On the upper surface of the cheeks, near the rear ends, are placed two projecting bolts which, with the curve of the cheeks, form resting places for the trunnions, when the piece is in position for transportation. They are called _traveling trunnion-beds_. When the piece is in this position, its breech rests upon the bolster, which is a curved block of wood, bolted to the upper side of the stock. On each side of the trail, and perpendicular to it, a strong manœuvring bolt is placed to serve as places to apply the handspikes in manœuvering the carriage. 27. What is the object of the traveling trunnion-beds? For the purpose of distributing the load more equally over the carriage. 28. Mention the parts composing the limber. The fork, the splinter-bar, the hounds, the sweep-bar, the tongue, the pintle, the lashing-chain, the axle-tree (iron). The sweep-bar is of iron, and on it rests the trail, which by its weight keeps up the tongue. 29. Why is it unnecessary for siege-carriages to have the same degree of mobility and flexibility as field carriages? Because siege-carriages are, properly speaking, transportation wagons for use on roads, and never intended for manœuvring with troops. 30. How many horses does the transportation of siege-guns require? A 24-pdr. requires ten horses (five drivers); a 12 or 18-pdr., eight horses (four drivers). 31. What are stationary gun-carriages used for? To fire the piece from, and not to transport it except for short distances. [Sidenote: 130]] 32. For what service are these carriages used? For garrison and sea-coast pieces; although the siege-gun carriages just described may also be used in a fortification or garrison. Mortar-beds, to be described hereafter, are used either for siege or garrison service. 33. What are the chief requisites for garrison and sea-coast carriages? Strength, durability, and facility in serving the guns, as they are intended only for the works of a place, coast-batteries, and situations where they are permanently fixed. 34. Why should these carriages be required to possess great strength and durability? Unless made strong they would soon be shaken by the continued and rapid fire which the defense of a work may demand; and from their constant exposure to the weather they would soon decay if made of a very perishable material. 35. Is the weight of garrison carriages a matter of great importance? It is of less importance in this class of carriages than in any other, as they are seldom removed from their situations: their weight adds but little to the labor of running them up. 36. Mention the different _stationary_ carriages. The carriage from which a mortar is fired, called its _bed_; the barbette-carriage; the columbiad-carriage; the casemate-carriage; and that for the 24-pdr. iron howitzer, called the flank-casemate carriage. 37. How many kinds of _siege mortar_ beds have we? Four; the 8-in., 10-in., the stone, the coehorn. [Sidenote: 131]]