AID-DE-CAMP. A military staff officer, who carries and circulates the general's orders; and another class selected as expert at carving and dancing. In a ship, flag-lieutenant to an admiral, or, in action, the quarter-deck midshipmen to a captain. AIGRE. The sudden flowing of the sea, called in the fens of Lincolnshire, _acker_. (_See_ BORE.) AIGUADE [Fr.] AGUADA [Sp.] Water as provision for ships. AIGUADES. Watering-places on French coasts. AIGUILLE _aimantee_, magnetic needle. ---- _de carène_, out-rigger. ---- _d'inclinaison_, dipping needle. ---- _de tré_, or _à ralingue_, a bolt-rope needle. AIGUILLES. The peculiar small fishing-boats in the Garonne and other rivers of Guienne. AIGULETS [Fr. _aiguillettes_]. Tagged points or cords worn across the breast in some uniforms of generals, staff-officers, and special mounted corps. AILETTES. Small plates of steel placed on the shoulders in mediæval armour. AIM. The direction of a musket, cannon, or any other fire-arm or missile weapon towards its object.--_To take aim_, directing the piece to the object. AIR. The elastic, compressible, and dilatable fluid encompassing the terraqueous globe. It penetrates and pervades other bodies, and thus animates and excites all nature.--_Air_ means also a gentle breath of wind gliding over the surface of the water.--_To air_, to dry or ventilate. AIR-BLADDER. A vesicle containing gas, situated immediately beneath the spinal column in most fish, and often communicating by a tube with the gullet. It is the homologue of the lungs of air-breathing vertebrates. AIR-BRAVING. Defying the winds. AIR-CONE, in the marine engine, is to receive the gases which enter the hot-well from the air-pump, where, after ascending, they escape through a pipe at the top. AIRE. A name in our northern islands for a bank of sand. AIR-FUNNEL. A cavity formed by omission of a timber in the upper works of a vessel, to admit fresh air into the hold of a ship and convey the foul out of it. AIR-GUN. A silent weapon, which propels bullets by the expansive force of air only. AIRING-STAGE. A wooden platform, on which gunpowder is aired and dried. AIR-JACKET. A leathern garment furnished with inflated bladders, to buoy the wearer up in the water. (_See_ AYR.) AIR-PIPES. Funnels for clearing ships' holds of foul air, on the principle of the rarefying power of heat. AIR-PORTS. Large scuttles in ships' bows for the admission of air, when the other ports are down. The Americans also call their side-ports by that name. AIR-PUMP. An apparatus to remove the water and gases accumulating in the condenser while the engine is at work. AIR-SCUTTLES. The same as _air-ports_. AIR-SHAFTS. Vertical holes made in mining, to supply the adits with fresh air. Wooden shafts are sometimes adopted on board ship for a similar purpose. AIRT, OR ART. A north-country word for a bearing point of the compass or quarter of the heavens. Thus the song--