In almost all the instruments now enumerated, the limb was subdivided by diagonal lines, a method which Tycho first brought into use, but which, in modern times, has been superseded by the inventions of Nonius and Vernier.
When Tycho had thus furnished his observatory, he devoted himself to the examination of the stars; and during the twenty-one years which he spent in this delightful occupation, he made vast additions to astronomical science. In order to instruct the young in the art of observation, and educate assistants for his observatory, he had sometimes under his roof from six to twelve pupils, whom he boarded and educated. Some of these were named by the King, and educated at his expense. Others were sent by different academies and cities; and several, who had presented themselves of their own accord, were liberally admitted by the generous astronomer.
As Tycho had spent nearly a ton of gold (about 100,000 dollars) in his outlay at Uraniburg, his own income was reduced to very narrow limits. To supply this defect, Frederick gave him an annual pension of 2000 dollars, beside an estate in Norway, and made him Canon of the Episcopal Church of Rothschild, or Prebend of St Laurence,[38] which had an annual income of 1000 dollars, and which was burdened only with the expense of keeping up the chapel containing the Mausolea of the Kings of the family of Oldenburg.
It would be an unprofitable task, and one by no means interesting to the general reader, to give a detailed history of the various astronomical observations and discoveries which were made by Tycho during the twenty years that he spent at Uraniburg. Every phenomenon that appeared in the heavens, he observed with the greatest care; while he at the same time carried on regular series of observations for determining the places of the fixed stars, and for improving the tables of the sun, moon, and planets. Though almost wholly devoted to these noble pursuits, yet he kept an open house, and received, with unbounded hospitality, the crowds of philosophers, nobles, and princes who came to be introduced to the first astronomer of the age, and to admire the splendid temple which the Danish Sovereign had consecrated to science.
Among the strangers whom he received under his roof, there were some who returned his kindness with ingratitude. Among these was Paul Witichius, a mathematician; who, under the pretence of devoting his whole life to astronomy, insinuated himself into the utmost familiarity with Tycho. The unsuspecting astronomer explained to his guest all his inventions, described all his methods, and even made him acquainted with those views which he had not realised, and with instruments which he had not yet executed. When Witichius had thus obtained possession of the methods, and inventions, and views of Tycho, and had enjoyed his hospitality for three months, he pretended that he was obliged to return to Germany to receive an inheritance to which he had succeeded. After quitting Uraniburg, this ungrateful mathematician neither returned to see Tycho, nor kept up any correspondence with him; and it was not till five years after his departure that Tycho learned, from the letters of the Prince of Hesse to Ranzau, that Witichius had passed through Hesse, and had described, as his own, the various inventions and methods which had been shewn to him in Huen.
Being unable to reconcile his own observations with those of Copernicus, and with the Prutenic Tables, Tycho resolved to obtain new determinations of the latitude of Frauenburg, in Prussia, where Copernicus made his observations, and of Konigsberg, to the meridian of which Rheinhold had adapted his Prutenic Tables. For these purposes he sent one of his assistants, Elias Morsianus, with a proper instrument, under the protection of Bylovius, Ambassador of the Margrave of Anspach, to the King of Denmark, who was returning by sea to Germany; and after receiving the greatest attention and assistance from the noble Canons of Ermeland, he determined, from nearly a month’s observations on the sun and stars, that the latitude of Frauenburg was 54° 22½´, in place of 54° 19½´, as given by Copernicus. In like manner he determined that the latitude of Konigsberg was 54° 43´, in place of 54° 17´, as adopted by Rheinhold. When Morsianus returned to Huen in July, he brought with him, as a present to Tycho, from John Hannovius, one of the Canons of Ermeland, the Ptolemaic Rules, or the Parallactic Instrument which Copernicus had used and made with his own hands. It consisted of two equal wooden rules, five cubits long, and divided into 1414 parts. Tycho preserved this gift as one peculiarly dear to him, and, on the day of his receiving it, he composed a set of verses in honour of the great astronomer to whom it belonged.
Among the distinguished visits which were paid to Tycho, we must enumerate that of Ulric, Duke of Mecklenburg, in 1586. Although his daughter, Sophia, Queen of Denmark, had already paid two visits to Uraniburg in the same year, yet such was her love of astronomy, that she accompanied her father and his wife Elizabeth on this occasion. Ulric was not only fond of science in general, but had for many years devoted himself to chemical pursuits, and he was therefore peculiarly gratified in examining the splendid laboratory and extensive apparatus which Tycho possessed. It has been said by some of the biographers of Tycho, that the Landgrave of Hesse visited Uraniburg about this period; but this opinion is not correct, as it was only his astronomer and optician, Rothman, who made a journey to Huen in 1591 for the recovery of his health. Tycho had long carried on a correspondence with this able astronomer respecting the observations made at the observatory of Hesse-Cassel, and, during the few months which they now spent together, they discussed in the amplest manner all the questions which had previously been agitated. Rothman was astonished at the wonderful apparatus which he saw at Uraniburg, and returned to his native country charmed with the hospitality of the Danish astronomer.
Hitherto we have followed Tycho through a career of almost unexampled prosperity. When he had scarcely reached his thirtieth year he was established, by the kindness and liberality of his sovereign, in the most splendid observatory that had ever been erected in Europe; and a thriving family, an ample income, and a widely extended reputation were added to his blessings. Of the value of these gifts he was deeply sensible, and he enjoyed them the more that he received them with a grateful heart. Tycho was a christian as well as a philosopher. The powers of his gifted mind have been amply displayed in his astronomical labours; but we shall now have occasion to witness his piety and resignation in submitting to an unexpected and an adverse destiny.