Part 4 (2/2)

The a.n.a.logy between electric attraction and fluids is a most concrete one, yet lying beneath this image is a hypothesis that is difficult to fix into a mechanical system based upon contact forces. This is the a.s.sumption that under the proper conditions bodies tend to move together in order to partic.i.p.ate in a more complete unity.[119] The steps in electrical attraction were described as occurring on two different levels of abstraction: first one has physical contact through an effluvium or ”spiritus” that connects the two objects physically. Then, as a result of this contact, the objects somehow sense[120] that a more intimate harmony is possible, and move accordingly. Gilbert called the motion that followed contact, attraction. However, this motion did not connote what we would call a force:[121] it did not correspond directly to a push or pull, but it followed from what one might term the apprehension of the possibility of a more complete partic.i.p.ation in a formal unity. The physical unity due to the ”spiritus” was the prelude to a formal organic unity, so that _humor_ is ”rerum omnium unitore.” Gilbert's position can be best seen in the following:[122]

Spiritus igitur egrediens ex corpora, quod ab humore aut succo aqueo concreverat, corpus attrahendum attingit, attactum attrahenti unitur; corpus peculiari effluviorum radio continguum, unum effecit ex duobus: unita confluunt in conjunctissimam convenientiam, quae attractio vulgo dicitur.

Quae unitas iuxta Pythagorae opinionem rerum omnium principium est, per cuius partic.i.p.ationem unaquaeque res una dicitur. Quoniam enim nullo actio a materia potest nisi per contactum, electrica haec non videntur tangere, sed ut necesse erat demitt.i.tur aliquid ab uno ad aliud, quod proxime tangat, et eius incitationis principium sit. Corpora omnia uniuntur & quasi ferruminantur quodammodo humore ...

Electrica vero effi via peculiaria, quae humoris fusi subtilissima sunt materia, corpuscula allectant. Aer (commune effluvium telluris) & partes disjunctis unit, & tellus mediante aere ad se revocat corpora; aliter quae in superioribus locis essent corpora, terram non ita avide appelerent.

Electrica effluvia ab aere multum differunt, & u aer telluris effluvium est, ita electrica suahabent effluvia & propria; peculiaribus effluviis suus cuique; est singularis ad unitatem ductus, motus ad principium, fontem, & corpus effluvia emittens.

A similar hypothesis will reappear in his explanation of magnetic attraction.

[119] M: pp. 91, 92: ”This unity is, according to Pythagoras, the principle, through partic.i.p.ation, in which a thing is said to be one” (see footnotes 30 and 122).

[120] ”Sense” is probably too strong a term, and yet the change following contact is difficult to describe in Gilbert's phraseology without some such subjective term. See Gilbert's argument on the soul and organs of a loadstone, M: pp. 309-313.

[121] M: pp. 112, 113.

[122] Gilbert, _De magnete_, London, 1600, bk. 2, ch. 2, pp.

56-57.

Following the tradition of the medieval schoolmen Gilbert started his examination of the nature of the loadstone by pointing out the different kinds of motion due to a magnet. The five kinds (other than up and down) are:[123]

(1) coitio (vulgo attractio, dicta) ad unitatem magneticam incitatio.

(2) directio in polos telluris, et telluris in mundi destinatos terminos verticitas et consistentia.

(3) variatio, a meridiano deflexio, quem motum nos depravatum dicimus.

(4) declinatio, infra horizontem poli magnetici descensus.

(5) motus circularis, seu revolutio.

Of the five he initially listed, three are not basic ones. Variation and declination he later explained as due to irregularities of the surface of the earth, while direction or verticity is the ordering motion that precedes coition.[124] This leaves only coition and revolution as the basic motions. How these followed from ”the congregant nature of the loadstone can be seen when the effusion of forms has been considered.”

Coition (he did not take up revolution at this point) differed from that due to other attractions. There are two and only two kinds of bodies that can attract: electric and magnetic.[125] Gilbert refined his position further by arguing that one does not even have magnetic attraction[126] but instead the mutual motion to union that he called coition.[127] In electric attraction, one has an action-pa.s.sion relation of cause and effect with an external agent and a pa.s.sive recipient; while in magnetic coition, both bodies act and are acted upon, and both move together.[128] Instead of an agent and a patient in coition,[129] one has ”conactus.” Coition, as the Latin origin of the term denoted, is always a concerted action. [130] This can be seen from the motions of two loadstones floating on water.[131] The mutual motion in coition was one of the reasons for Gilbert's rejection of the perpetual motion machine of Peregrinus.[132]

[123] _Ibid._, ch. 1, pp. 45-46.

[124] M: pp. 110, 314.

[125] M: pp. 82, 105, 170, 172, 217.

[126] M: p. 98.

[127] M: pp. 100, 112, 113, 143, 148. It need hardly be pointed out that coitus is not an impersonal term.

[128] M: p. 110.

<script>