. The London, Edinburgh and Dublin philosophical magazine and journal of science. dielectrics whichhave the effect of closing the currents. 12. Now, if it be true, as Maxwell teaches, that in nature, orwithin the range of our experiments, all currents are closed,there can be no necessity for devising elaborate laws of have only to assume for each pair of elements the potential V=jdi —-— ds dsj and we cannot fail to obtain results in accordance with expe-riment, and, in fact, exactly the same results as are obtainedfrom any of the more complicated laws above stated ; so that,on this vi
. The London, Edinburgh and Dublin philosophical magazine and journal of science. dielectrics whichhave the effect of closing the currents. 12. Now, if it be true, as Maxwell teaches, that in nature, orwithin the range of our experiments, all currents are closed,there can be no necessity for devising elaborate laws of have only to assume for each pair of elements the potential V=jdi —-— ds dsj and we cannot fail to obtain results in accordance with expe-riment, and, in fact, exactly the same results as are obtainedfrom any of the more complicated laws above stated ; so that,on this view, no experiment could furnish any reason foraccepting one law rather than the other. It appears to us, then,that if Maxwells theory, that all currents are closed, be ac-cepted, the law that, for each pair of elementary currents, -r7 .., cos 6 , V=ixi% dsds r ought to find provisional acceptance also. 13. But as Maxwells theory is not accepted universally,we proceed to examine some of the experimental evidence onwhich the doctrine is based, that a closed circuit exerts a. 458 Messrs. Watson and Burbury on the Laio normal force only on every elementary current (canons VI.), this being the only experimental fact inconsistentwith the simple law. The experiments quoted in support of this are the follow-ing:— (1) A current in a circularconductor, movable about an axisthrough its centre perpendicularto its plane, remains unmoved inthe field of another closed cir-cuit. (2) A current in a rectangularconductor A B C D, movableabout one side A D, which coin-cides with a line through thecentre, 0, of a circular conduc-tor, the line A D being perpen-dicular to the plane of the latter,remains immovable when a cur-rent passes through the circularconductor. (3) (Maxwell, vol. ii. p. 149, cited above.) A circularconductor, C D, movable about its centre in its ownplane, passes through two mercury-cups fixed at Aand B, at which a current enters and leaves theconductor respectively
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