"I cannot omit this opportunity of relating to you what happened to myself at the time when this opinion (the Copernican system) began to be discursed. I was then a very young man, and had scarcely finished my course of philosophy, which other occupations obliged me to leave off, when there arrived in this country, from Rostoch, a foreigner, whose name, I believe, was Christian Vurstisius (Wurteisen), a follower of Copernicus. This person delivered, on this subject, two or three lectures in a certain academy, and to a crowded audience. Believing that several were attracted more by the novelty of the subject than by any other cause, and being firmly persuaded that this opinion was a piece of solemn folly, I was unwilling to be present. Upon interrogating, however, some of those who were there, I found that they all made it a subject of merriment, with the exception of one, who assured me that it was not a thing wholly ridiculous. As I considered this individual to be both prudent and circumspect, I repented that I had not attended the lectures; and, whenever I met any of the followers of Copernicus, I began to inquire if they had always been of the same opinion. I found that there was not one of them who did not declare that he had long maintained the very opposite opinions, and had not gone over to the new doctrines till he was driven by the force of argument. I next examined them one by one, to see if they were masters of the arguments on the opposite side; and such was the readiness of their answers, that I was satisfied they had not taken up this opinion from ignorance or vanity. On the other hand, whenever I interrogated the Peripatetics and the Ptolemeans (and, out of curiosity, I have interrogated not a a few), respecting their perusal of Copernicus's work, I perceived that there were few who had seen the book, and not one who understood it. Nor have I omitted to enquire among the followers of the Peripatetic doctrines, if any of them had ever stood on the opposite side; and the result was, that there was not one. Considering, then, that nobody followed the Copernican doctrine, who had not previously held the contrary opinion, and who was not well acquainted with the arguments of Aristotle and Ptolemy; while, on the other hand, nobody followed Ptolemy and Aristotle, who had before adhered to Copernicus, and had gone over from him into the camp of Aristotle; weighing, I say, these things, I began to believe that, if any one who rejects an opinion which he has imbibed with his milk, and which has been embraced by an infinite number, shall take up an opinion held only by a few, condemned by all the schools, and really regarded as a great paradox, it cannot be doubted that he must have been induced, not to say driven, to embrace it by the most cogent arguments. On this account, I have become very curious to penetrate to the very bottom of the subject."[6]
It appears, on the testimony of Galileo himself, that he taught the Ptolemaic system, out of compliance with the popular feeling, after he had convinced himself of the truth of the Copernican doctrines. In the treatise on the sphere, indeed, which bears his name[7], and which must have been written soon after he went to Padua, and subsequently to 1592, the stability of the earth, and the motion of the sun, are supported by the very arguments which Galileo afterwards ridiculed; but we have no means of determining whether or not he had then adopted the true system of the universe. Although he might have taught the Ptolemaic system in his lectures, after he had convinced himself of its falsehood; yet it is not likely that he would go so far as to publish to the worlds as true, the very doctrines which he despised. In a letter to Kepler, dated in 1597, he distinctly states that he had, many years ago, adopted the opinions of Copernicus; but that he had not yet dared to publish his arguments in favour of them, and his refutation of the opposite opinions. These facts would leave us to place Galileo's conversion somewhere between 1593 and 1597; although many years cannot be said to have elapsed between these two dates.
At this early period of Galileo's life, in the year 1593, he met with an accident; which had nearly proved fatal. A party at Padua; of which he was one, were enjoying; at an open window; a current of air, which was artificially cooled by a fall of water. Galileo unfortunately fell asleep under its influence; and so powerful was its effect upon his robust constitution; that he contracted a severe chronic disorder, accompanied with acute pains in his body, and loss of sleep and appetite, which attacked him at intervals during the rest of his life. Others of the party suffered still more severely, and perished by their own rashness.
Galileo's reputation was now widely extended over Europe; and the archduke Ferdinand (afterwards emperor of Germany), the landgrave of Hesse, and the princes of Alsace and Mantua honoured his lectures with their presence. Prince Gustavus of Sweden also received instructions from him in mathematics, during his sojourn in Italy; and it has been supposed that this was the celebrated Gustavus Adolphus.
When Galileo had completed the first period of his engagement at Padua, he was re-elected for other six years, with an increased salary of 320 florins. This liberal addition to his income is ascribed by Fabbroni to the malice of one of his enemies, who informed the senate that Galileo was living in illicit intercourse with Marina Gamba. Without inquiring into the truth of the accusation, the senate is said to have replied, that if "he had a family to support, he had the more need of an increased salary." It is more likely that the liberality of the republic had been called forth by the high reputation of their professor, and that the terms of their reply were intended only to rebuke the malignity of the informer. The mode of expression would seem to indicate that one or more of Galileo's children had been born previous to his re-election in 1598; but as this is scarcely consistent with other facts, we are disposed to doubt the authenticity of Fabbroni's anecdote.
The new star, which attracted the notice of astronomers in 1604, excited the particular attention of Galileo. The observations which he made upon it, and the speculations which they suggested, formed the subject of three lectures, the beginning of the first of which only has reached our times. From the absence of parallax, he proved that the common hypothesis of its being a meteor was erroneous, and that, like the fixed stars, it was situated far beyond the bounds of our own system. The popularity of the subject attracted crowds to his lecture-room; and Galileo had the boldness to reproach his hearers for taking so deep an interest in a temporary phenomenon, while they passed unnoticed the wonders of creation which were daily presented to their view.
In the year 1606, Galileo was again appointed to the professorship at Padua, with an augmented stipend of 520 florins. His popularity had now risen so high, that his audience could not be accommodated in his lecture-room; and even when he had assembled them in the school of medicine, which contained 1000 persons, he was frequently obliged to adjourn to the open air.
Among the variety of pursuits which occupied his attention, was the examination of the properties of the loadstone. In 1607, he commenced his experiments; but, with the exception of a method of arming loadstones, which; according to the report of Sir Kenelm Digby, enabled them to carry twice as much weight as others, he does not seem to have made any additions to our knowledge of magnetism. He appears to have studied with care the admirable work of our countryman; Dr. Gilbert; "De Magnete," which was published in 1600; and he recognised; in the experiments and reasonings of the English philosopher; the principles of that method of investigating truth which he had himself adopted. Gilbert died in 1603; in the 63d year of his age, and probably never read the fine compliment which was paid to him by the Italian philosopher:—"I extremely praise, admire, and envy this author."
In the preceding pages we have brought down the history of Galileo's labours to that auspicious year in which he first directed the telescope to the heavens. No sooner was that noble instrument placed in his hands, than Providence released him from his professional toils, and supplied him with the fullest leisure and the amplest means for pursuing and completing the grandest discoveries.
Although he had quitted the service and the domains of his munificent patron; the grand duke of Tuscany, yet he maintained his connection with the family, by visiting Florence during his academic vacations, and giving mathematical instruction to the younger branches of that distinguished house. Cosmo, who had been one of his pupils, now succeeded his father Ferdinand; and having his mind early imbued with a love of knowledge, which had become hereditary in his family, he felt that the residence of Galileo within his dominions—and still more his introduction into his household—would do honour to their common country, and reflect a lustre upon his own name. In the year 1609, accordingly, Cosmo made proposals to Galileo to return to his original situation at Pisa. These overtures were gratefully received; and in the arrangements which Galileo on this occasion suggested, as well as in the manner in which they were urged, we obtain some insight into his temper and character. He informs the correspondent through whom Cosmo's offer was conveyed, that his salary of 520 florins at Padua would be increased to as many crowns at his re-election; and that he could enlarge his income to any extent he pleased, by giving private lectures, and receiving pupils. His public duties, he stated, occupied him only sixty half-hours in the year; but his studies suffered such interruptions from the domestic pupils and private lectures, that his most ardent wish was to be relieved from them, in order that he might have sufficient rest and leisure, before the close of his life, to finish and publish those great works which he had in hand. In the event, therefore, of his returning to Pisa, he hoped that it would be the first object of his serene highness to give him leisure to complete his works without the drudgery of lecturing. He expresses his anxiety to gain his bread by his writings, and he promises to dedicate them to his serene master. He enumerates, among these books, two on the system of the universe; three on local motion; three books of mechanics; two on the demonstration of principles, and one of problems; besides treatises on sound and speech, on light and colours, on the tides, on the composition of continuous quantity, on the motions of animals, and on the military art. On the subject of his salary, he makes the following curious observations:—