On the magnet, magnetick bodies also, and on the great magnet the earth: a new physiology, demonstrated by many arguments & experiments
History
On the magnet, magnetick bodies also, and on the great magnet the earth: a new physiology, demonstrated by many arguments & experiments
Magnetism -- Early works to 1800
These facts have been pointed out to me and confirmed by our most
illustrious Sea-god, Francis Drake, and by another circumnavigator of the
globe, Thomas Candish; our terrella also indicates the same thing. This is
demonstrated in the case of the {118} [Illustration] orbicular stone, whose
poles are A and B; an iron wire CD, which is placed upon the stone, always
points directly along the meridian toward the poles AB, whether the centre
of the wire is on the central line or æquator of the stone, or on any other
part situated between the æquator and the poles, as at H, G, F, E. So the
cusp of a versorium on this side of the æquator points toward the north; *
on the other side the cross is always directed toward the south; but the
cusp or lily[198] does not, as some one has thought, turn toward the south
beyond the æquator. Some inexperienced people indeed, who in distant parts
beyond the æquator have seen the versorium sometimes become more sluggish
and less prompt, thought that the distance from the arctick pole or from
the magnetick rocks was the cause of this. But they are very much mistaken;
for it is as powerful[199], and adjusts itself as quickly to the meridian
or to the point of variation in the southern as in the northern parts of
the earth. Yet sometimes the motion appears slower, namely, when the
supporting pin by lapse of time and long voyaging has become somewhat
blunt, or the magnetick iron parts have lost, by age or rust, some of their
acquired vigour. This may also be shown experimentally by the versatory
iron of a small sun-dial placed on a very short pin set perpendicular to
the surface of the stone, for the iron when touched by a loadstone points
toward the poles of the stone and leaves the poles of the earth; for the
general and remoter cause is overcome by the particular and powerful cause
which is so near at hand. Magnetick bodies have of themselves an
inclination toward the position of the earth and are influenced by a
terrella. Two equal stones of equal strength adjust themselves to a
terrella in accordance with magnetick laws. The iron conceives vigour from
the loadstone and is influenced by the magnetical motions. Wherefore true
direction is the motion of a magnetick body in regard to the verticity of
the earth, the natures of both agreeing and working together toward a
natural position and unity. For indeed we have found out at length, by many
experiments and in many ways, that there is a disposing nature, moving them
together by reason of their various positions by one form that is common
{119} to both, and that in all magnetick substances there is attraction and
repulsion. For both the stone[200] and the magnetick iron arrange
themselves by inclination and declination, according to the common position
of their nature and the earth. And the force of the earth by the virtue of
the whole, by attracting toward the poles, and repelling, arranges all
magneticks which are unfixed and loose. For in all cases all magneticks
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