Astrolabe
An instrument for taking the altitude of stars, from which time and latitude can be calculated.

Balance
The balance wheel of a watch is the controlling device which regularly turns backwards and forwards like the pendulum on a clock. It can be plain steel or a compensated balance such as the bi-metallic types which compensate for changing temperatures.

Bracket clock
A rather misleading name given to English spring driven table clocks.They rarely stood on brackets.

Chamber clock
A name given to some domestic clocks of the medieval and Renaissance period, meaning room (chamber) clocks as distinct from turret clocks.

Champlevé
A type of decorative metalwork in which some areas are hollowed out and filled with wax or enamel and others are left proud and polished. Early watch dials are frequently of this type.

Chronograph
A type of watch movement with an additional centrally-mounted seconds band which can he stopped, started and returned to zero using a push piece. This mechanism is independent of the normal running of the watch.

Count Wheel Striking
The earliest form of striking mechanism. As the clerk strikes so the countwheel turns to the next position for the following hour. The main disadvantage is that the mechanism can get out of sequence with the hands.

Diptych
A rectangular pocket sundial, hinged on one side which opens up to a 90 degree angle, such m the Ivory Nuremberg type. The name comes from the ancient hinged writing-tablets and medieval altar paintings which also open in this way.

Escapement
The part of a clock or watch which alternately stops and releases the driving force of the mechanism, i.e. the part that ticks. More time and inventive energy have been spent on this aspect of horology than any other . it is the performance of the escapement, with the balance or pendulum, that determines the accuracy of the timepiece.

Gnomon
The part of a sundial which casts a shadow from which the time is read.

Lantern clock
A brass-cased, weight-driven, wall clock made in England, which hangs like a lantern, hence its name.

Marquetry
A form of wooden inlay in varied and complex patterns used on English clock cases between 1675 and 1730.

Piqué
Otherwise known as pin-work in which gold, silver or brass pins are used both to secure and decorate the leather or tortoiseshell covering found on certain cases.

Rack striking
Invented in the late seventeenth century, rack striking mechanisms se a snail-shaped cam, rack and pinion. They cannot get or of sequence with the hands as they are attached to the wheel that controls the hour hand.

Repoussé
A decorative metalwork technique, sometimes called embossing, which creates shaped patterns or scenes using dozens of specially designed hammers on the underside of the metal.

Springs
Table clocks and some wall clocks and watches are powered by coiled steel springs wound by a key or button. Additionally, watches have balance springs, also called hair springs, which give precisely equal motion in each direction (isochronous) to the balance.

Tabernacle clock
A miniature spring-driven clock, usually surmounted by a dome or gallery - like a temple or tabernacle - usually made in Renaissance Augsburg.

Train
A series of clock or watch wheels geared together; for example. a longcase clock has separate going and striking trains.

Horology

British Horological Institute - [ http://www.bhi.co.uk/ ]
Horology Index - [ http://www.horology.com/ ]
Horology newsgroup - [ alt.horology ]

Sundials

British Sundial Society - [ http://www.sundials.co.uk/bsshome.htm ]
My favourite sundials in Suffolk, England - [ http://www.sundials.co.uk/~suffolk.htm ]
Sundial Resources on the Internet - [ http://www.ph-cip.uni-koeln.de/~roth/slinks.html ]

Watches

Pieces of Time - Antique Pocket Watches - [ http://www.antique-watch.com/ ]

Time

Greenwich 2000 - [ http://www.greenwich2000.com/time.htm ]

Horological Collections

British Horological Collections - [ http://www.bhi.co.uk/collect.htm ]