An accessible height or distance, in geometry, is that which may be measured by applying a rule, &c. to it: or rather, it is a height, the foot whereof may be approached, and from whence any distance may be measured on the ground. Heights, both accessible, and inaccessible, may be taken with a quadrant. See ALTITUDE; and the article on Field Fortifications in the _American Military Library_, Theorem 11, 12, 13, 14, 15. One of the objects of surveying, is the measuring both accessible and inaccessible distances. ACCLIVITY, in a military sense, is the steepness or slope of any work, inclined to the horizon, reckoned upwards. Some writers on fortification use acclivity as synonymous with _talus_; though _talus_ is commonly used to denote all manner of slopes, either in its ascendent or descendent state. ACCONTIUM, in ancient military writers, a kind of Grecian dart or javelin, somewhat resembling the Roman _pilum_. ACCOUTREMENTS, in a military sense, signify habits, equipage, or furniture, of a soldier, such as belts, pouches, cartridge-boxes, saddles, bridles, &c. Accoutrements should be made of stout leather, not of the spongy kind, which is always stretching, and difficult to clean. The belts are about 2¹⁄₄ inches broad, with two buckles to fix them to the pouch. Pouches are made of the stoutest blackened leather, especially the outside flaps, which are of such a substance as to turn the severest rain. Cartridge-boxes are made as light as possible, with holes in each, to hold cartridges. See CARTRIDGE. ACLIDES, in Roman antiquity, a kind of missive weapon, with a thong fixed to it, whereby it might be drawn back again. Most authors describe the _aclides_ as a sort of dart or javelin: but Scaliger makes it roundish or globular, with a wooden stem to poise it by. ACOLUTHI, in military antiquity, was a title in the Grecian empire, given to the captain or commander of the _varangi_, or body-guards, appointed for the security of the emperor’s palace. ACTIAN _games_ in antiquity, were games instituted, or at least restored, by Augustus, in memory of the famous victory, at Actium, over Mark Antony. ACTIAN _years_, in chronology, a series of years, commencing with the epocha of the battle of Actium, otherwise called the æra of Augustus. ACTION, in the military art, is an engagement between two armies, or any smaller body of troops, or between different bodies belonging thereto. The word is likewise used to signify some memorable act done by an officer, soldier, detachment or party. ACTIVITY, in a military sense, denotes laboriousness, attention, labor, diligence and study. ACUTE _angle_. See ANGLE. ADACTED applies to stakes, or piles, driven into the earth by large malls shod with iron, as in securing ramparts or pontoons. ADDICE, a sort of axe which cuts horizontally. It is sometimes called an Adze. ADIT, a passage under ground, by which miners approach the part they intend to sap. See GALLERY.