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 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.