First Argument, from Comets

[Margin: Seneca’s ambiguity about the diurnal motion of Comets.]

[I.] Seneca once doubted (bk. 7 of the Natural [Questions], ch. 2) whether the Comets are snatched by the diurnal conversion of the heaven, and yet are not dissolved; or rather whether they are not dissipated so quickly for this reason, that not the heaven but the Earth is revolved by the diurnal whirling. Let us repeat thence his [own] words: “It will be profitable to inquire whether the Comets are of that condition of which the higher [bodies] are: for they seem to have certain [things] in common with them—risings and settings; also [their] very appearance, although they are scattered and go forth farther; for they are equally fiery and shining. And so, if all the heavenly bodies are earthy, then for these [comets] too the same lot will be. But if they are nothing else than pure fire, and remain for six months, and the conversion and velocity of the world does not dissolve them—they too can consist of thin matter, nor on that account be shaken apart by the assiduous wheeling-round of the heaven. To that [purpose] also it will pertain to have examined this, that we may know whether the world goes round, the earth standing still, or whether, the world standing still, the earth turns. For there have been those who said that it is we whom the nature of things carries [along], unknowing; and that the risings and settings come about not by the motion of the heaven, but [that] we ourselves rise and set. The matter is worthy of contemplation, that we may know in what state of things we are: whether we have been allotted the laziest, or the swiftest seat; whether God moves all things around us, or [moves] us.” Thus that noble Philosopher.

[Margin: Copernicus’s opinion on the diurnal motion of Comets.]

But it was once held by Aristotle and the rest of the Peripatetics that the diurnal motion of Comets is attributed to the conversion of the fire, or of the supreme region of the air, snatched toward the West by the heaven. On the contrary, Copernicus (bk. 1, ch. 8) ascribes the apparent motion of those [comets]—by which they seem after 24 hours to be revolved back to nearly the same place—to the Earth; by whose whirling, however, he denies that that air is snatched in which the Comets are generated: for let us repeat his words too: “In turn, with no unlike wonder, they say that the supreme region of the air follows the celestial motion”—namely the Peripatetics—“which those sudden heavenly bodies (Comets, I say, and [those] called by the Greeks Pogoniae [bearded stars]) indicate: to whose generation they assign this very place, [the comets] which, like the other heavenly bodies too, rise and set.” Thus far from the opinion of others; presently he subjoins from his own: “We can say that, on account of the great distance from the earth, that part of the air is destitute of [exempt from] that terrestrial motion. Accordingly the air will appear tranquil which is nearest the earth, and the [things] suspended in it; unless they be agitated to and fro (as happens) by wind or by some other impetus.”

[Margin: Gassendi’s opinion on the diurnal motion of Comets, before he had hearkened to the sacred decrees.]

[II.] Hence, therefore, Gassendi hammered out an argument for the diurnal whirling of the Earth (Epistle 2 On motion impressed by a translated mover), reckoning it far more probable that Comets have no other motion than their own proper and wandering one; but [that] the diurnal [motion] which appears in them is from the conversion of the earth. For he discourses thus there (p. 110): “I note meanwhile, concerning the Comets, that—since, besides their proper trajectories (which are now toward the north, now toward the south, now elsewhere), they appear also to be borne by the diurnal conversion from east to west—what could be thought more likely than that they are moved by a single motion, that is, by their proper trajectory; but that that circumduction toward the west is merely apparent, [arising] from the diurnal conversion of the Earth toward the east? For this conversion is of such a kind that whatever is, or is born, or passes, upward or beyond the Earth and through the mundane spaces, it [the conversion] feigns to it (as it also appears) a conversion toward the West.” The whole argument of Gassendi, therefore, consists in a likelihood—greater, as he himself judges—and so it can be gathered into form.

[Margin: The argument reduced into form.]

[III.] “If the Comets have in reality no other motion than their proper trajectory, the diurnal motion which besides appears in them is to be attributed to the Earth. But it is more likely that the Comets have in reality no other motion than their proper trajectory: therefore the diurnal motion which besides appears in them is to be attributed to the Earth.” The Major is proved, because that diurnal motion can no longer be attributed to the conversion of the fire or of the air, since the heavens of the Planets are not solid, and accordingly the sphere of fire, much less of air, cannot be snatched round in an orbit by the concave of the Moon. The Minor is proved, because there is no small difficulty in assigning the cause of so wandering a trajectory; therefore we ought not to increase it by adding another real motion, which would render the agitation of the Comets more entangled, and of more uncertain cause.

[Margin: Response to the First Argument.]

It is answered, however, the Major being granted, by denying the Minor, and the validity of its proof. For that is not more likely which is against the physical evidence acquired through the senses—of which kind is the diurnal motion of the Comets, equally as [that] of the other heavenly bodies; and the cause which moves the Comets by [their] trajectory-motion can at the same time move [them] by the diurnal motion—especially since most probably there is some Intelligence [moving them], as I taught (bk. 8, sect. 1, ch. 6, num. 12). As, therefore, we do not take away the diurnal motion from the Planets—although they have a proper [motion] in longitude, latitude, and altitude so various and anomalous—because the Intelligences lead them round toward the West along a spiral line: so neither ought we to take it away from the Comets; for all [things], as to this, appear in the Comets similarly as in the other stars, as we saw just before rightly asserted by Seneca; nor do I see why a greater argument for the motion of the Earth ought to be taken from the Comets than from the Planets. For the greater difficulty in determining the moving cause of the Comets arises not from the diurnal motion toward the West, but from the admirable variety of their proper trajectory—whatever cause be assigned to it, that [cause]

[…continues on p. 327 (PDF 362) with the catchword “illa”: “…that [cause] itself will be able much more easily to move them by the common, or diurnal, motion”—then the Second Argument, from the perpetual westward Tropical breeze.]

(printed p. 327 — within Chapter VII. Completes the reply to the first argument (from comets), then proposes the Second Argument, from the perpetual westward breeze within the Tropics: a long survey of José de Acosta on the Torrid Zone and the causes of the trade-winds, with Robert Dudley’s confirmation of the fixed tropical easterlies, followed by Galileo’s and Sagredo’s use of the trade-wind as a confirmation of the Earth’s diurnal motion.)

[Header: ON THE SYSTEM OF THE MOVED EARTH — 327]

—that [cause] itself will be able much more easily to move them [the comets] also by the common, or diurnal, motion.

Second Argument, from the Breeze [blowing] within the Tropics by perpetual gusts toward the West

[Margin: The Torrid Zone — by what causes habitable?]

[IV.] It has been handed down by the ship-masters, as the Dutch and Ramusio relate in the history of the navigations, but far more eloquently our Joseph [José de] Acosta (bk. 2 On the nature of the new world, ch. 10, and from 13 to 16), that the Torrid Zone is very habitable—not only on account of the vast abundance of sea-waters, which do not so reflect the rays of the Sun as does the Earth from its fields, valleys, [and] hills, nor only on account of the shortness of the summer days and winter nights, but also (God so sweetly providing) on account of the frequency of vapors and summer showers, and especially on account of the singular benefit of a most gentle breeze, whose coolness has so great a sweetness that not incongruously some—with Juan Luis Vives (on bk. 13 of The City of God, ch. 21)—have placed the terrestrial Paradise, or the land of Eden, under the Equinoctial. But I shall here note the choicer [points], that the force of the proposed argument and its solution may shine forth more. And so (ch. 13) Father Acosta narrates that, in those regions within the Torrid [Zone] which are blown through by a sea-wind rather than a land-[wind], there is in a manner a perpetual spring, especially in the Peruvian sea: “In which we remember [that] we were cold when first we sailed [it], and that at the time when the Sun lay most directly [overhead]—that is, near the Equinoctial, in the month of March,” says the same Author; who nevertheless confesses that in the plains of greater Ethiopia, of Brazil, of Paititi, and of Paraguay the winds are so sultry that you would think [them] kindled furnaces; and that certain seas too within the Tropics are heavy with heat—namely the Ormuz [sea], the Mozambique, the Brazilian, and the Panama [sea]; but that in the same Climate many other seas are of a most temperate breeze.

[Margin: The variety of the winds within the Tropics, and [their] admirable effects.]

Therefore, from the abundance and variety of these winds, he renders the reason of certain admirable effects in that tract of the world: why the summer and midday Sun, though [it shine], is better warded off there by the lightest shade—say a mat or straw—than in Spain by brick roofs; nor are the summer nights there hot; and in the province of Collao there is cold even under a thin shade, although for those dwelling in the nearby Sun there is intolerable heat; but the Peruvian region, although full of sand and gravel, is nevertheless wonderfully temperate; again, the city of La Plata is most temperate and most sweet, and most fruitful; but on the contrary Potosí, although it too is mountainous, and in the same climate, distant by a very short interval, is nevertheless squalid, very cold, and sterile. “Therefore all these varieties the winds chiefly make by nature,” says Father Joseph: “for where the supply of the gentler breeze is withdrawn, the Sun’s heat is so great that it burns amid the snows; where it is restored, all the heat easily abates; but where this cold wind is familiar and as it were a [household] tenant, it in no way allows the earthy exhalations, as from burnt matter, to be gathered—which one cause in Europe makes the summer nights almost more oppressive than the days themselves, because the earth, scorched by the Sun’s force, gives back blasts thick and smoky, and as if proceeding from a furnace.” He adds that in Europe the most pleasant time through the summer is the morning, and the most oppressive the afternoon; but on the contrary in the Torrid Zone, especially in the Windward Islands [Barlovento], from early morning until about the tenth hour the chief heat is felt, sometimes to [the point of] sweat; then about midday and afterward, the sea breathing [a breeze], the rest of the day is passed pleasantly; and toward midday the Euroaquilo [NNE wind], there called the Brisa, cools the sailors and inhabitants.

[Margin: José de Acosta’s encomium [of his homeland] on the temperateness of the Torrid Zone.]

[V.] Acosta proceeds (ch. 14), concerning the temperateness of the air repeatedly found within the Torrid [Zone], and concludes: “To me, gazing upon this benignity—as it were of a perpetual spring—since neither does winter press with cold, nor summer scorch with heats (so much so that by a small turf [shelter] all injuries are sufficiently warded off, and there is scarcely need of a change of garments)—it has surely often come into my mind that, if men were freed from the bonds of cupidity and of depraved opinions, they would easily have lived here a pleasant and blessed life. For what the Poets [feign or tell] of the Elysian [fields], what of Tempe, what Plato feigns or narrates of his Atlantis—that, surely, they would have found in these regions, if they had resolved to rule by an honest liberty rather than to be slaves to money.” Then (ch. 15) he runs out into the causes of the winds, which, although he touches [them] from the teachings of Peripatetic philosophy, yet the chief [cause] he refers to God; who, as [in] Psalm 134 [135], “brings forth the winds out of his treasuries”—so that most truly the Truth [Christ] said (John 3): “Thou hearest its voice”—that is, of the wind and the breath [spirit]—“and knowest not whence it comes, or whither it goes.” For it is difficult to explain why, along the whole maritime coast of Peru, through very long spaces, one wind only blows; and [why] the same South wind, which with them is most pleasant on this side of the Equator, presently, the Equator being crossed, becomes heavy and murky; why the North wind there gathers the clouds and presses them out into rains, and is held [to be] drowsy-making; why the Windward Islands are cooled by perpetual North winds, bringing copious rains, and there scarcely an approach lies open to the South or Southwest wind; why the Brazilian region before the promontory of St. Augustine is perpetually infested by land winds, while the Peruvian, in the same climate, is always blown through by sea winds, [and] most pleasant. This he notes at the end of the chapter—what can be the cause of these varieties: namely, that the Torrid Zone is either full of very high mountains, or for the greatest part interfused or surrounded by the Ocean, whence the winds [are] coolish and more subtle.

[VI.] Finally (ch. 16), from the narration of nautical observation, he affirms that within the Tropics, here and there—especially on the high Ocean—the winds blowing from the East and North perpetually prevail, but [those] from the West and South are rare and almost none; from which he rightly, and no less elegantly, concludes [that] this is the cause of so different a navigation:

[Margin: The voyages to the Indies and from the Indies.]

“For not,” says Acosta, “as the way from Thebes to Athens, and from Athens to Thebes, is the same, [is it] so from Spain to the Indies, and from the Indies to Spain. But the arrival [outbound voyage] is indeed downhill—and, that I may play poetically, [it is] an easy descent to the Indies; but to recall [one’s] step, and to escape back to the old world, is no easy labor.” The cause, he says, is that the fleets from Spain to the West Indies use perpetual and nearly always-favorable Euro-Aquilo [NNE] winds; but returning thence they have the same [winds] adverse, which, to flee, they sail out to the degrees of a higher heaven [latitude] beyond the Tropics, that by returning they may obtain favorable South or South-West winds—but by a longer course than before. For the customary route to the West Indies and New Spain from the Fortunate Islands [Canaries] is nearly straight; but the return is from New Carthage [Cartagena], through Havana the port of Cuba, and thence to the sight of Florida, through the misfortunes [hazards] of Bermuda, [to] Terceira, and by [the way past] the holy promontory of St. Vincent. So from New Spain and Peru, through the Pacific sea, to the Solomon Islands the journey is easy, but the return difficult—unless beyond the Equinoctial and the Tropic of Cancer, toward the shores of New Spain, the West wind be sought, or, the Tropic of Capricorn being passed, you bend toward the region of Chile. From Mexico likewise to China and the Philippine Islands the navigation is short and expeditious, but the re-navigation [return] tedious and arduous.

[Margin: Robert Dudley’s assertion about the winds within the Tropics.]

He confesses, however, that this general law has its exceptions somewhere; for in the maritime region of the Southern Ocean, although situated within the Tropics, the South wind predominates nearly the whole year. Nor does Robert Dudley, Duke of Northumberland, [hold] otherwise, in his Maritime Secrets [Arcana del Mare], lately published in Italian; for he (bk. 2, ch. 20) [holds] that the winds within the Tropics are fixed—that is, perpetual—from the East, both from Africa toward the Americas, and from the Americas toward the Moluccas and Philippines, as [also] from here toward Africa; and that they are wont to blow with a uniform tenor, and are healthful: so much so that, in the return from the East Indies toward the island of St. Helena, the return is nearly twice shorter than the navigation thence to those Indies was. [And] finally, that it is a sure rule, that those who navigate according to [in the direction of] the diurnal motion mostly enjoy favorable, healthful, and serene winds, etc. Which [things] have perhaps been narrated more at length [than needed], but [so] that, from the very narration of so religious and experienced a man as we know Acosta to have been, the fiction of Galileo and Gassendi may at once fall.

[Margin: Galileo’s opinion on the motion of the air apparent toward the West.]

[VII.] For indeed Galileo (Dialogue 4 On the System of the World, Latin p. 327), when he saw it to follow that within the Tropics and on the open plains of the Ocean—where there is a smaller supply of thicker vapors—the air would not so obey the snatching of the terrestrial whirling, and therefore, by resisting it [the earth] revolved toward the East, would make a perpetual wind toward the West, or the appearance of a wind, which would be more perceptible where the whirling of the terrestrial globe is swifter, namely near the Equator: [Galileo] does not hesitate, from the perpetual winds which navigators experience within the Tropics from the Mexican port through the Pacific to the East Indies, etc., to confirm the diurnal motion of the Earth; to which experiment Sagredo there subscribes, affirming that in the Medi-

[…continues on p. 328 (PDF 363) with the catchword “diter-”: “…in the Medi[terranean]“—Sagredo’s testimony, and Riccioli’s reply to the trade-wind argument.]

(printed p. 328 — within Chapter VII. Completes the second (trade-wind) argument with Gassendi’s corroboration, casts it in form, and gives two Responses: the wind is no convertible sign of the Earth’s motion, and the tropical wind is neither universal nor directly easterly. The Third Argument, from the similitude of the chemical earth and the magnetic Terrella, then begins — Lansberge’s “chemical earth” is dismissed, and Gilbert’s and Cabeo’s magnetic experiments on the Terrella are introduced.)

[Header: BOOK IX. SECTION IV. — 328]

—in the Mediterranean too—unless accidental and transverse winds stand in the way—the re-navigation from Syria into Italy is quicker than from here into Syria, and indeed nearly fourfold; which, however, Salviati not undeservedly refers back also to the waters running toward the Strait of Hercules [Gibraltar]—granted that in the Sicilian Strait the water runs along one shore to the East, and along the other to the West.

[Margin: Gassendi’s corroboration for the same motion.]

But Gassendi too (Epistle 2 On impressed motion, p. 92), having asserted that the air near the earth is snatched by the diurnal rolling of the Earth, nevertheless added that it [the air], on account of its fluidity, is not so compliant with the earth but that it is somewhat retarded toward the western parts: “They say this is plain,” he says in the same place, “—not so much in the valleys, within which the air is on this side and that confined, and is not free, as in the plains and open fields, where the little breezes are observed, whenever calm prevails, to be turned toward the West; but it is plain most of all on the sea, and especially under the Equator itself, where the sails of the ships are with one tenor and uniformly filled from the East; and therefore the sailors experience that they measure out the same journey both far more easily, and in a shorter time, toward the West than toward the East.” Hence, therefore, Galileo and Gassendi confirm the whirling of the Earth, because, that being asserted, the cause of that perpetual and even wind within the Tropics is readier: from which [premises] one may thus argue.

[Margin: The Second Argument in Form.]

[VIII.] “If a perpetual and uniform Wind blew toward the West within the Tropics, it would be a very probable indication of the diurnal revolution by which the Earth would be turned toward the East. But it is established by experiment that a Wind of this kind blows within the Tropics: therefore it is an indication of the diurnal revolution by which the Earth is turned toward the East.” The Minor now seems proved from the historical credit of the ship-masters; the Major too is sufficiently confirmed by Galileo and Gassendi, for no other more likely cause can be brought [to say] why such a wind is felt perpetually within the Tropics rather [than elsewhere], and toward the West rather [than another direction], except that the air, in that open tract least entangled with watery and earthy vapors, neither moves of itself to the motion of the earth and water (since it is not of their nature), nor is it at all snatched by their whirling toward the East—because, on account of its thinness and flux, it is unfit to conceive so great an impetus, and therefore, by not following—or deserting—that motion, it behaves just as if it were moved toward the West.

[Margin: First Response.]

It is answered, first, by denying the Major: for it would not be a convertible sign of such a motion—granted that, such a motion of the Earth being posited, it could very probably be brought forward as at least a partial cause of such a wind, provided that it were perceptible universally within the Tropics, and in the neighboring Climates too, where the fields and seas are more widely spread out. For it is no more an indication of the Earth going toward the East than of the Sun, by [its] diurnal motion, together with the whole choir of stars, [going] toward the West, and leading round with it the vapors and exhalations [it has] raised—or successively raising others and others toward that region into which it is borne; or also [an indication] of the maritime waters, which it is agreed run toward the West, as of a cause concurring [in] the generation and motion of that breeze: since it is plain that all the waters of rivers, torrents, [and] channels draw with them some breeze and little wind to where they run down. And thus the ship-masters, as we saw from Dudley, refer the benefit of that wind, received, to the diurnal motion of the Sun. And indeed it is confessed among the Meteorologists that the winds are mostly and more strongly excited at the rising, or soon-to-rise, Sun, and these more often from the Eastern region than from the Western; and that on the broad plains of the Ocean they are on that account more even, because there is not there the inequality of mountains, valleys, woods, [and] cities, which is wont to furnish the matter of unequal winds—as Descartes briefly but clearly teaches (in his Meteors, ch. 4, marginal numbers 3, 4, 12, and 13).

[Margin: Second Response.]

I answer, secondly, by denying the Minor taken universally, or with those conditions which are required, that such a wind be the effect and indication of the terrestrial whirling: for neither in all—however widely-open—seas or fields within the Torrid [Zone] does a wind of this kind blow; nor, where it blows, [does it blow] directly from the eastern region, but mostly from a lateral region situated between the East-wind [Solanus] and the North-wind [Aquilo], or even between the East-wind and the South-wind; and the Euroaquilones [NNE winds] are more frequent; nor do they keep the same tenor the whole day, but are sensibly varied at the rising and the afternoon Sun, as we have already seen from the history of Father Acosta.

Third Argument, from the similitude of the Chemical Earth and the Magnetic Terrella. Where, in passing, [are treated] certain notable magnetic experiments made by means of a Terrella

[Margin: The Chemical Earth.]

[IX.] Jacob Lansberge, in the Apology for Philip Lansberge on the motion of the Earth (ch. 5), brings this as the eighth argument for him [Philip], and says: “The Physical Earth of the Chemists (which is not a magnet, as Fromondus thought in his Vesta) is moved from West to East; therefore the whole Earth too, of which it [the chemical earth] is the image.” George Polacco answers (in his Anticopernicus, assertion 176) that this Hermetic Earth is to be left to the Paracelsians and the Fludd-ists, and that from its motion the motion of the whole Earth is not sufficiently argued. To me, however, it has not yet been permitted to see this experiment. But, granting it, we deny the consequence—[for] just as from the rectilinear motion of a clay ball, or of a clod of earth let down [downward], it is not permitted to infer the downward motion of the whole Earth: wherefore, this being dismissed, let us come to the argument drawn from the Magnetic Terrella.

[Margin: What the Terrella is.]

[X.] The Terrella—that is, the Magnetic [little-globe]—is nothing else than a little sphere fashioned on a lathe out of Magnet-stone [lodestone], or is a globose Magnet, [which is] thus wont to be formed by art, because this figure of all is the most apt for entering upon various magnetic experiments; as William Gilbert teaches (bk. 1 On the Magnet, ch. 3, and bk. 6, ch. 1), who hands down experiments of this kind (bk. 1, ch. 4; bk. 2, ch. 27; bk. 3, chh. 4, 7, 8, 9, 17; bk. 4, ch. 2; bk. 6, ch. 4); and Father Nicolò Cabeo (Magnetic Philosophy, bk. 1, chh. 5, 17, 18, 22, 24; and bk. 2, chh. 10, 11, 15; bk. 3, chh. 4, 12, 16, 17, 19, 21, 34, 37; and bk. 4, chh. 9, 11, 17, 36, 37, 39, 40, 41, 45). For in all these places experiments made by means of the Terrella are explained; from which we shall select three or four, that the reasoning of this argument may be made more manifest—the following diagram being premised, in which let there be the Meridian AZBN, and in it the South Pole of the World A, and the North [Pole] B; and the Zenith Z, and the Nadir N. Let there then be made, from

[Translator’s note — engraved Terrella (magnetic-globe) diagram: an outer circle is the Meridian A·Z·B·N — A the world’s South Pole (left), B the North Pole (right), Z the Zenith (top), N the Nadir (bottom). Within it sits the lodestone-globe Terrella, the sphere C (top)–b (right)–D (bottom)–a (left), with center P; its axis a–b is horizontal and C–D vertical (both dotted), crossing at P. Small magnetic needles (drawn as little crosses with arrowheads) are set at points around the Terrella to show their orientation in its field — K, M, I clustered at the left pole a; S at the right pole b; H and one at the foot near D; G at the lower right; E, F above. The Terrella is suspended by a thread along Z–C.]

—a Magnet as good as possible (say an Arabian one), a sphere as round as possible, CbDa, which henceforth shall be named the Terrella.

[Margin: The investigation of the poles of the Terrella.]

But since every Magnet has two faces, one austral [southern], the other boreal [northern], one must first investigate in this Terrella each of these faces, or its poles. But this is not done by suspending it from a thread ZC and noting which part, by its conversion, it turns to the South, and which to the North—as if the points a and b were to be held for the Poles of the Terrella: for, as Cabeo notes (bk. 5, ch. 5), thence it is only concluded that the austral pole of the Terrella is in the hemisphere CaD, and the boreal in CbD; and it can happen that the former be in F, or in G, but the latter in H, or in E—because the point C, from which the Terrella was suspended, is not distant a whole quadrant from its Poles, but less than a quadrant, say by 45 degrees.

[Margin: First Experiment.]

A surer way, therefore, is if little bits of finer iron wire, and scarcely longer than a barley-grain,

[…continues on p. 329 (PDF 364) with the catchword “grano”: ”…[scarcely longer than a barley-]grain, you bring [them] near to various points of the Terrella”—the rest of the magnetic experiments and Riccioli’s reply to the Terrella-argument.]

(printed p. 329 — within Chapter VII, the third argument (magnetic Terrella). Continues the magnetic experiments, gives Gilbert’s conclusion that the Earth as a great magnet has a natural power of circular motion, casts the argument in form, and answers it: the Earth is not a perfect magnet, the Terrella has no eastward whirling at all, and by retortion the Terrella’s rest in its natural position rather proves the Earth’s immobility — confirmed by the magnetic evidence of Cabeo and Zucchi.)

[Header: ON THE SYSTEM OF THE MOVED EARTH — 329]

—grain, you bring [them] near to various points of the Terrella: for where they shall have adhered most directly and to the perpendicular of the Terrella, know that there are its poles; but where they shall have touched the Terrella with equal balance and inclination on both sides, those points will be distant from the poles by a whole quadrant of a circle.

[Margin: Third Experiment.]

Another way, which Cabeo suggests in the same chapter 5, is of this kind. Apply a versorium—that is, a magnetic needle—on a pivot turnable over the Terrella, to different parts of the Terrella’s surface, until at some [point] it obtains the most exact equilibrium, as at C—that is, [so that] it inclines to the Terrella no more by its point than by its little cross [tail], but makes equal angles on both sides with its periphery. By the same artifice inquire several other points, say R, P, D; for a circumference being drawn through them, you will have the Equator of the Terrella, which namely is equally distant from either Pole; wherefore, one leg of a compass being fixed in any one point of the circle CRPD, you will be able, with the other curved leg of the compass, to describe some meridian of the Terrella, say aCbD; for in it the points a and b, [being] at a quadrant’s distance from the designated Equator, will be the Poles of the Terrella. But then, if from C, a point of the Equator, you suspend the Terrella by a thread least twisted, it will so turn itself to the poles of the World that, with its boreal pole b, it will look toward the Boreal pole B of the World; but with its austral pole a, it will face the Austral Pole A of the World; and the axis of the magnetic direction will be ba—the declination from the Meridian, however, being kept (as to the Meridian’s position) which the place in which you dwell requires, and which the magnetic needles otherwise keep. And so, if the experiment be made at Bologna, the axis ba of the Terrella will decline toward the East 3½ degrees; but elsewhere otherwise, according to what was said (bk. 2, ch. 18). But, versoria or needles being applied to other points, say to E, F, G, H, you will see them incline more, by point or by little cross, toward the Terrella, as the magnetic face and poles of the Terrella require; and at I and K the points will converge toward the pole a, but the little crosses, turning away from each other, will diverge.

[Margin: Fourth Experiment.]

But what most makes for our purpose: if you enclose the Terrella in a wooden box or in a cork net[-float], and place the box upon the water of an ample vessel, so that it can float on the surface and freely turn itself; and you close the room or chamber so that no wind can enter, and the iron tools be far off: you will see, not so long after, the Terrella at last settle itself, by its [own] conversion, in a position congruous to itself, so that with its pole b it looks toward the Boreal pole B, and with its pole a toward the Austral pole A, and there rest—the axis ab being elevated toward the pole visible to you, as much as nearly the altitude of your pole requires; but if you dwelt under the Equator, that axis would be equidistant from the horizontal plane AB.

[Margin: The argument in form.]

Hence, therefore, Gilbert (bk. 6 On the Magnet, ch. 4) concludes that, just as the Terrella has a natural faculty for circular motion about its center, by which in the horizontal plane it turns with its poles to the poles of the World: so the whole earth—which in the same book he contends to be a great Magnet—has a natural power for circular motion about its center, so much so that if it were dragged from its position, and its boreal pole twisted elsewhere by some force, it would itself run back to its pristine position, by a natural whirling. He adds (ch. 6) that all terrestrial things, although separated from the earth, are nevertheless drawn by it into a gyre [rotation] through the magnetic effluvia—just as he thinks that the parts of each primary globe (say the Sun, Moon, and the other Planets) would have to be drawn [back] by them, if they were separated from them. These [things] being posited, he seems to argue in this form: “The whole Earth is disposed, as to the motion of whirling about its center, just as the Terrella [is disposed] toward the motion of whirling about its center. But the Terrella is moved circularly about its center; therefore the Earth too about its center; therefore also by a diurnal motion.”

[Margin: First Response.]

Someone might answer by denying the Major, on the ground that the Earth is not (as Gilbert contends, bk. 6 and elsewhere) a great magnet, or of the same lowest species as the magnet; for that our Cabeo excellently refuted (bk. 1 of the Magnetic Philosophy, ch. 19) with many arguments indeed, but especially by this: that if the Earth were a perfect magnet, it would snatch iron to itself from a far greater distance, in proportion to its mass, than the tiny magnetic Terrella snatches a needle. But let us grant the Major meanwhile. It is answered, however, first, the Major being granted, by distinguishing the Minor and the first Consequent; and by conceding the Minor and the Consequence if the Terrella and the Earth be moved from their position, [but] denying [it] if they remain in their natural position, which the axis requires; but [also] by denying the second Consequence: for more is inferred than can be inferred from the premised propositions; for neither does the Terrella have any whirling upon its poles toward the East, even if it be suspended upon its poles in the Meridian—whatever Petrus Peregrinus may have feigned, whom Gilbert himself (bk. 6, ch. 4), not to say Cabeo (bk. 3, ch. 4), reject, as we shall presently see. Nor could it be proved to Father Athanasius Kircher, nor to Father Nicolò Zucchi, most learned writers on the Magnet—since rather they confirm the immobility of the Earth from the magnetism of the Earth.

[Margin: Second Response.]

It is answered, therefore, secondly, by retorting the argument: “The whole Earth is disposed, as to motion and rest, just as the Terrella; but the Terrella, so long as it is in its natural position, is not moved; and when it is in an unnatural position, it is not moved toward the East about its axis, but by another, axis-turning, motion toward the poles of the world: therefore the whole Earth too, so long as it is in its natural position, is not moved; and if it were in an unnatural position, it would not be moved toward the East, but by another motion, etc.” Now it is established, from the tradition of all the centuries in which observations of the polar altitudes have been had, that the Earth has been in its natural position, and has always, with the axis of its Equator, looked directly toward the poles of the world: therefore the Earth has always rested immobile, as it now rests.

[Margin: The arguments of Nicolò Cabeo and Zucchi for the magnetic power of the Earth.]

The Major is now assumed by Gilbert, and is urged by certain experiments (bk. 1, last chapter)—namely, that the Earth has a magnetic power, by force of which it directs itself toward the poles of the World, or keeps that direction once acquired from the beginning of the world; and it is further proved by Cabeo (bk. 1 of the Magnetic Philosophy, chh. 17 and 18) and by Father Nicolò Zucchi (in the new Philosophy of Machines, part 5, sect. 3): because it has been observed that the veins of the earth and of stones, which after floods are seen in the sides of mountains, run parallel to the axis of the world—which Kepler testifies was observed in Germany too—and to the sense fall upon the horizon at as great an angle as is the altitude of the pole; then, the Earth communicates magnetic power to iron tools, as Gilbert tries to show (bk. 2, ch. 12), but Cabeo shows [it] by firmer experiments (bk. 1, ch. 17). But no one gives what he does not have; therefore the Earth has a magnetic power, which it communicates to iron tools—so much so that the little bars of iron lattices [window-grilles], extracted from very old windows, draw, by their upper part, the Northern point of the versorium, and by their lower part the Southern little-cross [tail], in our regions, where the Northern pole is elevated; and they draw [it] from a distance of four ells and more, which no magnet, however strong, can do. Again, if you bring a dagger or sword, grasped by the hilt, perpendicularly to the horizon, near to a versorium or magnetic needle, the part which overhangs the needle draws the Southern part of the needle; and if you bring the same sword to it from below, beneath the needle, by a perpendicular ascent, the tip of the sword draws the Northern part of the needle. Then (ch. 18) he teaches that this magnetic power has been given to the whole terrestrial globe, so that it conserves itself in its position toward the poles of the world, nor can it, by the force of winds or by a change of the center of gravity, be moved about its center. From which also the immobility of the Earth is confirmed.

[Margin: Petrus Peregrinus’s fiction about a Terrella’s diurnal whirling.]

[XI.] But since Petrus Peregrinus, as Gilbert relates (bk. 6, ch. 4), constantly affirms that a Terrella suspended upon its poles in the Meridian is moved circularly by a complete revolution of 24 hours, let us hear what those most experienced in magnetic matters judge of this: and first indeed Gilbert, in the same place, subjoins: “Which, however, it has not yet befallen us to see; about which motion we also doubt, on account of the weight of the stone itself; and also because the whole earth, as it is moved by itself, so also is helped along by the other stars—which does not happen proportionally in any part [of it], as in the Terrella. The primary earth is moved by its own form, and by a natural desire, toward the conservation, perfection, and adornment of its parts.”

[Margin: Cabeo’s doctrine on the motion of the Terrella and Magnet.]

But Cabeo (bk. 3, ch. 4) teaches that the magnet, and accordingly the Terrella, has no power of directing itself toward other regions than the polar [ones], nor has any eastern or western face—either a posteriori or a priori. A posteriori indeed, because if you place a magnetic globe most exquisitely round upon its poles (as found above), so that it can most easily be turned, and set its axis parallel to the axis of the earth; or insert it in two circles in nearly that manner in which the nautical compass [box] is wont to be enclosed in brazen circles, so that at any motion of the ship the compass is equidistant from its plane of the horizon; and [if] you place it, thus inserted, magnetically—that is, by direct-

[…continues on p. 330 (PDF 365) with the catchword “do”: “…by direct[ing]“—the rest of Cabeo’s refutation of a self-whirling Terrella.]

(printed p. 330 — closes Chapter VII and opens Chapter VIII. Finishes Cabeo’s proof that the magnet looks to the Earth’s poles, with the magnetic-dip experiments, and adds Kircher’s and Zucchi’s judgments that no magnetic experiment proves the diurnal rotation; Galileo’s tides argument is deferred to a separate chapter. Chapter VIII then opens, setting out the order of examination in four heads, and begins the First Argument, from the greater nobility of the Sun than of the Earth (the Pythagorean central fire).)

[Header: BOOK IX. SECTION IV. — 330]

—[by direct]ing its axis to the poles of the Earth, and parallel to the axis of the Earth, it will never be moved toward another region of the heaven, except in so far as the magnetic declination in that place requires—which is a sign that the Terrella does not look to, nor love, anything but the polar points. But a priori [it is shown] because the Magnet, properly speaking, does not look to the heaven or the points of the heaven; nor, as Marsilio Ficino thought, to the Lesser Bear; nor to other stars, as Paracelsus [held]; nor to the rising of the star in the tail of the Greater Bear, as Gauricus and Cardano [held]; nor to the Pole of the Zodiac, as Bessard the Frenchman [held]; nor to a point near the pole of the world, as the Conimbricenses and Martín Cortés [held]; but [it looks] to the poles of the Earth—as Robert Norman, a most experienced sailor and ingenious craftsman, first observed; which Cabeo too (bk. 1, ch. 15), Zucchi (in the place cited above), and Athanasius Kircher (bk. 1 of his Magnet) confirm by experiments.

For if you suspend a most slender strip of steel, very straight, eight or ten fingers in length, and perforated in the middle, by an untwisted silken thread, and you excite it magnetically—that is, [if] with one face of the magnet you touch one head [end] of the strip, and with the other [face] the other [end]—you will see that the part which is turned toward the Northern hemisphere (if you dwell in some Northern Climate) is not raised upward, so as to look to the Boreal pole, or [to raise] any part

[Margin: The Magnet does not look to Heaven, but to the poles of the Earth.]

near to this pole; but [you will see it] depressed downward toward the earth, and the more so the higher the pole is in that climate; and the other head raised, so that it falls crosswise upon the axis of the world. And lest you think this comes from a less-than-exact balance, destroy the magnetic power by a contrary touch—that is, that head of the strip which you had touched with the austral [southern] face, touch [now] with the boreal face, etc.—and you will see that head, which before was depressed, raised, and the other, which was raised, depressed. By another experiment (from bk. 5 of Gilbert, ch. 9, and Cabeo bk. 3, ch. 4) this is confirmed: namely, if you set a straight iron wire, passed equally through a little cork sphere on both sides, upon still water—and [water] safe from every breeze, so that it descends beneath the surface of the water, yet not to the bottom, and can turn itself freely; but before you let the wire into the water, its heads must be rubbed with a magnet: these things done, you will discern the wire declining toward the earth, below the plane of the horizon, by its boreal head, and indeed by nearly as much as is the altitude of the Pole in that place. Again, magnetic needles brought near to a Terrella direct themselves to the poles of the Terrella; therefore they do not regard the poles of the world or the stars. Lastly, behold the instrument which—invented by Gilbert (bk. 5)—Cabeo perfected (bk. 1, ch. 20), and Kircher reported (bk. 1 of the Magnet): for by it is taught a way of so suspending a very long magnetic needle in the most exact equilibrium that, inside a vessel covered with a glass hemisphere, one may observe its motion, and by how many degrees—marked on the semicircle of the little basin or lower hemisphere—it descends below the horizon with its boreal point: granted that the measure of these inclinations, which Gilbert reckoned, does not answer to the observations entered upon by the experienced beyond the Equator, as Kircher testifies (in his Magnet, bk. 1, part 2) and Zucchi (part 5 of the Philosophy of Machines, sect. 8). Since these things are so, and it is sufficiently clear hence that magnetic bodies do not look to nor love the poles of the heaven of themselves and immediately, but rather the poles of the Earth—or [rather] the Earth itself so looks to the poles of the world that, since it is spherical and homogeneous, it has no part of itself which is absolutely eastern or western; since the same part—say the Roman land, which to the Mexicans is eastern, yet to the Goans is western (which cannot be said of the parts situated under the same Meridian, for some are absolutely boreal and on this side of the Equator)—it follows, says Cabeo (bk. 3, ch. 4), that the whole earth has no power of directing itself or moving toward other points of the heaven than toward the poles of the world.

[Margin: Athanasius Kircher’s opinion on the Earth’s motion impeded by Magnetism.]

[XII.] Moreover, Athanasius Kircher too (bk. 1 of his Magnet, part 2, from p. 53) teaches that circular motion is repugnant to the Earth more than rectilinear [motion is]—since gravity alone impedes the rectilinear motion upward or downward, but by magnetism [the Earth] is directed along the axis of the world, so much so that even if there were given a mountain as high as the diameter of the Earth, it could nevertheless not, by the wind’s impelling, be moved from its position; and (bk. 2, part 5) [he says] that there is an intolerable itch of building up the Copernican motion, by force of which occasions for persuading it are begged from everywhere out of uncertain and slippery experiments.

[Margin: Zucchi’s opinion on the magnetism of the Earth.]

But Father Nicolò Zucchi (in the new Philosophy of Machines, part 5, sect. 10) indeed disapproves the motion of the Earth, but nevertheless asserts that the magnetic power is not in the globe of the Earth so as to impede the diurnal whirling about its axis, because the direction of the axis to the poles of the world can stand, and yet that motion be carried through. Then he makes mention of a certain new experiment, undertaken by some observer of nature [I know not whom], by which it is proved that a Magnet turns and situates itself, according to its determined plane, in the Meridian of whatever region: if it be set up through its axis in a vertical line, so that one pole of the magnet—which is wont to be turned toward the North—be erected upward; for then certainly those parts of it are turned to the West which, with the same [pole] turned downward, always stood toward the East: of which thing he renders the reason there, and in section 6, from the refraction of the magnetic rays diffused from the poles of the Earth to the mass out of which the Magnet was formed—which refraction was then made in the plane of the stone congruent to the Earth’s meridian, precisely along the up-and-down, and not of itself by the magnetic power. But consult the Author yourself. Meanwhile it is sufficiently clear that this motion itself is not made from West to East upon the axis of the Equator, at the very Equator of the Magnet. Wherefore by no magnetic experiments has the diurnal conversion of the earth as yet been proved.

[XIII.] Thus far concerning the arguments which seem able to be devised for the diurnal revolution of the Earth about its axis and center. For what Galileo inquired from the flux and reflux of the sea pertains not to the diurnal [motion] only, but to establishing other motions of the Earth at the same time, and therefore it will have to be examined below in a separate chapter.