73. Steam tube. 74. } } Holes in steam tube. 75. } 76. Slide valve. 77. Steam escape hole. 78. Milled heads of oil brushes. 79. Oil brush. 80. Sight, tangent. 81. Sight, fore. 82. Shutter. 83. Shutter spring. 84. Shutter catch. 85. Notch for shutter catch. 86. Screwed plug for emptying. 87. Slides, right and left. 88. Gib spring cover. 89. Check lever collar. 90. Cover lock spring. 91. Safety catch spring. 92. Tangent sight spring. 93. Bottom lever feed block. 94. Trunnions of barrel. 95. Extractor stop. 96. Firing lever spring. 97. Shutter pivot screw. [Illustration: Plate I. GUN MAXIM, ·303 INCH. SIDE ELEVATION. ] [Illustration: Plate II. GUN MAXIM ·303 INCH. PLAN WITH COVER REMOVED. ] MOUNTING, TRIPOD, ·303-in. MAXIM GUN, MARK IV. The mounting consists of a crosshead (_a_), elevating gear (_b_), and socket (_c_), mounted on three legs. It is constructed to give 13 degrees elevation and 25 degrees depression at heights varying from 14½-in. to 30-in. from the axis of the gun to the ground. By arranging the position of the rear and front legs respectively, elevation may be given up to about 43 degrees and depression to 55 degrees. An all-round traverse can be obtained. The crosshead (_a_), to which the gun is pivoted, is formed with a pivot to fit into the socket (_c_) and an arm (_d_) which carries the elevating gear (_b_). The elevating gear, which is actuated by a hand wheel (_v_), consists of an inner and outer screw (right and left-handed) and a nut working within a tumbler (_g_). The tumbler is split and provided with a jamming bolt (_h_), by which the wear may be taken up. The inner part of the screw is attached to the crosshead by a chain. Chains also, for future manufacture and replacement, will secure the joint pins to the mounting. The socket (_c_) is bored to receive the crosshead and is provided with three lugs (_n_), to which the legs are hinged; a jamming block and screw with handle (_f_) is attached to the front to secure the crosshead in any desired angle of traverse; the block works in a recess in the upper portion of the crosshead and prevents it from rising. Both faces of the rear lug and one face of each front lug are fitted with clutch plates having radial serrations to correspond with similar serrations on the faces of the leg joints. Joint studs with disc spring and jamming handle (_s_) are [Illustration: Plate III. MOUNTING TRIPOD ·303 INCH, MAXIM GUN MARK. SCALE = ⅛ SIDE ELEVATION. ] _A_ _Crosshead_ _B_ _Elevating gear_ _C_ _Socket_ _D_ _Arm, crosshead_ _F_ _Screw, clamp checking traverse_ _G_ _Tumbler, elevating gear_ _H_ _Bolt, jamming elevating gear_ _J_ _Front legs_ _K_ _Rear leg_ _M_ _Shoes_ _N_ _Socket lugs_