CAISSON _des bombes_, is a tub which is filled with loaded shells and buried even with the ground. It is inclined a little on one side, and by means of a quantity of powder which is scattered on the top and connected with the bottom by a saucisson, an explosion may be effected so as to throw the shells into the open air towards any given point. _Caissons_ which are buried in the glacis produce great effect. CAISSON _pour les vivres_, _Fr._ a large chest whose lid rises in the centre somewhat like the capital of a pillar, in order that the rain may run off. The following dimensions were adopted to contain eight hundred rations at least. The caisson or chest must be 8 French feet 4 inches long at least, 3 feet 4 inches high from the bottom to the extreme point of the lid, or chapiter, 2 feet 6 inches from its square sides to the bottom, 2 feet 5 inches broad at the bottom, outside, 2 feet 9 inches broad at top, and the cover or lid must be 5 feet 4 inches long. Poplar trees afford the best wood for the construction of caissons, because that species has a close grain, and is calculated to keep out rain. CALATRAVA, a Spanish military order so called from a Fort of that name. The knights of Calatrava bear a cross; gules, fleur-de-lissed with green, &c. CALCULATION, in military affairs, is the art of computing the amplitudes of shells, time of flight, projectile curve, velocity of shots, charges of mines, &c. together with the necessary tables for practice. CALIBER, in gunnery, signifies the same as the bore or opening: and the diameter of the bore is called the diameter of its caliber. This expression regards all pieces of artillery.