MOBILE CARRIAGES. Carriages for field guns and howitzers and for siege guns and howitzers differ in detail and size, while the same in prin ciple. Siege carriages are generally high enough to fire over a five-foot or six-foot parapet. and much heavier than field carriages because of the greater energy of recoil and because they in not require so great mobility. They weigh about 5.300 pounds, with limber, while field carriages are limited to 4000 pounds, Ihnber. and three cannoneers and 700 pounds or more of ammunition.
Mortars for field and siege use are generally fired from immobile carriages and transported on wagons. Siege carriages generally require plat forms to which they are attached to assist in con trol of recoil.
A carriage, field or siege, must have two wheels with axletree and a trail giving a third point of support on the ground when tiring. The trail also connects with the limber for traveling. Until recently trunnion beds were formed in the front ends of the sides or flasks of the trail and the gun had no recoil relative to the carriage, which ran back on the ground until the energy was absorbed by friction of brake and resistance of ground.
Up to the United States Civil War all mobile carriages were made mostly of wood, although with metal bracings, axletrees. and other parts. At this time iron was recognized as the (-wiling material and was soon adopted. Since 1880 all carriage's have been made of iron or steel. now al mo-t entirely of the latter. Earlier iron ear rias. ha 1 flasks i f plates and angles. The Buffington etrrivige (United States), of steel pressed with bulb has been iu use from Is-fl to the present tin e.
braking and helical springs for returning the gun to the firing position. The carriage is so stable that cannoneers sit on the trail, aiming, etc.. during firing. This is the result of careful calculation of the forces in equilibrium during To enable carriages to stand guns of increased power without undue recoil, brakes were de vised, -et by recoil, and released 1w running for ward. Later, spades were introduced. When power increased so a- to work the spade too hard, a short recoil was given the piece upon the carriage. this being applied to siege, and later to field carriages. This enabled the spade to hold. hut resulted in the wheels of the carriage jumping from six to twelve inches from the ground with derangement of aim and loss of rapidity of fire. In the last few years rapidity 14111 much discussed and sought for in ideal rapid-tire field guns to fire about twenty aimed shot= 1.er minute. This result has been nearly attained in a number of recent constructions.
Such a system a carriage unmoved by discharge (necessitating about 45-ineh recoil of the piece upon it, with automatic return to fir ing position—quiek. lint without shoek—and a
spade to take sure hold of earth) ; also means for traVel?illg the gun on the earriage and for ele Nating by cranks within reach of one man at the sights. The Ehrhardt carriage (adopted by Eng land I has the gun on a slide which i= hydraulic brake or cylinder surrounded by a helical Spring. Its trail can be extended for stability. Krupp uses a similar arrangement for recoil springs. The United States conducted in 1902 experiments for of a type; testing two carriages made by the Bethlehem Steel Com pany, one by the Coekerill Company. one by the Vicker--)laxim Company. and several others. in cluding two Ordnance Department designs by Captain Wheeler, one with S-inch and the other with 4f-inch recoil, have been sulunitted. In the latter the gun recoils through a bronze cradle which holds two cylinders containing oil for discharge. To prevent jump, the moment of the pull on the piston rod about the spade must not exceed that of the weights about the same point. The guns selected embraced the best points of the Ehrhardt gun, with the improvements and original features of the United States Ordnance Department's models. All parts must he re duced to minimum weight needed for strength. to keep within the limit of weight allowed for draught. See FIELD ARTILLERY.
BIBLIOGRAPHY. Of the many publications on Bibliography. Of the many publications on ordnance matters. the reader is referred to the following few as comprehensive and most accessi ble, viz.: Bruff, Ordnance and Gunnery (New York, ItifHi) ; Ingersoll, Text-book of Ordnance and Gunnery (United States Naval Academy, ItiST. used in the United States ::\lilitary and Naval academies) ; Annual Reports of the Chiefs of Ordnance, United 81atcs Army and ary ( Washingt on ) : Treatise on Military Carriages, English War Office (London. ISIM) ; Treatise on Serrice Ordnance, English War 011ice (ib., 1591). Also numerous official pamphlets and books of instruction, issued by the United States and foreign war departments, advertising, mat ter of private firms, especially Armstrong and and the numerous technic-al period icals, Mitt heiluagen fiber Gegenstande des Aral lerie- and Genie-Wesens (Vienna, bimonthly) Militiir-Worhenblatt (Berlin, semi-weekly) ; Re vue (Paris, monthly); Berne Mili taire (Lausanne. monthly): Revue de lielge bimonthly) ; Journal of the roiled States Artillery (Fort Monroe), etc. See ARTILLERY: GUNS. NAVAL: GuxPownER: Ex I'LoSIVES: :MACHINE GUN; PROJECTILES; RAPID FIRE GUNS; SIEGE GUN; COAST ARTILLERY; etc.