Clock Folklore

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Clock folklore, apprehesions and myths about mecahnical Grandfather clocks, Regulator wall clocks and Mantel clocks


Turning the hands backwards (back-set) will damage the clock!

The overwhelming majority of modern clocks as well as the majority of those built in the last sixty years, have a mechanism incorporated into their movement that allows the hands to be back-set and avoid damage to the mechanism.

For rarer clocks not designed to allow the backward movement of the hands, an attempt to back-set will simply lock up the hands when they reaches a specific point. Stop there, forcing the hands beyond this point will damage the mechanism.

With clocks that cannot be back-set, the time can only be set by moving the minute hand forwards – clockwise.

On chiming clocks, when moving the hands forward, you should stop at each quarter hour to let the chime play out before moving on. Similarly, on a striking clock, stop at each striking point, which will always be on the hour and on most clocks the half hour as well.

You should never move the hour hand independently of the minute hand. While the minute hand is attached to the mechanism’s gear wheels and moves with them; the hour hand is held on to the arbour of the centre wheel with friction alone and if it is moved manually will not turn the arbour or affect the clock’s mechanism in any way, and so, will be put out of sync.

You can over-wind the mainspring on a cable controlled clock!

This is untrue. Unless the winding key if forced – using a vice grip, beyond the point it that it will not move anymore. Some mainsprings never break, but some do on occasion and it can happen while they are not being wound as well as when they are, however winding is not the cause of failure.

This failure is usually the result of faults in the spring itself, which can take years even decades to materialise; a small defect in the metal slowly growing over time until it reaches breaking point, or particularly on newer or poor quality springs, the material was not heated correctly during manufacture, leaving it hard and brittle at points, and susceptible to breaking early in its life span.

Nevertheless, winding has to be done the keep the clock working and it does put stress on the spring; and, to have the clock run for the full week, or other period stipulated by the manufacturer, it needs to be wound “fully”.

Yet, “fully” do not necessarily mean winding the spring all the way to its very end. People tend to wind until the key stops. After a short period, most become accustomed to winding the clock and through feel, begin to anticipate that the end is near and stop just short of a full wind.

There are two reasons why stopping just short of a full wind is good.

Firstly, repeatedly forcing the key to make sure that it is at the end of the wind (wound fully) could eventually tear the end of the mainspring over time.

Secondly, in an ideal situation the clock should never run on a full wind, nor should it run fully unwound. This is because the power output of a mainspring depreciates as it is run down. This decreasing power – running faster at the full wind point and slower as it nears fully unwound, can affect the clock’s accuracy, particularly on clocks with smaller pendulums. This is known as the isochronal error

Most mainsprings have a little more power than necessary to run the clock for a full week. So stopping just short of a full wind, will still produce the full week/period run; while minimising any drop in accuracy.

Other Causes

Ratchet failure – A failed ratchet can have symptoms similar to a broken spring yet the cause is completely different.

A ratchet system produces the click sound while winding. It is used to keep the spring wound after you let go of the key. When this fails, the mainspring unwinds rapidly, spinning the key as it does so. If your fingers are still close to the key when this happens, they will be hit and hurt!

To avoid this, it is essential to always be in control of the winding key. After turning the key as far as you can and before you it let go to re-grip it, you should ease the winding pressure and allow the key to move backwards and engage fully with the ratchet, which will hold the mainspring and key in place while you adjust your grip.

Should the key continue to move backwards and not engage the ratchet, then it is best to pull the key clear of the clock and let the spring unwind. Although this unwinding could cause damage to the mechanism, this is not always the case but will save injury to fingers.

It is important to pay attention to the clicking sound, when winding the clock and become familiar with it. Any distinct change in that sound is a indicator that the ratchet system may be failing and need looking at.

Neglect – other causes of a clock stopping after winding are the result of poor maintenance and neglect over many years; allowing component wear and tear to develop unaddressed.

You should lift the weight when winding a Chain controlled Floor Clock!

The thinking here is to reduce stress on parts and the risk of wear and tear over time, but it is simply not true. If anything repeatedly lifting the weights, while winding, could knock the chain or a weight off. Weight driven clocks are designed to handle the forces and stresses of the correct weight.

It is worth noting that throughout the winding process, the arbour of main/centre wheel is not turning as it does when the clock is running. So during winding there is no wear on this bearing surface, as there is when the clock is running, which contributes over time, to a clock stopping. Meanwhile, any wear between the chain wheel and its arbour – where the stress is greatest, is in fact insignificant.

To maintain the pulley system – when winding, always leave a gap between the top of the weight and the bottom of the movement. This is to avoid the weight hitting the bottom of the movement or the seat board, which can stretch chain links. Also avoid touching the polished chains or weights with your bare hands. Using a cloth of glove will stop the oil on your hands and fingers getting on to the metal and discolouring it over time.

A Clock Must Be Level to Run!

This is a misleading statement. In reality a clock must be “in beat” to run.

A clock’s “beat” is the sound a clock makes when it ticks. When a clock is “in beat” the tick and the tock sounds will be evenly spaced i.e tick—tock—tick… The beat of a clock is factory set for a level position, as clocks aesthetically looks better when level, whether they are sitting on a shelf or floor, or hanging on a wall

However, a clock that is not perfectly level can run fine if its beat is reset for that position, as long as the pendulum is able to move unrestricted.

In people’s homes it is not always practical to level the clock. In instances, where a floor clock is near a doorway that is not square, or when a wall clock is sitting against lined wallpaper, which is not quite vertical; the clock will look crooked even though it is actually not.

In these cases, levelling the clock by eye, against its surroundings, will give the aesthetic appearance of being positioned correctly. Assuming that the pendulum can move freely, the beat can then be adjusted to be “even” in that position and the clock will run OK.

Most modern clocks have what is called a “automatic beat adjustment”. With this facility, as long as the clock is stable* and somewhere close to level, simply over-swinging the pendulum to either side will enable the beat to set itself, and the clock will run OK.

Other types of clocks
The above information applies mainly to pendulum clocks. Clocks, with floating or platform balances, can run OK without being level. With these cocks, if it looks right and it works, then it is right.

* With pendulum clocks, particularly weight driven floor clocks, stability is really important. Any sway from instability may stop the clock. This is caused by what is known as “sympathetic vibration or motion”.
The unstable clock case picks up the motion from the swinging pendulum, and when the weights reach a point near the pendulum bob, causes them to swing slightly; usually in the opposite direction to the pendulum’s swing, which eventually stops the clock.

You can stabilise a Floor Clock sitting on a carpet with a board under it!

This is only true if you fix the board through the carpet into your floor below.

A wooden board or piece of marble etc. sitting on a carpet will tend to “float” on the carpet even with the weight of the clock on it. The weight of the clock will be spread across the board, reducing the downward force into the carpet.

Without any board, the weight of the clock will be distributed between the four levellers/feet of the clock. This produces a greater downward force, pushing the levellers/feet deeper into the carpet and providing greater stability, than with a board, by reducing the floating effect.

Against a wall – To maximise stability, the clock should also be allowed to contact the wall in some way. If the clock is positioned against a flat wall, then the front leveller/feet should adjusted to allow the clock to lean back slightly towards the wall.

Once this is achieved, place or fix a small shim/spacer, the same thickness of the skirting board, behind the clock near the top. This gives the appearance that the clock is not touching the wall and pushes the top of the clock forward, levelling the clock front to back.

In a corner – If the clock is positioned at an angle in a corner, then only the top corners of the clock touch the wall when leaning back and a shim/spacer would be visible. However, it may be that the clock leaning back slightly in this location looks OK, and no shim/spacer is needed.

Otherwise, the clock should be positioned and fixed to the wall, near the top, with a hidden bracket of some kind. Alternately if the design of the clock allows, you can add weight into the bottom of the clock case, ideally five Kilograms should suffice for a grandfather clock.

You should not place a cock on an outside wall!

This is not true in modern centrally heated buildings, where temperature can be easily regulated.

It may have been relevant in the past, with poorly insulated homes and rooms heated individually by their own source, when walls could get noticeably cold in the winter. Any cold transferring to a clock case could affect the wooden case or even the accuracy of the mechanism. Also, in areas and situations where condensation on the walls was common, the droplets would also affect the clock.

History and Origins of the Ship’s Bell Clock

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 SALCOME 35065-000132 Ships Bell Wall Clock

The ship’s bell strikes in 30 minute increments over a four hour  period of the day. There is one bell strike for each 30 minute segment beginning with a single bell strike at half past midnight and counting up to eight bell strikes at 4:00 a.m. marking the end of the four hour period.

At this point the bell strike pattern begins again at a single strike at 4:30 a.m. and counts up to eight strikes to 8:00 a.m.. This pattern of bell strikes – one to eight at half hour increments over four hours, is repeated throughout the day, breaking the 24 hours in the day into six distinct periods.


The ship’s bell system of chimes evolved from a crude sand clock dating back to the time of Columbus. This primitive clock was called a sand or sandglass clock, was a glass tube pinched to a narrow point in the middle, to allow sand to pass from the top half of the tube to the bottom half at a specific rate of time; and was an essential device for marking the time at sea.

Records of epic voyages tell us about this device and how the helmsman used it to measure time in half-hour increments by turning the glass when the sand ran through. It became customary to strike a bell at the same time so that whole crew knew the time; starting with one bell strike at the end of the first half hour, two at second and so on until reaching eight bells, which signalled the end of the four hour period. The tradition of the sand clock continued for hundreds of years and was replaced only by the development of the mechanical clock. But, it was not until the 19th century that the first mechanical ship’s bell clock was produced in America. The principle of this American innovation remains almost unchanged to this day.

Work shifts or “Watches”, were organized into increments of four hours on ships’ as mariners need to work 24 hours a day to keep the ship sailing; these four hour period are indicated by the ship’s bell system. Crews were organised into into teams that would work one four hour Watch and then rest before their next working Watch.  However, as this four hour pattern resulted in six distinct periods in 24 hours – an even number, this meant that watch keepers would work the same Watches, repeatedly, day in, day out.

To introduce variation in the Watches and avoid this scenario, a mechanism called the “Dog Watches” is used.  This occur in the 4:00 pm to 8:00 pm period, by splitting it into two shorter two-hour stints, and by doing so introduce a seventh – uneven number of periods.  These short Watches also assist in the logistics of providing an evening meal for the whole crew, around the same time slot.

Noon to 4:00 p.m. Afternoon watch
4:00 p.m. to 6:00 p.m. First dog watch
6:00 p.m. to 8:00 p.m. Second dog watch
8:00 p.m. to midnight First night watch
Midnight to 4:00 a.m. Middle watch or mid watch
4:00 to 8:00 a.m. Morning watch
8:00 a.m. to noon Forenoon watch

Ship’s Bell Code





8 Bells





1 Bells





2 Bells





3 Bells





4 Bells





5 Bells





6 Bells





7 Bells





8 Bells

Moon Phase Dial

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 Moon Phase Dial - PhasesFunction

The purpose of a moon phase dial – like the time dial that tracks the time through the day, is to keep tract of the moon’s position as it travels around the earth, every 291/2 days – which is one lunar month.


The Moon Phases

The moon has no light, so what we see looking at the moon is the Sun’s light reflected from the Moon’s surface.

Consequently as the moon travels around the earth, the amount of sunlight reflecting from its surface changes; giving us eight distinct phases we can easily identify.

Waxing Phases

When the moon is moving away from the sun, the amount of light on its surface increases and we see more of the moon; until it reaches it furthest point away from the Sun and we see the whole (full) moon. We call these phases “waxing” (increasing light). 

Waning Phases

On the other hand when the moon is moving toward the sun the amount of light on its surface decreases and we see less of the moon.  We call these phases “waning” (decreasing light).


Moon Phase Dial – Setting up the correct Phase

Moon Phase Dial


The moon phase dial is designed to show the shape of the moon as it appears in the sky, the number alongside it being the lunar date – from the lunar calendar, which as mentioned above is 291/2 days.

Typically a moon phasedial consist of a round disk displaying two pictures of the moon. One half rotation of the disk occurs every 29.5 days – one lunar cycle. The Full Moon always occurs on the 15th day of the lunar calendar.


  • Find the date of the last New Moon, from an almanac, lunar calendar or an online source (copy and paste this link into your browser:
  • Position the moon phase dial so the moon is in the centre of the display, with the number 15, above it on the moving disc, showing (or under the number15 showing on the arch above the dial).
  • Count the number of days past the last full moon on a calendar.
  • Turn the moon phase dial Clockwise one click for each of the number of days past the last full moon.

If the moon phase dial will not rotate, wait a few hours and try again. The moon dial should move easily so never force it to move. It may be in the 3 hour movement cycle; therefore wait a few hours and try again; you should then be able to easily move it.

Example 1: If today was a full moon, the moon image on the dial would be centred in the display below the 15 on the dial, or the 15 on the arch above the dial. There are two moons on the dial and it makes no difference which one is under the 15.

 Example 2: If the last full moon was 10 days ago, Once the Full moon is centred in the display below  15, move the dial clockwise 10 clicks – one for each day since the last full moon.

If the Clock with moon phase dial stops for more than 24 hours, the moon dial will also stop, and must be reset when the Clock is started again.


Clocks with Moon Phase Dials

Moon Phase Dails can be found on table, wall and floor clocks. Here is link to a Grandfather clock with a Moon Phase Dail.


Long Case Grandfather Floor Clock

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Long Case Grandfather Floor ClockGrandfather Clocks

Long Case Grandfather Floor Clock – Origins

The long case grandfather floor clock, standing between six and eight feet tall, is commonly known as a Grandfather Clock, but is technically known as a Long Case Clock, a descriptive name, as the clock’s mechanism – driven by a falling weight, and regulated by a swinging pendulum – is placed within a long narrow case.

Around 1660, long case floor clocks evolved from the early weight driven “Lantern-Bracket” clocks which were hung on a wall bracket to provide space underneath for the weights to drop.  Enclosing the clock movement within a long (or tall) narrow case to accommodate the dropping weights, enabled the clock to be removed from the wall, and the floor-standing or free-standing clock was born.

Generally, these early clocks’ cases were plain wooded boxes with a wood door. This type of clock – in a tall wood container, resembled a coffin in many people’s eyes, and “coffin clock” is what some called them, alongside the term “long case clock”.

At this time, behind the door of these free-standing floor clocks was a short pendulum, producing a poor level of accuracy.  Clock movements then used a verge escapement mechanism that needed a wide pendulum swing of around 90°, and a pendulum with such wide swings, could not be fitted inside a case.

For this reason, although it was known that the longer pendulums were more accurate; it was not until the invention of the anchor escapement mechanism – by Robert Hook circa 1670, which shortened the pendulum’s swing to around 5° that clock makers were able to incorporate long pendulums into their long case clocks, which although narrow, accommodated them easily.

The longer pendulum not only improved the clock’s accuracy, it produced a slower “beat” and so used less power.  This enabled clocks to run for longer periods, which in turn caused less friction between the component parts of the movement, reducing wear and extending the clock’s life.

William Clement is acknowledged as creating the first long case clock, as we would recognise it today – with a long pendulum, in England around 1680.  A decade after the anchor escapement mechanism was invented; and he in fact disputed credit for it with Robert Hooke.  Within the year, the concept was adopted by Britain’s most prominent clock maker Thomas Tompion, and was quickly taken up by others.

Almost all long case clocks today use a “seconds pendulum” meaning that each swing from left to right (or right to left) takes one second of time.  So, a full swing starting and finishing at the same point (the period) takes two seconds. These pendulums are about a metre (39 inches) long – to the centre of the pendulum bob.

Further improvements in the accuracy of modern clock movements is achieved using a more precise variation of the anchor escapement – called the deadbeat escapement, which is manufacturer to tighter tolerances than its predecessor, reducing friction and recoil against the escape wheel, allowing the pendulum to swing more freely.

While the technical term for the Floor Clock is a “Long Case Clock”, which is still relevant in the 21st century – reflecting the clocks design; most people refer to these clocks as grandfather clocks (the reason – read on!).

Long Case Grandfather Floor Clock – Description

As indicated above, the height of a long case grandfather floor clock arises from housing a long pendulum and set of dropping weights driving the clock’s movement.  Traditionally, long case grandfather clocks were made with two types of movement: an eight-day that requires winding only once a week and one-day (30-hour) movements, which has to be wound every day.

30-hour clocks usually have a single weight to drive both the timekeeping and striking mechanisms.

By contrast, eight-day movements are often driven by two weights – one for the pendulum and the second for the striking mechanism, which usually consisted of a bell ring or chimes – from hammers striking rods. These movements usually have two arbours (keyholes) on either side of the dial to wind each weight separately.

All modern striking long case clocks have eight-day movements. Most of these clocks are cable-driven, which means that the weights are suspended by cables, each of which is wrapped around a pulley mounted above the respective weight. This arrangement doubles the running time allowed by a given weight drop.

As the weights drop, unwinding each cable, they drive the movement, turning the clock hands and displaying the time and striking the bell/chimes. To keep the clock running the weights have to be raised again, building up potential power, by inserting a crank/key into arbours (holes) in the clock’s face and turning it.

Not all grandfather floor clocks use cables; others are chain-driven, where the weights are suspended on one end of a chain that wraps around gears in the clock’s movement, with the other end of each chain hanging free at the side of the weight.  In this design, to raise the weights and wind a chain-driven long case clock up, the free end of each chain is pulled, until the weights settle just under the clock’s face/dial.

Long Case Grandfather Floor Clock – Striking Sequences/Tunes

Around the beginning of the 20th century, 15 minute chime sequences were added to long case clocks.  At a quarter past the hour, 1/4 of the chime sequence plays, at each half hour, 1/2 of the chime sequence then plays, and at the quarter to the hour, 3/4 of the chime sequence plays. Finally, on each hour, a full chime sequence sounds, immediately followed by the hour strike: 1 for one o’clock, 2 for two o’clock etc.

The most common chime tune used in long case clocks is Westminster chimes. Many movements offer alternative options, usually Whittington chimes or St. Michael’s chimes.  The chosen tune is selected by use of a lever/switch mounted on the right side of the dial, which also includes a silence option if desired.

As a result of adding chime sequences, many modern mechanical long case clocks have three weights instead of just two. The left weight provides power for the hour strike; the middle weight provides power for the clock’s pendulum and general timekeeping functions, while the right weight provides power for the quarter-hour chime sequences.

An alternative to this is the power for the strike (left arbour) and the chimes (right arbour) are spring driven, where the spring unwinds over time and wound up again using the crank/key. The power for the clock’s pendulum and general timekeeping functions is provided by a single weight or a pair of weights together on a single yoke attached to the cable/chain.

Long Case Grandfather Floor Clock – Styles

The long case grandfather floor clock come in a variety of styles, traditionally there is the French “Comtoise clock” distinguished by the use of curved lines and featuring a “potbellied” appearance with curved wider middle section, and a heavy elongated ornamented pendulum bob extending up the case.  This style is also referred to as Morbier or Morez.

From Denmark we have the “Bornholm clock” which often had a square-ish head with a crown, and on some a pointed decoration, as well as a window in each side, to view the movement within.  Another variation has bowed broken cornices and a third variation has large bowed cornices.  The case is in three sections: head body and foot, normally with straight lines and always painted sometimes with motifs, and occasionally with simulated Chinese lakarbejde.

Another style is the “pinch waist” clock, with a body/middle section narrower than the head and foot sections.  Variations of this and the other styles can be found in the range of traditional designs built over the years

As well as the traditional styles, Grandfather Clocks today are manufacturer in two other broad categories: Contemporary – to sit in modern designed living and working environments, and Curio clocks, which can be designed for both classical and modern surrounding.

logn case clocks crownsThe crown of the long case grandfather clock – the top, adds a great deal to the clock’s overall appearance and this aspect of design is incorporated in all three style categories mentioned above: contemporary, curio and traditional.

These crowns can themselves be categorised:

          ~ the “Split pediment” also referred to as the Swans Neck Top;

          ~ the “Bonnet pediment” featuring a decorative top centre piece;

          ~ the “Flat top”, which is obviously named for its flat top, and;

          ~ the “Rounded top”, a full circle sitting on a base or a half-circle integrated into the clock’s design.

Whatever the style, all long case grandfather clocks are striking and inspirational pieces of furniture, some with intricate designs, other made with simplicity in mind, but all presenting a classy and grand look.

Grandfather | Grandmother |Grand Daughter

Grandfather clock, grandmother clock, and granddaughter clocks are terms that are all associated with long case floor clocks.  There is no appreciable difference between them, apart from height.

Grandfather clock are usually over 1.8 meters (6ft), while grandmother clocks are between 1.5 meters (5ft), and 1.8 meters (6ft), anything smaller than 1.5 meters (5ft) is classed as a granddaughter clock.

Other elements that distinguish these clocks are, that grandmother clocks tend to be very slim, are spring driven, and have a domed top; along with a dial that is a maximum of eight inches in diameter.  The majority of granddaughter clocks have round, electroplated silver dials with the numbers painted on, not engraved.

So why is it called a Grandfather Clock?

In 1876 an American visiting Great Britain, Henry Clay Work, stayed at the George Hotel in County Durham, England, where he found an old Long Case clock that no longer worked. When Henry asked about the clock he was told that it had always kept perfect time, which in an era when clocks were not so accurate as today, was quite unusual.

However, when one of the brothers who owned the hotel died, the clock started losing time and could not be fixed. It then stopped altogether when the second brother died, aged ninety, and it was never repaired.

Inspired by the story, Henry wrote a song based on it, which became hugely popular. In the song he referred to the long case clock as “Grandfather’s Clock” and afterwards people began calling all long case clocks, grandfather clocks.

Lyrics to My Grandfather’s Clock

by Henry Clay Work

“My grandfather’s clock was too tall for the shelf, so it stood ninety years on the floor.
It was taller by half than the old man himself, but it weighed not a penny weight more.

It was bought on the morn on the day that he was born; it was always his treasure and pride.
But it stopped, short, never to go again, when the old man died.

Ninety years without slumbering tic toc tic toc His life’s seconds numbering tic toc tic toc

In watching its pendulum swing to and fro, many hours he had spent when a boy.
And through childhood and manhood, the clock seemed to know and to share both his grief and his joy.

For, it struck 24 when he entered at the door with a blooming and beautiful bride.
But it stopped, short, never to go again, when the old man died.


My grandfather said that of those he could hire, not a servant so faithful he’d found.
For it kept perfect time and it had one desire, at the close of each day to be wound

At it kept to its place, not a frown upon its face and its hands never hung by its side.
But it stopped, short, never to go again, when the old man died.


It rang an alarm in the still of the night, an alarm that for years had been dumb.
And we knew that his spirit was pluming for flight that his hour of departure had come

Still the clock kept the time with a soft and muffled chime, as we silently stood by his side. But it stopped, short, never to go again, when the old man died.”

Why not have a look at our selection of grandfather  and Grandmother clocks using the menu at the top of the page or this Floor Clocks link.

Clocks History | A brief history of clocks

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Clocks History

Clocks History – article sources:

Clocks history Antique mechanical clock History of Clocks
The History of clocks  covers a very long period, and there have been many different types of clocks over the centuries. Not all historians agree on the history of the clock. The word clock was first used in the 14th century (about 700 years ago). It comes from the word for bell in Latin (“clocca”). At best, historians know that 5000 – 6000 years ago, great civilisations in the Middle East and North Africa started to examine forms of clock-making instead of working with only the monthly and annual calendar. Little is known on exactly how these forms worked or indeed the actual deconstruction of the time, but it has been suggested that the intention was to maximise time available to achieve more as the size of the population grew. Perhaps such future periods of time were intented to benefit the community by allotting specific lengths of time to tasks. Was this the beginning of the working week?
Using the Sun
The first way that people could tell the time was by looking at the sun as it crossed the sky. When the sun was directly overhead in the sky, it was the middle of the day, or noon. When the sun was close to the horizon, it was either early morning (sunrise) or early evening (sunset). Telling the time was not very accurate.
Sundial Clocksclocks history sundial1
With the disappearance of any ancient civilisation, such as the Sumerian culture, knowledge is also lost. Whilst we can but hypothesise on the reasons of why the equivalent to the modern wristwatch was never completed, we know that the ancient Egyptians were next to layout a system of dividing the day into parts, similar to hours. ‘Obelisks’ (tall four-sided tapered monuments) were carefully constructed and even purposefully geographically located we believe around 3500 BC. A shadow was cast as the Sun moved across the sky by the obelisk, which it appears was then marked out in sections, allowing people to clearly see the two halves of the day. Some of the sections have also been found to indicate the ‘year’s longest and shortest days’, which it is thought were developments added later to allow identification of other important time subdivisions. Another ancient Egyptian ‘shadow clock’ or ‘sundial’ has been discovered to have been in use around 1500 BC, which allowed the measuring of the passage of ‘hours’. The sections were divided into ten parts, with two ‘twilight hours’ indicated, occurring in the morning and the evening. For it to work successfully then at midday or noon, the device had to be turned 180 degrees to measure the afternoon hours. The Egyptians also used the ‘Merkhet’, the oldest known astronomical tool, which is believed to have been developed around 600 BC. Two merkhets were used to establish a north-south line which was achieved by lining them up with the ‘Pole Star’. This enabled the measurement of night-time hours, when certain stars crossed the marked meridian. By 30 BC, ‘Vitruvius’ describes thirteen different sundial styles being used across Greece, Asia Minor, and Italy, inherently demonstrating how the development must have grown to be more complex.
Water Clocksclocks history water clock
Around 1400 B.C. (about 3,400 years ago), water clocks were invented in Egypt. The name for a water clock is clepsydra (pronounced KLEP-suh-druh). A water clock was made of two containers of water, one higher than the other. Water traveled from the higher container to the lower container through a tube connecting the containers. The containers had marks showing the water level, and the marks told the time. Look at the picture right. Water drips from the higher container to the lower container. As the water level rises in the lower container, it raises the float on the surface of the water. The float is connected to a stick with notches, and as the stick rises, the notches turn a gear, which moves the hand that points to the time. ‘Water clocks’ were among the earliest time keeping devices that didn’t use the observation of the celestial bodies to calculate the passage of time. The ancient Greeks, it is believed, began using water clocks around 325 BC. Most of these clocks were used to determine the hours of the night, but may have also been used during daylight. An inherent problem with the water clock was that they were not totally accurate, as the system of measurement was based on the flow of water either into, or out of, a container which had markers around the sides. Another very similar form was that of a bowl that sank during a period as it was filled of water from a regulated flow. It is known that water clocks were common across the Middle East, and that these were still being used in North Africa during the early part of the twentieth-century. In the Far East, mechanised ‘astronomical’ and ‘astrological’ clock-making is known to have developed between 200-1300 AD. In 1088 AD, ‘Su Sung’ and his colleagues designed and constructed a highly complex mechanism that incorporated a water-driven escapement, invented about 725 AD. It was over seven metres in height and had all manor of mechanisms running simultaneously. During each hour an observer could view the movement of a power-driven armillary sphere, constructed of bronze rings, an automatically rotating celestial globe, together with five doors that allowed an enticing glimpse of seeing individual statues, all of which rang bells, banged gongs or held inscribed tablets showing the hour or a special time of the day. The appearance and actions would have appeared similar to the automaton we know so well today.
Dividing the Year into Months and Days
The Greeks divided the year into twelve parts that are called months. They divided each month into thirty parts that are called days. Their year had a total of 360 days, or 12 times 30 (12 x 30 = 360). Since the Earth goes around the Sun in one year and follows an almost circular path, the Greeks decided to divide the circle into 360 degrees.
Dividing the Day into Hours, Minutes, and Seconds
The Egyptians and Babylonians decided to divide the day from sunrise to sunset into twelve parts that are called hours. They also divided the night, the time from sunset to sunrise, into twelve hours. But the day and the night are not the same length, and the length of the day and night also changes through the year. This system of measuring the time was not very accurate because the length of an hour changed depending on the time of year. This meant that water clocks had to be adjusted every day. Somebody finally figured out that by dividing the whole day into 24 hours of equal length (12 hours of the day plus 12 hours of the night), the time could be measured much more accurately. Why was the day and night divided into 12 parts? Twelve is about the number of moon cycles in a year, so it is a special number in many cultures. The hour is divided into 60 minutes, and each minute is divided into 60 seconds. The idea of dividing the hour and minute into 60 parts comes from the Sumerian sexagesimal system, which is based on the number 60. This system was developed about 4,000 years ago.
Mechanical Clocks
In 1656, ‘Christian Huygens’ (Dutch scientist), made the first ‘Pendulum clock’, with a mechanism using a ‘natural’ period of oscillation. ‘Galileo Galilei’ is credited, in most historical books, for inventing the pendulum as early as 1582, but his design was not built before his death. Huygens’ clock ,when built, had an error of ‘less than only one minute a day’. This was a massive leap in the development of maintaining accuracy, as this had previously never been achieved. Later refinements to the pendulum clock reduced this margin of error to ‘less than 10 seconds a day’. Huygens, in 1657, developed what is known today as the ‘balance wheel and spring assembly’, which is still found in some of today’s wrist watches. This allowed watches of the seventeenth-century to keep accuracy of time to approximately ten minutes a day. Meanwhile, in London, England (UK) in 1671, ‘William Clement’ began building clocks with an ‘anchor’ or ‘recoil’ escapement, which interfered even less with the perpetual motion of the pendulum system of clock. ‘George Graham’, in 1721, invented a design with the degree of accuracy to ‘one second a day’ by compensating for changes in the pendulum’s length caused by temperature variations. The mechanical clock continued to develop until they achieved an accuracy of ‘a hundredth-of-a-second a day’, when the pendulum clock became the accepted standard in most astronomical observatories.
Pendulum Clocksclocks history pendulum clock
Before pendulum clocks were invented, Peter Henlein of Germany invented a spring-powered clock around 1510. It was not very precise. The first clock with a minute hand was invented by Jost Burgi in 1577. It also had problems. The first practical clock was driven by a pendulum. It was developed by Christian Huygens around 1656. By 1600, the pendulum clock also had a minute hand. The pendulum swings left and right, and as it swings, it turns a wheel with teeth (see the picture to the right). The turning wheel turns the hour and minute hands on the clock. On the first pendulum clocks, the pendulum used to swing a lot (about 50 degrees). As pendulum clocks were improved, the pendulum swung a lot less (about 10 to 15 degrees). One problem with pendulum clocks is that they stopped running after a while and had to be restarted. The first pendulum clock with external batteries was developed around 1840. By 1906, the batteries were inside the clock. As you already learned, a clock only shows 12 hours at a time, and the hour hand must go around the clock twice to measure 24 hours, or a complete day. To tell the first 12 hours of the day (from midnight to noon) apart from the second 12 hours of the day (from noon to midnight), we use these terms: A.M.–Ante meridiem, from the Latin for “before noon”
P.M.– Post meridiem, from the Latin for “after noon”
Quartz Crystal ClocksQuartz is a type of crystal that looks like glass. When you apply voltage, or electricity, and pressure, the quartz crystal vibrates or oscillates at a very constant frequency or rate. The vibration moves the clock’s hands very precisely. Quartz crystal clocks were invented in 1920. Europe. During the period of 500-1500 AD, the development of time measuring devices in Europe is known not to have improved in any great way technologically, relying mainly on the use of the sundial and principles of measurement used in ancient Egypt. These dials were placed above doorways and indicated the midday and four ‘tides’ or times of the sunlit day. In the tenth-century, one English (UK) model showed the marking of the tides compensated for including seasonal changes caused by the Sun’s altitude. In Italy, during the early-to-mid fourteenth-century, large mechanical clocks housed in towers began to appear in several of the large cities. These clocks appear to have been plagued by the same problem as that of the ‘water clock’, that of regulating the mechanisms and maintaining the accurate time. This appears to have been due to the oscillation period of the escapement depending on a driving force which had sufficient friction in the drive mechanism. A technological advance came with the invention of the ‘Spring-powered’ clock, around 1500-1510, credited to ‘Peter Henlein’ of Nuremberg (Germany). These were instantly popular although the spring-powered clock did have one problem, that of slowing down when the mainspring unwound. In the sixteenth-century, and even through until the nineteenth-century, these clocks were mainly the reserve of the wealthy, when the reduced size meant it could now be put on a mantle shelf or table. The development of the spring-powered clock was the precursor to accurate time keeping.
time zones
Time Zones
Because the Earth turns, it is daytime in part of the world when it is nighttime on the other side of the world. In 1884, delegates from 25 countries met and agreed to divide the world into time zones. If you draw a line around the middle of the Earth, it is a circle (equator). The delegates divided the 360 degrees of the circle into 24 zones, each 15 degrees (24 x 15 = 360). They decided to start counting from Greenwich, England, which is 0 degrees longitude. To see a larger picture of the standard time zones of the world, click the picture below.