both in respect to experiment and theory; the latter consists of vague
conjectures the more probable of which are perhaps those of Elpinus, as
they assimulate it to electricity.

One conjecture I shall add, viz. that the polarity of magnetism may be
owing to the earth's rotatory motion. If heat, electricity, and
magnetism are supposed to be fluids of different gravities, heat being
the heaviest of them, electricity the next heavy, and magnetism the
lightest, it is evident that by the quick revolution of the earth the
heat will be accumulated most over the line, electricity next beneath
this, and that the magnetism will be detruded to the poles and axis of
the earth, like the atmospheres of common air and of inflammable gas, as
explained in the note on Canto I. l. 123.

Electricity and heat will both of them displace magnetism, and this
shows that they may gravitate on each other; and hence when too great a
quantity of the electric fluid becomes accumulated at the poles by
descending snows, or other unknown causes, it may have a tendency to
rise towards the tropics by its centrifugal force, and produce the
northern lights. See additional notes, No. I.]


"Hail, adamantine STEEL! magnetic Lord!
King of the prow, the plowshare, and the sword!
True to the pole, by thee the pilot guides
His steady helm amid the struggling tides,
205 Braves with broad sail the immeasurable sea,
Cleaves the dark air, and asks no star but Thee.--
By thee the plowshare rends the matted plain,
Inhumes in level rows the living grain;