Notwithstanding the speculative character of this volume, it obtained for its author a high name among astronomers. Galileo and Tycho, whose opinions of it he requested, spoke of it with some commendation. The former praised the ingenuity and good faith which it displayed; and Tycho, though he requested him to try to adapt something of the same nature to the Tychonic system, saw the speculative character of his mind, and advised him “to lay a solid foundation for his views by actual observation, and then, by ascending from these, to strive to reach the causes of things.”
In 1592, before Kepler had quitted Tubingen, he was on the eve of entering into the married state. Though the foolish scheme was fortunately broken off, yet he resumed it again in 1596, when he paid his addresses to Barbara Millar of Muleckh, who was a widow for the second time, though only twenty-three years of age. Her parents, however, would not consent to the match till Kepler proved his nobility; and, owing to the delay which arose from this circumstance, the marriage did not take place till 1597. The income which Kepler derived from his professorship was very small, and as his wife’s fortune turned out much less than he had been led to expect, he not only was annoyed with pecuniary difficulties, but was involved in disputes with his wife’s relations. These evils were greatly increased by the religious troubles which took place in Styria. The Catholics at Gratz rose against the Protestants, and threatened to expell them from the city. Kepler, who openly professed the Protestant religion, saw the risks to which he was exposed, and retired with his wife into Hungary. Here he continued nearly a year, during which he composed and transmitted to his friend Zehentmaier, at Tubingen, several small treatises, “On the Magnet,” “On the cause of the Obliquity of the Ecliptic,” and “On the Divine Wisdom, as shewn in the Creation”—all of which seem to have been lost. In 1599, Kepler was recalled to Gratz by the States of Styria, and resumed his professorship; but the city was still divided into two factions, and Kepler, who was a lover of peace, found his situation very uncomfortable. Having learned from Tycho that he had been able to determine more accurately than had been done the eccentricities of the orbits of the planets, Kepler was anxious to avail himself of these observations, and set out on a visit to Tycho at Prague, where he arrived in January 1600. Tycho received him with great kindness, notwithstanding the part which he had taken against him along with Raimar, and he spent three or four months with him at Benach. It was then arranged that Kepler should be appointed Tycho’s assistant in the observatory, with a salary of 100 florins, provided the States of Styria should, on the Emperor’s application, allow him to be absent for two years and retain his salary. Kepler had returned to Gratz before this arrangement was completed, and new troubles having broke out in that city, he resigned his professorship. Dreading lest this step would frustrate his scheme of joining Tycho, he resolved to ask the patronage of the Duke of Wirtemberg for the professorship of medicine at Tubingen; and with this view he corresponded with Mœstlin and his other friends in that University. When Tycho heard of this plan, he pressed him to abandon it, and promised his best exertions to procure a permanent situation for him from the Emperor.
Encouraged by these promises, Kepler and his wife set off for Prague, but he was unfortunately attacked on the road with a quartan ague, which lasted seven months; and having exhausted the little money which he had along with him, he was obliged to apply to Tycho for a supply. After his arrival at Prague he was supported entirely by the bounty of his friend, and he endeavoured to make some return for this kindness by attacking in a controversial pamphlet two of the scientific opponents of Tycho. Kepler’s total dependence on the generosity of his friend had made him suspicious of his sincerity. He imagined that Tycho had not freely communicated to him all his observations, and that he had not been sufficiently liberal in supplying his wife with money in his absence. While absent a second time from Prague, and influenced by these feelings, he addressed a violent letter to Tycho, filled with reproaches. On the plea of being occupied with his daughter’s marriage, Tycho requested Ericksen, one of his assistants, to reply to Kepler’s letter; and he did this with so much effect, that Kepler saw his mistake, and in the noblest and most generous manner supplicated the forgiveness of his friend. Tycho exhibited the same good feeling; and the kindness of Hoffman, President of the States of Styria, completed the reconciliation of the two astronomers.
On his return to Prague in 1601, he was presented by Tycho to the Emperor, who conferred upon him the title of Imperial Mathematician, on the condition that he would assist Tycho in his calculations. This connexion was peculiarly valuable to Kepler, as the observations of his colleague were the only ones made in the world which could enable him to carry on his own theoretical inquiries. These two astronomers now undertook to compute, from Tycho’s observations, a new set of astronomical tables, to be called the Rudolphine Tables, in honour of the Emperor. This scheme flattered the vanity of their master, and he pledged himself to pay all the expenses of the work. Longomontanus, Tycho’s principal assistant, took upon himself the labour of arranging and discussing the observations on the stars, while Kepler devoted himself to the more congenial task of examining those on the planet Mars, with which Tycho was at that time particularly occupied. The appointment of Longomontanus to a professorship in Denmark, and the death of Tycho in October 1601, put a stop to these important schemes.
Kepler succeeded Tycho as principal mathematician to the Emperor, and was provided with a handsome salary, which was partly charged on the imperial treasury, and partly on the States of Silesia, and the first instalment of which was to be paid in March 1602. The generosity of the Emperor did not fail to excite the jealousy of ignorant individuals, who were not aware of the value of science to the state; but the increasing fame of Kepler, and the valuable works which he published, soon silenced their opposition.
In September 1604, astronomers were surprised with the appearance of a new star in the foot of Serpentarius. It was not seen before the 29th of September, and Mœstlin informs us that, on account of clouds, he did not obtain a good view of it till the 6th of October. Like that of 1572,[44] it at first surpassed Jupiter in brightness, and rivalled even Venus, but it afterwards became as small as Regulus, and as dull as Saturn, and disappeared at the end of a few months. It constantly changed its colour, and was at first tawny, then yellow, then purple and red, and often white at great altitudes. It had no parallax, and therefore was a fixed star. Kepler wrote a short account of this remarkable body, and maintained its superiority to that of 1572, as this last came in an ordinary year, while the other appeared in the year of the fiery trigon, or that in which Saturn, Jupiter, and Mars, are in the three fiery signs, Aries, Leo, and Sagittarius, an event which occurs only every 800 years. After discussing a great variety of topics, but little connected with his subject, and in a style of absurd jocularity, he attacks the opinions of the Epicureans, that the star was a fortuitous concourse of atoms, in the following remarkable paragraph, which is a good specimen of the work:—“When I was a youth with plenty of idle time on my hands, I was much taken with the vanity, of which some grown men are not ashamed, of making anagrams by transposing the letters of my name, written in Latin. Out of Joannes Keplerus came Serpens in Akuleo (a serpent in his sting); but not being satisfied with the meaning of these words, and being unable to make another, I trusted the thing to chance, and taking out of a pack of playing cards as many as there were letters in the name, I wrote one upon each, and then began to shuffle them, and at each shuffle to read them in the order they came, to see if any meaning came of it. Now, may all the Epicurean gods and goddesses confound this same chance, which, although I have spent a good deal of time over it, never shewed me anything like sense even from a distance. So I gave up my cards to the Epicurean eternity, to be carried away into infinity; and, it is said, they are still flying about there in the utmost confusion among the atoms, and have never yet come to any meaning. I will tell those disputants, my opponents, not my own opinion, but my wife’s. Yesterday, when weary with writing, and my mind quite dusty with considering these atoms, I was called to supper, and a salad I had asked for was set before me. ‘It seems then,’ said I, aloud, ‘that if pewter dishes, leaves of lettuce, grains of salt, drops of water, vinegar, and oil, and slices of egg, had been flying about in the air from all eternity, it might at last happen by chance that there would come a salad.’ ‘Yes,’ says my wife, ‘but not so nice and well dressed as this of mine is.’”
CHAPTER II.
Kepler’s Pecuniary Embarrassments—His Inquiries respecting the Law of Refraction—His Supplement to Vitellio—His Researches on Vision—His Treatise on Dioptrics—His Commentaries on Mars—He discovers that the orbit of Mars is an Ellipse, with the Sun in one focus—And extends this discovery to all the other Planets—He establishes the two first laws of Physical Astronomy—His Family Distresses—Death of his Wife—He is appointed Professor of Mathematics at Linz—His Method of Choosing a Second Wife—Her Character, as given by Himself—Origin of his Treatise on Gauging—He goes to Ratisbon to give his Opinion to the Diet on the change of Style—He refuses the Mathematical Chair at Bologna.