dinarie 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.

[Illustration]

* * * * *

{65} INDEX TO AUTHORITIES

Abano, Pietro di, 6.
Acosta, Josephus, 16.
Addison, Joseph, 35.
Aepinus, 44.
Aetius Amidenus, 6.
Affaytatus, 16, 39.
Agricola, Georgius, 25, 31, 36, 50.
Agrippa, H. Cornelius, 7.
Albategnius, 29.
Albertus Magnus, 6, 17, 38, 39, 40, 50.
Aldrovandi, Ulisse, 13, 36, 53.
Alexander Aphrodiseus, 3, 21.
Amatus Lusitanus, 6, 31.
Apponensis, Petrus, 6. _See_ Abano.
Aquinas, St. Thomas, 8, 45.
Ardoynis, Santes de, 6.
Aristotle, 4, 19, 25, 61.
Arnaldus de Villa nova, 6.
Augustani, 29.
Augustine, St., 4, 21, 43.
Aurifaber, 36.
Averroes, 29.
Avicenna, 6, 29, 30, 34.
Azuni, 8.

Ba