[616] Gassendi Vita Peirescii, p. 77.
Other discoveries by him. 27. This is the greatest and most important of the discoveries of Galileo. But several others were of the deepest interest. He found that the planet Venus had phases, that is, periodical differences of apparent form like the moon; and that these are exactly such as would be produced by the variable reflection of the sun’s light on the Copernican hypothesis; ascribing also the faint light on that part of the moon which does not receive the rays of the sun, to the reflection from the earth, called by some late writers earth-shine; which, though it had been suggested by Mæstlin, and before him by Leonardo da Vinci, was not generally received among astronomers. Another striking phenomenon, though he did not see the means of explaining it, was the triple appearance of Saturn, as if smaller stars were conjoined as it were like wings to the planet. This, of course, was the ring.
Spots of the sun discovered. 28. Meantime the new auxiliary of vision which had revealed so many wonders could not lie unemployed in the hands of others. A publication, by John Fabricius, at Wittenberg, in July, 1611, De Maculis in Sole visis, announced a phenomenon in contradiction of common prejudice. The sun had passed for a body of liquid flame, or, if thought solid, still in a state of perfect ignition. Kepler had, some years before, observed a spot, which he unluckily mistook for the orb of Mercury in its passage over the solar orb. Fabricius was not permitted to claim this discovery as his own. Scheiner, a Jesuit, professor of mathematics at Ingolstadt, asserts in a letter, dated 12th of November, 1611, that he first saw the spots in the month of March in that year, but he seems to have paid little attention to them before that of October. Both Fabricius, however, and Scheiner may be put out of the question. We have evidence, that Harriott observed the spots on the sun as early as December 8th, 1610. The motion of the spots suggested the revolution of the sun round its axis, completed in twenty-four days, as it is now determined; and their frequent alterations of form, as well as occasional disappearance, could only be explained by the hypothesis of a luminous atmosphere in commotion, a sea of flame, revealing at intervals the dark central mass of the sun’s body which it envelopes.
Copernican system held by Galileo. 29. Though it cannot be said, perhaps, that the discoveries of Galileo would fully prove the Copernican system of the world to those who were already insensible to reasoning from its sufficiency to explain the phenomena, and from the analogies of nature, they served to familiarise the mind to it, and to break down the strong rampart of prejudice which stood in its way. For eighty years, it has been said, this theory of the earth’s motion had been maintained without censure; and it could only be the greater boldness of Galileo in its assertion which drew down upon him the notice of the church. But, in these eighty years since the publication of the treatise of Copernicus, his proselytes had been surprisingly few. They were now becoming more numerous: several had written on that side; and Galileo had begun to form a school of Copernicans who were spreading over Italy. The Lincean society, one of the most useful and renowned of Italian academies, founded at Rome by Frederic Cesi, a young man of noble birth, in 1603, had, as a fundamental law, to apply themselves to natural philosophy; and it was impossible that so attractive and rational a system as that of Copernicus could fail of pleasing an acute and ingenious nation strongly bent upon science. The church, however, had taken alarm; the motion of the earth was conceived to be as repugnant to Scripture as the existence of antipodes had once been reckoned; and in 1616, Galileo, though respected and in favour with the court of Rome, was compelled to promise that he would not maintain that doctrine in any manner. Some letters that he had published on the subject were put, with the treatise of Copernicus and other works, into the Index Expurgatorius, where, I believe, they still remain.[617]
[617] Drinkwater’s Life of Galileo. Fabroni, Vitæ Italorum, vol. i. The former seems to be mistaken in supposing that Galileo did not endeavour to prove his system compatible with Scripture. In a letter to Christina, the Grand Duchess of Tuscany, the author (Brenna) of the Life in Fabroni’s work, tells us, he argued very elaborately for that purpose. In ea videlicet epistolâ philosophus noster ita disserit, ut nihil etiam ab hominibus, qui omnem in sacrarum literarum studio consumpsissent ætatem, aut subtilius aut verius aut etiam accuratius explicatum expectari potuerit, p. 118. It seems, in fact, to have been this over-desire to prove his theory orthodox, which incensed the church against it. See an extraordinary article on this subject in the eighth number of the Dublin Review (1838). Many will tolerate propositions inconsistent with orthodoxy, when they are not brought into immediate juxtaposition with it.
His dialogues, and persecution. 30. He seems, notwithstanding this, to have flattered himself that, after several years had elapsed, he might elude the letter of this prohibition by throwing the arguments in favour of the Ptolemaic and Copernican systems into the form of a dialogue. This was published in 1632; and he might, from various circumstances, not unreasonably hope for impunity. But his expectations were deceived. It is well known that he was compelled by the Inquisition at Rome, into whose hands he fell, to retract, in the most solemn and explicit manner, the propositions he had so well proved, and which he must have still believed. It is unnecessary to give a circumstantial account, especially as it has been so well done in a recent work, the Life of Galileo, by Mr. Drinkwater Bethune. The papal court meant to humiliate Galileo, and through him to strike an increasing class of philosophers with shame and terror; but not otherwise to punish one, of whom even the inquisitors must, as Italians, have been proud; his confinement, though Montucla says it lasted for a year, was very short. He continued, nevertheless, under some restraint for the rest of his life, and though he lived at his own villa near Florence, was not permitted to enter the city.[618]
[618] Fabroni. His Life is written in good Latin, with knowledge and spirit, more than Tiraboschi has ventured to display.
It appears from some of Grotius’s Epistles, that Galileo had thought, about 1635, of seeking the protection of the United Provinces. But on account of his advanced age he gave this up: fessus senio constituit manere in quibus est locis, et potius quæ ibi sunt incommoda perpeti, quam malæ ætati migrandi onus, et novas parandi amicitias imponere. The very idea shows that he must have deeply felt the restraint imposed upon him in his country. Epist. Grot. 407, 446.
Descartes alarmed by this. 31. The church was not mistaken in supposing that she should intimidate the Copernicans, but very much so in expecting to suppress the theory. Descartes was so astonished at hearing of the sentence on Galileo, that he was almost disposed to burn his papers, or at least to let no one see them. “I cannot collect,” he says, “that he who is an Italian, and a friend of the pope, as I understand, has been criminated on any other account than for having attempted to establish the motion of the earth. I know that this opinion was formerly censured by some cardinals; but I thought I had since heard that no objection was now made to its being publicly taught even at Rome.”[619] It seems not at all unlikely that Descartes was induced, on this account, to pretend a greater degree of difference from Copernicus than he really felt, and even to deny, in a certain sense of his own, the obnoxious tenet of the earth’s motion.[620] He was not without danger of a sentence against truth nearer at hand; Cardinal Richelieu having had the intention of procuring a decree of the Sorbonne to the same effect, which, by the good sense of some of that society, fell to the ground.[621]
[619] Vol. vi., p. 239. He says here, of the motion of the earth, Je confesse que s’il est faux, tous les fondemens de ma philosophie le sont aussi.