The earliest known examples of the "wind-rose" are those in certain parchment charts preserved in the Biblioteca Marciana in Venice. These go back to 1426 or 1436, the best being ascribed to Andrea Bianco. They have the North indicated by a fleur-de-lys, a trident, a simple triangle, or a letter T; while the East is distinguisht by a cross. The West is marked with a P. (see Fincati,op. citat.). The eight marks in order, clock wise, run thus,Lily.(or T).   G.Cross.(or L)   S.   O.   A (or L).   P.   M.The letters correspond to the Italian names of the principal winds:TramontanoNorth.GrecoNorth-East.LevanteEast.SiroccoSouth-East.OstroSouth.Africo or LibeccioSouth-West.PonenteWest.MaestroNorth-West.Wind-roses marked with the names of the minor winds are found in Nautonier'sMécometrie de l'Eyman(Vennes, 1602-1604, pp. 151-152), and Kircher'sMagnes Siue de Arte Magnetica(Colon. Agripp., 1643, p. 432). The description above given of the early Venetian wind-rosesexactlydescribes the compass-card as depicted by Pedro de Medina in hisArte de Nauegar(Valladolid, 1545, folio lxxx.), in the sixth book entitled "las aguias de navegar"; while in theBreve compendio de la spheraof Martin Cortes (Sevilla, 1551, cap. iii.,de la piedrayman) a similar wind-rose, without the letters, is found.In theDe Ventis et navigationeof Michaele Angelo Blondo (Venet., 1546, p. 15) is given a wind-rose, described as "Pixis uel Buxolus instrumentum et dux nauigantium," having twenty-six points inscribed with the names of the winds, there being six between north and east, and six between south and west, and only five in each of the other quadrants. In the middle is a smaller wind-rose exactly like the early Italian ones just mentioned.In theDella Guerra di Rhodiof Jacobo Fontano (Venet., 1545, pages 71-74) is a chapterDei Venti, e della Bvssola di nauicare di Giovanni Quintino, giving a wind-rose, and a table of the names of the winds, the north being indicated by a pointer, at the cusp of which are seven stars, and the west by an image of the sun. The other cardinal points are marked with letters.Barlowe, inThe Navigators Supply(Lond., 1597), speaks thus:"The merueilous and diuine Instrument, called theSayling Compasse(being one of the greatest wonders that this World hath) is a Circle diuided commonly into 32. partes, tearmed by our Seamen Windes,Rumbes, or Points of Compasse."It is a disputed point with whom the method of naming the winds originated. Some ascribe it to Charlemagne. Michiel Coignet (Instruction novvelle ... touchant l'art de naviguer, Anvers, 1581, p. 7) ascribes it to Andronicus Cyrrhestes. See Varro,De Re Rustica, iii., 5, 17, and Vitruvius, i., 6, 4.Gilbert's complaint of the evil practice of setting the needles obliquely beneath the card, with the intention of allowing for the variation, is an echo of a similar complaint in Norman'sNewe Attractiue. In chapter x. of this work Norman thus enumerates the different kinds of compasses:"Of these common Sayling Compasses, I find heere (inEuropa) five sundry sortes or sets. The first is ofLevant, made inScicile,Genoüa, andVenice: And these are all (for the most parte) made Meridionally, with the Wyers directlye sette under the South, and North of the Compasse: And therefore, duely shewing the poyntRespective, in all places, as the bare Needle. And by this Compasse are the Plats made, for the most part of all theLevantsSeas."Secondly, there are made inDanske, in the Sound ofDenmarke, and inFlanders, that have the Wyers set at 3 quarters of a point to the Eastwards of the North of the compasse, and also some at a whole point: and by these Compasses they make both the Plats and Rutters for the Sound."Thirdly, there hath beene made in this Countrey particulary, for SaintNicholasandRuscia, Compasses set at 3 seconds of a point, and the first Plats of that Discoverie were made by this Compasse."Fourthly the Compasse made atSevill,Lisbone,Rochell,Bourdeaux,Roan, and heere inEngland, are moste commonly set at halfe a point: And by this Compasse are the Plats of the East and WestIndiesmade for their Pylotes, and also for our Coastes neere hereby, asFrance,Spayne,Portugall, andEngland: and therefore best of these Nations to bee used, because it is the most common sorte that is generally used in these Coastes."Bessard (op. citat., pages 22 and 48) gives cuts of compasses showing the needle displaced one rumbe to the East.Gallucci, in hisRatio fabricandi horaria mobilia et permanentia cum magnetica acu(Venet., 1596), describes the needle as inclined 10 degrees from the south toward the south-west.The frontispiece of the work of Pedro Nuñez,Instrumenta Artis Navigandi, Basil., 1592, depicts a compass with the lily set one point to the east.Reibelt,De Physicis et Pragmaticis Magnetis Mysteriis(Herbipolis, 1731), depicts the compass with the needle set about 12 degrees to the East of North. See also Fournier,Hydrographie(Paris 1667); De Lanis,Magisterium Natvræ et Artis(Brixiæ, 1684); Milliet Deschales,Cursus seu MundusMathematicus(Lugd., 1674). Both the latter works give pictures of the compass-cards as used in South Europe, and in North Europe, and of the various known shapes of needles.[227]Page 168, line 29.Page 168, line 33.Directio igitur inualidior est propè polos.Here as in many passagesdirectionmeansthe force which directs. A similar usage prevails with the nounsvariationanddeclination, meaning frequently the force causing variation or declination respectively.Page 172, line 13.perquirere.The edition of 1633 readsperquirero, in error.[228]Page 172, line 29.Page 172, line 33.Ad pyxidis nauticæ veræ & meridionalis formam ... fiat instrumentum.—An excellent form of portable meridian compass, provided with sights for taking astronomical observations, is described by Barlowe (The Navigators Supply, London, 1597), and is depicted in an etched engraving. An identical engraving is repeated in Dudley'sArcano del Mare(Firenze, 1646). Gilbert's new instrument was considerably larger.[229]Page 174, line 19.Page 174, line 21.addendo vel detrahendo prostaphæresin.—"Prosthaphæresis, conflata dictione, ex additione et subtractione speciebus logistices, nomen habet ab officio, quia vt in semicirculo altero ad æquabilem motum adijcitur, ita in altero subtrahitur, vt adparens motus ex æquabili taxetur: atque hinc fit, quòd quæ Prosthaphæresis dicitur Ptolemæo, ea vulgò æquatio vocetur." (Stadius,Tabulæ Bergenses, Colon. Agripp., 1560, p. 37.)[230]Page 174, line 28.Page 174, line 31.Stellæ Lucidæ.—According to Dr. Marke Ridley (Magneticall Animadversions, London, 1617, p. 9), this chapter xii. of book iv., with the Table of Stars, was written by Edward Wright, the author of the Prefatory Epistle ofDe Magnete. Wright was Lecturer on Navigation to the East India Company, and author of sundry treatises on Navigation.[231]Page 187, line 14.Page 187, line 16.hic qui versus boream constitit ... meridionalis est, non borealis, quem antè nos omnes existimabant esse borealem.—Earlier on, on pages15and125, Gilbert had mentioned this point. His insistence caused Barlowe (Magneticall Aduertisements, 1616, p. 4) to speak of the south-pointing end of the needle as the "true North," and thereby drew on himself the animadversions of Marke Ridley.[232]Page 188, line 15.Page 188, line 16.in rectâ sphærâ.—Seenoteto p.134.[233]Page 190, line 14.Page 190, line 19.declinans in Borealibus.—Dipping as it does in northern regions; that is, with the north-seeking or true-south pole downward.[234]Page 195, line 20.Page 195, line 24.multa maiora pondera.—Many greater weights. All editions readmulta, but the sense requiresmulto: "much greater weights."[235]Page 196, line 10.Page 196, line 12.constans est.—This must not be read "is constant," for it is constant only in any given latitude.[236]Page 196, line 15.Page 196, line 18.De proportione declinationis pro latitudinis ratione.—Gilbert here announces, and proceeds in the next seven pages to develop, the proposition that to each latitude there corresponds a constant dip to a particular number of degrees. If this were accurately so, then a traveller by merely measuring the dip would be able to ascertain, by calculation, by reference to tables, or by aid of some geometrical appliance,the latitude of the place. In this hope Gilbert fought to perfect the dipping-needle; and he also worked out, on pages199and200, an empirical theory, and a diagram. This theory was still further developed by him, and given to Thomas Blundevile (see theNoteto p.240). Briggs of Gresham College, on Gilbert's suggestion, calculated a table of Dip and Latitude on this theory. It was found, however, that the observed facts deviated more or less widely from the theory. Kircher (Magnes, 1643, p. 368) gives a comparative table of the computed and observed values. Further discovery showed the method to be impracticable, and Gilbert's hope remained unfulfilled.[237]Page 197, line 18.Page 197, line 21.progressionis centri.—Note Gilbert's precision of phrase.[238]Page 200, line 12.Page 200, line 11.subintelligūtur.—This is printedsubintelligitur, and is altered in ink in all copies of the folio edition. The editions of 1628 and 1633 readsubintelliguntur. Similarly in line14the wordducithas had a smallradded in ink, making it readducitur, as also the other editions.[239]Page 203.This figure of the experiment with the simple dipping needle suspended in water in a goblet is due to Robert Norman. In hisNewe Attractiue(London, 1581, chap. vi.) he thus describes it:"Then you shall take a deepe Glasse, Bowle, Cuppe, or other vessell, and fill it with fayre water, setting it in some place where it may rest quiet, and out of the winde. This done, cut the Corke circumspectly, by little and little, untill the wyre with the Corke be so fitted, that it may remain under the superficies of the water two or three inches, both ends of the wyer lying levell with the superficies of the water, without ascending or descending, like to the beame of a payre of ballance beeing equalie poysed at both ends."Then take out of the same the wyer without mooving the Corke, and touch it with theStone, the one end with the South of theStone, and the other end with the North, and then set it againe in the water, and you shall see it presentlie turne it selfe upon his owne Center, shewing the aforesay'dDecliningpropertie, without descending to the bottome, as by reason it should, if there were anyAttractiondownewards, the lower part of the water being neerer that point, then the superficies thereof."[240]Page 212, line 7.Page 212, line 8.ex altera parte.—The sense seems to requireet altera parte, but all editions readex.[241]Page 213, line 1.Page 213, line 2. The passage here quoted from Dominicus Maria Ferrariensis, otherwise known as the astronomer Novara, does not occur in any known writing of that famous man. It is, however, quoted as being by Novara in at least three other writings of the same epoch. See theTabulæ secvndorum mobilium coelestiumof Maginus (Venet., 1585, p. 29, line 19 to p. 30, line 11); theEratosthenes Batavvsof Willebrord Snell (Lugd. Batav., 1617, pp. 40-42); and theAlmagesti novi (Pars Posterior)of Riccioli (Bonon., 1651, p. 348). The original document appears to have perisht. See a notice by M. Curtze in Boncompagni'sBullettino di Bibliografia, T. iv., April, 1871.[242]Page 214, line 26.Page 214, line 31.Philolaus Pythagoricus."Philolaüs a le premier dit que la terre se meut en cercle; d'autres disent que c'est Nicétas de Syracuse.""Les uns prétendent que le terre est immobile; mais Philolaüs le pythagoricien dit qu'elle se meut circulairement autour du feu (central) et suivant un cercle oblique, comme le soleil et la lune."—(Chaignet,Pythagore et la Philosophie pythagoricienne, Paris, 1873.)It appears that the first of thesedictais taken from Diogenes Laërt., viii. 85; and the second from Plutarch,Placit. Philos., III. 7. The latterpassage may be compared with Aristotle,De Coelo, II. 13, who, referring to the followers of Pythagoras, says: "They say that the middle is fire, that the earth is a star, and that it is moved circularly about this centre; and that by this movement it produces day and night."[243]Page 214, line 34.Page 214, line 42.Copernicus.—His work isDe revolutionibus orbium coelestium, libri vi.(Basil., 1566).[244]Page 215, line 27.Page 215, line 24.quæ ... in cælo varijs distantijs collocata sunt.—This remark appears to be Gilbert's one contribution to the science of Astronomy; the stars having previously been regarded as fixed in the eighth sphere all at the same distance from the central earth, around which it revolved.[245]Page 220, line 6.Page 220, line 6.quem nycthemeron vocamus.—The 1628 and 1633 editions readnyctemoron.[246]Page 221, line 10.Page 221, line 11.poli verè oppositi sint.—Forverè, the 1628 and 1633 editions readrectæ. All editions readsint, thoughsuntseems to make better sense.[247]Page 223, line 7.Page 223, line 8.ad telluris conformitatem.—The wordconformitasis unknown in classical Latin.[248]Page 223, line 16.Page 223, line 17.Omitto quod Petrus Peregrinus constanter affirmat, terrellam super polos suos in meridiano suspensam, moveri circulariter integrâ revolutione 24 horis: Quod tamen nobis adhuc videre non contingit; de quo motu etiam dubitamus.This statement that a spherical loadstone pivotted freely with its axis parallel to the earth's axis will of itself revolve on its axis once a day under the control of the heavens, thus superseding clocks, is to be found at the end of chap. x. of Peregrinus'sEpistola De Magnete(Augsb., 1537).Gilbert, who doubted this experiment because of the stone's own weight is taken to task by Galileo, in the third of his Dialogues, for his qualified admission."I will speak of one particular, to which I could have wished thatGilberthad not lent an ear; I mean that of admitting, that in case a little Sphere of Loadstone might be exactly librated, it would revolve in it self; because there is no reason why it should do so" (p. 376 of Salusbury'sMathematical Collections, London, 1661). The Jesuit Fathers who followed Gilbert, but rejected his Copernican ideas, pounced upon this pseudo-experiment, as though by disproving it they had upset the Copernican theory.[249]Page 227, line 6.Page 227, line 7. This line is left out in the 1628 edition. In the 1633 edition it was also left out by the printer, and subsequently printed in in the margin, being page 219 of that edition.[250]Page 234, line 35.Page 234, line 40.vt poli telluris respectus à polis.—If it may be permitted to readrespectuforrespectusthe sense is improved, and the passage may then be translated thus: "that just as it was needful ... that the poles of the Earth as to direction should be 23 degrees and more from the poles of the Ecliptick; so now, &c."[251]Page 237, line 19.Page 237, line 22.vt motus quidem obscuri saluarentur.—It has been conjectured thatquidemis here a misprint forquidam, but the adverbquidemadds a satirical flavour to his argument against the folly of those who held the doctrine of the moving spheres. The verbsalvaredoes not occur in classical Latin.[252]Page 240, line 13.Page 240, line 17.à Copernico (Astronomiæ instauratore).—Gilbert was the first in England to uphold the doctrines ofCopernicus as to the motion of the earth on its axis and its revolution around the sun. He considered that his magnetic observations brought new support to that theory, and his views are quoted with approbation by Kepler,Epitome Astronomiæ Copernicanæ... Authore Ioanne Keplero ... (Francofurti, 1635); and by Galileo,Dialogus de Systemate Mundi(Augustæ Treboc., 1635), an English translation of which appeared in Salusbury'sMathematical Collections and Translations(London, 1661, pp. 364 to 377).For this the bookDe Magnetewas considered by many as heretical. Many of the copies existing in Italy are found to be either mutilated or else branded with a cross. For example, the copy in the library of the Collegio Romano in Rome has book VI. torn out. Galileo states that the Book of Gilbert would possibly never have come into his hands "if a Peripatetick Philosopher, of great fame, as I believe to free his Library from its contagion, had not given it me." In England Barlowe, in hisMagneticall Aduertisements(1616), expressly repudiated Gilbert's Copernican notions, while praising his discoveries in magnetism. Marke Ridley, while upholding Gilbert's views, in hisMagneticall Animadversions(1617) did not consider him "skilfull in Copernicus." The Jesuit writers, Cabeus, Kircher, Fonseca, Grandamicus, Schott, Leotaudus, Millietus, and De Lanis, one and all, who followed Gilbert in their magnetic writings, repudiated the idea that the magnetism of the globe gave support to the heretical modern Astronomy.The works referred to are:Cabeus,Philosophia Magnetica, in qua Magnetis natura penitus explicatur ... auctore Nicolao Cabeo Ferrarensi Soc. Jesv.(Ferrariæ, 1629).Kircher,Magnes, Siue de Arte Magnetica, Libri tres, Authore Athanasio Kirchero ... e Soc. Iesv.(Romæ, 1641).Grandamicus,Nova Demonstratio immobilitatis terræ petita ex virtute magnetica(Flexiæ, 1645). This work is most beautifully illustrated with copper-plate etchings of cupids making experiments with terrellas.Schott, Gaspar,Thaumaturgus Physicus(Herbipolis, 1659).Leotaudus,R. P. Vincentinii Leotavdi Delphinatis, Societ. Iesv., Magnetologia; in qva exponitvr Nova de Magneticis Philosophia, (Lvgdvni, 1668).Millietus (Milliet Deschales),Cursus seu Mundus Mathematicus(Lugd., 1674),Tomus Primus, Tractatus de Magnete.De Lanis,Magisterium Natvræ et Artis. Opus Physico-Mathematicvm P. Francisci Tertii de Lanis, Soc. Jesv.(Brixiæ, 1684).[253]Page 240, line 24.Page 240, line 31.hic finem & periodum imponimus.On February 13 [1601] Gilbert wrote to Barlowe (seeMagneticall Aduertisements, p. 88):"I purpose to adioyne an appendix of six or eight sheets of paper to my booke after a while, I am in hand with it of some new inventions, and I would haue some of your experiments, in your name and inuention put into it, if you please, that you may be knowen for an augmenter of that arte."This he never did. Perhaps his appointment (in February, 1601) as chief physician in personal attendance on the Queen interfered with the project; or his death, of the plague, in 1603, intervened before his intention had been carried into effect. But it is probable that the substance of the proposed additions is to be found in the chapter, publisht in Gilbert's lifetime, in Blundevile'sTheoriques of the seuen Planets(London, 1602), thus described in the title-page of the work: "There is also hereto added,The making, description, and vse, of two most ingenious and necessarie Instruments for Sea-men, to find out thereby the latitude of any Place vpon the Sea or Land, in the darkest night that is, without the helpe of Sunne, Moone, or Starre. First inuented by M. Doctor Gilbert, a most excellent Philosopher, and one of the ordinarie Physicians to her Maiestie: and now here plainely set downe in our mother tongue by Master Blundeuile."Of these two instruments the first consists of a mechanical device, with movable quadrants, to be cut out in cardboard, to be used in connection with the diagram of spiral lines which Gilbert had given as a folding plate between pages200and201ofDe Magnete. The intention was that the Sea-man having found by experiment with a dipping-needle the amount of the dip at any place, should by applying this diagram and its moving quadrants, ascertain the latitude, according to the theory expounded in book V., chap. VII.The second instrument is a simplified portable dipping-needle, having the degrees engraved on the inner face of a cylindrical brass ring.Blundevile adds a Table, calculated by Briggs, and "annexed to the former Treatise byEdward Wright, at the motion of the right Worshipful M. DoctorGilbert." This gives the values of the dip for different latitudes, as calculated from Gilbert's empirical theory.The other work,De Mundo nostro Sublunari Philosophia Nova, which Gilbert left in manuscript at his death, does not contain any additional matter on the magnetical investigations. Though it contains several direct references to thede Magnete, and particularly to Book VI. on the rotation of the earth, it is doubtful whether it was written after or before the publication ofde Magnete. On pages 137 to 144 of the posthumous edition (Amsterdam, 1651) Gilbert refers to Peregrinus's alleged perpetually revolving sphere, and denies its possibility. The greater part of the work is an anti-Aristotelian discussion on Air, Meteorology, Astronomy, the Winds, Tides, and Springs.
The earliest known examples of the "wind-rose" are those in certain parchment charts preserved in the Biblioteca Marciana in Venice. These go back to 1426 or 1436, the best being ascribed to Andrea Bianco. They have the North indicated by a fleur-de-lys, a trident, a simple triangle, or a letter T; while the East is distinguisht by a cross. The West is marked with a P. (see Fincati,op. citat.). The eight marks in order, clock wise, run thus,
Lily.(or T). Â Â G.Cross.(or L) Â Â S. Â Â O. Â Â A (or L). Â Â P. Â Â M.
The letters correspond to the Italian names of the principal winds:
Wind-roses marked with the names of the minor winds are found in Nautonier'sMécometrie de l'Eyman(Vennes, 1602-1604, pp. 151-152), and Kircher'sMagnes Siue de Arte Magnetica(Colon. Agripp., 1643, p. 432). The description above given of the early Venetian wind-rosesexactlydescribes the compass-card as depicted by Pedro de Medina in hisArte de Nauegar(Valladolid, 1545, folio lxxx.), in the sixth book entitled "las aguias de navegar"; while in theBreve compendio de la spheraof Martin Cortes (Sevilla, 1551, cap. iii.,de la piedrayman) a similar wind-rose, without the letters, is found.
In theDe Ventis et navigationeof Michaele Angelo Blondo (Venet., 1546, p. 15) is given a wind-rose, described as "Pixis uel Buxolus instrumentum et dux nauigantium," having twenty-six points inscribed with the names of the winds, there being six between north and east, and six between south and west, and only five in each of the other quadrants. In the middle is a smaller wind-rose exactly like the early Italian ones just mentioned.
In theDella Guerra di Rhodiof Jacobo Fontano (Venet., 1545, pages 71-74) is a chapterDei Venti, e della Bvssola di nauicare di Giovanni Quintino, giving a wind-rose, and a table of the names of the winds, the north being indicated by a pointer, at the cusp of which are seven stars, and the west by an image of the sun. The other cardinal points are marked with letters.
Barlowe, inThe Navigators Supply(Lond., 1597), speaks thus:
"The merueilous and diuine Instrument, called theSayling Compasse(being one of the greatest wonders that this World hath) is a Circle diuided commonly into 32. partes, tearmed by our Seamen Windes,Rumbes, or Points of Compasse."
"The merueilous and diuine Instrument, called theSayling Compasse(being one of the greatest wonders that this World hath) is a Circle diuided commonly into 32. partes, tearmed by our Seamen Windes,Rumbes, or Points of Compasse."
It is a disputed point with whom the method of naming the winds originated. Some ascribe it to Charlemagne. Michiel Coignet (Instruction novvelle ... touchant l'art de naviguer, Anvers, 1581, p. 7) ascribes it to Andronicus Cyrrhestes. See Varro,De Re Rustica, iii., 5, 17, and Vitruvius, i., 6, 4.
Gilbert's complaint of the evil practice of setting the needles obliquely beneath the card, with the intention of allowing for the variation, is an echo of a similar complaint in Norman'sNewe Attractiue. In chapter x. of this work Norman thus enumerates the different kinds of compasses:
"Of these common Sayling Compasses, I find heere (inEuropa) five sundry sortes or sets. The first is ofLevant, made inScicile,Genoüa, andVenice: And these are all (for the most parte) made Meridionally, with the Wyers directlye sette under the South, and North of the Compasse: And therefore, duely shewing the poyntRespective, in all places, as the bare Needle. And by this Compasse are the Plats made, for the most part of all theLevantsSeas."Secondly, there are made inDanske, in the Sound ofDenmarke, and inFlanders, that have the Wyers set at 3 quarters of a point to the Eastwards of the North of the compasse, and also some at a whole point: and by these Compasses they make both the Plats and Rutters for the Sound."Thirdly, there hath beene made in this Countrey particulary, for SaintNicholasandRuscia, Compasses set at 3 seconds of a point, and the first Plats of that Discoverie were made by this Compasse."Fourthly the Compasse made atSevill,Lisbone,Rochell,Bourdeaux,Roan, and heere inEngland, are moste commonly set at halfe a point: And by this Compasse are the Plats of the East and WestIndiesmade for their Pylotes, and also for our Coastes neere hereby, asFrance,Spayne,Portugall, andEngland: and therefore best of these Nations to bee used, because it is the most common sorte that is generally used in these Coastes."
"Of these common Sayling Compasses, I find heere (inEuropa) five sundry sortes or sets. The first is ofLevant, made inScicile,Genoüa, andVenice: And these are all (for the most parte) made Meridionally, with the Wyers directlye sette under the South, and North of the Compasse: And therefore, duely shewing the poyntRespective, in all places, as the bare Needle. And by this Compasse are the Plats made, for the most part of all theLevantsSeas.
"Secondly, there are made inDanske, in the Sound ofDenmarke, and inFlanders, that have the Wyers set at 3 quarters of a point to the Eastwards of the North of the compasse, and also some at a whole point: and by these Compasses they make both the Plats and Rutters for the Sound.
"Thirdly, there hath beene made in this Countrey particulary, for SaintNicholasandRuscia, Compasses set at 3 seconds of a point, and the first Plats of that Discoverie were made by this Compasse.
"Fourthly the Compasse made atSevill,Lisbone,Rochell,Bourdeaux,Roan, and heere inEngland, are moste commonly set at halfe a point: And by this Compasse are the Plats of the East and WestIndiesmade for their Pylotes, and also for our Coastes neere hereby, asFrance,Spayne,Portugall, andEngland: and therefore best of these Nations to bee used, because it is the most common sorte that is generally used in these Coastes."
Bessard (op. citat., pages 22 and 48) gives cuts of compasses showing the needle displaced one rumbe to the East.
Gallucci, in hisRatio fabricandi horaria mobilia et permanentia cum magnetica acu(Venet., 1596), describes the needle as inclined 10 degrees from the south toward the south-west.
The frontispiece of the work of Pedro Nuñez,Instrumenta Artis Navigandi, Basil., 1592, depicts a compass with the lily set one point to the east.
Reibelt,De Physicis et Pragmaticis Magnetis Mysteriis(Herbipolis, 1731), depicts the compass with the needle set about 12 degrees to the East of North. See also Fournier,Hydrographie(Paris 1667); De Lanis,Magisterium Natvræ et Artis(Brixiæ, 1684); Milliet Deschales,Cursus seu MundusMathematicus(Lugd., 1674). Both the latter works give pictures of the compass-cards as used in South Europe, and in North Europe, and of the various known shapes of needles.
[227]Page 168, line 29.Page 168, line 33.Directio igitur inualidior est propè polos.Here as in many passagesdirectionmeansthe force which directs. A similar usage prevails with the nounsvariationanddeclination, meaning frequently the force causing variation or declination respectively.
Page 172, line 13.perquirere.The edition of 1633 readsperquirero, in error.
[228]Page 172, line 29.Page 172, line 33.Ad pyxidis nauticæ veræ & meridionalis formam ... fiat instrumentum.—An excellent form of portable meridian compass, provided with sights for taking astronomical observations, is described by Barlowe (The Navigators Supply, London, 1597), and is depicted in an etched engraving. An identical engraving is repeated in Dudley'sArcano del Mare(Firenze, 1646). Gilbert's new instrument was considerably larger.
[229]Page 174, line 19.Page 174, line 21.addendo vel detrahendo prostaphæresin.—"Prosthaphæresis, conflata dictione, ex additione et subtractione speciebus logistices, nomen habet ab officio, quia vt in semicirculo altero ad æquabilem motum adijcitur, ita in altero subtrahitur, vt adparens motus ex æquabili taxetur: atque hinc fit, quòd quæ Prosthaphæresis dicitur Ptolemæo, ea vulgò æquatio vocetur." (Stadius,Tabulæ Bergenses, Colon. Agripp., 1560, p. 37.)
[230]Page 174, line 28.Page 174, line 31.Stellæ Lucidæ.—According to Dr. Marke Ridley (Magneticall Animadversions, London, 1617, p. 9), this chapter xii. of book iv., with the Table of Stars, was written by Edward Wright, the author of the Prefatory Epistle ofDe Magnete. Wright was Lecturer on Navigation to the East India Company, and author of sundry treatises on Navigation.
[231]Page 187, line 14.Page 187, line 16.hic qui versus boream constitit ... meridionalis est, non borealis, quem antè nos omnes existimabant esse borealem.—Earlier on, on pages15and125, Gilbert had mentioned this point. His insistence caused Barlowe (Magneticall Aduertisements, 1616, p. 4) to speak of the south-pointing end of the needle as the "true North," and thereby drew on himself the animadversions of Marke Ridley.
[232]Page 188, line 15.Page 188, line 16.in rectâ sphærâ.—Seenoteto p.134.
[233]Page 190, line 14.Page 190, line 19.declinans in Borealibus.—Dipping as it does in northern regions; that is, with the north-seeking or true-south pole downward.
[234]Page 195, line 20.Page 195, line 24.multa maiora pondera.—Many greater weights. All editions readmulta, but the sense requiresmulto: "much greater weights."
[235]Page 196, line 10.Page 196, line 12.constans est.—This must not be read "is constant," for it is constant only in any given latitude.
[236]Page 196, line 15.Page 196, line 18.De proportione declinationis pro latitudinis ratione.—Gilbert here announces, and proceeds in the next seven pages to develop, the proposition that to each latitude there corresponds a constant dip to a particular number of degrees. If this were accurately so, then a traveller by merely measuring the dip would be able to ascertain, by calculation, by reference to tables, or by aid of some geometrical appliance,the latitude of the place. In this hope Gilbert fought to perfect the dipping-needle; and he also worked out, on pages199and200, an empirical theory, and a diagram. This theory was still further developed by him, and given to Thomas Blundevile (see theNoteto p.240). Briggs of Gresham College, on Gilbert's suggestion, calculated a table of Dip and Latitude on this theory. It was found, however, that the observed facts deviated more or less widely from the theory. Kircher (Magnes, 1643, p. 368) gives a comparative table of the computed and observed values. Further discovery showed the method to be impracticable, and Gilbert's hope remained unfulfilled.
[237]Page 197, line 18.Page 197, line 21.progressionis centri.—Note Gilbert's precision of phrase.
[238]Page 200, line 12.Page 200, line 11.subintelligūtur.—This is printedsubintelligitur, and is altered in ink in all copies of the folio edition. The editions of 1628 and 1633 readsubintelliguntur. Similarly in line14the wordducithas had a smallradded in ink, making it readducitur, as also the other editions.
[239]Page 203.This figure of the experiment with the simple dipping needle suspended in water in a goblet is due to Robert Norman. In hisNewe Attractiue(London, 1581, chap. vi.) he thus describes it:
"Then you shall take a deepe Glasse, Bowle, Cuppe, or other vessell, and fill it with fayre water, setting it in some place where it may rest quiet, and out of the winde. This done, cut the Corke circumspectly, by little and little, untill the wyre with the Corke be so fitted, that it may remain under the superficies of the water two or three inches, both ends of the wyer lying levell with the superficies of the water, without ascending or descending, like to the beame of a payre of ballance beeing equalie poysed at both ends."Then take out of the same the wyer without mooving the Corke, and touch it with theStone, the one end with the South of theStone, and the other end with the North, and then set it againe in the water, and you shall see it presentlie turne it selfe upon his owne Center, shewing the aforesay'dDecliningpropertie, without descending to the bottome, as by reason it should, if there were anyAttractiondownewards, the lower part of the water being neerer that point, then the superficies thereof."
"Then you shall take a deepe Glasse, Bowle, Cuppe, or other vessell, and fill it with fayre water, setting it in some place where it may rest quiet, and out of the winde. This done, cut the Corke circumspectly, by little and little, untill the wyre with the Corke be so fitted, that it may remain under the superficies of the water two or three inches, both ends of the wyer lying levell with the superficies of the water, without ascending or descending, like to the beame of a payre of ballance beeing equalie poysed at both ends.
"Then take out of the same the wyer without mooving the Corke, and touch it with theStone, the one end with the South of theStone, and the other end with the North, and then set it againe in the water, and you shall see it presentlie turne it selfe upon his owne Center, shewing the aforesay'dDecliningpropertie, without descending to the bottome, as by reason it should, if there were anyAttractiondownewards, the lower part of the water being neerer that point, then the superficies thereof."
[240]Page 212, line 7.Page 212, line 8.ex altera parte.—The sense seems to requireet altera parte, but all editions readex.
[241]Page 213, line 1.Page 213, line 2. The passage here quoted from Dominicus Maria Ferrariensis, otherwise known as the astronomer Novara, does not occur in any known writing of that famous man. It is, however, quoted as being by Novara in at least three other writings of the same epoch. See theTabulæ secvndorum mobilium coelestiumof Maginus (Venet., 1585, p. 29, line 19 to p. 30, line 11); theEratosthenes Batavvsof Willebrord Snell (Lugd. Batav., 1617, pp. 40-42); and theAlmagesti novi (Pars Posterior)of Riccioli (Bonon., 1651, p. 348). The original document appears to have perisht. See a notice by M. Curtze in Boncompagni'sBullettino di Bibliografia, T. iv., April, 1871.
[242]Page 214, line 26.Page 214, line 31.Philolaus Pythagoricus.
"Philolaüs a le premier dit que la terre se meut en cercle; d'autres disent que c'est Nicétas de Syracuse.""Les uns prétendent que le terre est immobile; mais Philolaüs le pythagoricien dit qu'elle se meut circulairement autour du feu (central) et suivant un cercle oblique, comme le soleil et la lune."—(Chaignet,Pythagore et la Philosophie pythagoricienne, Paris, 1873.)
"Philolaüs a le premier dit que la terre se meut en cercle; d'autres disent que c'est Nicétas de Syracuse."
"Les uns prétendent que le terre est immobile; mais Philolaüs le pythagoricien dit qu'elle se meut circulairement autour du feu (central) et suivant un cercle oblique, comme le soleil et la lune."—(Chaignet,Pythagore et la Philosophie pythagoricienne, Paris, 1873.)
It appears that the first of thesedictais taken from Diogenes Laërt., viii. 85; and the second from Plutarch,Placit. Philos., III. 7. The latterpassage may be compared with Aristotle,De Coelo, II. 13, who, referring to the followers of Pythagoras, says: "They say that the middle is fire, that the earth is a star, and that it is moved circularly about this centre; and that by this movement it produces day and night."
[243]Page 214, line 34.Page 214, line 42.Copernicus.—His work isDe revolutionibus orbium coelestium, libri vi.(Basil., 1566).
[244]Page 215, line 27.Page 215, line 24.quæ ... in cælo varijs distantijs collocata sunt.—This remark appears to be Gilbert's one contribution to the science of Astronomy; the stars having previously been regarded as fixed in the eighth sphere all at the same distance from the central earth, around which it revolved.
[245]Page 220, line 6.Page 220, line 6.quem nycthemeron vocamus.—The 1628 and 1633 editions readnyctemoron.
[246]Page 221, line 10.Page 221, line 11.poli verè oppositi sint.—Forverè, the 1628 and 1633 editions readrectæ. All editions readsint, thoughsuntseems to make better sense.
[247]Page 223, line 7.Page 223, line 8.ad telluris conformitatem.—The wordconformitasis unknown in classical Latin.
[248]Page 223, line 16.Page 223, line 17.Omitto quod Petrus Peregrinus constanter affirmat, terrellam super polos suos in meridiano suspensam, moveri circulariter integrâ revolutione 24 horis: Quod tamen nobis adhuc videre non contingit; de quo motu etiam dubitamus.
This statement that a spherical loadstone pivotted freely with its axis parallel to the earth's axis will of itself revolve on its axis once a day under the control of the heavens, thus superseding clocks, is to be found at the end of chap. x. of Peregrinus'sEpistola De Magnete(Augsb., 1537).
Gilbert, who doubted this experiment because of the stone's own weight is taken to task by Galileo, in the third of his Dialogues, for his qualified admission.
"I will speak of one particular, to which I could have wished thatGilberthad not lent an ear; I mean that of admitting, that in case a little Sphere of Loadstone might be exactly librated, it would revolve in it self; because there is no reason why it should do so" (p. 376 of Salusbury'sMathematical Collections, London, 1661). The Jesuit Fathers who followed Gilbert, but rejected his Copernican ideas, pounced upon this pseudo-experiment, as though by disproving it they had upset the Copernican theory.
[249]Page 227, line 6.Page 227, line 7. This line is left out in the 1628 edition. In the 1633 edition it was also left out by the printer, and subsequently printed in in the margin, being page 219 of that edition.
[250]Page 234, line 35.Page 234, line 40.vt poli telluris respectus à polis.—If it may be permitted to readrespectuforrespectusthe sense is improved, and the passage may then be translated thus: "that just as it was needful ... that the poles of the Earth as to direction should be 23 degrees and more from the poles of the Ecliptick; so now, &c."
[251]Page 237, line 19.Page 237, line 22.vt motus quidem obscuri saluarentur.—It has been conjectured thatquidemis here a misprint forquidam, but the adverbquidemadds a satirical flavour to his argument against the folly of those who held the doctrine of the moving spheres. The verbsalvaredoes not occur in classical Latin.
[252]Page 240, line 13.Page 240, line 17.à Copernico (Astronomiæ instauratore).—Gilbert was the first in England to uphold the doctrines ofCopernicus as to the motion of the earth on its axis and its revolution around the sun. He considered that his magnetic observations brought new support to that theory, and his views are quoted with approbation by Kepler,Epitome Astronomiæ Copernicanæ... Authore Ioanne Keplero ... (Francofurti, 1635); and by Galileo,Dialogus de Systemate Mundi(Augustæ Treboc., 1635), an English translation of which appeared in Salusbury'sMathematical Collections and Translations(London, 1661, pp. 364 to 377).
For this the bookDe Magnetewas considered by many as heretical. Many of the copies existing in Italy are found to be either mutilated or else branded with a cross. For example, the copy in the library of the Collegio Romano in Rome has book VI. torn out. Galileo states that the Book of Gilbert would possibly never have come into his hands "if a Peripatetick Philosopher, of great fame, as I believe to free his Library from its contagion, had not given it me." In England Barlowe, in hisMagneticall Aduertisements(1616), expressly repudiated Gilbert's Copernican notions, while praising his discoveries in magnetism. Marke Ridley, while upholding Gilbert's views, in hisMagneticall Animadversions(1617) did not consider him "skilfull in Copernicus." The Jesuit writers, Cabeus, Kircher, Fonseca, Grandamicus, Schott, Leotaudus, Millietus, and De Lanis, one and all, who followed Gilbert in their magnetic writings, repudiated the idea that the magnetism of the globe gave support to the heretical modern Astronomy.
The works referred to are:
Cabeus,Philosophia Magnetica, in qua Magnetis natura penitus explicatur ... auctore Nicolao Cabeo Ferrarensi Soc. Jesv.(Ferrariæ, 1629).
Kircher,Magnes, Siue de Arte Magnetica, Libri tres, Authore Athanasio Kirchero ... e Soc. Iesv.(Romæ, 1641).
Grandamicus,Nova Demonstratio immobilitatis terræ petita ex virtute magnetica(Flexiæ, 1645). This work is most beautifully illustrated with copper-plate etchings of cupids making experiments with terrellas.
Schott, Gaspar,Thaumaturgus Physicus(Herbipolis, 1659).
Leotaudus,R. P. Vincentinii Leotavdi Delphinatis, Societ. Iesv., Magnetologia; in qva exponitvr Nova de Magneticis Philosophia, (Lvgdvni, 1668).
Millietus (Milliet Deschales),Cursus seu Mundus Mathematicus(Lugd., 1674),Tomus Primus, Tractatus de Magnete.
De Lanis,Magisterium Natvræ et Artis. Opus Physico-Mathematicvm P. Francisci Tertii de Lanis, Soc. Jesv.(Brixiæ, 1684).
[253]Page 240, line 24.Page 240, line 31.hic finem & periodum imponimus.
On February 13 [1601] Gilbert wrote to Barlowe (seeMagneticall Aduertisements, p. 88):
"I purpose to adioyne an appendix of six or eight sheets of paper to my booke after a while, I am in hand with it of some new inventions, and I would haue some of your experiments, in your name and inuention put into it, if you please, that you may be knowen for an augmenter of that arte."
This he never did. Perhaps his appointment (in February, 1601) as chief physician in personal attendance on the Queen interfered with the project; or his death, of the plague, in 1603, intervened before his intention had been carried into effect. But it is probable that the substance of the proposed additions is to be found in the chapter, publisht in Gilbert's lifetime, in Blundevile'sTheoriques of the seuen Planets(London, 1602), thus described in the title-page of the work: "There is also hereto added,The making, description, and vse, of two most ingenious and necessarie Instruments for Sea-men, to find out thereby the latitude of any Place vpon the Sea or Land, in the darkest night that is, without the helpe of Sunne, Moone, or Starre. First inuented by M. Doctor Gilbert, a most excellent Philosopher, and one of the ordinarie Physicians to her Maiestie: and now here plainely set downe in our mother tongue by Master Blundeuile."
Of these two instruments the first consists of a mechanical device, with movable quadrants, to be cut out in cardboard, to be used in connection with the diagram of spiral lines which Gilbert had given as a folding plate between pages200and201ofDe Magnete. The intention was that the Sea-man having found by experiment with a dipping-needle the amount of the dip at any place, should by applying this diagram and its moving quadrants, ascertain the latitude, according to the theory expounded in book V., chap. VII.
The second instrument is a simplified portable dipping-needle, having the degrees engraved on the inner face of a cylindrical brass ring.
Blundevile adds a Table, calculated by Briggs, and "annexed to the former Treatise byEdward Wright, at the motion of the right Worshipful M. DoctorGilbert." This gives the values of the dip for different latitudes, as calculated from Gilbert's empirical theory.
The other work,De Mundo nostro Sublunari Philosophia Nova, which Gilbert left in manuscript at his death, does not contain any additional matter on the magnetical investigations. Though it contains several direct references to thede Magnete, and particularly to Book VI. on the rotation of the earth, it is doubtful whether it was written after or before the publication ofde Magnete. On pages 137 to 144 of the posthumous edition (Amsterdam, 1651) Gilbert refers to Peregrinus's alleged perpetually revolving sphere, and denies its possibility. The greater part of the work is an anti-Aristotelian discussion on Air, Meteorology, Astronomy, the Winds, Tides, and Springs.