[134] PAGE 52, LINE 38. Page 52, line 41. _duæ propositæ sunt causæ ... materia & forma._--Gilbert had imbibed the schoolmen's ideas as to the relations of matter and form. He had discovered and noted that in the magnetic attractions there was always a verticity, and that in the electrical attractions the rubbed electrical body had no verticity. To account for these differences he drew the inference that since (as he had satisfied himself) the magnetic actions were due to _form_, that is to say to something immaterial--to an "imponderable" as in the subsequent age it was called--the electrical actions must necessarily be due to _matter_. He therefore put forward his idea that a substance to be an electric must necessarily consist of a concreted humour which is partially resolved into an effluvium by attrition. His discoveries that electric actions would not pass through flame, whilst magnetic actions would, and that electric actions could be screened off by interposing the thinnest layer of fabric such as sarcenet, whilst magnetic actions would penetrate thick slabs of every material except iron only, doubtless confirmed him in attributing the electric forces to the presence of these effluvia. See also p. 65. There arose a fashion, which lasted over a century, for ascribing to "humours," or "fluids," or "effluvia," physical effects which could not otherwise be accounted for. Boyle's tracts of the years 1673 and 1674 on "effluviums," their "determinate nature," their "strange subtilty," and their "great efficacy," are examples. [135] PAGE 53, LINE 9. Page 53, line 11. _Magnes vero...._--This passage from line 9 to line 24 states very clearly the differences to be observed between the magnetical and the electrical attractions. [136] PAGE 53, LINE 36. Page 53, line 41. _succino calefacto._--Ed. 1633 reads _succinum_ in error. [137] PAGE 54, LINE 9. Page 54, line 11. _Plutarchus ... in quæstionibus Platonicis._--The following Latin version of the paragraph in _Quæstio sexta_ is taken from the bilingual edition publisht at Venice in 1552, p. 17 _verso_, liber vii., cap. 7 (or, _Quæstio Septima_ in Ed. Didot, p. 1230). "Electrum uero quæ apposita sunt, nequaquàm trahit, quem admodum nec lapis ille, qui sideritis nuncupatur, nec quicqu[=a] à seipso ad ea quæ in propinquo sunt, extrinsecus assilit. Verum lapis magnes effluxiones quasdam tum graves, tum etiam spiritales emittit, quibus aer continuatus & iunctus repellitur. Is deinceps alium sibi proximum impellit, qui in orbem circum actus, atque ad inanem locum rediens, ui ferrum fecum rapit & trahit. At Electrum uim quandam flammæ similem & spiritalem continet, quam quidem {44} tritu summæ partis, quo aperiuntur meatus, foras eijcit. Nam leuissima corpuscula & aridissima quæ propè sunt, sua tenuitate atque imbecillitate ad seipsum ducit & rapit, cum non sit adeo ualens, nec tantum habeat ponderis & momenti ad expellendam aeris copiam, ut maiora corpora more Magnetis superare possit & uincere."