_A_, _A_ electric switches (on bulwarks under bridge). _B_, _B_ forward terminals. _C_, _C_ after ” _D_, _D_ forward permanent wires. _E_, _E_ after ” ” _G_, _G_ permanent wires leading from bridge to lower binding-posts of electric switches. _H_, _H_ wires leading from bridge to common-return terminals, below switches. _K_ terminal on bridge for wires _H_, _H_. _L_, _L_ ” ” ” ” ” _G_, _G_. _X_ firing-battery connected to terminals on bridge. FIG. 2, CONNECTIONS WITH FIRING-KEY OF “A” MACHINE. _B_, _B_ terminals of firing-key. _T_, _T_ ” ” ” Key “_T_” test key. Key “_F_” firing key. _M_, _M_ wires to terminals _L_, _L_ on bridge. (Fig. 1.) _N_ wire to terminal _K_ on bridge (common return). (Fig. 1.) _O_, _O_ machine-connecting wires. FIG. 3, CONNECTIONS WITH FIRING-BATTERY. _B_, _B_ terminals of battery. _M_, _M_ wires to terminals _L_, _L_ on bridge. (Fig. 1.) _N_ wire to terminal _K_ on bridge (common return). (Fig. 1.) _H_ hand-firing key. [Illustration: PLATE IX. _Fig. 2._] [Illustration: _Fig. 3._] [Illustration: _Fig. 1._] =PLATE X.= FIG. 1, ELECTRIC SWITCH. _A_ permanent wire to forward torpedo. _B_ ” ” ” after ” _C_, _C_ ” ” common return. _D_ wire to battery or firing-key of machine. _E_ commutator of switch. [Illustration: PLATE X. _Fig. 1._] FIG. 2, TERMINAL. _H_ binding-screw. _I_ permanent wire. _w_ wire temporarily connected. [Illustration: _Fig. 2._] =PLATE XI.= HEEL FITTINGS FOR SHIP‘S SPAR. _a_ ship‘s spar. _b_ thrust-plate (30″ diameter). _c_ eye-bolt through thrust-plate and ship‘s side. _d_ heel-bolt. [Illustration: PLATE XI. _Fig. 2._] [Illustration: _Fig. 1._] =PLATE XII.= SHIP’S SPAR FITTINGS. _a_ ship’s spar. _b_ topping lift. _c_ forward guy. _d_ after ” _e_ span for topping lift (16′ long). _f_ ” ” forward guy (16′ long). _x_, _x_, _x_, _x_ bands on spar (5′ apart). [Illustration: PLATE XII.] =PLATE XIII.= BATTERY CELL. _a_ okonite jar. _b_, _b_ zinc cylinder. _c_ platinum plate. _d_ muslin bag filled with crushed carbon. _e_ ebonite disc. _f_ ” plug. _g_ sal-ammoniac solution. _h_ positive terminal. _i_ negative ” _k_ rubber cover. _r_ rubber ring. [Illustration: PLATE XIII.] =PLATE XIV.= BATTERY TESTER.