ARCHIPELAGO. A corruption of Aegeopelagus, now applied to clusters of islands in general. Originally the Ægean Sea. An archipelago has a great number of islands of various sizes, disposed without order; but often contains several subordinate groups. Such are the Ægean, the Corean, the Caribbean, Indian, Polynesian, and others. ARCHITECTURE. _See_ NAVAL ARCHITECTURE. ARCTIC. Northern, or lying under _arktos_, the Bear; an epithet given to the north polar regions comprised within the _arctic circle_, a lesser circle of the sphere, very nearly 23° 28′ distant from the north pole. ARCTIC OCEAN. So called from surrounding the pole within the imaginary circle of that name. ARCTIC POLE. The north pole of the globe. ARCTURUS. α Boötis. A star of the first magnitude, close to the knee of Arctophylax, or Boötes. One of the nautical stars. ARD, OR AIRD. A British or Gaelic term for a rocky eminence, or rocks on a wash: hence the word _hard_, in present use. It is also an enunciation. ARDENT. Said of a vessel when she gripes, or comes to the wind quickly. ARE. The archaism for _oar_ (which see). A measure of land in France containing 100 square metres. AREA. The plane or surface contained between any boundary lines. The superficial contents of any figure or work; as, the _area_ of any square or triangle. ARENACEOUS. Sandy; partaking of the qualities of sand; brittle; as, _arenaceous_ limestone, quartz, &c. ARENAL. In meteorology, a cloud of dust, often so thick as to prevent seeing a stone's-throw off. It is common in South America, being raised by the wind from adjoining shores. Also off the coast of Africa at the termination of the desert of Zahara. ARENATION. The burying of scorbutic patients up to the neck in holes in a sandy beach, for cure; also spreading hot sand over a diseased person. AREOMETER. An instrument for measuring the specific gravity of fluids. ARGIN. An old word for an _embankment_. ARGO. A name famous from Jason's romantic expedition, but absurdly quoted as the first ship, for the fleets of Danaus and Minos are mentioned long before, and the _Argo_ herself was chased by a squadron under Æetes. ARGO NAVIS. The southern constellation of the Ship, containing 9 clusters, 3 nebulæ, 13 double and 540 single stars, of which about 64 are easily visible. As most of these were invisible to the Greeks, the name was probably given by the Egyptians. ARGOL. The tartaric acid or lees adhering to the sides of wine-casks, particularly of port-wine; an article of commerce; supertartrate of potass. ARGOLET. A light horseman of the middle ages. ARGONAUTA. The paper-nautilus. The sail which it was supposed to spread to catch the wind, is merely a modified arm which invests the outer surface of the shell.