Kepler was kept in a state of constant anxiety from the delay in the Government to pay up the arrears of his pension, while their repeated promises prevented him from accepting of other employments. He had hoped that the affair of the Bolognese chair would rouse the imperial treasury to a sense of its duty, and enable him to publish the Rudolphine Tables,—that great work which he owed to the memory both of Tycho and of Rudolph. But though he was disappointed in this expectation, an event now occurred which at least held out the prospect of a favourable change in his circumstances. The Emperor Mathias died in 1619, and was succeeded by Ferdinand III., who not only continued him in the situation of his principal mathematician, with his former pension, but promised to pay up the arrears of it, and to furnish the means for publishing the Rudolphine Tables.
The year 1619, so favourable to Kepler’s prospects in life, was distinguished also by the publication, at Linz, of one of his most remarkable productions, entitled “The Harmonies of the World.” It is dedicated to James I. of England, and will be for ever memorable in the history of science, as containing the celebrated law that the squares of the periodic times of the planets are to one another as the cubes of their distances. This singular volume, which is marked with all the peculiarities which distinguish his Cosmographical Mystery, is divided into five books. The two first books are principally geometrical, and relate to regular polygons inscribed in a circle; the third book is a treatise on music, in which musical proportions are derived from figures; the fourth book is astrological, and treats of the harmony of rays emanating on the earth from the heavenly bodies, and on their influence over the sublunary or human soul; the fifth book is astronomical and metaphysical, and treats of the exquisite harmonies of the celestial motions, and of the celebrated third law of the universe, which we have already referred to.
This law, as he himself informs us, first entered his mind on the 8th March 1618; but, having made an erroneous calculation, he was obliged to reject it. He resumed the subject on the 15th May; and having discovered his former error, he recognised with transport the absolute truth of a principle which for seventeen years had been the object of his incessant labours. The delight which this grand discovery gave him had no bounds. “Nothing holds me,” says he; “I will indulge in my sacred fury; I will triumph over mankind by the honest confession, that I have stolen the golden vases of the Egyptians, to build up a tabernacle for my God, far away from the confines of Egypt. If you forgive me, I rejoice; if you are angry, I can bear it. The die is cast; the book is written, to be read either now or by posterity, I care not which. It may well wait a century for a reader, as God has waited six thousand years for an observer.”
About the same time, in 1618, Kepler published, at Linz, the three first books of his “Epitome of the Copernican Astronomy,” of which the fourth was published at the same place in 1622, and the fifth, sixth, and seventh at Frankfort in the same year. This interesting work is a kind of summary of all his astronomical views, drawn up in the form of a dialogue for the perusal of general readers. Immediately after its publication, it was placed by the Inquisition in the list of prohibited books; and the moment Kepler learned this from his correspondent Remus, he was thrown into great alarm, and requested from him some information respecting the terms and consequences of the censure which was then pronounced against him. He was afraid that it might compromise his personal safety if he went to Italy; that he would be compelled to retract his opinions; that the censure might extend to Austria; that the sale of his work would be ruined; and that he must either abandon his country or his opinions.
The reply of his friend Remus calmed his agitated mind, by explaining to him the true nature of the prohibition; and he concluded his letter with a piece of seasonable exhortation, “There is no ground for your alarm either in Italy or in Austria, only keep yourself within bounds, and put a guard upon your own passions.”
In the year 1620, Sir Henry Wotton, the English ambassador at Venice, paid a visit to Kepler on his way through Germany. It does not appear whether or not this visit was paid at the desire of James I., to whom Kepler had dedicated one of his works, but from the nature of the communication which was made to him by the ambassador, there are strong reasons to think that this was the case. Sir Henry Wotton urged Kepler to take up his residence in England, where he could assure him of a welcome and an honourable reception; but, notwithstanding the pecuniary difficulties in which he was then involved, he did not accept of the invitation. In referring to this offer in one of his letters, written a year after it was made, he thus balances the difficulties of the question—“The fires of civil war,” says he, “are raging in Germany. Shall I then cross the sea whither Wotton invites me? I, a German, a lover of firm land, who dread the confinement of an island, who presage its dangers, and must drag along with me my little wife and flock of children?” As Kepler seems to have entertained no doubt of his being well provided for in England, it is the more probable that the British Sovereign had made him a distinct offer through his ambassador. A welcome and an honourable reception, in the ordinary sense of these terms, could not have supplied the wants of a starving astronomer, who was called upon to renounce a large though an ill-paid salary in his native land; and Kepler had experienced too deeply the faithlessness of royal pledges to trust his fortune to so vague an assurance as that which is implied in the language of the English ambassador. During the two centuries which have elapsed since this invitation was given to Kepler, there has been no reign during which the most illustrious foreigner could hope for pecuniary support, either from the Sovereign or the Government of England. What English science has never been able to command for her indigenous talent, was not likely to be proffered to foreign merit. The generous hearts of individual Englishmen, indeed, are always open to the claims of intellectual pre-eminence, and ever ready to welcome the stranger whom it adorns; but through the frozen life-blood of a British minister such sympathies have seldom vibrated; and, amid the struggles of faction and the anxieties of personal and family ambition, he has turned a deaf ear to the demands of genius, whether she appeared in the humble posture of a suppliant, or in the prouder attitude of a national benefactor.
If the imperial mathematician, therefore, had no other assurance of a comfortable home in England than that of Sir Henry Wotton, he acted a wise part in distrusting it; and we rejoice that the sacred name of Kepler was thus withheld from the long list of distinguished characters whom England has starved and dishonoured.
In the year 1620, Kepler was exposed to a severe calamity, which continued to harass him for some time. His mother, Catherine Kepler, to whose peculiarities of temper we have already referred, was arrested on the 5th April, upon a charge of a very serious nature. One of her friends having some years before suffered a miscarriage, was subsequently attacked with violent headaches, and Catherine was charged with having administered poison to her friend. This accusation was indignantly repelled, and a young doctor of the law, whom she consulted, advised her to raise an action against her calumniator. From professional reasons, or probably pecuniary ones, this zealous practitioner continued to delay the lawsuit for five years. The judge who tried it happened to be displaced, and was succeeded by another, who had a personal quarrel with the prosecutor. The defender, who was aware of this favourable change in her case, became the accuser, and, in July 1620, Catherine Kepler was sent to prison, and condemned to the torture. The moment this event reached the ears of her son, he quitted Linz, and arrived in time to save her from punishment. He found that the evidence upon which she was condemned had no other foundation but her own intemperate conduct; and, though his interference was successful, yet she was not finally released from prison till the 4th November 1621. Convinced of her innocence, this bold woman, now in the 79th year of her age, raised a new action for damages against her opponent; but her death, in April 1622, put an end to her own miseries, as well as to the anxiety of her son. Among the virtues of this singular woman, we must number that of generosity. Mœstlin, the old preceptor of Kepler, had generously declined any compensation for his instructions. Kepler never forgot this act of kindness, and, in the midst of his poverty, he found means to send to Mœstlin a handsome silver cup in token of his gratitude. In acknowledging this gift, Mœstlin remarks, “Your mother had taken it into her head that you owed me 200 florins, and had brought 15 florins and a chandelier towards reducing the debt, which I advised her to send to you. I asked her to stay to dinner, which she refused. However, we hanselled your cup, as you know she is of a thirsty temperament.”
In the same year in which his mother was arrested, the States of Styria ordered all the copies of the Kalendar for 1624 to be publicly burnt. There does not seem to be any reason for supposing that this insult proceeded from his old enemies the Catholics. They would, no doubt, take an active share in carrying it into effect; but it would appear that his former patrons were affronted at Kepler’s giving the precedence in his title page to the States of Upper Ens, where he then resided, above the States of Styria.
In 1622, the Emperor Ferdinand, notwithstanding his own pecuniary difficulties, ordered the whole of Kepler’s arrears to be paid, even those which had been due by Rudolph and Mathias; and so great was his anxiety to have the Rudolphine Tables published, that he supplied the means for their immediate completion. New difficulties, however, sprung up to retard still longer the appearance of this most important work. The wars of the reformation, which were then agitating the whole of Germany, interfered with every peaceful pursuit. The library of Kepler was sealed up by order of the Jesuits, and it was only his position as imperial mathematician that saved him from personal inconvenience. A popular insurrection followed in the train of these disasters. The peasantry blockaded Linz, the place of Kepler’s residence, and it was not till the year 1627, as the title page bears, or 1628, as Kepler elsewhere states, that these celebrated Tables were given to the world.