+

pascer possa la terra nel suo seno." The work to which I refer is "La Cena de le Cenere," and narrates what took place at a supper held on the evening of Ash Wednesday (about 1583, see p. 145), at the house of Sir Fulk Greville, in order to give "Il Nolano" an opportunity of defending his peculiar opinions. His principal antagonists are two "Dottori d' Oxonia," whom Bruno calls Nundinio and Torquato. The subject is not treated in any very masterly manner on either side; but the author makes himself have greatly the advantage not only in argument, but in temper and courtesy: and in support of his representations of "pedantesca, ostinatissima ignoranza et presunzione, mista con una rustica incivilità, che farebbe prevaricar la pazienza di Giobbe," in his opponents, he refers to a public disputation which he had held at Oxford with these doctors of theology, in presence of Prince Alasco, and many of the English nobility".

Among the evidences of the difficulties which still lay in the way of the reception of the Copernican system, we may notice Bacon, who, as is well known, constantly refused his assent to it. It is to be observed, however, that he does not reject the opinion of the earth's motion in so peremptory and dogmatical a manner as he is sometimes accused of doing: thus in the "Thema Coeli" he says, "The earth, then, being supposed to be at rest (for that now

2

Opere di Giordano Bruno, vol. i. p. 146.

3 vol. i. p. 179.

appears to us the more true opinion)." And in his tract "On the Cause of the Tides," he says, "If the tide of the sea be the extreme and dimished limit of the diurnal motion of the heavens, it will follow that the earth is immovable; or at least that it moves with a much slower motion than the water." In the "Descriptio Globi Intellectualis" he gives his reasons for not accepting the heliocentric theory. "In the system of Copernicus there are many and grave difficulties: for the threefold motion with which he encumbers the earth is a serious inconvenience; and the separation of the sun from the planets, with which he has so many affections in common, is likewise a harsh step: and the introduction of so many immovable bodies into nature, as when he makes the sun and the stars immovable, the bodies which are peculiarly lucid and radiant; and his making the moon adhere to the earth in a sort of epicycle; and some other things which he assumes, are proceedings which mark a man who thinks nothing of introducing fictions of any kind into nature, provided his calculations turn out well." We have already explained that, in attributing three motions to the earth, Copernicus had presented his system encumbered with a complexity not really belonging to it. But it will be seen shortly, that Bacon's fundamental objection to this system was his wish for a system which could be supported by sound physical considerations; and it must be allowed, that at the period of which we are speaking, this had not yet

been done in favour of the Copernican hypothesis. We may add, however, that it is not quite clear that Bacon was in full possession of the details of the astronomical systems which that of Copernicus was intended to supersede; and that thus he, perhaps, did not see how much less harsh were these fictions, as he called them, than those which were the inevitable alternatives. Perhaps he might even be liable to a little of that indistinctness, with respect to strictly geometrical conceptions, which we have remarked in Aristotle. We can hardly otherwise account for his not seeing any use in resolving the apparently irregular motion of a planet into separate regular motions. Yet he speaks slightingly of this important step*. "The motion of planets, which is constantly talked of as the motion of regression, or renitency, from west to east, and which is ascribed to the planets as a proper motion, is not true; but only arises from appearance, from the greater advance 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 stedfastness with which he looked forwards to physical astronomy as the great and proper object of philosophical interest, we cannot give him credit for seeing the full

* Thema Coli, p. 246.

value and meaning of what had been done, up to his time, in Formal Astronomy.

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 Magneta," (printed 1600,) he gives the principal arguments in favour of the Copernican system, and decides that the earth revolves on its axis". He connects this opinion with his magnetic doctrines; and especially endeavours 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 1651; ("De Mundo Nostro Sublunari Philosophia Nova,") he appears to hesitate between the systems of Tycho and Copernicus. 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 stedfast though she seem,
Insensibly three different motions move?

P. L. b. viii.

5 Lib. vi. cap. 3,

4.

Lib. ii. cap. 20.

Sect. 3.-The Heliocentric Theory confirmed by Facts. Galileo's Astronomical Discoveries.

THE long interval which elapsed between the last great discoveries made by the ancients and the first made by the moderns, had afforded ample time for the developement of all the important consequences of the ancient doctrines. But when the human mind had been thoroughly roused again into activity, this was no longer the course of events. Discoveries crowded on each other; one wide field of speculation was only just opened up, when a richer promise tempted the labourers away into another quarter. Hence the history of this period contains the beginnings of many sciences, but exhibits none fully worked out into a complete or final form. Thus statics, soon after its revival, was eclipsed and overlaid by dynamics; and the Copernican system, considered merely with reference to the views of its author, was absorbed in the commanding interest of physical astronomy.

Still, advances were made which had an important bearing on the heliocentric theory, in other ways than by throwing light upon its physical principles. I speak of the new views of the heavens which the telescope gave; the visible inequalities of the moon's surface; the moon-like phases of the planet Venus; the discovery of the satellites of Jupiter, and of the ring of