obe."(6)

Gilbert had tried the familiar experiment of placing the loadstone on a
float in water, and observed that the poles always revolved until
they pointed north and south, which he explained as due to the earth's
magnetic attraction. In this same connection he noticed that a piece of
wrought iron mounted on a cork float was attracted by other metals to
a slight degree, and he observed also that an ordinary iron bar, if
suspended horizontally by a thread, assumes invariably a north and
south direction. These, with many other experiments of a similar nature,
convinced him that the earth "is a magnet and a loadstone," which he
says is a "new and till now unheard-of view of the earth."

Fully to appreciate Gilbert's revolutionary views concerning the earth
as a magnet, it should be remembered that numberless theories to explain
the action of the electric needle had been advanced. Columbus and
Paracelsus, for example, believed that the magnet was attracted by some
point in the heavens, such as a magnetic star. Gilbert himself tells of
some of the beliefs that had been held by his predecessors, many of whom
he declares "wilfully falsify." One of his first steps was to refute
by experiment such assertions as that of Cardan, that "a wound by a
magnetized needle was painless"; and also the assertion of Fracastoni
that loadstone attracts silver; or that of Scalinger, that the diamond
will attract iron; and the statement of Matthiolus that "iron rubbed
with garlic is no longer attracted to the loadstone."

Gilbert made extensive experiments to explain the dipping of the needle,
which had been first noticed by William Norman. His deduction as to
this phenomenon led him to believe that this was also explained by the
magnetic attraction of the earth, and to predict where the vertical dip
would be found. These deductions seem the more wonderful because at the
time he made them the dip had just been discovered, and had not been
studied except at London. His theory of the dip was, therefore, a
scientific prediction, based on a preconceived hypothesis. Gilbert found
the dip to be 72 degrees at London; eight years later Hudson found the
dip at 75 degrees 22' north latitude to be 89 degrees 30'; but it was
not until over two hundred years later, in 1831, that the vertical
dip was first observed by Sir James Ross at about 70 degrees 5' north
latitude, and 96 degrees 43' west longitude. This was not the exact
point assumed by Gilbert