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Rh lifetime. On account of the wider scope of its contents he gave it the title Astronomiæ Instauratæ Progymnasmata, or Introduction to the New Astronomy, a title which marks the work as paving the way for the new planetary theory and tables which Tycho had hoped to prepare, but which it fell to Kepler's lot to work out in a very different manner from that contemplated by Tycho. The second volume was devoted to the comet of 1577, and as the subject did not lead to the introduction of extraneous matter, this volume was finished long before the first one. The third volume was in a similar manner to treat of the comets of 1580 and following years, but it was never published, nor even written, though a great deal of material about the comet of 1585 was put together and first published in 1845 with the observations of this comet.

The two volumes about the new star and the comet of 1577 were printed in Tycho's own printing-office at Uraniborg, and after some delay caused by want of paper, the second volume was completed in 1588. The title is "Tychonis Brahe Dani, De Mundi ætherei recentioribus phænomenis Liber secundus, qui est de illustri stella caudata ab elapso fere triente Nouembris anno usque in finem Januarii sequentis conspecta. Vraniburgi cum Privilegio." The book is in demy 4to, 465 pp., and the