WILLIAM GILBERT.
55
The first chapter of Book I. is devoted to a review of the older
writers and their various opinions and vanities, which he scornfully
dismisses by remarking that only plebeian philosophers delight them-
selves in such nonsense, and names the following as the men who
have really added to magnetic knowledge : Thomas Hariot, Robert
Hues, Edward Wright, Abraham Kendall, William Borough, William
Barlowe, and Robert Norman—all Englishmen.
In the second chapter he enters upon a learned discussion as to
the etymology of the word magnet, the origin of its discovery in
prehistoric times, and the localities whence the loadstone is procured.
In the third chapter begins the experimental method. The proposition
that a magnet possesses certain parts, or poles, distinguished by their
natural power is established by experiment; a loadstone ground down
on a lapidary's wheel to a spherical shape being the form preferred,
as being geometrically the most perfect and as being fittest for experi-
ments as resembling the globe of the earth. Such a globular load-
stone Gilbert called a "Terrella." To the pole pointing southwards
Gilbert assigned the name "boreal" on account of the law of
attraction between opposite kinds of poles, arguing that the polarity
of the pole which pointed southwards must be a pole of the opposite
kind. This led to further experiments on loadstones, which were cut
into two parts, the parts being floated on water in little vessels.
Subsequent chapters deal with the attraction of the loadstone for iron,
and with the properties of iron as contrasted with those of other
metals; many a passing hit at the absurdities of astrologists and
alchemists being interposed. He then shows that iron which has not
been touched by any loadstone can nevertheless act magnetically on
other iron. To show this a light piece of iron wire is thrust through
a small ball of cork and set to float, and toward it is brought the
lower end of a long iron rod held above it. The one turns toward
the other. Another experimental discovery is that a long iron rod,
delicately hung by a special silk thread, will turn, even though not
previously magnetised by contact with any magnet, and place itself in
the direction of the compass. In chapters fourteen and fifteen is
interpolated a description of the alleged medicinal powers of the
magnet, beginning with its use, as prescribed by Dioscorides and
Galen, to drive away melancholy, and ending with Paracelsus who
recommended poultices containing powdered magnets. Short shrift
would modern magnetopathic quacks have got, with their magnetic
belts and rings, at the hands of the outspoken doctor. After a short