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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-passion relation of cause and effect with an external agent and a passive 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. [129] M: p. 110. [130] M: pp. 109, 115, 148, 149, 155, 166, 174. [131] M: pp. 110, 155. [132] M: pp. 166, 332. See also footnote 84. Magnetic coition, unlike electric attraction, cannot be screened.[133] Hence it c
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