&fist] The phrases what o'clock? it is nine o'clock, etc., are contracted from what of the clock? it is nine of the clock, etc.

Alarm clock. See under Alarm. -- Astronomical clock. (a) A clock of superior construction, with a compensating pendulum, etc., to measure time with great accuracy, for use in astronomical observatories; -- called a regulator when used by watchmakers as a standard for regulating timepieces. (b) A clock with mechanism for indicating certain astronomical phenomena, as the phases of the moon, position of the sun in the ecliptic, equation of time, etc. -- Electric clock. (a) A clock moved or regulated by electricity or electro-magnetism. (b) A clock connected with an electro-magnetic recording apparatus. -- Ship's clock (Naut.), a clock arranged to strike from one to eight strokes, at half hourly intervals, marking the divisions of the ship's watches. -- Sidereal clock, an astronomical clock regulated to keep sidereal time.