[Margin: A summary of our system.]

[I.] After the various systems of the ancients and of the more recent [authors], resting on the immobility of the Earth, two at last seem to me—after the Tychonic—more probable: one semi-Ptolemaic, the other semi-Tychonic, as to the center from which the Eccentrici—

[…continues on p. 289 (PDF 324): “…ties [are measured]…” — Riccioli’s exposition of his own two preferred world-systems (the semi-Ptolemaic and the semi-Tychonic), no doubt with their diagram(s).]

(printed p. 289 — Chapter IX concludes with the common frame of Riccioli’s system, its two forms — Semi-Ptolemaic and Semi-Tychonic — supported by five reasons, the System V (“Our System”) diagram, and the intervals and thicknesses of the heavens. This is the last page of Section III.)

…[the center from which the] Eccentricities of the orbs are to be measured. For as to the order of the Planets, it is plainly Egyptian; and as to the number of the heavens, it differs from each [form]. For in it we place the Earth in the center of the world, immune from all motion; and around it the orb of the Moon, above which the circulation of the Sun is so situated that nevertheless around the Sun Mercury, and around Mercury Venus, is carried—and they are found sometimes above the Sun, sometimes below; then Mars so encircles Venus that, in opposition with the Sun, it comes nearer to the earth than the Sun. Above Mars rises Jupiter, carrying around four satellites, which describe their epicycles around it; and above Jupiter, Saturn, itself also girded with two companions, or side-attendants. All of which, in reality in a single fluid heaven, are freely carried around—through helicoid spirals, or screw-wise, by the Intelligences—by a single motion obliquely toward the West. Above Saturn is the solid sphere of the fixed [stars], by a single spiral motion likewise, [moved] by one Intelligence or by several, exhibiting apparently a threefold motion—namely, in longitude toward the West, in longitude toward the East, and in latitude on account of the variation of declination—which, however, in reality is single, toward the West. Above the sphere of the Fixed [stars] is the aqueous, or crystalline, heaven, for that use which is known to God; and above this, the immobile Empyrean, coruscating with admirable splendor, and the most happy and everlasting dwelling-place of the Blessed.

The arguments for the immobility of the earth we shall adduce in the following section; but for the solidity of the heaven containing the Fixed stars, and for the fluidity of the planetary heaven, I have already adduced [them] (sect. 1, ch. 3 & 7); for the fivefold number of the heavens (the aerial included), see what was said (sect. 3, ch. 1); for the Intelligences moving the heaven, (sect. 2, ch. 1). Further, for the order of the Planets, see what I said (bk. 7, sect. 1, ch. 4); and for the ascent and descent of the Planets, (bk. 7, sect. 6, ch. 1). Now for the exclusion of the diverse orbs or circles, and for the single spiral motion, see what we said (this book, sect. 2, ch. 3, schol. 4, & bk. 6, ch. 18). Finally, for the approach of Mars to the lands, see what was said (bk. 7, sect. 2, ch. 3, schol. 4, & sect. 6, ch. 4, scholium 3, 4, & 5, & ch. 10, scholium 1). But if, with the new stars [satellites]—as some would prefer—a distinct heaven is to be given between the Planetary [heaven] and [that] of the Fixed [stars]; and to the Planets having their Companions [moons], their own heaven is to be assigned separately; and the Aqueous be reduced to the Empyrean—there will be 6 heavens, and 7 great bodies of the world, according to the economy handed down (bk. 7, sect. 6, ch. 4, schol. 5).

[Margin: The first form of the new System.]

[II.] These [things] being supposed, as it were, as the general elements of the mundane system: the first form is the Semi-Ptolemaic, which, namely, employs the center of the Earth as the terminus from which it measures the Eccentricities of the orbs—but in such a way that it describes the Epicycles of Venus and Mercury around the Sun, and supposes the Eccentricities of five (or at least four) Planets, nay also Epicycles not always of the same magnitude, according to the hypotheses already explained (bk. 7, sect. 2, ch. 6, & sect. 3, ch. 6). To which form, indeed, the figure of the Egyptian system set forth in ch. 4 could serve—if Mars, at opposition to the Sun, came nearer to the earth than the Sun.

[Margin: The latter form of the System.]

The second form is the Semi-Tychonic—namely that which, long ago, while I was dictating the treatise On the Heaven at Parma (where I professed Philosophy), I devised: namely, that the Sun should be the center of the motions of Mercury, Venus, and Mars; but the Earth [the center] of the Lunar motion and of the Fixed [stars], and also of the motions of Saturn and Jupiter. To which the following reasons impelled me. First, because I saw that Saturn has its own [planets], and Jupiter its own planets, around themselves, but Mars, Venus, and Mercury [have] none; therefore I esteemed it probable that Saturn and Jupiter exercise their [own] monarchy in the heaven, and are not satellites of the Sun; but that Mars is the greatest satellite of the Sun, inasmuch as it embraces the Earth by its circuit; and that Venus and Mercury are the interior and nearer attendants of the Sun. Secondly, because I saw, in the variation of Eccentricity, a greater connection of Mars, Venus, and Mercury with the Sun, than of Saturn and Jupiter. Thirdly, because I judged that Saturn and Jupiter—slower and more ponderous Planets—have a greater affinity with the most slow sphere of the Fixed [stars], and accordingly with the center of the Earth—since the Fixed [stars] too regard the Earth rather than the Sun in their motion. Fourth, because, since Mars (like Venus and Mercury) enters the heaven of the Sun as to [their] designation [mapping], it seemed far more probable that these three have the Sun as the center of their motion, and that distinct regions of the ether are not to be distributed to them, but a single [one]; but that to Jupiter and Saturn distinct realms are to be ascribed, and so the confusion of the heavens is avoided—[heavens] distinct even by designation alone. Which inclusion of Mars, Venus, and Mercury in the single heaven of the Sun, I see pleased Amici (On the Heaven, p. 285), and Oviedo (the single controversy On the Heaven, p. 468). Wherefore, if we should wish to divide the visible heaven into several regions, we could distribute the first to the Fixed [stars], the second to Saturn, the third to Jupiter, the fourth to the Sun together with Mars, Venus, and Mercury, the fifth to the Moon. Fifth, it is very probable that there is found one among the Planets which is the middle between the superior and the inferior, and which in its motions has many [things] in common with Saturn and Jupiter, [and] many also with Venus and Mercury—namely, Mars. All which [things], when more observations shall have been collected and weighed in vol. 3, will be subjected to examination, that it may be established whether this form satisfies the Phenomena. Meanwhile, let no one of the Astronomers take it ill that it is reviewed by us in this place among the other systems. And the figure of this system is [drawn] below, as to the visible heavens; for around it must be understood the Aqueous, or Crystalline, heaven, and around this the Empyrean.

System V — Our System

[Translator’s note — engraved diagram: Riccioli’s own geo-heliocentric system. At the center, the immobile Earth (a dark disc), encircled by the ☽ Moon. About the Earth runs the orbit of the ☉ Sun (a radiant face); tight about the Sun ride ☿ Mercury and ♀ Venus, and on a larger Sun-centered circle ♂ Mars (its orbit “embracing the Earth,” coming nearer than the Sun at opposition). Higher up, circling the Earth, are ♃ Jupiter (girt by its four satellites on little epicycles) and ♄ Saturn (with its two companions / “ansae”). The outermost band is the starry firmament. Thus Mercury, Venus, and Mars are heliocentric, while the Sun, Moon, Jupiter, and Saturn are geocentric — the three Sun-attendants being “satellites,” Jupiter and Saturn “monarchs” with their own moons.]

[Margin: On the interval and thickness of the primary heavens.]

[III.] It must be noted, further, in this our System, that the intervals are not so constructed that the lowest [point] of the concave of Saturn’s heaven touches the highest [point] of the convex of Jupiter’s, or the lowest of Jupiter the highest of Mars, etc.—as happens in the Ptolemaic hypothesis—but [that] some interval, empty of stars, is left between the Fixed [stars] and the highest [point] of Saturn, namely of at least 9824 semidiameters of the Earth; and between the lowest of Saturn and the highest of Jupiter, an interval of 10045 terrestrial semidiameters. But between the lowest of Jupiter and the highest of Mars the interval is 5310 terr. semid.; and between the lowest of Venus and the highest of the Moon, 1850. Moreover, the thickness of the whole heaven of Saturn, the Satellites being computed, is 32454 semidiameters of the earth; of Jupiter, the satellites computed, [it] is 21361; of the Sun, Mars, Venus, and Mercury, as of a single heaven, [it] is 19091 terrestrial semidiameters. Wherefore the thicknesses of the heavens of these three Monarchs with their satellites stand thus—that, as it were, 32 such [units] befit Saturn, 21 Jupiter, and 19 the Sun with [its] three satellites. But for the interval between Saturn (♄) and Jupiter (♃), and between Jupiter (♃) and Mars (♂), etc. […] But about these measures you have more, digested into their tables, at the end of bk. 7.

[End of Section III. The page closes with the page-signature “O o” and the catchword “SECTIO” — Section IV (Sectio Quarta) begins on the next printed page. Section III (“De Systemate Mundi circa Terram Immobilem”) has run from printed p. 271 through p. 289, presenting the world-systems from the most ancient down to Riccioli’s own (the “Ricciolan” semi-Tychonic system). The promised arguments for the Earth’s immobility are reserved for Section IV.]