To understand the effect of this discovery upon Galileo requires a person who has himself watched the stars, not, as a dilettante, seeking recreation or amusement, but with that deep reverence that comes only to him who feels--nay, knows--that in the moment of observation just passed he too has added his mite to the great fund of human knowledge. Galileo's mummied forefinger still points toward the stars from its little pedestal of wood in the _Museo_ at Florence, a sign to all men that he is unforgotten. But Galileo knew on that 11th of January, 1610, that the memory of him would never fade; that the very music of the spheres would thenceforward be attuned to a truer note, if any would but hearken to the Jovian harmony. For he recognized at once that the visible revolution of these moons around Jupiter, while that planet was himself visibly travelling through space, must deal its death-blow to the old Ptolemaic system of the universe. Here was a great planet, the centre of a system of satellites, and yet not the centre of the universe. Surely, then, the earth, too, might be a mere planet like Jupiter, and not the supposed motionless centre of all things. The satellite discovery was published in 1610 in a little book called "Sidereus Nuncius," usually translated "The Sidereal Messenger." It seems to us, however, that the word "messenger" is not strong enough; surely in Papal Italy a _nuncius_ was more than a mere messenger. He was clothed with the very highest authority, and we think it probable that Galileo's choice of this word in the title of his book means that he claimed for himself similar authority in science. At all events, the book made him at once a great reputation and numerous enemies. But it was not until 1616 that the Holy Office (Inquisition) issued an edict ordering Galileo to abandon his opinion that the earth moved, and at the same time placed Copernicus's _De Revolutionibus_ and two other books advocating that doctrine on the "Index Librorum Prohibitorum," or list of books forbidden by the Church. These volumes remained in subsequent editions of the "Index" down to 1821, but they no longer appear in the edition in force to-day.