On the 15th May 1618, Kepler has left it on record, that he discovered the beautiful relation between the squares of the periodic times and the cubes of the distances of the pla nets. In the same year, lie published at Lintz, his Epitome Astronomic Copernicanc in septem libris conscripta. This work contained only the three first books ; the fourth ap peared in 1622, and the tin ee last in 1621. In 1619, he published at Lintz his Harmonices Mundi libri quinque, geoznetricus, architectonicus, harmonicas, psychologicus, as tronomicus, cunt appendice contmens mysterium cosmogra phicum ; also his treatis De Cornelis Libelli tres astronomi cus. physicas, astrologicus. Ejusdenz Cometarunz physiola gm nova et paradoxos ; z.nu another work, entitled Frog nosticon, the Prediction of Misfyrtunes for Govern mints and Churches, principally from the Comet and the Earthquake in 1618 and 19. The first of these works, viz. the Harmonices, is dedicated to James VI. of Scotland. Kepler attempts to shew, that there is a resemblance be tween the distances of the heavenly bodies, as seen from the sun in their aphelia and perihelia, and the division of the musical octave ; but though this pact of his book is in every respect absurd, yet he appears from this work to have studied music as a science, and also to have been practi catiy acquainted with it. The discovery of the four sate] lit( s of Jupiter seems to have first pointed out to him the error which he had committed.
It, 1624, appeared at Marpurg, his Chiaas Logarithmo rum, to which a supplement was added m 1625, he also published his Hyperaspistes, tic. quo libro doctrine prestantissima de parallaxibus, degree novorum siderum in sublimer cethere discursionibus repetitur et confirmatur.
Atter the death of Tycho, the emperor Rudolph com manded Kepler to complete the astronomical tables which had been begun by his friend ; hut he was not able to bring his labours to a termination till the year 1627, when they at last appeared at Ulm, under the Litle, Tabula. Radolphince, guibus astronomicze scientice. temporum longinquitate collajzsee, restauratio continetur, a Tychone Brake primum animo concePta et destinata anno (hr. 1564, exinde observatianibus siderum post annum pr.ecipue 1572, serio of fectata, tandem traducta in Germaniam, inque ?ulanz et no , men Rodolphi imp. anno 1598. The delay in the publica tion of this work arose front the difficulties which Kepler experienced in obtaining the pecuniary means which were necessary for carrying it on. The emperor Rodolph had given orders in 1609, that, besides the expense of the edi tion, the arrears of his pension, amounting to 2000 crowns, and also 2000 crowns more, should be paid ; yet it was not till two years after that these orders were executed. Un der the emperors Matthias and Ferdinand, he experienced the same difficulties ; but after the year 1621, Ferdinand paid all his arrears, and all the expenses necessary for com pleting the work.
As soon as these tables were completed, Kepler solicit ' ed, and obtained the emperor's leave, to take up his resi dence at Sagan it Silesia, where he spent the remainder of his life. Here he published, in 1629, his Responsio ad Epistolam Jac. Partschii preefixam Ephemeridi anni 1629 de computatione et editione Ephenteridum ; anti, in the same t year, his Sportula Genethliacis missa de Tab. Radolphi usu in computationibus astrologicis cum modo dirigendi 2101,0 et naturali.
In this remote situation, Kepler suffered great inconve I nience from the irregular payment of his pension. He
was therefore obliged, in 1630, to make a journey to Ratis ' bon, to solicit the arrears which were due to him ; and, in consequence of the fatigue (ob nimianz equitationem) which he experienced, he was seized with a fever, of which he died, in that city, on the 30th of November 1630, in the 59th year of his age.
As we have already given a brief view of Kepler's dis coveries in our History of AsTaoxomy, and in the part of that article which treats of Physical AsTitoramy, we have directed the reader's attention, in the preceding sketch, principally, to the events of his life, and the titles and gene ral object of his various works. The abstracts which we have given, short and imperfect as they are, are not unin structive.
It is a very difficult matter to form an estimate of the true character of Kepler's genius. The ingenious absurdities with which he began his career were a very unfavourable omen of his future success. But he seems, from his in fancy, to have been impressed with the conviction, that there were analogies or laws to be discovered with regard to the distances of the planets ; and every view which pre seined itself to his ardent fancy seems to have been em braced as the real law of the universe. The advice of Ty cho, however, seems to have given a right direction to his inquiries ; and the observations of that illustrious astrono mer on the planet Mars, and on the other planetary bodies, presented him with the tests by which his speculations could be tried. But while we admire those brilliant dis coveries to which Kepler was thus conducted, it is impossi ble to restrain our indignation against those wild and almost insane speculations, in which he afterwards chose to in dulge. That he was a believer in astrology it is impossible to doubt ; and though, in order to save his reputation, La Lunde has affirmed that Kepler published his reveries merely in order to proem e a sale for his works, by flatter ing the prejudices of the vulgar ; yet, in drawing the cha racter of this great man, we should be unwilling to apolo gise for his superstition, by such a heavy imputation upon his integrity. The physical notions of Kepler respecting the planets are still more ridiculous than his astrological convictions. In his Harmonices Mundi, (tab. iv. cap. vii.) he endeavours to prove, that the earth has a sympathy with the heavens, and, by a natural instinct, perceives the posi tion of the stars. He maintains, also, that the earth is a vast animal, breathing out the winds from holes in the moun tains; and that all the planets are animated, and have mus cles proportioned to their bulk, by means of which they move through absolute space. He even supposes, that the faculty of the earth is terrified at the approach of a comet, that it " sweats out a great quantity of vapour through terror, and that hence arise great rains and floods." In the year 1634 appeared a posthumous work of Kep ler, entitled, J. Kepleri Somniunz, set opus posthumum de 4stranamia Lunari, in which he treats of the phenomena which will be seen by the inhabitants of the moon and the other planets. Kepler himself died during the printing of this work ; and his son-in-law Bartschius, who took the charge of the impression, did not live to complete it. Lew is Kepler, the son of our author, who was a physician at Koningsberg, was with difficulty prevailed upon to finish an undertaking, during which his father and his brother in-law had died.