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ARMILLA, ARMIL or ARMILLARY SPHERE (from the Lat. armiltd, a bracelet), an instrument used in astronomy. In its simplest form, consisting of a ring fixed in the plane of the equator, the armilla is one of the most ancient of astronomical instruments. Slightly ...

ARMADILLO, the Spanish designation for the small mail-clad Central and South American mammals of the order Edentata, constituting the family Dasypodidae. The armature consists of a bony case, partly composed of solid buckler-like plates, and partly of movable

ARIA (Ital. for " air "), a musical term, equivalent to the English " air," signifying a melody apart from the harmony, but especially a musical composition for a single voice or instrument, with an accompaniment of other voices or instruments. The aria origin

... ngle subtended by the two objects P and Q at the eye. The earliest forms were " armillae " and spherical. Gradually, from Eratosthenes to Tycho, Hipparchus playing the most important part among ancient astronomers, the complex astrolabe was evolved, large spec ...

... regulated time by water clocks, and used measuring instruments of the nature of armillary sphere* and quadrants. In or near noo B.C., C'hou Rung, an able mathematician, determined with surprising accuracy the obliquity of the ecliptic; but his attempts to esti ...