(John), one of the greatest astronomers of his age, was born at Wiel, in the country of Wurttemberg, in 1571. In the year 1595, he wrote an excellent book, which was printed at Tubingen the year following, under the title of Prodromus dissertationum de proportionibus orbium celestium, deque causis coelorum numeri, magnitudinis, motuumque periodicorum genuinis et propriis, &c. Tycho Brahe having settled in Bohemia, and obtained from the emperor all sorts of conveniences for the perfecting of astronomy, was so passionately desirous of having Kepler with him, and wrote so many letters to him on that subject, that he prevailed upon him to leave the university of Gratz, and remove into Bohemia with his family and library, in the year 1600. Kepler in his journey was seized so violently with the quartan ague, that he could not do Tycho Brahe all the services of which he was before capable. He was even a little dissatisfied with the reservedness which Tycho Brahe showed towards him; for the latter did not communicate to him all he knew; and as he died in 1601, he did not give time to Kepler to be very useful to him, or to receive any considerable advantage under him. From that time Kepler enjoyed the title of Mathematician to the emperor, all his life; and gained more and more reputation by his works. The emperor Rodolphus ordered him to finish the tables of Tycho Brahe, which were to be called the Rodolphine Tables. Kepler applied himself to it vigorously; but unhappy are those learned men who depend upon the good-humour of the intendants of the finances. The treasurers were so ill-affected toward our author, that he could not publish these tables till 1627. He died at Ratibon, where he was soliciting the payment of the arrears of his pension in 1630.

The principal works of this great astronomer are, 1. Prodromus dissertationum, above mentioned, to which he has also given the title of Mysterium Cosmographicum; which he deemed more than any other of his works, and was for some time so charmed with it, that he said he would not give up the honour of having invented what was contained in that book for the electorate of Saxony. 2. Harmonia mundi, with a defence of that treatise. 3. De cometa, libri tres. 4. Epitome astronomiae Copernicanae. 5. Astronomia nova. 6. Chilias logarithmorum, &c. 7. Novo stereometriae doctrine vinariorum, &c. 8. Disputae. 9. De vero natali anno Christi. 10. Ad Vitellionem Paralipomena, quibus Astronomia pars optica traditur, &c. 11. Semonium Lunaris Astronomia; in which he began to draw up that system of comparative astronomy which was afterwards pursued by Kircher, Huygens, and Gregory. His death happened while the work was printing; upon which James Bartchius, his son-in-law, undertook the care of the impression; but was also interrupted by death; and Lewis Kepler his son, who was then a physician at Konigberg in Prussia, was so much startled at these disasters, that it was with the utmost difficulty he could be prevailed upon to attempt to finish it, lest it should prove fatal to him; he completed the task, however, without receiving any personal injury.