Vol. X. This contains, at pp. 269–272, the “Inquiry respecting the Magnet,” of which the original paper is to be found in Vol. IV. pp. 121–125. In Dr. Rawley’s list of works composed by Bacon, during the last five years of his life, this “Inquisitio de Magnete,” first published in 1658, stands last but two. At p. 335 this same Vol. X will be found an extract from “De fluxu et reflexu maris” (“The ebb and flow of the sea”) relative to the inquiry as to whether the earth itself is a magnet, as was asserted by Gilbert. Besides the “Clandestine Instances” or “Instances of the Twilight” alluded to above, mention could have been made more particularly of Bacon’s observations (in s. 3 of the “Nov. Organ.”) under the direct headings of “Instantiæ Citantes ... Supplementi ... Radii ... Magicæ,” as well as of “Motus Magneticus ... Excitationis ... Fugæ,” etc., which are fully explained at ss. 190–200 of Sir John Herschel’s “Discourse on the study of Natural Philosophy.” They have been analyzed as follows: _Instantiæ Citantes_, to which may be reduced the “discovery of a moving magnetic fluid, or an action circular and perpendicular to the electrical current, yet connected with it.” _Instantiæ Supplementi_, such as the magnet which attracts iron through many substances that may be interposed. Perhaps, says he, “some medium may be found to deaden this virtue more than any other medium; such an instance of _substitution_, would be in the way of degree, or _approximation_”; that is, it would approach toward destroying the magnetic virtue. Iron possesses, perhaps, this quality in a more marked manner than any other substance. _Instantiæ Radii_, leading to the suggestion that there may exist some kind of “magnetic virtue which operates by consent, between the globe of the earth and heavenly bodies; or between the globe of the moon and the waters of the sea; or between the starry heavens and the planets, by which they may be drawn to their apogees,” or greatest distances from the earth. _Instantiæ Magicæ_, such as the loadstone animating a number of needles without loss of its own magnetism. _Motus Magneticus_, such as the attraction of the heavenly bodies, from an idea, perhaps, that it might be due to a species of magnetism. _Motus Excitationis_, such as the new property which is given to iron by the magnet without any loss of power by the latter. _Motus Fugæ_, such as “the repulsion of electrified pith balls; also of the similar poles of two magnets. In the latter case, all the force of a strong man has proved insufficient to make the two north poles touch each other.”