What is "variation compass"

Compass \Com"pass\ (k[u^]m"pas), n. [F. compas, fr. LL. compassus circle, prop., a stepping together; com- + passus pace, step. See Pace, Pass.]

1. A passing round; circuit; circuitous course.

   They fetched a compass of seven day's journey.
   --2 Kings iii. 9.

   This day I breathed first; time is come round, And where I did begin, there shall I end; My life is run his compass.
   --Shak.

2. An inclosing limit; boundary; circumference; as, within the compass of an encircling wall.

3. An inclosed space; an area; extent.

   Their wisdom . . . lies in a very narrow compass.
   --Addison.

4. Extent; reach; sweep; capacity; sphere; as, the compass of his eye; the compass of imagination.

   The compass of his argument.
   --Wordsworth.

5. Moderate bounds, limits of truth; moderation; due limits; -- used with within.

   In two hundred years before (I speak within compass), no such commission had been executed.
   --Sir J. Davies.

6. (Mus.) The range of notes, or tones, within the capacity of a voice or instrument.

   You would sound me from my lowest note to the top of my compass.
   --Shak.

7. An instrument for determining directions upon the earth's surface by means of a magnetized bar or needle turning freely upon a pivot and pointing in a northerly and southerly direction.

   He that first discovered the use of the compass did more for the supplying and increase of useful commodities than those who built workhouses.
   --Locke.

8. A pair of compasses. [R.] See Compasses.

   To fix one foot of their compass wherever they please.
   --Swift.

9. A circle; a continent. [Obs.]

   The tryne compas [the threefold world containing earth, sea, and heaven.
   --Skeat.]
   --Chaucer.

   Azimuth compass. See under Azimuth.

   Beam compass. See under Beam.

   Compass card, the circular card attached to the needles of a mariner's compass, on which are marked the thirty-two points or rhumbs.

   Compass dial, a small pocket compass fitted with a sundial to tell the hour of the day.

   Compass plane (Carp.), a plane, convex in the direction of its length on the under side, for smoothing the concave faces of curved woodwork.

   Compass plant, Compass flower (Bot.), a plant of the American prairies ( Silphium laciniatum), not unlike a small sunflower; rosinweed. Its lower and root leaves are vertical, and on the prairies are disposed to present their edges north and south.

   Its leaves are turned to the north as true as the magnet: This is the compass flower.
   --Longefellow.

   Compass saw, a saw with a narrow blade, which will cut in a curve; -- called also fret saw and keyhole saw.

   Compass timber (Shipbuilding), curved or crooked timber.

   Compass window (Arch.), a circular bay window or oriel window.

   Mariner's compass, a kind of compass used in navigation. It has two or more magnetic needles permanently attached to a card, which moves freely upon a pivot, and is read with reference to a mark on the box representing the ship's head. The card is divided into thirty-two points, called also rhumbs, and the glass-covered box or bowl containing it is suspended in gimbals within the binnacle, in order to preserve its horizontal position.

   Surveyor's compass, an instrument used in surveying for measuring horizontal angles. See Circumferentor.

   Variation compass, a compass of delicate construction, used in observations on the variations of the needle.

   To fetch a compass, to make a circuit.

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; alternation; mutation; diversity; deviation; as, a variation of color in different lights; a variation in size; variation of language.

   The essences of things are conceived not capable of any such variation.
   --Locke.

2. Extent to which a thing varies; amount of departure from a position or state; amount or rate of change.

3. (Gram.) Change of termination of words, as in declension, conjugation, derivation, etc.

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.

5. (Alg.) One of the different arrangements which can be made of any number of quantities taking a certain number of them together.

   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.

   Syn: Change; vicissitude; variety; deviation.