mer _Longitude_. For it is the
Assertion of _Mr. Dr. Gilberts_. _Variatio vnicuiusq; Loci constans
est_, that is to say, the same place doth alwayes retaine the same
variation. Neither hath this Assertion (for ought I ever heard) been
questioned by any man. But most diligent magneticall observations have
plainely offred violence to the same, and proved the contrary, namely
that the variation is accompanied with a variation."

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 _perfecta_, 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
_Mecometrie de l'Eyman_ of G. Nautonier (1602). Here the name
_Borrolybicus_ is given as a synonym for _Nortouest Galerne_, or [Greek:
Olumpias], while the two winds on the points next on the western and
northern sides respectively are called _Upocorus_ and _Upocircius_.

{56} 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.)