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x Galileo’s later astronomical discoveries of Saturn's ring and the phases of Venus is taken from the preface of this work.—(Kepler’s Dioptrics; Augsburg, 1611.)

In 1612 Galileo published a series of observations of solar spots, 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, was made as late as 1637, and the announcement of it is dated “dalla mia carcere di Arcetri.” 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.

Sidereus Nuncius.

1. Venice, 1610.

2. London, 1653.