have in recent times been found to be erroneous. As a pioneer in an
unexplored field of science, however, his work is remarkably accurate.
"On the whole," says Dr. John Robinson, "this performance contains more
real information than any writing of the age in which he lived, and is
scarcely exceeded by any that has appeared since."(4)

In the preface to his work Gilbert says: "Since in the discovery of
secret things, and in the investigation of hidden causes, stronger
reasons are obtained from sure experiments and demonstrated arguments
than from probable conjectures and the opinions of philosophical
speculators of the common sort, therefore, to the end of that noble
substance of that great loadstone, our common mother (the earth), still
quite unknown, and also that the forces extraordinary and exalted of
this globe may the better be understood, we have decided, first, to
begin with the common stony and ferruginous matter, and magnetic bodies,
and the part of the earth that we may handle and may perceive with
senses, and then to proceed with plain magnetic experiments, and to
penetrate to the inner parts of the earth."(5)

Before taking up the demonstration that the earth is simply a giant
loadstone, Gilbert demonstrated in an ingenious way that every
loadstone, of whatever size, has definite and fixed poles. He did this
by placing the stone in a metal lathe and converting it into a sphere,
and upon this sphere demonstrated how the poles can be found. To this
round loadstone he gave the name of terrella--that is, little earth.

"To find, then, poles answering to the earth," he says, "take in your
hand the round stone, and lay on it a needle or a piece of iron wire:
the ends of the wire move round their middle point, and suddenly come
to a standstill. Now, with ochre or with chalk, mark where the wire lies
still and sticks. Then move the middle or centre of the wire to another
spot, and so to a third and fourth, always marking the stone along
the length of the wire where it stands still; the lines so marked will
exhibit meridian circles, or circles like meridians, on the stone or
terrella; and manifestly they will all come together at the poles of the
stone. The circle being continued in this way, the poles appear, both
the north and the south, and betwixt these, midway, we may draw a large
circle for an equator, as is done by the astronomer in the heavens and
on his spheres, and by the geographer on the terrestrial gl