_A_, _A_, Cylinders. _B_, Main driving-axle. _C C_, Main connecting-rods. _D D_, Main crank-pins. _E_, _E_, Truck-wheels. _F_, Axle of trailing-wheels. _G_, Fire-box. _H_, _H_, _H_, Frames. _I_, _I_, Frame-clamps. _J_, _J_, Eccentrics. _K_, _K_, Rockers. _L L_, Links. _M_, Lifting-shaft. _N_, _N_, Lifting arms. _O O_, Reverse-lever. _P P_, Cylinder part of boiler. _Q_, Smoke-box. _R R_, Smoke stack or chimney. _S_, Pilot or cow-catcher. _T_, Head-light. _U_, Bell. _V_, Sand-box. _W_, Whistle. _X_, Dome. _Y Y_, Cab or house. _Z_, Back or trailing-wheel crank-pin. _A′_, Pump air-chamber. _B′_, _B′_, Main driving-wheels. _C′ C′ C′_, Supply-pipe. _D′_, Front platform. _E′_, Bumper timber. _F′ F′_, Back driving-wheels. _G′_, Coupling-pin. _H′_, Friction-plate. _I′_, Check-valve. _K′ K′_, Foot-board. _L′_, Lazy cock. _M′_, Mud drum. _N′ N′_, Driving springs. _P′_, Pump. _R′_, Drop-door or grate. _S′_, Steam gauge. _T′ T′_, Feed pipe. _U′ U′_, Forward eccentric rods. _V′ V′_, Backward eccentric rods. _X′_, Lifting-shaft spring. _Y′ Y′_, Dampers. _Z′_, Pushing-bar. _a a′_, Tubes. _b b_, Grate. _c_, Fire-box door. _d d_, Ash pan. _f f_, Exhaust-nozzles or blast-pipes. _g_, Safety-valve lever. _h h_, Cross-heads. _i i_, Running-board. _j_, Throttle-stem. _l_, Throttle-pipe. _m m_, Dry pipe. _n_, T-pipe. _o o_, Steam-pipe. _p_, Petticoat pipe. _q_, Smoke-box door. _r_, Piston. _s_, Spark-deflector or cone. _t t_, Wire-netting in stack. _u u u_, Boiler-lagging. _v v_, Truck-spring. _w w_, Sector or quadrant. _x_, Blow-off cock. _e k_, Reversing-rod. _y_, Truck centre-pin. _z_, Throttle-lever. _a′ a_, Tubes. _b′ b′_, Truck frame. _c′ c′_, Bed-plate. _d′_, Boiler brace. _e′ e′_, Sand pipe. _f′ f′_, Equalizing lever for driving wheels. _g′ g′_, Guide-bars or rods. _h′ h′_, Receptacle for sparks. _i′ i′_, Bell rope. _j′ j′_, Guide yoke. _k′_, Valve-stem. _l′ l′_, Truck equalizing lever. _m′ m′ m′_, Hand-rail. _n′_, Blow-off cock in mud drum. _o′_, Spring balance. _p′_, Pump plunger. _q′ q′_, Foot steps. _r′_, Brace to smoke-box and frame. _s′ s′_, Steam-chests. _t′ t′ t′_, Crown-bars. _u′_, Head-light lamp. _v′_, Main valve. _w′_, Blow-off cock handle. _x′_, Bell-crank for throttle-valve. _y′_, Piston-rod. _z′_, Draw-bar. PART VII. THE LOCOMOTIVE BOILER. QUESTION 82. _How does the quantity of steam generated in locomotive boilers in a given time compare with that generated in the boilers of stationary and marine engines?_ _Answer_. Locomotive engine boilers must produce much more steam in a given time, in proportion to their size, than is required of the boilers of any other class of engines, (excepting perhaps those of steam fire-engines,) because the space which locomotive boilers can occupy and also their weight is limited.