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370 Hulsius of Nürnberg, a well-known writer and publisher, to whom the heirs would seem to have sold them, as some copies have on the title-page: "Noribergæ, apud Levinum Hulsium MDCI."

The stock of copies of the Astronomiæ instauratæ Mechanica appears to have been exhausted, but most of the wood-cuts and copper-plates were in the possession of the heirs, who sold them to Levin Hulsius. He printed a new edition at Nürnberg in 1602, exactly like the original, but with narrower margins, and without the neat border which in the original runs round the pages. Paper and print are also somewhat inferior, and Tycho's portrait is on the title- page substituted for the vignette of the original.

On the state of Tycho's other manuscripts Kepler drew up a short report, from which it appears that the printing of the second volume of letters had been commenced, and that Tycho had thought of adding some astronomical tables to the volume to make it more saleable. Kepler suggested that matter of astronomical interest occurring in the unprinted letters might be extracted and printed, so that the sheets already in print would not be wasted. This was, however, not done, and only a few of the letters have yet been published. For the third volume of Progymnasmata (on the comets of 1582, 1585, &c.), the materials were ready, but nothing was put into shape. As to the Tabulæ Rodolpheæ, Kepler stated that the materials were abundant, "nec deerunt ingenia, si Maecenates sint, et exiguum aliquid in certis pensionibus annuis in hunc usum erogetur." The Theatrum astronomicum (of which Tycho had sketched the plan in his letter to Peucer in 1588 ) should contain the theory on which the tables were based, but nothing of it had been written.

It seems that Kepler received Tycho's observations, originals and copies, after signing a contract with Tengnagel in 1604. He found them so indispensable to his studies that he never returned them, but it was not forgotten that they were in his possession, and in November 1621 (when he had been obliged to stay more than a year in Würtemberg to watch the trial of his mother for witchcraft) Ferdinand II wrote to the Duke of Würtemberg requesting him to command Kepler to return the manuscripts. Kepler was probably back again at Linz (where he