In the uppermost division stands the form of the Saviour holding the banner of Victory in his left hand and giving the sign of blessing with his right hand, which is movable. At the twelfth hour the twelve apostles, one after another, pass by the Saviour, toward whom, in passing, they turn to receive the sign of blessing. The apostles having passed, the sign of blessing is repeated to the visitors, a large number always being present in the cathedral. On the apex of the turret, to the left in the Figure, is a cock, which, as the apostles pass by, flaps his wings, moves his head and tail, puffs up his neck, and crows thrice. The ornamentations in the highest point of the central turret are composed of the figures of Josiah, of the evangelists, of seraphs with musical instruments, etc. The smaller turret contains the weights of the supplementary works, which, being unlocked from time to time by the central mechanism, actuate the moving figures. The works of the central turret set in motion the entire mechanism, which is wound every eight days. The stairs lead not only to the central part, but also to the large dial-plate (16 feet in diameter), which is placed over the portal of the cathedral, on the south side, and which indicates the hour, the day, and the week.
Electric Clocks may be divided into two classes: (1) primary or auto matic clocks, whose impelling power is exclusively the electric current, and which are controlled by their own pendulum; and (2) secondary elec tric clocks, or time telegraphs, whose source of impelling power is also exclusively the electric current, but which are operated by a separate pendulum-clock. Primary electric clocks were invented in 184o by Alexander Bain, and though many ingenious inventions have brought them to a high state of perfection, they are of little general interest. The secondary electric clock, however, is an important advance in elec tric time-distribution, and through its great utility has made rapid strides toward general adoption. It has for its purpose the distribution of cor rect and uniform time to localities however far apart. The secondary clock is not of itself a time-keeper, but is controlled, through the medium of electric wires, by a well-regulated pendulum-clock called the "master clock," from which it receives the time telegraphed; hence the name " time telegraph." It was invented by Steinheil in 1839, and by Wheatstone and Bain in IS4o. The pendulum-clock, to operate the time telegraph, needs a contrivance to close and to open an electric battery, which connects the time telegraph by electric wires with the master clock; such an arrangement is called the "contact-maker" or "circuit-breaker." When the contact-maker closes the galvanic battery, an electric current passes through the clock and energizes an electromagnet, which attracts a piece of iron, thereby moving the train of the time telegraph. Contacts are made as often as needed, according to the construction of the electric dial. Most of them move every minute, and some move every second.
Bain's Electric Clock, shown in Figure i (p. 126), although one of the earliest types, has since its invention been one of the leading devices in various modifications, and even many recent arrangements retain its characteristic features. When the galvanic battery is closed at the master clock, the electric current passes over the connecting wires through the coil of the electro-magnet E, and becoming magnetized attracts the soft piece of iron called the "armature" a, which is movable on pivots at x and is free to oscillate. On its lower extremity the armature bears a pawl h which glides over the teeth of the ratchet-wheel R when the armature is attracted am] moves toward the poles of the electro-magnet; the moment the electric battery is opened at the master clock, the spring f brings the armature back to its former position and the pawl moves the ratchet wheel to the extent of one tooth. The arbor of the ratchet-wheel gears into a clock-train which moves the hands in front of a clock-dial; a second pawl It' prevents the retrograding of the ratchet-wheel when the armature moves toward the poles of the electro-maguct.
Garai er' s Electric electric clock with features quite dis tinct from those of Iiain's is the one which was invented in 1847 by Paul Gamier of Paris (pr. 126, fig. 3), and which, though more complicated, is more durable in construction and more reliable in its action than Bain's clock. The armature a, suspended over the poles of the electro-magnet E by a metal rod and drawn down when attracted, moves the lever which has its fulcrum at x; the pawl s moves the ratchet-wheel k while the paw] s', which is rigid to the lever /z near its fulcrum, enters a space between the teeth to prevent the wheel from moving more than one tooth at a time. The pawl prevents the ratchet-wheel from making a retro grade movement.
Siemens & Halske' s Electric Dial is noted for the peculiar arrange ment of its armature (fig. 2), which moves in its bearings at x, and has its extremities in such position, relative to the north and the south pole respectively, that they are vibrated, similar to the movement of a scale beam. The ratchet-wheel R is moved similarly to that of Bain's clock, but with the action reversed; while the movement in Ilain's clock was effected by the retrograde movement of the armature, the power of the retracting spring being used for that purpose, in the Siemens clock the ratchet-wheel is moved at the time the armature is approaching the poles of the electro-magnet E, —a feature which, as we shall learn later, is not at all beneficial to the clock. To prevent the ratchet-wheel from moving more than one tooth at each impulse, the lever /z has at z a little tooth-shaped pro jection which enters the space between the teeth of the ratchet-wheel and stops its further progress.