[3] Clerk Maxwell employed German capitals to denote vector quantities. J. A. Fleming first recommended the use of blockletters as being more convenient both to printers and readers.
[4] The C.G.S. unit of current = 10 amperes.
[5] The principal theoretical investigations are summarized in Mascart and Joubert’s Electricity and Magnetism, i. 391-398 and ii. 646-657. The case of a long iron bar has been experimentally studied with great care by C. G. Lamb, Proc. Phys. Soc., 1899, 16, 509.
[6] Wied. Ann., 1884, 22, 411.
[7] See C. G. Lamb, loc. cit. p. 518.
[8] Hopkinson specified the retentiveness by the numerical value of the “residual induction” (= 4πI).
[9] For all except ferromagnetic substances the coefficient is sensibly equal to κ.
[10] See W. Thomson’s Reprint, §§ 615, 634-651.
[11] Ibid. §§ 646, 684.
[12] Faraday, Exp. Res. xxi.