In front, this bent end is bolted to the flange of the front strengthening plate. In rear the bent portion is longer, and terminated at top by another bend, which serves as a point of application for a lever on a wheel, when running to and from battery. The trunnion-plates fit over the top ends of the strengthening plates, which meet around the bed, and are fastened to the flanges of the latter by movable bolts and nuts. The _cheeks_ are joined together by transoms made of bar-iron. _They_ are parallel to each other, and in order that the _base ring_ on the gun may not interfere with giving it the full elevation by striking against them, it is proposed to dispense with the _base ring_ in sea-coast and garrison pieces, and to retain the preponderance by reducing the swell of the muzzle. The front of the carriage is mounted on an axle-tree, with truck wheels similar to the wooden casemate carriages. 70. Describe the chassis. It consists of two rails of wrought iron, the cross section of each being in form of a T, the flat surface on top being for the reception of the shoe-rail of the gun-carriage. The rails are parallel to each other, and connected by iron transoms and braces. The chassis is supported on traverse-wheels. A prop is placed under the middle transom of the chassis, to provide against sagging. 71. What carriage is used for conveying ammunition for a field battery? The CAISSON. [Sidenote: 143]] 72. Describe it. A four-wheel carriage, consisting of two parts, one of which is a limber similar to that of the gun carriage, and connected in a similar way by a wooden stock and lunette. On the axle-body of the rear part, and parallel to the stock, are placed three rails upon which are fastened two ammunition boxes, one behind the other, and similar to the one on the limber; so that the caisson has three ammunition boxes which will seat nine cannoneers. The interior compartments of the ammunition boxes vary according to the nature of the ammunition with which they are loaded. In rear of the last box is placed a spare wheel, axle of iron, with a chain and toggle at the end of it. On the rear end of the middle rail is placed a carriage hook, similar to a pintle-hook, to which the lunette of a gun carriage whose limber has become disabled, may be attached, and the gun carried off the field. The caisson has the same turning capacity and mobility as the gun carriage, so that it can follow the piece in all its manœuvres, if necessary. It also carries a spare wheel, spare pole, &c. 73. What provision is made for repairing the carriages of a field battery when required? Every field battery is provided with a FORGE. 74. Describe this wagon.