° 55′, 5° 21, and 5° 1′; while Progymnasmata, p. 344, gives 7° 50′.5, 5° 19′, and 5° 2′. Tycho remarks (ibid., p. 593) that the latter results are corrected for the error of excentricity, and were made with the improved pinnules which he afterwards adopted.
17. He assumed that the parallax would be = 0 at the upper culmination, but in his later work he remarks that this is a mistake, and that it would be nearly 7′.
18. Fol. D. 2 verso to E. 3.
19. As some readers may not be familiar with the phraseology of astrology, it may be well to mention here that each Trigonus consists of three signs of the Ecliptic, 120° from each other; the four Trigoni correspond to the four elements, and each of them is in turn the ruling one, until a conjunction of planets has taken place within one of its signs. In about 800 years the four Trigoni will all have had their turn, and a cycle is completed. See, e.g., Cyprianus Leovitius, De Conjunctionibus Magnis, London, 1573; Kepler, De Stella Nova, 1606, p. 13 (Opera Omnia, ii. p. 623); Ideler, Handbuch der Chronologie, ii. p. 401. More about this in Chapter VIII.
20. No doubt he was right, as this would be a capital day for a celestial explosion to take place! The date and time of the first appearance was required to prepare the horoscope of the star in the usual manner (see below, Chapter VI.).
21. The year 1572 was, according to the custom of the age, remembered by the line "LVtetIa Mater sVos natos DeVoraVIt."
22. One of these was De variis Astrologorum in Cœlestium Domorum Divisione Opinionibus, earumque Insufficientia, in which he proposed a new plan of dividing the heavens into "houses" by circles through the points of intersection of the meridian and horizon. The other treatise was De Horis Zodiaci inæqualibus, quas Planetarias vocant.
23. O audaces astronomos, O exquisites & subtiles calculatores, qui Astronomiam in Tuguriis & popinis, vel post fornacem, in libris & chartis, non in ipso cœlo (quod par erat) exercent. Plerique enim ipsa sidera (pudet dicere) ignorant. Sic itur ad astra" (fol. G.).
24. It may not be without interest to insert these data here:—

    ⁠

    Tabulæ Prut.

    Ex propria
    Motuum ratione.

    H.

    M.

    S.

    H.

    M.

    Initium primæ obscurationis .      .      .      .      .      .      .      .      .      .      .      .      .      .      .      .      .      .      .      .      .      .      .      .      .      .      .      .      .      .      .      .      .      .      .      .      .      .      .      .      .      .      .

    5

    55

    41

    6⁠

    15

    Initium totius obscurationis .      .      .      .      .      .      .      .      .      .      .      .      .      .      .      .      .      .      .      .      .      .      .      .      .      .      .      .      .      .      .      .      .      .      .      .      .      .      .      .      .      .      .

    6

    59

    50

    7⁠

    20

    Medium .      .      .      .      .      .      .      .      .      .      .      .      .      .      .      .      .      .      .      .      .      .      .      .      .      .      .      .      .      .      .      .      .      .      .      .      .      .      .      .      .      .      .

    7

    51

    29

    8⁠

    10

    Finis totius obscurationis .      .      .      .      .      .      .      .      .      .      .      .      .      .      .      .      .      .      .      .      .      .      .      .      .      .      .      .      .      .      .      .      .      .      .      .      .      .      .      .      .      .      .

    8

    43

    ⁠8

    9⁠

    ⁠0

    Finis ultimæ obscurationis .      .      .      .      .      .      .      .      .      .      .      .      .      .      .      .      .      .      .      .      .      .      .      .      .      .      .      .      .      .      .      .      .      .      .      .      .      .      .      .      .      .      .

    9

    47

    17

    10⁠

    ⁠5

    Locus in Sagit. .      .      .      .      .      .      .      .      .      .      .      .      .      .      .      .      .      .      .      .      .      .      .      .      .      .      .      .      .      .      .      .      .      .      .      .      .      .      .      .      .      .      .

    26° 29′

    26° 40′

25. "Nil tamen his moveor. Nam qvæ non fecimus ipsi
    ⁠Et genus et proavos, non ego nostra voco."
26. The triquetrum had been much in use from the time of Ptolemy. It consisted of two arms of equal length and movable round a hinge, while a third and carefully graduated arm gave the means of measuring the angle between the two former by the aid of a table of chords.
27. "Dialexis de novæ et prius incognitæ Stellæ invsitatæ Magnitudinis et splendissimi Luminis Apparitione et de eiusdem Stellæ vero loco constituendo. Per Thaddæum Hagecium ab Hayck." Francofurti, a. M. 1574. 176 pp. 4to. In an appendix are two papers on the star by Paul Fabricius and Corn. Gemma. Some years after Hagecius sent Tycho a copy with many MS. corrections and additions, which Tycho quotes extensively in his Progymnasmata (p. 505 et seq.). In this corrected copy the most erroneous measures had been improved or struck out, whereby the greatest differences from Tycho's results were reduced to 4′ or 6′.
28. "Alæ seu Scalæ Mathematicæ, quibus visibilium remotissima Cœlorum Theatra conscendi, et Planetarum omnia itinera novis et inauditis methodis explorari . . . Thoma Diggeseo authore." Londini, 1573. 4to.
29. Digges, l.e., chapter x., fol. K 3. By a mistake he says that the two lines join δ Cassiopeæ, β Cephei, and ι Cephei, γ Cassiopeæ. Tycho remarks that one can see at a glance that these two lines do not intersect each other between the stars, but pretending not to see that it is merely a lapsus calami, he gravely calculates places from these data, using his own distances, and of course gets absurd results (Progymn., p. 681), after which he interchanges the stars, and gets the correct result given above.
30. Thus Paul Fabricius at Vienna, Hainzel (using the great quadrant at Augsburg), Reisacher at Vienna, Corn. Gemma (not stating how found), Hieronimus Munosius at Valencia, Valesius from Covarruvias (physician to Philip II. of Spain), and Johan Prætorius (Richter), professor at Wittenberg.
31. Progymn., i. p. 760.
32. Ibid., p. 692. Tycho never saw the book, and only knew it from a MS. abstract made for him by Hagecius. It is in the Poulkova Library, and W. Struve mentions that the writer states in two places that he saw it "principle Octobris." Astron. Nachr., xix. p. 334. Elias Camerarius is not mentioned in Jöcher's Gelehrten Lexicon, nor in any other historical work that I have at hand.
33. Progym., i. pp. 721-723. Tycho remarks that Raimundus has forgotten the proverb that liars should have a good memory.
34. La novvelle Estoille apparve sur tous les Climats dv Monde: Et de ses effects. Paris, 1590. 28 pp. small 8vo. This book was not known to Tycho Brahe.
35. Hagecii Dialexis, p. 129. Tycho remarks (Progym., p. 548) that if it had been visible in October, Mœstlin (who saw it "the first week in November") would probably have noticed it.
36. Progymn., i. pp. 565, 566.
37. Progymn., i. p. 621.
38. Ibid., p. 536.
39. Rudolf Wolf in Astr. Nachr., lxv. p. 63.
40. About the observation of Maurolycus, see Nature, xxxii. p. 162 (June 18, 1885). About Chytræus, see R. Wolf, Geschichte der Astronomie, p. 415.
41. "Nona Nouembris, die Dominico vesperi, cum tamen obseruantibus proximum cœli locum die octauo, etiam sereno æthere non apparuerit" (Hagecii Dialexis, p. 137), also in his separate pamphlet, "Stellæ Peregrinæ iam primum exortæ et Coelo constanter hærentis Φαινὀμενον . . . . per D. Cornelium Gemmam." Lovanij, 1573. 13 pp. 4to (fol. A2). There is one reprint (s.a.e.l.) of this, with some omissions, and coupled with a paper by Postellus, and another coupled with a reprint of a paper by Cyprianus Leovitius. Among writers who have quoted Gemma may be mentioned Newton (Principia, iii., ed. Le Seur and Jacquier, p. 670), who thought that Gemma himself had looked at the sky on the 8th without seeing it; but this was a mistake, as we have just shown above.
42. Gemma's book is a very curious one. The first volume is about terrestrial curiosities, Siamese twins, and much queerer beings (well illustrated); vol. ii. is about celestial wonders, comets, &c., chapter iii. being "De prodigioso Phænomeno syderis noui" (pp. 111-155). Page 113: "Sed qui se primos obseruasse voluerunt, nonum diem pro initio tradiderunt: cum tamen interea conuenerim plures, quorum alij diem secundum aut tertium annotarint, plerique vel ante Octobris finem ferant etiain a vulgaribus obseruatum. . . . Primum observationis tempus fuit nobis die Nou. 26."
43. In a pamphlet, "La Declaration d'vn comete ou estoille prodigieuse laqvelle a commencé a nous apparoistre à Paris, en la partie Septentrionale du ciel, au mois de Nouembre dernier en l'an present 1572, & se monstre encores auiourd'huy. Par I.G.D.V.," Paris, 1572, 4to, 8pp., it is said that people who had good sight could see several rays, of which the longest, which might be called the tail of the comet, was always turned to the east! Its distance from the pole-star, when above the pole, was "le plus souvent" 25° 30′, but afterwards it became 24° 40′, and below the pole 24° 30′, which the author takes to be the effect of parallax! The author was probably Jean Gosselin de Vize, librarian to the King. The pamphlet was not known to Tycho; it is not in Lalande's Bibliographie.
44. Leovitius, writing in February 1573, says it seems to him that the star had during the last month moved three degrees towards the north!
45. The English astronomer, John Dee, was of the same opinion (Progymn., p. 691).
46. "Thaddæi Hagecij ab Hayek, Aulas Cesareæ Medici, Responsio ad virulentum et maledicum Hannibalis Raymundi Scriptum," &c. Pragæ, 1576. 4to.
47. Progymnasmata, p. 743.
48. About this star see Calvisii Opus Chronologicum, p. 413 (second edit., 1620), and The Observatory, vii. p. 75.
49. "De Nova Stella. Judicium Cypriani Leovitii a Leonicia, Mathematici, de nova stella siue cometa, viso mense Nouembri ac Decembri A.D. 1572. Item mense Januario & Februario A.D. 1573. Lavingæ ad Danubium, 1573." 4to, 8 fol.:—"Historiæ perhibent tempore Ottonis primi Imperatoris, similem stellam in eodem fere loco Coeli arsisse, A.D. 945. Vbi magnæ mutationes plurimaque mala, uarias Prouincias Europæ peruaserunt, potissimum propter peregrinas gentes infusas in Germaniam. Verum multo locupletius testimonium in historijs extat de A.D. 1264, quo Stella magna & lucida in parte Coeli Septentrionali circa Sydus Cassiopeæ apparuit, carens similiter crinibus, ac destituta motu suo proprio." In the margin, opposite the date 1264, is: "Descriptio huius Cometæ desumpta est ex antiquo codice, manu scripto. Euentus hi congruent cum significationibus stellæ propositæ: quod bene notandum est: videoque hic aliquid insigne." Tycho has reprinted the whole pamphlet (pp. 705-706), leaving out the "Judicium breve" at the end, and also the marginal notes. The latter are also omitted from a reprint published (s. l.) in 1573, together with a reprint of Gemma's pamphlet.
50. According to Klein, Der Fixsternhimmel, p. 102, the Chronicle of Albertus Stadensis (Oldenburg) mentions a bright star in Capricornus in 1245 (not alluded to elsewhere), as bright as Venus, but more red, and which lasted for two months.
51. "Orationes duae. Vna de legibus et disciplina. Altera de Cometa inter Sidera lucente in mensem septimum, continens commonefactionem de impendentibus periculis. A Joh. Comite Hardeci. Wittenberg, 1573." 8vo. Fol. C., p. 2:—"Reperimus Cometas qui ante hæc tempora in eodem octaui orbis loco fulserunt, fere gentes concitasse Boreas, suis excitas sedibus, ad quærendas nouas. Qui Honorij principatu conspectus est, cuius meminit Claudianus, haud dubie finem Imperio occidentis cum tristi ac horribili ruina attulit . . . Qui Ottone primo imperante ad eandem Cassiopæam flagrauit Cometa, Vngaros in Germaniam, Ottonem in Italiam impulit . . . Qui anno a nato Christo sexagesimo supra millesimum ducentesimum ibidem luxit interregni tempore, coma ad coeli medium usque dispersa, Carolum Andegauensem e Gallia, per furiosa & scelerata consilia Clementis Pontificis attraxit in Italiam." This book is not mentioned by Tycho Brahe. In his Cometographia, p. 817, Hevelius quotes Christianus as mentioning the star of 945. This may seem to some readers to refer to the Chronicle of Christianus of 1472 (Pulkova Cat., p. 76), but, as Professor Copelaud has pointed out to me, it is merely a quotation of D. Christiani Tractatus de Cometarum Essentia, 1653, and therefore it does not prove anything as to the correctness of the statement of Cyprianus.
52. D'Arrest, Oversigt over det kgl. Danske Vidensk. Selskabs Forhandlinger, 1864, p. 1, where a list of stars near the place and a map are given. Micrometric observation of the star No. 129 in Astr. Nachr., vol. lxiv. p. 75. Argelander, Ueber den neuen Stern vom Jahre 1572, Astr. Nachr., vol. lxii. p. 273.
53. Monthly Notices, R. Astr. Soc., xxxiv., p. 168; Astr. Nachr., vol. cxxiii. p. 365. D'Arrest in 1863–64 found no variability. The place was already examined by Edward Pigott between 1782 and 1786, but without finding any variable star (Phil. Trans., 1786); it was first photographed by Mr. Roberts in 1890 (Monthly Notices, L. p. 359).
54. Published in the above-mentioned reprint "De Nova Stella Judicia Dvorum Præstantium Mathematicorum, D. Cypriani Leovitii et D. Cornelii Gemmæ," 1573, s.l.; perhaps also elsewhere. Reprinted by Tycho, Progymn., p. 327.
55. "De Prodigiosa Specie Naturaque Cometæ . . . 1577. Per D. Cornelium Gemmam, Antwerp, 1578," 8vo, p. 42 (compare Progymnasmata, p. 565). There is a curious picture in this book of Belgica weeping amidst the burning ruins of a city, while the paternal government of Philip II. is represented by gibbets and wheels in the background, and the comet is blazing overhead.
56. "Erklerung oder Auslegung eines Cometen. . . . Durch Theodorum Graminæum Ruremundanum. Cöllen am Rhein, 1573, 4to." Tycho mentions him as "Autor Stramineus, Graminæus volebam dicere" (Prog., p. 778).
57. This beautiful remark is also made in Gosselin's Historia Imaginum Coelestium, Paris, 1577, 4to, p. 11.