_A_ hollow brass casting. _M_ water-cap. _G_ spherical rubber packing. _O_, _O_ feet for attaching circuit-closer to service torpedo, Pattern D. _B_ inner brass plunger. _C_ spiral spring. _N_ ebonite collar. _I_, _I_ binding-posts. _E_ contact-springs. _t_ screw-cover. _s_, _s_ contact arms. _K_ outer plunger. _l_ safety-pin. _V_ rubber diaphragm. _k_ friction-plate. [Illustration: PLATE III.] [Illustration] =PLATE IV.= SECONDARY SPARS. FIG. 1, SHIP‘S.—PATTERN A. _A_ main spar. _B_ secondary spar. _a_, _a_ spar-bands. _b_ key-way. _c_ key. _l_ hole for torpedo-pin. _m_ torpedo-pin. [Illustration: PLATE IV.] FIG. 2, BOAT‘S.—PATTERN A. _R_ main spar. _H_ secondary spar. _i_ butt. _k_ cap. _g_ toggle. _l_ hole for torpedo-pin. _m_ torpedo-pin. [Illustration] =PLATE V.= CONTACT SPAR LEADING-WIRES.—PATTERN B. _B_ battery. _C_ contact torpedo. _x_ circuit-closer. _D_ contact spar leading-wires. _H_ hand-firing key. _S_ safety-break. [Illustration: PLATE V.] =PLATE VI.= SPAR-TORPEDO BOAT-FITTINGS.—PATTERN B. _S_ heel-rest. _H_ swivel-crutch. _R_ cross-beam. _D_ ” bearing, riveted to cross-beam and bolted through rail. _E_ elevating-arm. _m_ plate washer. _n_ nut on end of securing rod. _G_ guide-ring. _K_ gear on elevating-arm. _M_ worm. _N_ worm-shaft, forward length. _O_ ” ” after ” _X_ hook-coupling. _P_ elevating-wheel. _Q_ clutch. _L_ detaching-lever. _T_ torpedo. _A_ main spar. _B_ secondary spar. [Illustration: PLATE VI.] [Illustration] =PLATE VII.= JUNCTION OF TUBES FORMING BOAT‘S SPAR.—PATTERN A. _A_ large tube. _B_ small tube. _c_, _c_ rings. _d_ shoulder. _e_ screw-holes. _f_ feather. _g_ score. [Illustration: PLATE VII.] [Illustration] =PLATE VIII.= FIG. 1, DETONATOR. _A_ copper case. _B_ plug. _c_, _c_ detonator-legs. _D_ bridge. _F_ gun-cotton priming. _H_ fulminate of mercury. FIG. 2, DETONATOR BLOCK. _A_ block. _B_ ” cover. _C_, _C_ detonators. _D_, _D_ tin box. [Illustration: PLATE VIII. _Fig. 1._] [Illustration: _Fig. 2._] =PLATE IX.= FIG. 1, PERMANENT WIRES.