even in the darkest night and in the thickest mist by
a declination instrument. Wherefore to bring our oration at length back to
you, most eminent and learned Dr. Gilbert (whom I gladly recognize as my
teacher in this magnetick philosophy), if these books of yours on the
Magnet had contained nothing else, excepting only this finding of latitude
from magnetick declination, by you now first brought to light, our
shipmasters, Britains, French, Belgians, and Danes, trying to enter the
British Channel or the Straits of Gibraltar from the Atlantick Ocean in
dark weather, would still most deservedly judge them to be valued at no
small sum of gold. But that discovery of yours about the whole globe of the
earth being magnetical, although perchance it will seem to many "most
paradoxical," producing even a feeling of astonishment, has yet been so
firmly defended by you at all points and confirmed by so many experiments
so apposite and appropriate to the matter in hand, in Bk. 2, chap. 34; Bk.
3, chap. 4 and 12; and in almost the whole of the fifth book, that no room
is left for doubt or contradiction. I come therefore to the cause of the
magnetick variation, which hitherto has distracted the minds of all the
learned; for which no mortal has ever adduced a more probable reason than
that which has now been set forth by you for the first time in these books
of yours on the Magnet. The [Greek: orthoboreodeixis] of the index
magnetical in the middle of the ocean, and in the middle of continents (or
at least in the middle of their stronger and more lofty parts), its
inclining near the shore toward those same parts, even by sea and by land,
agreeing with the experiments Bk. 4, chap. 2, on an actual terrella (made
after the likeness of the terrestrial globe, uneven, and rising up in
certain parts, either weak or wanting in firmness, or imperfect in some
other way),--this inclination having been proved, very certainly
demonstrates the probability that that variation is nought else than a
certain deviation of the magnetick needle toward those parts of the earth
that are more vigorous and more prominent. Whence the reason is readily
established of that irregularity which is often perceived in the magnetick
variations, arising from the inaequality and irregularity of those
eminences and of the terrestrial forces. Nor of a surety have I any doubt,
that all those even who have either imagined or admitted points attractive
or points respective in t