GALILEO-GALILEI 163 apparently varied like the earth, by land and water. He next applied to Jupiter and was struck by the appearance of three small stars, almost in a straight line and close to him. At first he did not suspect the nature of these bodies- but careful observation soon convinced him that these three, together with a fourth which was at first invisible, were in reality four moons revolving round their pri- mary planet. These he named the Medicean stars. They have long ceased to be known by that name ; but so highly prized was the distinction thus conferred upon the ducal house of Florence, that Galileo received an intimation that he would " do a thing just and proper in itself, and at the same time render himself and his family rich and powerful forever," if he " named the next star which he should discover after the name of the great star of France, as well as the most brilliant of all the earth," Henry IV. These discoveries were made known in 1610, in a work entitled " Nuncius Sidereus," the Newsman of the Stars; in which Galileo further announced that he had seen many stars invisible to the naked eye, and ascertained that the nebulae scattered through the heavens consist of assemblages of innumerable small stars. The ignorant and un- prejudiced were struck with admiration ; indeed, curiosity had been raised so high before the publication of this book, as materially to interfere with the conveni- ence of those who possessed telescopes. Galileo was employed a month in exhib- iting his own to the principal persons in Venice ; and our unfortunate astronomer was surrounded by a crowd who kept him in durance for several hours, while they passed his glass from one to another. He left Venice the next morning, to pursue his inquiries in some less inquisitive place. But the great bulk of the philosophers of the day were far from joining in the general feeling. They raiscu an outcry against the impudent fictions of Galileo, and one, a professor of Padua, refused repeatedly to look through the telescope, lest he should be compelled to admit that which he had pre-determined to deny. It was not long before Galileo had new and equally important matter to an- nounce. He observed a remarkable appearance in Saturn, as if it were composed of three stars touching each other ; his telescope was not sufficiently powerful to resolve them into Saturn and his ring. Within a month he ascertained that Venus exhibits phases like those of the moon a discovery of great importance in confirming the Copernican system. The same phenomenon he afterward de- tected in Mars. We close the list with the discovery of the revolution of the sun round his axis, in the space of about a lunar month, derived from careful ob- servation of the spots on his surface. About this time (1610-161 1) Galileo took up his abode in Tuscany, upon the invitation of the grand duke, who offered to him his original situation at Pisa, with a liberal salary, exemption from the necessity of residence, and complete leisure to pursue his studies. In 1612 he published a discourse on "Floating Bodies," in which he investigates the theory of buoyancy, and refutes, by a series of beautiful and conclusive experiments, the opinion that the floating or sinking of bodies depends on their shape. Neither Copernicus nor his immediate followers suffered inconvenience or re-
