De·pres·sion n.
 1. The act of depressing.
 2. The state of being depressed; a sinking.
 3. A falling in of the surface; a sinking below its true place; a cavity or hollow; as, roughness consists in little protuberances and depressions.
 4. Humiliation; abasement, as of pride.
 5. Dejection; despondency; lowness.
    In a great depression of spirit.   --Baker.
 6. Diminution, as of trade, etc.; inactivity; dullness.
 7. Astron. The angular distance of a celestial object below the horizon.
 8. Math. The operation of reducing to a lower degree; -- said of equations.
 9. Surg. A method of operating for cataract; couching. See Couch, v. t., 8.
 Angle of depression Geod., one which a descending line makes with a horizontal plane.
 Depression of the dewpoint Meteor., the number of degrees that the dew-point is lower than the actual temperature of the atmosphere.
 Depression of the pole, its apparent sinking, as the spectator goes toward the equator.
 Depression of the visible horizon. Astron. Same as Dip of the horizon, under Dip.
 Syn: -- Abasement; reduction; sinking; fall; humiliation; dejection; melancholy.

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 Dip, n.
 1. The action of dipping or plunging for a moment into a liquid. “The dip of oars in unison.”
 2. Inclination downward; direction below a horizontal line; slope; pitch.
 4. A liquid, as a sauce or gravy, served at table with a ladle or spoon. [Local, U.S.]
 5. A dipped candle. [Colloq.]
 6. A gymnastic exercise on the parallel bars in which the performer, resting on his hands, lets his arms bend and his body sink until his chin is level with the bars, and then raises himself by straightening his arms.
 7.  In the turpentine industry, the viscid exudation, which is dipped out from incisions in the trees; as, virgin dip (the runnings of the first year), yellow dip (the runnings of subsequent years).
 8.  Aëronautics A sudden drop followed by a climb, usually to avoid obstacles or as the result of getting into an airhole.
 Dip of the horizon Astron., the angular depression of the seen or visible horizon below the true or natural horizon; the angle at the eye of an observer between a horizontal line and a tangent drawn from the eye to the surface of the ocean.
 Dip of the needle, or Magnetic dip, the angle formed, in a vertical plane, by a freely suspended magnetic needle, or the line of magnetic force, with a horizontal line; -- called also inclination.
 Dip of a stratum Geol., its greatest angle of inclination to the horizon, or that of a line perpendicular to its direction or strike; -- called also the pitch.

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 Ho·ri·zon n.
 1. The line which bounds that part of the earth's surface visible to a spectator from a given point; the apparent junction of the earth and sky.
 And when the morning sun shall raise his car
 Above the border of this horizon.   --Shak.
 All the horizon round
 Invested with bright rays.   --Milton.
 2. Astron. (a) A plane passing through the eye of the spectator and at right angles to the vertical at a given place; a plane tangent to the earth's surface at that place; called distinctively the sensible horizon. (b) A plane parallel to the sensible horizon of a place, and passing through the earth's center; -- called also rational horizon or celestial horizon. (c) Naut. The unbroken line separating sky and water, as seen by an eye at a given elevation, no land being visible.
 3. Geol. The epoch or time during which a deposit was made.
    The strata all over the earth, which were formed at the same time, are said to belong to the same geological horizon.   --Le Conte.
 4. Painting The chief horizontal line in a picture of any sort, which determines in the picture the height of the eye of the spectator; in an extended landscape, the representation of the natural horizon corresponds with this line.
 Apparent horizon. See under Apparent.
 Artificial horizon, a level mirror, as the surface of mercury in a shallow vessel, or a plane reflector adjusted to the true level artificially; -- used chiefly with the sextant for observing the double altitude of a celestial body.
 Celestial horizon. Astron. See def. 2, above.
 Dip of the horizon Astron., the vertical angle between the sensible horizon and a line to the visible horizon, the latter always being below the former.
 Rational horizon, and Sensible horizon. Astron. See def. 2, above.
 Visible horizon. See definitions 1 and 2, above.

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