The Natural Philosophy of William Gilbert and His Predecessors Part 6

The formal forces of a loadstone emanate in all directions from it,[167] but there is a bound to it that Gilbert called the "orbis virtutis."[168] The shape of this "orbis virtutis" is determined by the shape of the stone.[169] This insensible effusion is a.n.a.logous to the spreading of light that reveals its presence only by opaque bodies.[170] Similarly, the magnetic forms are effused from the stone,[171] and can only reveal their presence by coition with another loadstone or by "awakening" magnetic bodies within the "orbis virtutis."[172] Unmagnetized iron that comes within the "orbis virtutis" is altered, and the magnetic virtue renews a form that is already potentially in the iron.[173] The formal energy is drawn not only from the stone but from the iron.[174] This is not generation, or alteration in the sense of a new impressed quality, but alteration in the sense of the entelechy or the activation of a form potentially present.[175] Those bodies magnetized by coming within the "orbis virtutis" have in turn an efflux of their own.[176] Iron can also receive verticity directly from the earth without the intervention of an ordinary loadstone.[177] Such verticity can be expelled and annulled by the presence of another loadstone.[178]

[167] M: pp. 121, 123, 124, 304, 305, 306, 307, 309.

[168] Gilbert defined the _orbis virtutis_ in the glossary at the beginning of his treatise as, "... totum illud spatium, per quod quaevis magnetis virtus extenditur." This is the core of the difference between electric and magnetic forces.

The substantial form of an electric could not be "effused,"

but was "imprisoned" in matter (as the Neoplatonic soul in the human body); while the primary form of a magnet did not require a material carrier and its effusion was similar to the propagation of a species in light.

[169] M: pp. 124, 150, 151.

[170] M: pp. 123, 307.

[171] M: pp. 304-307. See also p. 310, where it is stated that the sun and earth could awaken souls.

[172] M: pp. 101, 110, 112, 123, 148, 149, 304, 305. This awakening of the iron within the "orbis virtutis" is comparable (pp. 216, 350) to the birth of a child under the influence of the stars.

[173] M: pp. 110, 111, 112, 189, 216, 217. See also footnote 36.

[174] M: p. 106.

[175] M: pp. 106, 109, 110.

[176] M: pp. 113, 114.

[177] M: pp. 190, 192, 210-216.

[178] M: p. 209.

Although one does not normally find iron to be magnetized, a loadstone always has some magnetism. That two bodies such as iron and loadstone should have different properties is the result of the loss of a form by the iron, but this form is still potentially present in the iron.

The iron that has been obtained from an ore has been deformed,[179]

for it has been placed "outside its nature" by the fire.[180] The nature has not been removed, since, once the iron has cooled, the confused form can be reformed by a loadstone. [181] The latter "awakens" the proper form of iron.[182] After smelting, the magnetized iron may manifest stronger powers than a loadstone of equal weight, but this is because the primary matter of the earth is purer in the iron than in the loadstone.[183] If fire does not deform a loadstone too much, it can be remagnetized,[184] but a burnt loadstone cannot be reformed.[185] Corruption from external causes may also deform a loadstone or iron so that it can not be magnetized.[186] Bodies mixed with the degenerate substance of the earth or with aqueous humor spoilt by contamination with earth, do not show either electric attraction or magnetic coition.[187]

[179] M: pp. 107, 110, 111.

[180] M: p. 108.

[181] M: pp. 111, 112, 113.

[182] M: pp. 109, 111, 112, 148, 149.

[183] M: pp. 112, 149.

[184] M: pp. 142, 189.

[185] M: p. 190.

[186] M: pp. 85, 105, 113, 143, 226.

[187] M: p. 84.

In a manner suggestive of Peregrinus, Gilbert wrote that, "magnetic bodies seek formal unity."[188] Thus a dissected loadstone not only tends to come back together, as in the unordered coacervation of electric attraction, but to restore the organization it had before dissection.[189] Accordingly, opposite poles appear on the interfaces of the sections, not "from an opposition" but from "a concordance and a conformance."[190] This ensures that when the parts are joined together again, they have the same orientation as before. Gilbert compared this power of restoring the original loadstone with that of a plant's vital power under the process of cutting and grafting; the plant can be revived only when the parts are in a certain order.[191]

[188] M: p. 186.

[189] M: pp. 185-188. See also footnote 31.

[190] M: pp. 186, 193.

[191] M: pp. 199-200.

A hypothesis similar to that used to explain electric attraction lay beneath the explanation of magnetic coition: that bodies brought into contact will move together. In electric attraction, the contact is material and due to the "spiritus" from the electric body; in magnetic coition, it is formal and depends on the action of a primary form that spreads from a magnetized body to its limit of effusion, the "orbis virtutis." If iron is inside the "orbis virtutis," the two bodies "enter into alliance and are one and the same"[192] for within it "they have absolute continuity, and are joined by reason of their accordance, albeit the bodies themselves be separated."[193]

Gilbert's treatment of coition can be a.n.a.lyzed into the same two steps as can electric attraction. First occurs a contact, which in this case is not physical but formal, and from this initial formal contact follows movement to a more complete unity. Both the contact and the movement to unity are described on the same level of abstraction, instead of on two different levels as in electric attraction. Again one does not find any clear-cut concept of force as a push or pull,[194] but instead, a motion to a formal unity, this time a cooperative motion. The parts of a magnetic body are in greater harmony when they are a.s.sembled in a certain pattern and so they move accordingly.

[192] M. p. 111.

[193] M: p. 112.

[194] See, however, M: pp. 112, 113.

As to the nature of the primary form itself, Gilbert agreed with Thales that it is like a soul,[195] "for the power of self-movement seems to betoken a soul."[196] With Galen and St. Thomas he placed the form of the loadstone superior to that of inanimate matter.[197] In a sense, Gilbert even made it superior to organic matter, for it is incapable of error.[198] Like the soul, the primary form cannot be fragmented; when a loadstone is divided, one does not separate the poles but each part acquires its own poles and an equator.

[195] M: pp. 109, 312.

[196] M: p. 109.

[197] M: p. 309.

[198] M: pp. 311-312.

Like the soul, fire does not destroy it.[199] Like the soul of astral bodies, and of the earth itself, it produces complex but regular motions; the motion of two loadstones on water offers such an example.[200] Like the soul of a newborn child, whose nature depends on the configuration of the heavens, the properties in the newly awakened iron depend upon its position in the "orbis virtutis."[201]

Whence Gilbert declared:

... the earth's magnetic force and the animate form of the globes, that are without senses, but without error ... exert an unending action, quick, definite, constant, directive, motive, imperant, harmonious through the whole ma.s.s of matter; thereby are the generation and the ultimate decay of all things on the superficies propagated.[202] The bodies of the globes ... to the end that they might be in themselves, and in their nature endure, had need of souls to be conjoined to them, for else there were neither life, nor prime act, nor movement, nor unition, nor order, nor coherence, nor _conactus_, nor _sympathia_, nor any generation nor alteration of seasons, and no propagation; but all were in confusion....[203] Wherefore, not with reason, Thales ...

declares the loadstone to be animate, a part of the animate mother earth and her beloved offspring.[204]

Gilbert ended book 5 of his treatise on the magnet with a persuasive plea for his magnetic philosophy of the cosmos, yet his conceptual scheme was not too successful an induction in the eyes of his contemporaries. In particular the man from whom the Royal Society took the inspiration for their motto, "Nullius in verba," did not value his magnetic philosophy very highly. Whether Francis Bacon was alluding to Gilbert when he expounded his parable of the spider and the ant[205]

is not explicit, but he certainly had him in mind when he wrote of the Idols of the Cave and the Idols of the Theater.[206]

[199] M: p. 108.

[200] M: p. 110.

[201] M: p. 216.

[202] M: p. 311.

[203] M: pp. 310, 311.