Gilbert of Colchester, father of electrical science : a reprint of the chapter on electrics from De magnete, lib. 2 / with notes by Silvanus P. Thompson.

  • William Gilbert
Date:
1903
Catalogue details

Licence: In copyright

Credit: Gilbert of Colchester, father of electrical science : a reprint of the chapter on electrics from De magnete, lib. 2 / with notes by Silvanus P. Thompson. Source: Wellcome Collection.

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    towards all eledtricks all things move except fuch as are aflame or are too highly rarefied, as air, which is the uni- verfal effluvium of this globe and of the world. Vegetable fubftances draw moifture by which their fhoots are re- joiced and grow; from analogy with that, however, Hip- pocrates, in his De Natura Hominis, Book I., wrongly concluded that the purging of morbid humour took place by the fpecifick force of the drug. Concerning the adtion and potency of purgatives we fhall fpeak elfe- where. Wrongly alfo is attradlion inferred in other effects; as in the cafe of a flagon full of water, when buried in a heap of wheat, although well ftoppered, the moifture is drawn out; fince this moifture is rather re- folved into vapour by the emanation of the fermenting wheat, and the wheat imbibes the freed vapour. Nor do elephant’s tufks attract moifture, but drive it into vapour or abforb it. Thus then very many things are faid to attradl, the reafons for whofe energy muft be fought from other caufes. Amber in a fairly large mafs * allures, if it is polifhed; in a fmaller mafs or lefs pure it feems not to attradf without fridtion. But very many eledfricks (as precious ftones and fome other fubftances) do not attradl at all unlefs rubbed. On the other hand many gems, as well as other bodies, are polifhed, yet do not allure, and by no amount of fridtion are they aroufed; thus the emerald, agate, carnelian, pearls, jafper, chalce- * dony, alabafter, porphyry, coral, the marbles, touch- ftone,flint, bloodftone, emery, do not acquire any power; nor do bones, or ivory, or the hardeft woods, as ebony, nor do cedar, juniper, or cyprefs; nor do metals, filver, gold, brafs, iron, nor any loadftone, though many of them are finely polifhed and fhine. But on the other hand there are fome other poliftied fubftances of which we have fpoken before, toward which, when they have been rubbed, bodies incline. This we fhall under- ftand only when we have more clofely looked into the prime origin of bodies. It is plain to all, and all admit, that the mafs of the earth, or rather the ftrudture and cruft of the earth, confifts of a twofold material, namely, of fluid and humid matter, and of material of more con- *3
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