808 KEPLER was married for the second time, chiefly for the sake of his children. It has been well re- marked by Sir David Brewster, that the nar- rative of Kepler's search for a wife " is one of the most curious chapters in his history. No fewer than eleven ladies were presented to his choice," his patient scrutiny of their respective claims being comparable with his analysis and successive rejection of the epicyclic theories of Mars. In a jocular letter to Baron Strahlendorf he describes their various characters, and the negotiations preceding his marriage. During the preparations for the wedding, his wine- merchant having incorrectly measured the con- tents of the wine-casks, Kepler investigated the matter and produced his work on gauging ; the first in which the modern analysis is em- ployed. About the same time he presented to the diet at Ratisbon his views on the reforma- tion of the calendar, the substance of which he published in a short essay. In 1616 ap- peared his Ephemerides 1617-1620, the ex- pense attending the preparation of which he confessed he had been obliged to defray " by composing a vile, prophesying almanac, which is scarcely more respectable than begging, un- less from its saving the emperor's credit, who abandons me entirely, and would suffer me to perish from hunger." He nevertheless de- clined an invitation to fill the mathematical chair in Bologna, preferring poverty and the limited degree of freedom of speech and opin- ion he enjoyed in Germany, to the prospect of bettering his fortune in Italy. Between 1618 and 1622 appeared the seven books of his "Epitome of the Copernican Astronomy," which was placed by the inquisition on the list of prohibited books; and in 1619 he published his " Harmonies of the World," dedicated to James I. of England, which is memorable in the history of science as containing the third of his celebrated laws, viz. : that the squares of the periodic times of the planets are propor- tional to the cubes of their mean distances from the sun. Such was the transport with which this discovery, which for 17 years had baffled all his skill and patience, filled him, that he marked the day and year, May 15, 1618, when it became known to him; and, speaking of the book which promulgated it, he said : " It may well wait a century for a reader, as God has waited 6,000 years for an observer." The accession in 1619 of the em- peror Ferdinand II., who promised to pay the arrears of his salary, and to furnish the means of publishing the Rudolphine tables, seemed to open a more favorable era for the prosecution of Kepler's scientific labors; but snch were the drains upon the imperial trea- sury caused by the religious wars which then began to convulse Germany, that it was not until several years afterward that he was en- abled to collect even a part of the sums prom- ised him. In 1620 he was strongly urged by Sir Henry Wotton, the English ambassador at Venice, to take up his residence in England, but declined the offer. Finally in 1627, after more than a quarter of a century's delay and amid difficulties of all kinds, the Rudolphine tables were published in Ulm. They were the first ever calculated on the theory of the ellip- ticity of the planetary orbits, and are so re- markable a monument of patience and indus- try, that had Kepler done nothing more than compute them, he would be regarded as one of the benefactors of science. In 1629, for the sake of avoiding the religious dissensions which distracted Linz, at the invitation of Wallenstein, he removed with his family to Sagan in Sile- sia, and soon afterward secured a professorship in the university of Rostock. In the following year he went to Ratisbon, and made a final but fruitless effort to obtain from the imperial as- sembly his arrears, which now amounted to 8,000 crowns. The vexation which this occa- sioned, combined with fatigue of mind and body, brought on a fever which proved fatal. His remains were interred in St. Peter's church- yard, Ratisbon, and in 1803 a monumental tem- ple to his memory was erected on the spot by the prince bishop of Constance. The follow- ing epitaph, composed by himself, was en- graved on his tombstone : Mensus eram ccclos, nunc terrse metior umbras : Mens ccelestis erat, corporis umbra jacet. The ardor and patience with which Kepler pursued science have found few parallels among modern philosophers. Ever prone to indulge in fanciful theories, he never lost sight of the precise object of his search, and ingenuously renounced any hypothesis that he could not reconcile with his advancing knowledge of phenomena. Of his manifold attempts in va- rious branches of science Delambre says: " Those which have failed seem to us only fan- ciful, while those which have been more fortu- nate appear sublime." The history of science presents no discoveries more original, or which were deduced with so little assistance from the speculations of preceding philosophers, as his three celebrated laws, from which the discov- eries of Newton subsequently sprung, thus completing the great chain of truths which constitute the laws of the planetary system. He computed correctly the transit of Mercury on Nov. 7, 1631 (observed by Gassendi), and announced a transit of Venus in the same year, which was not observed, as it occurred during the night. (Sir David Brewster is mistaken in asserting that " the transit did not take place.") The transit of Venus in 1639 Kepler failed to announce, but that of 1761 he predicted. It is a sufficient evidence of his industry as an author that between 1594 and 1630 he pub- lished 33 works, besides leaving 22 volumes of manuscripts, 7 of which contain his epistolary correspondence. The latter was published in 1 vol. fol. in 1718, by Gottlieb Hansch ; but the enterprise proving unsuccessful, he was obliged to part with the remaining volumes, which are now in the possession of the imperial
