variation of the needle

Variation \Va`ri*a"tion\, n. [OE. variatioun, F. variation, L.
   variatio. See {Vary}.]
   1. The act of varying; a partial change in the form,
      position, state, or qualities of a thing; modification;
      alteration; mutation; diversity; deviation; as, a
      variation of color in different lights; a variation in
      size; variation of language.
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            The essences of things are conceived not capable of
            any such variation.                   --Locke.
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   2. Extent to which a thing varies; amount of departure from a
      position or state; amount or rate of change.
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   3. (Gram.) Change of termination of words, as in declension,
      conjugation, derivation, etc.
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   4. (Mus.) Repetition of a theme or melody with fanciful
      embellishments or modifications, in time, tune, or
      harmony, or sometimes change of key; the presentation of a
      musical thought in new and varied aspects, yet so that the
      essential features of the original shall still preserve
      their identity.
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   5. (Alg.) One of the different arrangements which can be made
      of any number of quantities taking a certain number of
      them together.
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   {Annual variation} (Astron.), the yearly change in the right
      ascension or declination of a star, produced by the
      combined effects of the precession of the equinoxes and
      the proper motion of the star.

   {Calculus of variations}. See under {Calculus}.

   {Variation compass}. See under {Compass}.

   {Variation of the moon} (Astron.), an inequality of the
      moon's motion, depending on the angular distance of the
      moon from the sun. It is greater at the octants, and zero
      at the quadratures.

   {Variation of the needle} (Geog. & Naut.), the angle included
      between the true and magnetic meridians of a place; the
      deviation of the direction of a magnetic needle from the
      true north and south line; -- called also {declination of
      the needle}.
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   Syn: Change; vicissitude; variety; deviation.
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