Chap. iii.
Opinions of others on Magnetick Coition, which they call Attraction.

D iscussion having now been made concerning electricks, the causes of magnetick coition must be set forth. We say coition, not attraction146. The word attraction unfortunately crept into magnetick philosophy from the ignorance of the ancients; for there seems to be force applied where there is attraction and an imperious violence dominates. For, if ever there is talk about magnetick attraction, we understand thereby magnetick coition, or a primary running together. Now in truth it will not be useless here first briefly to set forth the views given by others, both the ancient and the more modern writers. Orpheus in his hymns147 narrates that iron is attracted by loadstone as the bride to the arms of her espoused. Epicurus holds that iron is attracted by a loadstone just as straws by amber; "and," he adds, "the Atoms and indivisible particles which are given off by the stone and by the iron fit one another in shape; so that they easily cling to one another; when therefore these solid particles of stone or of iron strike against one another, then they rebound into space, being brought against one another by the way, and they draw the iron along with them." But this cannot be the case in the least; since solid and very dense substances interposed, even squared blocks of marble, do not obstruct this power, though they can separate atoms from atoms; and the stone and the iron would be speedily dissipated into such profuse and perpetual streams of atoms. In the case of amber, since there is another different method of attracting, the Epicurean atoms cannot fit one another in shape. Thales, as Aristotle writes, De Anima, Bk. I., deemed the loadstone to be endowed with a soul of some sort, because it had the power of moving and drawing iron towards it. Anaxagoras also held the same view. In the Timæus of Plato there is an idle fancy148 about the efficacy of the stone of Hercules. For he says that "all flowings of water, likewise the fallings of thunderbolts, and the things which are held wonderful in the attraction of Amber, and of the Herculean stone, are such that in all these there is never any attraction; but since there is no vacuum, the particles drive one another mutually around, and when they are dispersed and congregated together, they all pass, each to its proper seat, but with changed places; and it is forsooth, on account of these intercomplicated affections that the effects seem to arouse the wonder in him who has rightly investigated them." Galen does not know why Plato should have seen fit to select the theory of circumpulsion rather than that of attraction (differing almost on this point alone from Hippocrates), though indeed it does not agree in reality with either reason or experiment. Nor indeed is either the air or anything else circumpelled; and the bodies themselves which are attracted are carried towards the attracting substance not confusedly, or in an orbe. Lucretius, the poet of the Epicurean sect, sang his opinion of it thus:

149First, then, know,

Ceaseless effluvia from the magnet flow —

Effluvia, whose superior powers expel

The air that lies between the stone and steel.

A vacuum formed, the steely atoms fly

In a link'd train, and all the void supply;

While the whole ring to which the train is join'd

The influence owns, and follows close behind. &c.

Such a reason Plutarch also alleges in the Quæstiones Platonicæ: That that stone gives off heavy exhalations, whereby the adjacent air, being impelled along, condenses that which is in front of it; and that air, being driven round in an orbe and reverting to the place it had vacated, drags the iron forcibly along with it. The following explanation of the virtues of the loadstone and of amber is propounded by Johannes Costæus of Lodi150. For he would have it that "there is mutual work and mutual result, and therefore the motion is partly due to the attraction of the loadstone and partly to a spontaneous movement on the part of the iron: For as we say that vapours issuing from the loadstone hasten by their own nature to attract the iron, so also the air repelled by the vapours, whilst seeking a place for itself, is turned back, and when turned back, it impels the iron, lifts it up, as it were, and carries it along; the iron being of itself also excited somehow. So by being drawn out and by a spontaneous motion, and by striking against another substance, there is in some way produced a composite motion, which motion would nevertheless be rightly referred to attraction, because the terminus from which this motion invariably begins is the same terminus at which it ends, which is the characteristic proper of an attraction." There is certainly a mutual action, not an operation, nor does the loadstone attract in that way; nor is there any impulsion. But neither is there that origination of the motion by the vapours, and the turning of them back, which opinion of Epicurus has so often been quoted by others. Galen errs in his De Naturalibus Facultatibus, Book I., chap. 14, when he expresses the view that whatever agents draw out either the venom of serpents or darts also exhibit the same power as the loadstone. Now of what sort may be the attraction of such medicaments (if indeed it may be called attraction) we shall consider elsewhere. Drugs against poisons or darts have no relation to, no similitude with, the action of magnetical bodies. The followers of Galen (who hold that purgative medicaments attract because of similitude of substance) say that bodies are attracted on account of similitude, not identity, of substance; wherefore the loadstone draws iron, but iron does not draw iron. But we declare and prove that this happens in primary bodies, and in those bodies that are pretty closely related to them and especially like in kind one to another, on account of their identity; wherefore also loadstone draws lo............