As philosopher and principal mathematician to the grand duke of Tuscany, Galileo now took up his residence at Florence, with a salary of 1000 florins. No official duties, excepting that of lecturing occasionally to sovereign princes, were attached to this appointment; and it was expressly stipulated that he should enjoy the most perfect leisure to complete his treatises on the constitution of the universe, on mechanics, and on local motion. The resignation of his professorship at Padua, which necessarily followed his new appointment, created much dissatisfaction in that university: but though many of his former friends refused at first to hold any communication with him, this feeling gradually subsided; and the Venetian senate at last appreciated the views, as well as the powerful motives, which induced a stranger to accept of promotion in his native land.
While Galileo was enjoying the reward and the fame of his great discovery, a new species of enmity was roused against them. Simon Mayer, an astronomer of no character, pretended that he had discovered the satellites of Jupiter before Galileo, and that his first observation was made on the 29th of December, 1609. Other astronomers announced the discovery of new satellites: Scheiner reckoned five, Rheita nine, and others found even so many as twelve: these satellites, however, were found to be only fixed stars. The names of Vladislavian, Agrippine, Uranodavian, and Ferdinandotertian, which were hastily given to these common telescopic stars, soon disappeared from the page of science, and even the splendid telescopes of modern times have not been able to add another gem to the diadem of Jupiter.
A modern astronomer of no mean celebrity has, even in the present day, endeavoured to rob Galileo of this staple article of his reputation. From a careless examination of the papers of our celebrated countryman, Thomas Harriot, which baron Zach had made in 1784, at Petworth, the seat of lord Egremont, this astronomer has asserted[10] that Harriot first observed the satellites of Jupiter on the 16th of January, 1610; and continued his observations till the 25th of February, 1612. Baron Zach adds the following extraordinary conclusion:—"Galileo pretends to have discovered them on the 7th of January, 1610; so that it is not improbable that Harriot was likewise the first discoverer of these attendants of Jupiter." In a communication which I received from Dr. Robertson, of Oxford, in 1822[11], he informed me that he had examined a class of Harriot's papers, entitled, "De Jovialibus Planetis;" and that it appears, from two pages of these papers, that Harriot first observed Jupiter's satellites on the 17th of October, 1610. These observations are accompanied with rough drawings of the positions of the satellites, and rough calculations of their periodical revolutions. My friend, professor Rigaud[12], who has very recently examined the Harriot MSS., has confirmed the accuracy of Dr. Robertson's observations, and has thus restored to Galileo the honour of being the first and the sole discoverer of these secondary planets.
The great success which attended the first telescopic observations of Galileo, induced him to apply his best instruments to the other planets of our system. The attempts which had been made to deprive him of the honour of some of his discoveries, combined, probably, with a desire to repeat his observations with better telescopes, led him to announce his discoveries under the veil of an enigma; and to invite astronomers to declare, within a given time, if they had observed any new phenomena in the heavens.
Before the close of 1610, Galileo excited the curiosity of astronomers, by the publication of his first enigma. Kepler and others tried in vain to decipher it; but in consequence of the emperor Rodolph requesting a solution of the puzzle, Galileo sent him the following clue:—
"Altissimam planetam tergeminam observavi."
I have observed that the most remote planet is triple.
In explaining more fully the nature of his observation, Galileo remarked that Saturn was not a single star, but three together, nearly touching one another: he described them as having no relative motion, and as having the form of three o's, namely, oOo, the central one being larger than those on each side of it.
Although Galileo had announced that nothing new appeared in the other planets, yet he soon communicated to the world another discovery of no slight interest. The enigmatical letters in which it was concealed, formed the following sentence:—
"Cynthia figuras æmulatur mater Amorum."