Prehistoric man, knowing nothing of time, nevertheless sensed it in the rhythms of the sun, moon, and stars, and in the changes of the season. People became even more aware of time when they began to till the soil -- the ancient Egyptians, for example, realized that the planting season was correlated with the flooding of the Nile.
When man began to devise ways to divide the days into hours, it seems everyone welcomed timepieces with enthusiasm. Indeed, the usefulness of clocks to those in all walks of life sounded an enduring theme throughout the centuries.
Stroll through the exhibit you see here and join us on a journey through -- and about -- time.
"To tell the time by consulting the eye of a cat appears to be an absurdity; however, it is practically possible. The pupil of the eye of a cat undergoes a progressive change during the day. In the morning the pupil is round, but accordingly as the day advances it gradually contracts to a point at which, at noon it is only a narrow slit. From noon until evening the reverse occurs; it is oval at 3:00 and round again at 6:00. It is not a rare thing to see old men call the cat to examine its eyes and then tell approximately the time of day." Horological Review, October 3, 1917
One of the oldest methods of telling time is the sundial, which uses the projection of a shadow upon a dial marked with a pattern of lines representing hours of the day. The sundial is accurate only at its location, as the solar time elsewhere on the earth is different. Sundials are known to have been used by the ancient Egyptians as early as 1300 BC. They were usually more accurate than mechanical timepieces until about 120 years ago.
Sundials remain in use today, but usually as ornamental objects in a garden or plaza.They can be as small as a dinner plate or as large as a building..and some buildings have been constructed to act as sundials.
By the 19th century, mechanical clocks were being made in a variety of sizes and shapes, ranging from wrist watches to floor standing pendulum clocks to monster time pieces placed in community buildings. Our exhibit displays some of the typical timepieces our grandparents and great grandparents might have encountered during the course of a day. Some of these are pendulum clocks, others are spring and escapement designs..
Old Church Clock
The old church clock was made in the late 16th century in Northern Italy or Southern France. It originally had the old verge & foliot escapement (a dumbbell-shaped piece that rattled back and forth), which controlled the clock's rate. Timekeeping errors were in the range of a couple of hours per day.
During the late 17th century, the foliot was replaced with a pendulum; this improved the clock's accuracy so its timekeeping errors were within a few minutes per day.
The power source to run this clock was a pair of ropes that fitted into the grooved pulleys alongside the large gears at the bottom of the clock. A heavy weight at one end of the rope provided the driving power, while a light weight at the other end kept the rope from slipping in the groove.
The clock indicated the time with a dial and single hand, similar to the one shown. It also struck the hours on a bell; two dings at 2:00; six dings at 6:00, and so forth. Later, this clock was converted to "French strike": it struck the appropriate number of dings on the hour, but if you missed count, it repeated the time a few minutes later. An examination of the "count-wheel" will show the doubling up of the number of blows to be struck.
The fan fly which regulates the rate at which the clock strikes the bell is missing. It was simply a blade of sheet iron that spins in the air and acted as a brake.
The Pendulum Clock
"You dominate our parlor, standing as you do much taller than any of the human occupants of the house. Your dignity is immense and your moods steady -- you can quiet me from elation just as you can lift me from melancholy. You are a friend to all of us, a regulator on the speed of our lives, and a faithful link between a generation now gone and a generation yet to come. You keep reminding us of our place in the scheme of all things with a special finger that points to our days and a little harvest moon that travels in our private heaven. You are a spokesman for time as you whisper a gentle cadence for the marching seconds, and ring your bell to mark the passing of each hour's parade. You have the special power to lift past into present, to make that which had lived be alive again. You are the voice of my home -- may those who follow me listen too, and through the inward searching you inspire, also learn of peace, of beauty, and of love."
Unsigned note found inside a grandfather clock.
Clocks for mantel
The fireplace mantel was a favored place to keep a clock in the 1800s.
This Seth Thomas clock, manufactured in the 1890s, would have been such
a mantelpiece decoration. Its case, which appears to be fine hardwood,
is actually a cellulose based lamination placed on an inexpensive wood
shell. Collectors refer to this style of a clock as a "Black", because
the clock cases were usually black. This item appears to be an
exception. The clock mechanism is driven by a wound spring.
Time zones were established because railroads needed a standard for timekeeping at various points so timetables for operating trains could be prepared. Without time zones in which each community kept the same time, each town would use local solar time..and no two towns would agree on a common time.The potential for confusion - and collisions - was large.
India, Burma, Afghanistan, Iran, central Australia, Surinam, Newfoundland and several island nations observe time zones that differ from neighboring zones by a half-hour. Nepal is even more unusual -- it's five hours and 45 minutes ahead of Greenwich Mean Time, or 15 minutes ahead of India.
By international agreement, the Earth is divided into 24 time zones, each envisioned as 15 degrees wide --though countries can carve out whatever time zones they please. In the center of each zone, theoretically, the sun is overhead at noon. But at the boundary of two zones, the sun would be overhead at 11:30 a.m. or 12:30 p.m. Because of this, a country on a boundary is more in sync with solar time by choosing a time a half-hour off. Most of the countries with staggered time zones are located close to a boundary or straddle one.
For simplicity's sake, many countries keep only one time, even though they're larger than one time zone -- most notably China, which straddles five zones but keeps Beijing time nation-wide. Iran, Afghanistan, India and Burma all straddle two zones, with their centers more or less at the boundary. By choosing the odd time, they split the difference.
As for central Australia, it was put a half-hour behind eastern Australia, rather than a full hour, because of its business links to the east.
How to explain Nepal? Or Newfoundland, which distances itself by a half hour from neighboring provinces? In many cases a country or territory chooses the odd time to underscore its independence and to be different from its neighbors.
From "Q & A on the News," San Jose Mercury News, October 3, 1993
When ships began to roam the world, and navigation was by latitude, sailors died on foreign shores and reefs that were uncharted. A navigator had to know the exact time at home so that he could compute his location. (Note: See the London Economist account of "The Dawn of Modern Navigation", posted by the chronometer display.) When we had one railroad track and one train, we did not need accurate time. However, with one track and two trains, timing suddenly became very important! When we then added a multitude of railroad systems, with travelers throughout the country, timing became critical -- both for convenience and for personal safety.
And so: What sort of precision did timepieces display throughout the ages?
|DATE||TYPE OF MECHANISM||PRECISION|
|Foliot balance (horizontal swinging weights)||1 part per 10 (2 hours per day)|
|Huygen's first pendulum clocK||1 part per 104 (10 sec/day)|
|Nautical chronometer H4 (balance wheel)||1 part per 105 (1 sec/day)|
|Railroad watch (USA)||5 parts per 105 (30 sec/week)|
|Seth Thomas "Regulator" (pendulum)||6 parts per 106 (15 sec/month)|
|Finest compensated pendulum clock||6 parts per 108 (1 sec/7 months)|
|Bulova "Accutron" (tuning fork)||2 parts per 105 (2 sec/day)|
|Patek-Philippe wristwatch (balance wheel)||2 parts per 105 (2 sec/day)|
|Piezo-quartz watch (consumer grade)||6 parts per 106 (15 sec/month)|
|Quartz secondary standard||5 parts per 1010 (1 sec/63 years)|
|Cesium beam primary standard (HP)||2 parts per 1012 (315 microseconds over the life of the cesium tube[approximately 5 years])|
Henry Warren was a graduate of MIT (Massa-chusetts Institute of Technology) and lived in Ashland, Massachusetts. His new clock, first appearing in 1916, was built around a small motor designed to run on alternating current ("AC"). It was a synchronous movement, absolutely locked to the frequency of the incoming power line. However, Warren was quite surprised to note that his clock was terribly inaccurate, varying by more than 15 minutes a day, unpredictably either fast and slow. Knowing that his clock ran exactly at -- synchronous with -- the AC frequency, he was certain that the error was due to a generator that wandered in speed. He informed the power company of his findings; their response was that their meters showed the speed to be held exactly and precisely at the desired frequency. Their speed control -- sort of a "Cruise Control" for big generators -- obviously was not sufficiently precise. If he ever hoped to reach his goal of performance for his new clock, he had to stabilize the AC generator frequency.
Monitoring the Speed of Power Plant Generator
The Warren Telechron clock system was the answer to this problem. It consisted of two clocks: the first, with a readout on the lowest of the three dials, was a precise spring-driven pendulum movement, checked daily against the National Bureau of Standards reference. The second clock, with a readout on the top dial, was Warren's invention, the synchronous clock driven by the AC from the big generator. But the real novelty was the third dial, positioned between the two clocks and with a total calibration of only five minutes. It had two pointer hands: the first, a black one, was driven by the precision pendulum clock; another hand, colored gold, was driven directly from the AC synchronous clock.
At startup, the operator superimposed the gold and the black hands. From then on, as long as the generator clock ran at exactly the same speed as the precision pendulum reference clock, the gold and the black hands remained one on top of the other. However, if the speed changed on the big generator, causing the synchronous clock to run fast or slow, the two hands would separate. Upon seeing this separation, the power plant technician would change the speed of the big generator.
Note that the instantaneous speed was not constant, but the average speed change was held to zero over a few hours. Any synchronous clock might run a little fast, and then a little slow during the day; but from one day to the next it would average exactly right. The system worked so well that it was adopted not only in the United States, but in over 40 foreign countries.
Significance of Warren Telechron System
With each generator stabilized to a precision frequency, it then became possible to connect the power plants together so that any power plant can tie in to power plants in adjacent cities. If one plant fails, the others in the "power grid" can carry the extra load. With such connections, the electrical utilities developed near-perfect reliability in power delivery.
A drinking glass; the bezel on a watch; a detector for a radio set; the reference (or heart) of a time-keeping standard. What do these totally different objects all have in common?
Confusing but true: each is called a "crystal."
Let's take them one at a time:
1. Crystal, the wine glass: an ornamental object made from crystal, a high-quality clear, colorless glass. Outstanding social properties; no significant electrical properties.
2. Crystal, the bezel on a watch: originally made from this same quality of glass - fragile, subject to scratches, difficult to seal against the outside world. Now generally formed from flexible plastic or molded as part of the case housing a digital display.
3. Crystal, a detector for a radio set: Experimenters tried different metallic c rystal compounds in the inexpensive "crystal sets" betwee 1918-1928. Lead sulfide, better known as galena, turned out to be one of the most sensitive detectors (Fig 3-A).
Some of the lore and mystique of the early radio days centered about setting the "catwhisker" probe on the most sensitive spot of the crystal. There are still some of us around, particularly during our Saturday morning workshops, who recall that thrill of seeking out a radio station with our crystal set!
Two World Wars and untold millions of crystal detectors later, device fabrication and packaging became more sophisticated, but the units were still called crystal detectors. Microwave units for radar and point-to-point communication (Fig. 3-B), general-purpose diodes (Fig. 3-C), and power control devices (Fig 3-D) still appear on parts lists and circuit drawings with the symbol "CR" for crystal.
4. Crystal, a piezo-electric quartz element: Over 100 years ago, the Curie brothers, working in Paris, discovered the piezo-electric effect. When they applied pressure to a piece of quartz, it generated an electric charge. The inverse effect was discovered by Lippmann in 1881: when a voltage is applied to the quartz plate, it expands. But that was only the beginning of knowledge!
The natural quartz appears as a hexagonal crystal having pointed ends (Fig. 4-A shows a fractured section of the hex crystal). A small "plate" of crystal, cut from a slice (Fig 4-B) of the hex crystal, will vibrate at a remarkably precise rate, and deliver a corresponding alternating voltage that is precise in frequency.
These small crystal "plates" now can act as the resonant circuit in a tremendous number of applications. This crystal (Fig. 4-C for devices from the '40's) is the device that "knows" where to tune your auto radio or TV set; it keeps your cellular phone from wandering into the aircraft frequencies (among other places). It set the operating frequency of the long-distance telephone carrier systems (Fig. 4-D)
And do you want to know what time it really is? From the 1930s to the 1950s, a piezo-electric quartz oscillator, very finely polished for greater frequency stability, took over the time-keeping duties formerly dominated by the ultra-precise pendulum clock movements (Fig. 4-E). The Japanese in the late 1960's designed the quartz movement into watches as a replacement for the balance-wheel reference ....and instantly rendered obsolete the "tick-tock" timepiece. Next to the $5 quartz watch, Patek-Philippe and Vacheron-Constantin were second-rate performers.
Electric clocks were well-known by the 1950s. However; no one had ever made a production-model electric wristwatch. In early 1952, the Hamilton Watch Company of Lancaster, Pennsylvania embarked upon a research and development program for such a watch. Their quest was ill-fated almost from the beginning because of poor market release timing, second-best choices in technological trail-blazing, and the crippling permanence of poor quality in the early models.
This electric watch was basically a standard mechanical unit, with an electric drive instead of a hand-wound spring to keep it running. Initial design used a conventional balance wheel as the regulator. A coil and magnet system switched by a set of contacts pulsed the balance wheel, giving it a little push each time it swung past the trigger point. The R and D work was almost exclusively in: the magnetic coupling to the balance wheel; a tiny set of moving contacts to switch the energy to the magnetic system; and a new type of battery for use in watches.
Late in 1952, the research group considered the possibility of an electric watch using either a vibrating reed (resonant tuning fork!) or a piezo-electric crystal to regulate the timekeeping. Unfortunately, they decided against either of these techniques as being too advanced for the state of the transistor art, as well as being too radical a step from the classic mechanical watch.
Conquering many design problems, as well as being forced into new metallurgical techniques, the development group finally announced their first production unit, the Hamilton 500 Electric, on January, 1957. However, production problems and resultant poor quality persisted, giving the watch a lasting bad image.
The greatly improved successor model, the 505, appearing in 1961 and used in several different watch models such as the depicted Nautilus, came too late. The Bulova Accutron, selling against the faults of the 500, began to take over the precision watch market. The final blow was delivered by the new Timex, a watch design so closely resembling the Hamilton 505 that it was the target of a lawsuit. In 1969 Hamilton terminated the production program of the 500 series.
Anchor (verge) -- a device that regulates the speed of rotation of the escape wheel.
Arbor -- a steel shaft or rod on which wheels and pinions are affixed.
Bridge (cock) -- a bracket from which the pendulum suspends.
Bushing -- an insert of hard material in a clock plate at the point of arbor pivot to allow for added wear. In watches, bushing is usually a mineral substance known as a jewel.
Chapter -- the ring on the dial plate on which are painted or engraved the hour numerals and minute graduations.
Collet -- a brass collar that holds a wheel on an arbor.
Count wheel -- a wheel with spaced slots that indexes the correct number of blows the hammer makes on the bell when the clock is striking.
Crutch wire -- a wire that carries the impulse from the escapement to the pendulum.
Dial arch -- the arched portion at the top of many dials (some dials are square). It may contain a boss, a moon dial, or decoration.
Dial foot -- a pillar on the back of a dial for attaching the dial to a false plate or movement.
Dial plate -- a plate, usually brass, iron, or wood, on which the dial is engraved or painted.
Escapement -- a device by which the pendulum controls the rate of time keeping. It consists of an anchor and an escape wheel.
Escape wheel -- a wheel at the end of the wheel train that is engaged by the anchor to regulate the clock's running.
False plate -- an intermediate plate between the movement and dial on some clocks to aid fitting the dial to the movement.
Fly -- a wine-resistant fan that regulates the speed of striking or chiming.
Great wheel -- the first wheel in a train to which is usually attached the winding arbor and drum.
Moon dial -- a dial, often found in the arch portion of a clock dial, that indicates the cycle of the moon.
Motion train-- a series of wheels that regulates the rotation of the hour and minute hands.
Pallets -- the two projections from the ends of the anchor that engage with the escape-wheel teeth and allow one tooth to pass with each complete swing of the pendulum.
Pendulum -- a swinging device attached to the escapement by means of the crutch that controls the rate of time keeping.
Pillar -- a turned post of metal or wood that connects to the front and back plates and establishes a fixed distance between them.
Pinion -- a small wheel with twelve or less teeth, called leaves, that meshes with a larger wheel.
Pivot -- a hole in a clock plate in which an arbor end rotates.
Plates -- two parallel pieces of metal or wood between which the wheels, pinions, and arbors are fitted.
Rack and snail -- an indexing system for striking that sets itself for correct striking shortly before striking begins.
Seat board -- a wooden board on which a clock movement sits when in a case.
Spandrels -- painted or cast-metal decoration for dials.
Train -- a series of wheels and pinions through which power is transmitted from its source (usually weights or springs) to the escapement.
Wheel -- a circular piece of metal on the perimeter of which are cut teeth.
Winding drum (barrel) -- a cylinder onto which the cord holding the weight is wound.
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last updated: November 3, 2004
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