the Channel.” This was written before the submarine cable was thought of, and he once informed me that actual observation upon that cable had been found to be in accordance with his theoretic deduction. [Illustration: FIG. 11.] It may here be apposite to discuss a fundamental question raised in these researches. In Faraday’s mind there arose the conviction of a connection between the induction of currents by magnets and the magnetic lines which invisibly fill all the space in the neighbourhood of the magnet. That relation he discovered and announced in the following terms:-- [Sidenote: THE LAW OF INDUCTION.] “The relation which holds between the magnetic pole, the moving wire or metal, and the direction of the current evolved--_i.e._ _the law_ which governs the evolution of electricity by magneto-electric induction, is very simple, though rather difficult to express. If in Fig. 11, P N represent a horizontal wire passing by a marked [_i.e._ ‘north-seeking’] magnetic pole, so that the direction of its motion shall coincide with the curved line proceeding from below upwards; or if its motion parallel to itself be in a line tangential to the curved line, but in the general direction of the arrows; or if it pass the pole in other directions, but so as to cut the magnetic curves[39] in the same general direction, or on the same side as they would be cut by the wire if moving along the dotted curved line; then the current of electricity in the wire is from P to N. If it be carried in the reverse direction, the electric current will be from N to P. Or if the wire be in the vertical position, figured P´ N´, and it be carried in similar directions, coinciding with the dotted horizontal curve so far as to cut the magnetic curves on the same side with it, the current will be from P´ to N´.” [Sidenote: CUTTING THE MAGNETIC LINES.]