1910–1911
Britannica 11th
Encyclopaedia Britannica · 11th edition
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 developed, it was crossed by another ring fixed in the plane of the meridian. The first was an equinoctial, the second a solstitial armilla. Shadows were used as indices of the sun's position, in combination with angular divisions. When several rings or circle…
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- Vol. 2, pp. 575-576