of the starry heavens towards the west, by which the planets are left behind to the east." Undoubtedly those who spoke of such a motion of _regression_ were aware of this; but they saw how the motion was simplified by this way of conceiving it, which Bacon seems not to have seen. Though, therefore, we may admire Bacon for the steadfastness with which he looked forward to physical astronomy as the great and proper object of philosophical interest, we cannot give him credit for seeing the full value and meaning of what had been done, up to his time, in Formal Astronomy. [Note 21\5: _Thema Cœli_, p. 246.] Bacon's contemporary, Gilbert, whom he frequently praises as a philosopher, was much more disposed to adopt the Copernican opinions, though even he does not appear to have made up his mind to assent to the whole of the system. In his work. _De Magnete_ (printed 1600), he gives the principal arguments in favor of the Copernican system, and decides that the earth revolves on its axis.[22\5] He connects {275} this opinion with his magnetic doctrines; and especially endeavors by that means to account for the precession of the equinoxes. But he does not seem to have been equally confident of its annual motion. In a posthumous work, published in 1661 (_De Mundo Nostra Sublunari Philosophia Nova_) he appears to hesitate between the systems of Tycho and Copernicus.[23\5] Indeed, it is probable that at this period many persons were in a state of doubt on such subjects. Milton, at a period somewhat later, appears to have been still undecided. In the opening of the eighth book of the _Paradise Lost_, he makes Adam state the difficulties of the Ptolemaic hypothesis, to which the archangel Raphael opposes the usual answers; but afterwards suggests to his pupil the newer system: . . . . What if seventh to these The planet earth, so steadfast though she seem, Insensibly three different motions move? _Par. Lost_, b. viii. [Note 22\5: Lib. vi. cap. 3, 4.] [Note 23\5: Lib. ii. cap. 20.] Milton's leaning, however, seems to have been for the new system; we can hardly believe that he would otherwise have conceived so distinctly, and described with such obvious pleasure, the motion of the earth: Or she from west her silent course advance With inoffensive pace, that spinning sleeps On her soft axle, while she paces even, And bears thee soft with the smooth air along. _Par. Lost_, b. viii.