QUARTER or CHIME CLOCKS differ from the above only in having another barrel and train of wheels to provide the extra power for such striking and chiming. +----------------------------------------------------------------------+ | [Illustration: GAS WHEEL FOR ILLUMINATED DIALS.] | +----------------------------------------------------------------------+ In instances where it is requisite that the clock face should be visible at a great distance, it is necessary that the dial should be made of semi-transparent glass and be illuminated by gas, which is usually turned as low as possible by day and turned on at night by means of the 24-hour wheel, as shown in the annexed illustration, the time for the turning on being regulated by the man in charge of the clock, who takes out or screws in the pins placed in the rim for that purpose. +----------------------------------------------------------------------+ | [Illustration: NEST OF BEVELLED WHEELS FOR FOUR DIALS.] | +----------------------------------------------------------------------+ These wheels should be rather large, inasmuch as they have to carry the hands moving upon the face of the dial. The size of these wheels varies of course with the size of the clock, but they are seldom less than five inches and are generally from seven to nine inches wide. HAMMER AND BELL. The next engraving exhibits the relative positions of hammer and bell in a turret clock,--the hammer being fixed at right angles to the swing of the bell, so that the blow of the hammer should not drive the bell out of reach of its next blow, and this position least interfering with the ringing of the bell, when the bell is required to be rung. The hammer spring, as shown, is sometimes so adjusted as to allow of the hammer being brought nearer or further from the bell. +----------------------------------------------------------------------+ | [Illustration: Hammer and Bell.] | +----------------------------------------------------------------------+ THE GREAT CLOCKS OF THE INTERNATIONAL EXHIBITION OF 1862. BENSON'S GREAT CLOCK. +----------------------------------------------------------------------+ | [Illustration: Benson's Great Clock.--The Exterior.] | | | | [Illustration: Benson's Great Clock.--The Movement.] | +----------------------------------------------------------------------+