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Annealing:  
A process of heat treatment for reducing the degree of hardness of metal to give it maximum malleability or ductility. The purpose of annealing is to remove the effects of previous hardening, thus making the metal suitable for further work such as bending, cutting or drawing into wire.

Anvil:   See Beak iron.

Appointments clock:
( Pic )     An aid for the professional or business man to help in keeping appointments - an aural equivalent of the desk diary. One of the best known early appointments, or memorandum clocks was devised by John Davidson about 1890. An ordinary spring-driven clock turns a drum with 48 slots into which small ivory tablets, on which messages and times may be written, are inserted. Each slot is marked with the time, and the tablet on which the appointment is written is placed in the appropriate slot. On reaching the required time, the slot in the drum lies directly over a slot in the top of the clock; the tablet drops through a duct into a small tray below the dial, causing it to fall. Electrical contacts are closed by this action and an electric bell in the base rings continuously until the tablet is removed.

Arbor:
( Pic )     The axle upon which a clock's pinions and wheels are mounted. The arbor carrying the balance or pallets is often called a staff. Before the introduction of economic steel-making methods in the 19th century, clock arbors were usually made from case-hardened wrought iron and subsequently from hardened and tempered steel; but because of the difficulties involved in obtaining and working good-quality steel, early American and Black Forest clocks were often fitted with wooden arbors, steel pins forming the pivots.

Arch top:
( Pic )     A simple semicircular top to the cases of bracket and longcase clocks. The design appeared in the late 18th century and continued well into the 19th. It presented a satisfyingly simple shape to bracket and mantel clocks in the Adam and Sheratron Styles, and occurred in both mahogany and painted-satinwood bracket clocks with simple brass lion-head or disc-ring handles at the sides.

Art nouveau:
( Pic )     The name given to a style in the decorative arts which flourished in Europe and North America during the 1890s. Influenced by Japanese are, it is characterized by whiplash lines and stylized natural forms. First introduced in architectural design by Victor Horta in Belgium, it was taken up by other artists in different media, such as the English illustrator Aubrey Beardsley and the American glass designer Louis Comfort Tiffany.

Astronomical clock:
( Pic )     Public astronomical clocks were made in the late 14th and early 15th centuries. Most were inside cathedrals or churches, but some were outside and on public buildings. They represented a working model of a geocentric universe, and there were two types, the astrolabe and the armillary. Most of the medieval clocks have vanished, leaving only descriptions.

Atmos clock:
( Pic )     ( Pic )     The ancestor of the Atmos clock is the famous James Cox perpetual-motion clock c.1760, now in the Victoria and Albert Museum, London. In 1913 J.E. Reutter considered by what means a perpetual clock based on the expansion of liquids or gases could be made, and in 1926 the first commercial Atmos clock appeared. It had a torsion pendulum driven from a train, powered by a spring wound by the driving mechanism. A sealed U-tube containing liquefied gas in each limb, separated by mercury, has one side immersed in liquid of high specific heat insulated by a vacuum jacket; the other is exposed to the air in the glass dome protecting the clock. A slight rise in temperature expands the gas in the exposed limb, forcing mercury into the other limb insulated from the temperature change, unbalancing the mechanism on its axis. A ratchet wheel and click communicates the motion to the driving spring; reduction of temperature reverses the motion but still winds the spring.

Atomic clock:
Atomic and molecular vibrations constitute the most regular of motions in nature, but most are at such a high frequency as to be unusable as time standards. Radio-frequency techniques are used to generate energy at the frequency of the atomic transition from a lower frequency generated by a quartz-crystal oscillator, while the atomic vibration controls the absolute frequency of oscillation, frequency division by electronic circuits being used to obtain the low frequency required to drive the clocks indicating absolute time. Accuracy to less than one second error in 100,000 years is now available with the caesium atomic clock.

Augsburg clock:
( Pic )     Augsburg clockmakers specialized in automata which performed as the clock went, or when it struck, or indicated the time by slowly revolving and pointing to the hours on a dial. These clocks were mostly spring-driven table clocks, but during the 17th century metal cases gave way to wooden ones with the figures themselves of metal, highly decorated. An Augsburg clock in the British Museum, London, has a milkmaid milking a cow, and when a special receptacle is filled with milk it gradually fills the milkmaid's bucket; an aged peasant points to the time with his stick. Other Augsburg clocks have animals such as lion or a bear which blink their eyes as the clock ticks.

Automata clock:
( Pic )     Automata clocks are those with moving figures of persons or animals which function while the clock is going or when it strikes. The earliest-known clock to carry automata is the original Strasbourg clock of 1352-1354, of which only the crowing cock now remains. The distinction between automata and jacks is the jacks are always employed in striking bells, while automata performs a variety of different actions. Automata, which were often an ingenious form of advertising, are usually associated with large clocks on buildings.