INTRODUCTION.

The account of Galileo’s later astronomical discoveries regarding Saturn’s ring and the phases of Venus is taken from the preface of this work.—(Kepler’s Dioptrics Original Latin title: Dioptrice. This was Kepler's foundational work on the physics of lenses and how telescopes function.; Augsburg, 1611.)

In 1612 Galileo published a series of observations of solar spots Now called sunspots. At the time, the idea that the "perfect" sun had dark spots was a radical challenge to traditional philosophy., and in 1618 some observations of three comets. There exist also long series of minute observations of Jupiter and his satellites, continued to November 1619.—(Galileo’s Works; Florence, 1845.)

Further astronomical researches may have been hindered by failing sight. One more astronomical discovery, however, that of the moon’s librations Librations are the slight wobbling movements of the Moon as seen from Earth, which allow us to see a bit more than just one hemisphere., was made as late as 1637, and the announcement of it is dated “from my prison in Arcetri” original: “dalla mia carcere di Arcetri.” Galileo was under house arrest in his villa at Arcetri, near Florence, following his trial by the Roman Inquisition.. Galileo died January 8, 1642.

The following editions have been used for the translation:—

Galileo’s Works.
1. Florence, 1718.
2. Padua, 1744.
3. Florence, 1842-56.

The Starry Messenger Original Latin title: Sidereus Nuncius. This was the short treatise published by Galileo in 1610 that first announced his telescopic discoveries to the world.
1. Venice, 1610.
2. London, 1653.