This method of rendering bars of hardened steel magnetical consists in holding vertically two or more magnetic bars nearly parallel to each other with their opposite poles very near each other (but nevertheless separated to a small distance), these are to be slided over a line of bars laid horizontally a few times backward and forward. See Michell on Magnetism, also a detailed account in Chamber's Dictionary. What Mr. Michell proposed by this method was to include a very small portion of the horizontal bars, intended to be made magnetical, between the joint forces of two or more bars already magnetical, and by sliding them from end to end every part of the line of bars became successively included, and thus bars possessed of a very small degree of magnetism to begin with, would in a few times sliding backwards and forwards make the other ones much more magnetical than themselves, which are then to be taken up and used to touch the former, which are in succession to be laid down horizontally in a line. There is still a great field remains for future discoveries in magnetism 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; Intrusive forests quit the cultured ground, 210 And Ceres laughs with golden fillets crown'd.-- O'er restless realms when scowling Discord flings Her snakes, and loud the din of battle rings; Expiring Strength, and vanquish'd Courage feel Thy arm resistless, adamantine STEEL!