It consists, besides the limber, of a frame-work on which is fixed the bellows, fire-place, &c. Behind the bellows is placed a coal-box, which has to be removed before the bellows can be put in position. In the limber box are placed the smith’s tools, horse-shoes, nails, and spare parts (iron) of carriages, harness, &c. [Sidenote: 144]] 75. Describe the _battery wagon_. It consists, besides the limber, of a long-bodied cart with a round top, which is connected with the limber in the same way as all other field carriages. The lid opens on hinges placed at the side; and in rear is fixed a movable forage rack for carrying long forage. One of these wagons accompanies each field-battery, for the purpose of transporting carriage-maker’s and saddler’s tools, spare parts of carriages, harness and equipments, and rough materials for replacing different parts. Both this and the forge are made of equal mobility with the other field carriages, in order to accompany them wherever they may be required to go. 76. How many kinds of wheels are employed for field carriages? Two: No. 1 for the 6-pdr. gun carriage, the caisson, the forge, the battery-wagon, and for the limbers of all field-carriages. No. 2 for the 24-pdr. howitzer and the 12-pdr. gun carriages. 77. In what respects are these wheels similar? They are of the same form and height, and they fit on the same axle-tree arm. The height is 57 inches, and each wheel is composed of 14 spokes and 7 fellies. 78. How do they differ? In the dimensions of their parts, and in strength and weight. 79. What is the weight of these wheels? No. 1, 180 lbs., No. 2, 196 lbs. 80. What are the weight and height of a wheel of siege-gun carriages and limbers? Weight 404 lbs., and height 60 inches. 81. What is the _portable forge_ designed for? Service in a mountainous country, where wheeled vehicles cannot travel, for the purpose of making repairs, not only for the artillery but for all other arms of service taken on such expeditions. [Sidenote: 145]] 82. What is the _mortar wagon_ designed for? The transportation of siege mortars and their beds, or of guns or large shot and shells. 83. Describe this wagon. The limber and wheels are the same as those of the siege-gun carriage. The body consists of a platform of rails and transoms, resting on an axle-tree, the two middle rails being prolonged to form the stock; six stakes or standards are inserted in sockets on the side of this platform and used to secure the load. The side-rails are prolonged to the rear, and furnish pivots for a roller placed immediately in rear of the platform. This roller has holes for the insertion of handspikes, and is used in loading the wagon; the guns, mortars, &c., being drawn up on the stock. A muzzle bolster on the stock near the limber, and a breech-hurter near the hind part of the wagon, are provided and used when long ordnance is transported on it. Mortars are usually carried mounted on their beds.