ZENITH. The pole of the horizon, or that point in the heavens directly overhead, as nadir is that which is directly under our feet.
ZENITH-DISTANCE. The angular distance of any celestial object from the zenith at the time of observation. In navigation the meridional zenith-distance of a heavenly body is much used for finding the latitude.
ZEPHYR. The west wind, but generally considered to apply to any light pleasant breeze.
ZERO. The cypher or nought at the beginning of a graduated arc.
ZETETIC. The analytic method of investigating a mathematical problem.
ZIG-ZAG. The winding trench of approach of a besieger, directed by short turns alternately right and left of the defences of the place, to avoid being enfiladed by them. Called also a boyau.
ZIG-ZAG COURSE. Working to windward by very short tacks or angular turning boards.
ZODIAC. A broad zone or belt of the heavens, the middle of which is the ecliptic, extending 9° on either side of it. It is divided into twelve signs, each measuring 30° along the ecliptic.
ZODIACAL LIGHT. A pyramidal cone of light, apparently emanating from the rising and setting sun, commonly seen in the tropics; in higher latitudes most visible about the time of the equinoxes.
ZOLL, or Saul. An Indian timber, much used in the construction of country vessels.