1667); De Lanis,
_Magisterium Natvrae et Artis_ (Brixiae, 1684); Milliet Deschales, _Cursus
seu Mundus {59} 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
prope 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 nauticae verae &
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
prostaphaeresin._--"Prosthaphaeresis, conflata dictione, ex additione et
subtractione speciebus logistices, nomen habet ab officio, quia vt in
semicirculo altero ad aequabilem motum adijcitur, ita in altero
subtrahitur, vt adparens motus ex aequabili taxetur: atque hinc fit, quod
quae Prosthaphaeresis dicitur Ptolemaeo, ea vulgo aequatio vocetur."
(Stadius, _Tabulae Bergenses_, Colon. Agripp., 1560, p. 37.)

[230] PAGE 174, LINE 28. Page 174, line 31. _Stellae Lucidae._--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 ante 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.

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