(printed p. 381 — Caput XV presents the tidal hypothesis of the Genoese patrician Giovanni Battista Baliani through two 1650 letters to Riccioli: a monthly revolution of the Earth to produce the tides, offered strictly as hypothesis in deference to the Church’s decree. Riccioli publishes it as a model of keeping bold conceptions “within the swaddling-bands of mere hypothesis.” Caput XVI then opens, on the velocity of falling heavy and light bodies from Riccioli’s own experiments, beginning with the Aristotelian axiom that falling bodies accelerate.)

[Header: ON THE SYSTEM OF THE MOVED EARTH — 381]

[I.] I indeed persuade myself that the most illustrious Lord Giovanni Battista Baliani, a Genoese Patrician, will not be unwilling if I publish his Letter written to me—since it contains nothing secret that is not to be revealed, nor detracts anything from his reputation, which he long since acquired for himself, among prudent estimators of these matters, by his most learned books on the natural motion of heavy bodies, solid and liquid. Nay, from the following epistle his singular piety and prudence, joined with acuteness of intellect, will appear—since he defers, with as great reverence as is fitting, to the Sacred Congregation of Cardinals in this matter concerning the motion of the Earth. There is, therefore, his epistle given to me, and faithfully rendered into Latin, of this kind:

[Margin: The Letter of Lord Baliani to the Author of this Almagest.]

Some time ago Lord Girolamo Bardi showed me some letters of your Paternity, in which he signified [your] desire of seeing my System, in which the Earth would revolve around the Moon. To which I replied that I do not deny that this conception once came into my mind (or fancy); and little was lacking but that I should write to your Reverence about it. But from this I abstained, because I gave no assent to this figment, nor did I think it to be true, for many reasons—but especially because I would believe it to be against the decrees of those in whose power is the authority of judging concerning matters pertaining to the Faith. But when, very recently, I was discoursing with Fr. Nicolaus Cabeo (who, to my great sorrow, migrated from the living not long ago), and who vehemently commended to me your Almagest, an occasion arose for me of writing these few [words] to your Reverence, and of asking that you would deign to signify to me when it may be hoped that the new Almagest will come forth into light, and at the same time of rendering the reason why I once conceived in my mind the aforesaid system concerning the [revolution around the] Moon. But that took its occasion thence, that I had seen Galileo think it could be demonstrated that the Sun is the center of the flux and reflux of the Sea—in which matter he evidently erred, as I wrote at once to him himself, after his book had been transmitted by him to me. But by that occasion I detected that the true cause of the marine tide would result, if the Earth were to revolve around the Moon—yet not absolutely assenting to this hypothesis, for the aforesaid reason; and also because I do not yet see how the Moon can be set in the center of the universe, or how, the Sun being placed in this center and the Moon constituted in the center of the Earth’s Epicycle (which are the two ways of defending the sea’s tide), all the celestial Phenomena can be preserved. It pleased me, therefore, to signify to your Reverence this slight foundation, by which it was reported to him that I had had in mind to publish such a system; whose hand at length I reverently kiss. Given at Genoa, the 9th day of July, the Year 1650.

Of your Reverence the most Reverend, the most devoted Servant, Giovanni Battista Baliani.

[II.] When I had responded to this most kind epistle—[saying] that it seemed to me most difficult, by the aforesaid system, to preserve all the celestial Phenomena without multiplying motions in the Moon—he did not grudge to write back this second epistle to me:

[Margin: Another letter of the same to the same.]

What your Reverence signified to me, by [your] most kind letters, concerning the publication of the Almagest, would have been much more gratifying if by them a hope had been offered me of a much earlier edition of the aforesaid work. Nevertheless I pray that the life and health of your Reverence [be] most excellent, that you may be able to complete so great a work, for the use and erudition of lettered men. I considered then what your Reverence wrote to me concerning that system of mine. And although I persist in believing the Earth to be really at the center of the Universe, I do not yet hold [it] persuaded that, if the Sun were placed there and the Earth were turned around the Moon, it would be necessary that other motions be ascribed to the Moon beyond those which Copernicus conceived in mind and those which he himself followed. For it seems to me, at first sight, that the appearances can be defended without new motions of the Moon around the Earth which are worthy of consideration—but [that] it would nevertheless necessarily have to be feigned that the Great Orb [is] much ampler, and the Sun’s interval supposed far greater, and accordingly also the distance of the Fixed [stars] much longer, than even the Copernicans themselves judge. Which I do not doubt would be a great Paradox. But, this notwithstanding, it seems to me that, if GOD had wished to found such a system, it would answer to the experiments both of the celestial motions and of the marine tide. May your Reverence hold me excused, if I importunately thrust upon him these troublesome and tedious propositions, and may he deign to command me something for his own sake. Genoa, the 30th day of July, the Year 1650.

Of your Reverence the most Reverend, the most devoted Servant, Giovanni Battista Baliani.

[III.] These [things] I had to indicate to my Reader concerning the aforesaid system—not so much that I might adjoin the judgment of so great a man against Galileo, as that, by his example, the rest may learn, if perhaps the conceptions of their own mind agree not at all with the authority of the sacred letters or of Ecclesiastical sanctions, either not to bring [them] forth, but to suppress them by a pious and prudent—and therefore fruitful—abortion; or, if perhaps they have brought [them] forth, to confine them within the swaddling-bands and cradle of mere hypothesis.