He was at this time also deeply interested in a subject which originated as far back as 1610. It had occurred to him soon after the discovery of Jupiter’s moons, by a series of observations of them, to make astronomical calculations and tables which would enable him to predict every year their configurations, their relative positions and occasional eclipses with the utmost precision; this would furnish the means of ascertaining the longitude of the point of observation at any hour of the night, which appeared to be of special importance to navigation. For hitherto the eclipses of the sun and moon had had to be employed for the purpose, which, however, on account of their rarity and the want of precise calculation, were neither entirely to be relied on nor sufficient. Galileo had offered his discovery,—the practical value of which he overrated,—in 1612, to the Spanish Government, and in 1616 tedious negotiations were carried on about it, which however led to no result, were then postponed till 1620, and in 1630 entirely given up.[519] Now (August, 1636,) as he heard that the Dutch merchants had even offered a premium of thirty thousand scudi to any one who should invent a sure method of taking longitudes at sea, he ventured, without the knowledge of the Inquisition, to offer his invention to the Protestant States-General. Diodati at Paris was the mediator in these secret and ceremonious negotiations. On 11th November, Galileo’s offer was entertained in the most flattering manner in the Assembly of the States-General, and a commission was appointed, consisting of the four savans, Realius, Hortensius, Blavius, and Golius, to examine into the subject and report upon it.[520]
While Galileo was impatiently waiting for the decision that was never come to, he made his last great telescopic discovery, although suffering much in his eyes, that of the libration and titubation of the moon, about which he wrote his remarkable letter to Alfonso Antonini, bearing the signal date: “Della mia carcere di Arcetri li 10 febbrajo 1637.”[521]
The complaint in Galileo’s eyes grew rapidly worse. By the end of June the sight of the right eye was gone, and that of the other diminished with frightful rapidity from a constant discharge.[522] But in spite of this heavy calamity, combined with his other sufferings, his interest in science did not diminish for a moment. Even at this sad time we find him carrying on a brisk correspondence with the learned men of Germany, Holland, France, and Italy, continuing his negotiations with the States-General with great zest,[523] as well as occupying himself perpetually with astronomy and physics. He was indeed often obliged to employ the hand of another;[524] but his mind worked on with undiminished vigour, even though he was no longer able to commit to paper himself the ideas that continually occupied him.
On 2nd September he received a visit from his sovereign, who came to console and encourage him in his pitiable situation.[525] A few months later an unknown young man, of striking appearance from his handsome face and the unmistakable evidences which genius always exhibits, knocked at the door of the solitary villa at Arcetri: it was Milton, then twenty-nine years of age, who, travelling in Italy, sought out the old man of world-wide fame to testify his veneration.[526]
In December of the same year Galileo became permanently quite blind, and informed Diodati of his calamity on 2nd January, 1638, in the following words:—
“In reply to your very acceptable letter of 20th November, I inform you, in reference to your inquiries about my health, that I am somewhat stronger than I have been of late, but alas! revered sir, Galileo, your devoted friend and servant, has been for a month totally and incurably blind; so that this heaven, this earth, this universe, which by my remarkable observations and clear demonstrations I have enlarged a hundred, nay, a thousand fold beyond the limits universally accepted by the learned men of all previous ages, are now shrivelled up for me into such narrow compass that it only extends to the space occupied by my person.”[527]
Up to the time when Galileo entirely lost his sight, absolutely nothing had been able to be done for his liberation at Rome. Even the faithful Castelli wrote on 12th September, to Galileo’s son Vincenzo, that he had not been able to do anything whatever for his father; but he piously adds, “I do not fail every morning at holy mass to pray the Divine Majesty to comfort him, to help him, and to grant him His Divine grace.”[528] This precisely indicates the hopeless state of Galileo’s affairs. Just then, during the first few days of December of the same year, darkness closed round him for ever; and not long afterwards, 12th December, Castelli suddenly wrote to him, that he had been given to understand that Galileo had not been forbidden in 1634 to send petitions direct to the Holy Office, but only through other persons.[529] When the decided papal rescript of 23rd March, 1634,[530] is compared with this curious interpretation of it, there can be no doubt that it was intended to enable the curia to take a more lenient view without direct collision with a former mandate. Galileo at once sent Castelli’s letter to the Tuscan Court, with a request for instructions, as he did not wish to do anything without the concurrence of his sovereign.[531] He was informed that he had better draw up a petition to the Holy Office, and get it handed in at Rome through Castelli.[532] The latter had meanwhile informed himself under what formalities Galileo should make his request, and sent him on 19th January, 1638,[533] a draught of the petition, with the remark that it must be sent, together with a medical certificate, direct to the assessor of the Congregation of the Holy Office; this Galileo immediately did. The petition was as follows:—
“Galileo Galilei, most humble servant of your most worthy Eminence, most respectfully showeth that whereas, by command of the Holy Congregation, he was imprisoned outside Florence four years ago, and after long and dangerous illness, as the enclosed medical certificate testifies, has entirely lost his eyesight, and therefore stands in urgent need of medical care: he appeals to the mercy of your most worthy Eminences, urgently intreating them in this most miserable condition and at his advanced age to grant him the blessing of his liberty.”
The utmost caution was exercised at Rome before granting this petition. No confidence was placed in the medical certificate; but the Inquisitor-General of Florence, Father Fanano, was instructed to visit Galileo and to make an exact report of his health, and whether it was to be feared, if he lived at Florence, that he would promote the propagation of his errors.[534] Fanano at once conscientiously executed his commission, and on 13th February, 1638, sent the following report to Cardinal Francesco Barberini:—