Clock face

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Reading a modern clock face


'12:14' in both analog and digital representations.


A ship's radio room wall clock during the age of Wireless telegraphy showing '10:09' and 36 seconds' bean bag pattern


Most modern clocks have the numbers 1 through 12 printed on the face indicating the hour, and on many models, sixty dots or lines evenly spaced in a ring around the outside of the dial, indicating minutes and seconds. resin wicker chairs


The time is read by observing the placement of several "hands" which emanate from the center of the dial:


A short thick hand (hour);


A long, thinner hand (minute); and on some models,


A very thin 'sweep' hand (seconds)


...all of which continuously rotate around the dial in a 'clockwise' pattern - moving from 1 to 2, 2 to 3, and so on.


The sweep hand moves relatively quickly, taking a full minute (sixty seconds) to make a complete rotation from '12 to 12.' As the sweep had makes its rotation, the minute hand will slowly move from one minute mark to the next one.


As the minute hand rotates more slowly around the dial, it will take a full hour (sixty minutes) to make a complete rotation from '12 to 12.' As the minute hand makes its complete rotation, the hour hand will slowly move from one hour mark to the next one.


When all three hands are pointing at '12' it is either Noon or Midnight and the process begins again.


In the example picture, showing a two handed clock, the minute hand is on "14" minutes and the hour hand is moving from '12' to '1' - this indicates a time of '12:14'


Historical development


15th century rotating dial clock face, St. Mary's Church, Gdansk, Poland.


Clocks existed before clock faces. The first mechanical clocks, built in 13th century Europe, were striking clocks: their purpose was to ring bells upon the canonical hours, to call the public to prayer. These were erected as tower clocks in public places, to ensure that the bells were audible. It was not until these mechanical clocks were in place that their creators realized that their wheels could be used to drive an indicator on a dial on the outside of the tower, where it could be widely seen.


Before the late 14th century, a fixed hand (often a carving shaped like a hand) indicated the hour by pointing to numbers on a rotating dial; after this time the current convention of a rotating hand on a fixed dial was adopted. Minute hands (so named because they indicated the small or minute divisions of the hour) only came into regular use around 1690, after the invention of the pendulum and anchor escapement increased the precision of time-telling enough to justify it. In some precision clocks a third hand, which rotated once a minute, was added in a separate subdial. This was called the 'second-minute' hand (because it measured the secondary minute divisions of the hour), which was shortened to 'second' hand. The convention of the hands moving clockwise evolved in imitation of the sundial. In the Northern hemisphere, where the clock face originated, the shadow of the gnomon on a sundial moves clockwise during the day. This was also why noon or 12 o'clock was conventionally located at the top of the dial.


French decimal clock face


French Decimal Time


During the French Revolution in 1793, in connection with its Republican calendar, France attempted to introduce a decimal time system. This had 10 hours in the day, 100 decimal minutes per hour, and 100 decimal seconds per minute. Therefore the decimal hour was more than twice as long as the present hour, the decimal minute was slightly longer than the present minute and the decimal second was slightly shorter than the present second. Clocks were manufactured with this alternate face, usually combined with traditional hour markings. However, it didn't catch on, and France discontinued the mandatory use of decimal time on 7 April 1795, although some French cities used decimal time until 1801.


Stylistic development


Until the last quarter of the 17th century hour markings were etched into metal faces and the recesses filled with black wax. Subsequently, higher contrast and improved readability was achieved with white enamel plaques painted with black numbers. Initially, the numbers were printed on small, individual plaques mounted on a brass substructure. This was not a stylistic decision, rather enamel production technology had not yet achieved the ability to create large pieces of enamel. The "13 piece face" was an early attempt to create an entirely white enamel face. As the name suggests, it was composed of 13 enamel plaques: 12 numbered wedges fitted around a circle. The first single piece enamel faces, not unlike those in production today, began to appear c. 1735.


Footnotes


^ a b Milham, Willis I. (1945). Time and Timekeepers. New York: MacMillan. pp. 195. ISBN 0780800087. 


^ Lathrop, Don Haven (1996). "Why is clockwise Clockwise?". Workshop Hints. British Horological Institute. http://www.bhi.co.uk/aHints/clckwse.html. Retrieved 2008-06-27. 


^ "The Republican Calendar and Decimal Time". History. The Horological Foundation, Netherlands. 2008. http://www.antique-horology.org/_Editorial/RepublicanCalendar/default.htm. Retrieved 2009-01-08. 


Categories: Clocks | Horology