earth, which are perfectly
united to the earth and which are not separated from the true substance of
the earth by the interposition of bodies as are loadstones in the upper
portion of the earth, which is maimed, corrupt, and variable. Let A B be a
piece of magnetick ore; between which and the uniform globe of the earth
lie various soils or mixtures which separate the ore to a certain extent
from the globe of the true earth. It is therefore influenced by the forces
of the earth just in the same way as C D, a piece of iron, in the air. So
the face B of some ore or of that piece of it is moved toward the Boreal
pole G, just as the extremity C of the iron, not A or D. But the condition
of the piece E F is different, which piece is produced in one connected
mass with the whole, and is not separated from it by any earthy mixture.
For if the part E F were taken out and floated freely in a boat by itself,
it is not E that would be directed toward the Boreal pole, but F. So in
those substances which acquire their verticity in the air, C is the
southern part and is seen to be attracted by the Boreal pole G. In the case
of others which are found in the upper unstable portion of the earth, B is
the south, and in like manner inclines toward the Boreal pole. But if those
pieces deep down which are produced along with the earth are dug up, they
turn about on a different plan. For F turns toward the Boreal parts of the
earth, because * is the southern part; E toward the south, because it is
the northern. So of a magnetick body, C D, placed close to the earth, the
end C turns toward the Boreal pole; of one that is adnate to it B A, B
inclines to the North; of one that is innate in it, E F, E turns toward the
southern pole; which is confirmed by the {121} [Illustration] following
demonstration, and comes about of necessity according to all magnetick
laws. Let there be a terrella with poles A B; from its mass cut out a small
part E F; if this be suspended by a fine thread above the hole or over some
other place, E does not seek the pole A but the pole B, and F turns to A;
very differently from a rod of iron C D; because C, touching some northern
part of the terrella, being magnetically carried away makes a turn round to
A, not to B. And yet here it should be observed, that if the pole A of *
the terrella were moved toward the earth's south, the end E of the piece
cut out by itself, if not brought too near to the stone, would also move of
i