years younger than Copernicus, was sufficiently well educated to be able to follow Copernicus' studies. Giese bought his friend an ingenious sundial, and gave him an instrument with which he could observe the equinoxes. The mathematician, Rheticus, published a list of Giese's astronomical instruments, which he considered to have been made by men who really understood their mathematics. Giese actively encouraged his friend, Copernicus, to publish his findings in relation to the movement of the planets in the solar system. In turn, Copernicus regularly acknowledged his indedebtness to the many friends, especially Giese and Rheticus, who had supported him and encouraged him to publish. In 1516, Giese was the co-author, with Copernicus, of a letter to the Polish King Sigismund I the Old asking for the King's protection of Prussia against the Teutonic Knights, and generally supported the interests of the Polish Crown against that of the Teutonic Order. Danzig had been part of the State of the Teutonic Order since the Teutonic invasion of Gdańsk Pomerania in 1308. Its population became ethnically German as a result. In 1466 Danzig reverted to the Kingdom of Poland, within which it retained considerable independence (e.g. had its own judiciary and minted its own coinage). The region's ethnic German inhabitants resisted full incorporation into Poland, but turned to the Polish King for support against the Teutonic aggressors. He also worked on updating the Kulm law while a canon in Ermland . On 1 July 1536 he was designated by King of Poland, Sigismund I, who considered him a very valuable diplomat, as Bishop of Kulm, which was later confirmed by the Pope. After Mauritius Ferber's death, Giese became prince-bishop. Giese was described by his contemporaries as a very pious man, an extremely learned man, a loyal friend, generous and a man who supported those in need. Nicolaus Copernicus explained that his "devoted friend, Tiedeman Giese, [was] a man filled with the greatest zeal for the divine and the liberal arts." Giese was a prolific writer and correspondent. He regularly corresponded with young, ambitious scholars, encouraging them and following their careers with interest. In the preface of his book, De revolutionibus, Copernicus credits Giese with encouraging publication and urging him not to conceal the principles on which he deduced his theory of planetary motions. He carried out active correspondence with the humanist Erasmus of Rotterdam, the Lutheran reformer, Philip Melanchthon and the humanist philosopher,