BIBLIOGRAPHY OF DE MAGNETE. (continued 3)

In 1637 Henry Bond wrote in the Sea-Mans Kalendar that in the year 1657 the variation would be zero at London. Compare Bond's Longitude Found (Lond., 1676, p. 3).

As to inconstancy of the variation in one place see further Fournier's Hydrographie (Paris, 1667, liv. xi., ch. 12, p. 413), and Kircher, Magnes (Colon. Agripp., 1643, p. 418).

[220] Page 157, line 4. Page 157, line 5. perfecto.—Though this word is thus in all editions, it ought to stand perfectâ, as in line 10 below.

[221] Page 157, line 11. Page 157, line 13. varietas, for variatio.

[222] Page 160, line 20. Page 160, line 23. in Borrholybicum.—This name for the North-west, or North-North-West, is rarely used. It is found on the chart or windrose of the names of the winds on pp. 151 and 152 of the Mécometrie de l'Eyman of G. Nautonier (1602). Here the name Borrolybicus is given as a synonym for Nortouest Galerne, or Ὀλυμπιάς, while the two winds on the points next on the western and northern sides respectively are called Upocorus and Upocircius.

In Swan's Specvlvm Mundi (Camb., 1643, p. 174) is this explanation: "Borrholybicus is the North-west wind."

In Kircher's Magnes (Colon. Agripp., 1643, p. 434) is a table of the names of the thirty-two winds in six languages, where Borrolybicus is given as the equivalent of Maestro or North-West.

[223] Page 161, line 2. Page 161, line 2. Insula in Oceano variationem non mutat.—The conclusions derived from the magnetic explorations of the Challenger expedition, 1873-1876, are briefly these: That in islands north of the magnetic equator there is a tendency to produce a local perturbation, attracting the north-seeking end of the needle downwards, and horizontally towards the higher parts of the land; while south of the magnetic equator, the opposite effects are observed. (See Challenger Reports, Physics and Chemistry, vol. ii., part vi., Report on the Magnetical Results by Staff-Commander Creak, F.R.S.)

[224] Page 162, line 2. Page 162, line 3. quarè & respectiuum punctum ... excogitauit.—The passage referred to is in The newe Attractiue of Robert Norman (Lond., 1581), chap. vi.

"Your reason towards the earth carrieth some probabilitie, but I prove that there be no Attractive, or drawing propertie in neyther of these two partes, then is the Attractive poynt lost, and falsly called the poynt Attractive, as shall be proved. But because there is a certayne point that the Needle alwayes respecteth or sheweth, being voide and without any Attractive propertie: in my judgment this poynt ought rather to bee called the point Respective ... This Poynt Respective, is a certayne poynt, which the touched Needle doth alwayes Respect or shew ..."

[225] Page 165, line 2. Page 165, line 2. De pyxidis nauticæ vsitatæ compositione.—Gilbert's description of the usual construction of the mariner's compass should be compared with those given by Levinus Lemnius in The Secret Miracles of Nature (London, 1658); by Lipenius in Navigatio Salomonis Ophiritica (Witteb., 1660, p. 333); and with that given in Barlowe's Navigators Supply (London, 1597). See also Robert Dudley's Dell' Arcano del Mare (Firenze, 1646).

[226] Page 165 deals with the construction; the process of magnetizing by the loadstone had already been discussed in pp. 147 to 149. It is interesting to see that already the magnetized part attached below the compass-card was being specialized in form, being made either of two pieces bent to meet at their ends, or of a single oval piece with elongated ends. The marking of the compass-card is particularly described. It was divided into thirty-two points or "winds," precisely as the earlier "wind-rose" of the geographers, distinguisht by certain marks, and by a lily—or fleur-de-lys—indicating the North. Stevin in the Havenfinding Art (London, 1599), from which work the passage on p. 167 is quoted, speaking on p. 20 of "the Instrument which we call the Sea-directorie, some the nautical box, ... or the sea compasse," mentions the "Floure de luce" marking the North.

The legend which assigns the invention of the compass to one Goia or Gioja of Amalfi in 1302 has been already discussed in the Note to page 4. Gilbert generously says that in spite of the adverse evidence he does not wish to deprive the Amalfians of the honour of the construction adopted in the compasses used in the Mediterranean. But Baptista Porta the Neapolitan, who wrote forty years before Gilbert, discredited the legend. "Flavius saith, an Italian found it out first, whose name was Amalphus, born in our Campania. But he knew not the Mariners Card, but stuck the needle in a reed, or a piece of wood, cross over; and he put the needles into a vessel full of water that they might flote freely." (Porta's Natural Magick, English translation, London, 1658, p. 206.) See also Lipenius (op. citat. p. 390).

The pivotting of the needle is expressly described in the famous Epistle on the Magnet of Peter Peregrinus, which was written in 1269. Gasser's edition, Epistola Petri Peregrini ... de magnete, was printed in Augsburg in 1558. In Part II., cap. 2, of this letter, a form of instrument is described for directing one's course to towns and islands, and any places in fact on land or sea. This instrument consists of a vessel like a turned box (or pyxis) of wood, brass, or any solid material, not deep, but sufficiently wide, provided with a cover of glass or crystal. In its middle is arranged a slender axis of brass or silver, pivotted at its two ends into the top and the bottom of the box. This axis is pierced orthogonally with two holes, through one of which is passed the steel needle, while through the other is fixed square across the needle another stylus of silver or brass. The glass cover was to be marked with two cross lines north-south and east-west; and each quadrant was to be divided into ninety degrees. This the earliest described pivotted compass was therefore of the cross-needle type, a form claimed as a new invention by Barlowe in 1597. The first suggestion of suspending a magnetic needle by a thread appears to be in the Speculum Lapidum of Camillus Leonardus (Venet., 1502, fig. k ij, lines 25-31): "Nã tacto ferro ex una pte magnetis ex opposita eius pte appropinquato fugat: ut expiẽtia docet de acu appenso filo."

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,

(or T). G. (or L) S. O. A (or L). P. M.

The letters correspond to the Italian names of the principal winds:

Tramontano North.

Greco North-East.

Levante East.

Sirocco South-East.

Ostro South.

Africo or Libeccio South-West.

Ponente West.

Maestro North-West.

Wind-roses marked with the names of the minor winds are found in Nautonier's Mécometrie de l'Eyman (Vennes, 1602-1604, pp. 151-152), and Kircher's Magnes Siue de Arte Magnetica (Colon. Agripp., 1643, p. 432). The description above given of the early Venetian wind-roses exactly describes the compass-card as depicted by Pedro de Medina in his Arte de Nauegar (Valladolid, 1545, folio lxxx.), in the sixth book entitled "las aguias de navegar"; while in the Breve compendio de la sphera of Martin Cortes (Sevilla, 1551, cap. iii., de la piedrayman) a similar wind-rose, without the letters, is found.

In the De Ventis et navigatione of 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 the Della Guerra di Rhodi of Jacobo Fontano (Venet., 1545, pages 71-74) is a chapter Dei 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, in The Navigators Supply (Lond., 1597), speaks thus:

"The merueilous and diuine Instrument, called the Sayling 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's Newe Attractiue. In chapter x. of this work Norman thus enumerates the different kinds of compasses:

"Of these common Sayling Compasses, I find heere (in Europa) five sundry sortes or sets. The first is of Levant, made in Scicile, Genoüa, and Venice: 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 poynt Respective, in all places, as the bare Needle. And by this Compasse are the Plats made, for the most part of all the Levants Seas.

"Secondly, there are made in Danske, in the Sound of Denmarke, and in Flanders, 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 Saint Nicholas and Ruscia, Compasses set at 3 seconds of a point, and the first Plats of that Discoverie were made by this Compasse.

"Fourthly the Compasse made at Sevill, Lisbone, Rochell, Bourdeaux, Roan, and heere in England, are moste commonly set at halfe a point: And by this Compasse are the Plats of the East and West Indies made for their Pylotes, and also for our Coastes neere hereby, as France, Spayne, Portugall, and England: 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 his Ratio 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 Mundus Mathematicus (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 passages direction means the force which directs. A similar usage prevails with the nouns variation and declination, meaning frequently the force causing variation or declination respectively.

Page 172, line 13. perquirere. The edition of 1633 reads perquirero, 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's Arcano 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 of De 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 pages 15 and 125, 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.—See note to 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 read multa, but the sense requires multo: "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 pages 199 and 200, an empirical theory, and a diagram. This theory was still further developed by him, and given to Thomas Blundevile (see the Note to 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 printed subintelligitur, and is altered in ink in all copies of the folio edition. The editions of 1628 and 1633 read subintelliguntur. Similarly in line 14 the word ducit has had a small r added in ink, making it read ducitur, 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 his Newe 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 the Stone, the one end with the South of the Stone, 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'd Declining propertie, without descending to the bottome, as by reason it should, if there were any Attraction downewards, 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 require et altera parte, but all editions read ex.

[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 the Tabulæ secvndorum mobilium coelestium of Maginus (Venet., 1585, p. 29, line 19 to p. 30, line 11); the Eratosthenes Batavvs of Willebrord Snell (Lugd. Batav., 1617, pp. 40-42); and the Almagesti novi (Pars Posterior) of Riccioli (Bonon., 1651, p. 348). The original document appears to have perisht. See a notice by M. Curtze in Boncompagni's Bullettino 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 these dicta is taken from Diogenes Laërt., viii. 85; and the second from Plutarch, Placit. Philos., III. 7. The latter passage 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 is De 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 read nyctemoron.

[246] Page 221, line 10. Page 221, line 11. poli verè oppositi sint.—For verè, the 1628 and 1633 editions read rectæ. All editions read sint, though sunt seems to make better sense.

[247] Page 223, line 7. Page 223, line 8. ad telluris conformitatem.—The word conformitas is 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's Epistola 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 that Gilbert had 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's Mathematical 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 read respectu for respectus the 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 that quidem is here a misprint for quidam, but the adverb quidem adds a satirical flavour to his argument against the folly of those who held the doctrine of the moving spheres. The verb salvare does 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 of Copernicus 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's Mathematical Collections and Translations (London, 1661, pp. 364 to 377).

For this the book De Magnete was 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 his Magneticall Aduertisements (1616), expressly repudiated Gilbert's Copernican notions, while praising his discoveries in magnetism. Marke Ridley, while upholding Gilbert's views, in his Magneticall 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 (see Magneticall 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's Theoriques 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 pages 200 and 201 of De 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 by Edward Wright, at the motion of the right Worshipful M. Doctor Gilbert." 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 the de Magnete, and particularly to Book VI. on the rotation of the earth, it is doubtful whether it was written after or before the publication of de 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.

INDEX TO AUTHORITIES

CHISWICK PRESS: CHARLES WHITTINGHAM AND CO. TOOKS COURT, CHANCERY LANE, LONDON.