63. Where is the _flank-casemate_ carriage employed? It is especially adapted to the mounting of the 24-pdr. iron howitzer in the flanks of casemate batteries, for defending the ditch; and both the gun-carriage and chassis are narrower and lighter than the other casemate carriages. 64. Describe the gun-carriage. The cheeks are made of white oak, and connected by two iron transoms, the front one projecting below the cheeks, and resting on the chassis with a projection on the bottom of it, fitting in between the rails. The bottom of the trail has the same slope as the upper surface of the chassis on which it rests; so that when its eccentric-roller is out of gear, the rear parts of the cheeks fit the rails. The remaining portion of the bottom of the cheek makes an angle with the rail, and has in front a fork, and a roller which runs on the rail of the chassis when the eccentric is in gear. Each cheek has on the side a trail-handle and a manœuvring-ring. In rear of the rear transom is placed an eccentric-roller, having a projection in the middle of it, just large enough to fit in between the rails of the chassis, and guide the trail of the carriage. When this _roller_ is in gear, the weight of the trail rests upon _it_, while that of the front part of the carriage is thrown upon the front rollers, and the piece is then easily run in and out of battery; but the roller being out of gear, as when the piece is about to be fired, the weight rests upon the rear part of the cheeks and the front transom, and friction is brought into play to diminish the recoil. Cap-squares are used with this carriage. [Sidenote: 141]] 65. Describe the chassis. It consists simply of two rails 3 in. apart, and joined by four transoms and assembling-bolts. Hurters on the rear ends of the rails only are used, as the bottom projection of the front transom prevents the carriage running too far into battery. The front end of the chassis rests on the sole of the embrasure. The end is provided with a pintle-plate and a strap of half-in. iron through which the pintle passes to the masonry beneath. The rear of the chassis is supported by an iron prop, the lower end of which is attached to two traverse-wheels. 66. What kind of carriages have been recommended for use in garrisons, instead of wooden ones? Wrought iron carriages, for all except the flank-casemate; all made in a similar manner, differing only in weight and dimensions. 67. What is the objection to cast-iron? Its weight, and its great liability to splinter when struck by shot. 68. Of how many parts is this wrought iron carriage composed? Like the wooden ones, of a gun-carriage and chassis. 69. Describe the gun-carriage. It consists of two cheeks of thick sheet-iron, each one of which is strengthened by three flanged iron plates bolted to the cheeks. Along the bottom of each cheek, an iron shoe is fixed with the end bent upwards. [Sidenote: 142]]