The tire is made of steel, ½ inch thick. The bolts, clips, linch-pins, and washers are made of metal. The large nut on outside of nave-box is splined to the box. The linch-washers have a stud which prevents their turning with the wheel. The inner extremities of the spokes are put together by a powerful radial pressure, which subjects them to a stress many times greater than they are likely to receive. =To Replace a Box and that Portion of the Hub Attached.=--Unscrew and remove front hub-band; take off hub-nuts, and drive out old box. Replace box, and screw on the front hub-band, replacing hub-nuts. =To Replace a Spoke.=--Remove tire and felloe on the injured spoke; take out only the bolt that passes through the injured spoke; saw off this spoke as close as possible to the hub and bore or dig out the spoke; drive in the duplicate spoke as far as possible, and arrange the tenon at the felloe so that the tire may press the spoke about one eighth of an inch farther into the hub, and after the tire is on put in the hub-bolt. THE 3.2-INCH FIELD-GUN CARRIAGE. NOMENCLATURE. =Wheel= (1) consisting of tire; felloes; spokes; nave-box; nave-box flanges; nave-bolts and nuts. Linch-pins (5); linch-washers (5); axle (6); shoulder-washers (7); brake-eyes and straps (8); axle-plates (9); flasks (10); upper front transom (11); lower front transom (12); middle transom (13); trail-box transoms (14); rear transom (15); lunette (16); lunette-plate (16); trail-plate (16); trail-handles (17); cap-squares (18); chin-bolt (19); eye-bolt (20); eye-bolt key (20); eye-bolt key-chain (20); trail-box (21); trail-box lid (21); trail-box lid-hasp (21); trail-box turnbuckle (21); sponge-bucket compartment (22); wheel-guard (23); handspike attachments, front and rear (24); handspike-socket (24); handspike socket-pin and key (24); handspike (24); handspike-clasps (24); long sponge-toggle and plate (25); short rammer and sponge attachment (26); short rammer and sponge-clasps (26); short rammer and sponge-clasp locking-catches (26); sponge-bucket toggle-hole (27). [Illustration: FIG. 57.] [Illustration: FIG. 58.] =Axle-seats= (3), consisting of seat-plate, guard-rail, guard-rail standard, guard-rail catch, guard-rail hinge-pin, guard-rail locking-latch. =Bow-brake= (2), Fig. 59, consisting of shoe-piece (_a_), bow-springs (4) (_b_), bow-spring nuts and bolts (4) (_c_), attachment-socket (_d_), and the attachment consisting of clevis (_e_), clevis-bolt and nut (_f_), locking-lever (_g_), locking-bolt and nut (_h_). [Illustration: FIG. 59.]