Ultimate Collection of Clock Resources

Astronomical clock at the city hall on the Old Town Square in Prague, Czech republic.

Astronomical clock in Prague, Czech republic

A clock is an instrument used to measure and indicate time. It is derived from the Latin word “clocca” meaning bell. The current day clock has arrived after a whole lot of transformations and improvements while the actual clock dates back to around the fourteenth century.

History of Clocks

Measuring time started with just following the sun, and classification was based on its intensity as just morning, noon, afternoon, evening or night. Slowly, the sundial was built to tell the time in smaller parts. It consisted of a vertical stick on a horizontal surface with markings and the length and position of the shadows indicating the time of the day. This was used for nearly 2,000 years despite not being very accurate.

In the 1400’s the water clock (Clepsydra) was invented. It consisted of two containers of water, one placed at a higher level than the other. Water went from the higher to the lower container through a pipe and these containers had markings on them to indicate the time. This became very popular as it worked even at night, and the clouds could not affect it. Through a period of time, it evolved to become more accurate. The Greeks improved on this and created date, months, and year.

The first known clock was the spring powered clock. This spring powered clock did not work properly and was inaccurate. Initial clocks did not contain minute or seconds. In 1577, Jost Burgi invented the minute hand, a significant contribution though it was not appreciated initially due to the problems it caused. Christian Huygens invented the pendulum clock in 1656, and it became popular very soon.

The mechanism behind the pendulum is simple. The pendulum swings left to right causing a wheel inside it to turn. This wheel controls the minute and hour hand on the face of the clock. Pendulum clocks had some issues because they had to be restarted every now and then. However, they were instrumental in changing the way time was measured. Soon, batteries were installed and resolved any issues in the pendulum clock. Next were the Quartz Crystal clocks which use a combination of voltage and pressure, causing the quartz to vibrate at a constant speed. These vibrations move the minute and hour hand. Quartz Crystal clocks are accurate and cost effective. This is the mechanism in the clocks and watches today.

Earliest Clocks: An overview of the earliest clocks in history.
Sundial: Provides historical details on possibly the most ancient clock.
Water Clocks: A look at the history and workings of the water clock.
Clock a History: Runs through the history of clocks.

How Clocks Work

The clock needs a primary power source to run. It can be a battery, power line or a suspended weight in mechanical clocks. All clocks use oscillation to calculate time whether it’s a swinging pendulum or a vibrating quartz crystal. This oscillator moves at a particular speed over and over again. It is attached to a controller which maintains the movement of the oscillator, replacing lost energy, and converts the oscillation into a series of pulses to measure time. Counter chains are used to convert these pulse readings into seconds, minutes, and hours. Then, there’s the indicator that displays the time in a format that can be understood.

How Mechanical Clocks Work: Describes the history, the pendulum, and gears in mechanical clocks.
How Do Clocks Work?: Discusses how clock work with links to more information.
Pendulum Clocks: Explains how pendulum clocks work.
Atomic Clocks: Shows how atomic clocks work.
How Do Computer Clocks Work?: Outlines how computer clocks function.

Styles of Clocks

The main types are digital, analog, and auditory clocks. Digital Clocks display digits which can be in the twelve hour am/pm format or twenty four hour format. They use a LCD, LED or VFD display. Analog clocks have a face plate with numbers and dials or hands that move to indicate the time. It is normally circular in shape and contains numbers one to twelve indicating twelve hours of sixty minutes. Some clocks have a seconds hand to indicate the sixty seconds in each minute. An auditory or talking clock as it is known is especially helpful to those who are unable to see time. It can be a simple ringing of bells or numbers mentioned in a spoken language. Clocks can be further classified into different types depending on their mechanism, function and style. Some examples are:

Mechanism: Atomic Clock, Astronomical Clock, Candle Clock, Digital Clock, Electric Clock, Incense Clock, Hourglass, Pendulum Clock, Steam Clock, and Water Clock.

Style: American Clock, Balloon Clock, Grandfather Clock, Carriage Clock, Cartel Clock, Cat Clock, Doll's Head Clock, Lantern Clock, Lighthouse Clock, Mantel Clock, Skeleton Clock, and Tix Clock.

Function: Alarm Clock, Binary Clock, Cuckoo Clock, Chiming Clock, Chronometer Clock, Game Clock, Master Clock, Slave Clock, Striking Clock, Tide Clock. and World Clock.

The Clepsydra: A website dedicated to the water clock.
Atomic Clock: In-depth discussion about the atomic clock.
The Astronomical Clock: Provides information on this hard-to-read clock.
Electric Clocks: Offers some interesting information about electric clocks.
Pendulum Clock: Dedicated to Galileo and the pendulum clock.
Grandfather Clocks: A look at the history of grandfather clocks.
Slave Clocks: A look at slave clocks.
Lantern Clocks: Discusses some aspects of the lantern clock.
Candle Clock: Short history and description of the candle clock.
Binary Clock: A project to build a binary clock.
Skeleton Clocks: A collection of skeleton clock images.
Hourglass: Provides a look into the history of the hourglass.
The Marine Chronometer: A place to read the book by Rupert Thomas Gould.
The World Clock: Shows all the different times in the world.

Related Links

Black Forest Clock Association: Dedicated to the preservation of Black Forest clocks.
National Association of Watch & Clock Collectors: Seeks to encourage interest in the science and art of timekeeping.
JCWA: Official website of the Japan Clock & Watch Association.
British Horological Institute Limited: Formed in 1858 to promote horology.
The British Watch & Clock Makers Guild: A guild of watchmakers formed in 1907.
Pocket Horology: Dedicatd to research on the horology and history of pocket watches.
Clocks Magazine: Monthly publication dedicated to horology.
School of Horology: School that prepares students for entrance into the business of horology.
International Society of Talking Clock Collectors Museum: A virtual museum with more than 900 talking clocks.
The Canadian Clock Museum: Homepage of the only clock museum in Canada.
Willard House & Clock Museum: Situated in North Grafton, Massachusetts, the museum preserves Willard clocks.
Claphams National Clock Museum: Home of some of the most unique and significant clocks in the world.
Tymperleys Clock Museum: Exhibits part of the renowned Bernard Mason Collection.
Big Ben: One of the most famous clocks in the world.
Cosmo Clock 21: The world’s largest Ferris wheel and clock.
Prague Astronomical Clock: Splendid looking clock located in the Czech Republic.
The Doomsday Clock: A symbolic clock face used to represent estimation to global disaster.
ClockHistory.com: History of Westclox clocks and watches, and history of Telechron, Seth Thomas and Standard Electric Time Company clocks

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