ALLIANCE, in a military sense, signifies a treaty entered into by sovereign states, for their mutual safety and defence. In this sense alliances may be divided into such as are offensive, where the contracting parties oblige themselves jointly to attack some other power; and into such as are defensive, whereby the contracting powers bind themselves to stand by, and defend one another, in case of being attacked by any other power. Alliances are variously distinguished, according to their object, the parties in them, &c. Hence we read of equal, unequal, triple, quadruple, grand, offensive, defensive _alliances_, &c. ALLODIAL, independent; not feudal. The Allodii of the Romans were bodies of men embodied on any emergency, in a manner similar to our volunteer associations. ALLOGNE, the cordage used with floating bridges, by which they are guided from one side of a river to the other. ALLONGE, _Fr._ a pass or thrust with a rapier or small sword; also a long rein used in the exercising of horses. ALLOY, is the mixture of metals that enter into the composition of the metal proper for cannon and mortars. ALLY, in a military sense, implies any nation united to another--under a treaty, either offensive or defensive, or both. ALMADIE, a kind of military canoe, or small vessel, about 24 feet long, made of the bark of a tree, and used by the negroes of Africa. ALMADIE, is also the name of a long-boat used at Calcutta, often 80 to 100 feet long, and generally six or seven broad, they row from ten to thirty oars. ALTIMETRY, the taking or measuring altitude, or heights. ALTITUDE, height, or distance from the ground, measured upwards, and may be both accessible, and inaccessible. ALTITUDE _of a figure_, is the distance of its vertex from its base, or the length of a perpendicular let fall from the vertex to the base. See _American Mil. Lib._ Art. FIELD FORTIFICATION. ALTITUDE _of a shot or shell_, is the perpendicular height of the vertex above the horizon. See GUNNERY and PROJECTILES. ALTITUDE, _in optics_, is usually considered as the angle subtended between a line drawn through the eye, parallel to the horizon, and a visual ray emitted from an object to the eye. ALTITUDE, _in cosmography_, is the perpendicular height of an object, or its distance from the horizon upwards. ALTITUDES are divided into _accessible_ and _inaccessible_. _Accessible_ ALTITUDE _of an object_, is that whose base you can have access to, i. e. measure the nearest distance between your station and the foot of the object on the ground. _Inaccessible_ ALTITUDE _of an object_, is that when the foot or bottom of it cannot be approached, by reason of some impediment; such as water, or the like. The instruments chiefly used in measuring of _altitudes_, are the quadrant, theodolite, geometric quadrant, cross, or line of shadows, &c. ALTITUDE _of the eye_, in perspective, is a right line let fall from the eye, perpendicular to the geometrical plane.