Watches: A 500-year history of how to set the time

This article first appeared in The Edge Financial Daily, on August 7, 2019.

To be of any use, watches must be set to a time standard that is trustworthy.

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WATCHES, it hardly needs to be said, need to be set to be of any use; and to be of any use, they must be set to a time standard that is trustworthy. This is something we scarcely think about today — someone is taking care of it; the Internet is taking care of it or atomic clocks are taking care of it or the US Naval Observatory is taking care of it. But for most of the history of watchmaking, those resources were not available, and so other time standards had to be used if you wanted to set your watch precisely.

In the early days of watchmaking — the end of the 16th century and much of the 17th — setting a watch was not a particularly emotionally stressful experience because watches were not especially accurate anyway. Often they ran for less than a day, and if they kept time to within a half an hour a day, they were performing well. Serious timekeeping was a matter for public clocks and for sundials. The latter provided probably the most accurate time, as the performance of a sundial is based on the rotation of the earth, which is extremely stable. The earth’s rotation is slowing ever so slightly thanks to tidal effects from the moon, but it amounts to a minute lengthening of the day, which has only increased in length by 2.3 milliseconds per century. At night, the time could be told with extreme accuracy by observing stellar transits, which are the times at which a given star crosses a certain point in the night sky. The ancient Egyptians used a device called a merkhet, which means “an instrument of knowing”, to observe the transits of stars in order to tell the time at night. Needless to say, they were not using the merkhet to set watches but the basic principle of using astronomy as most precise time standard continued for many thousands of years.

Setting a watch, if you were lucky enough to own one in the 16th or 17th century — portable timekeepers were for the rich and often, even if a watch were cased in gold and precious stones, the movement would have been more valuable than the case — was not the obsessive matter that it is today. A sundial would suffice if the day were fine or, after the development of the first pendulum clock, a clock. The pendulum clock was invented by Dutch mathematician and physicist Christiaan Huygens in 1656 and patented the following year. After refinements to the design — including the invention of the deadbeat escapement by Englishman Richard Towneley in 1657, which was notably used for two precision regulators made by Tompion for the Greenwich Observatory in 1676 — the pendulum clock would be the most accurate timekeeping device up until the beginning of the production of practical quartz clocks in the mid-20th century.

It is interesting for watch lovers to reflect on the fact that from a technical perspective, the most fundamental problems in precision timekeeping were solved by pendulum clocks by the end of the 17th century and that the watch would spend the next two centuries or so basically trying to catch up. Public clocks in their earliest incarnations were often not much better timekeepers than watches, thanks to the erratic performance of the verge escapement but gradually, many of the earliest tower clocks had their verge escapements replaced with pendulums and anchor escapements. Later, high-precision, constant-force gravity escapements, such as the one used in the great clock in the Tower of Westminster (better known as Big Ben) came into use. Other than astronomical observations, the tolling of the time by such clocks and their dials provided the most reliable time standard for anyone wanting to set the time accurately on their watch.

One of the most interesting public time standards are so-called time balls, the first experience of which, for many of us, was probably seeing the ball drop at midnight over Times Square, New York, on New Year’s Eve. As it turns out, using the drop of a large ball as a signalling device is a time-honoured way of transmitting the time visually; it has the advantage over a bell of showing a precise moment in time. The system is quite old and they were much used to transmit the time to ships at harbour from a station on land, so mariners could set their chronometers before setting sail. One of the best known time balls is on top of the Octagon Room of the Greenwich Observatory, which was installed in 1833; it has been dropping at 1pm every day ever since. Generally, the procedure seems to have been to start lifting the time ball five minutes or so before the hour to alert the ships at anchor that the time signal was about to be sent; the time was recorded at the moment the ball began to drop, not when it reached the bottom. There are several dozen time balls still in operation around the world, including the Deal Time Ball in Deal, England (Deal was an anchorage for fighting ships during the Napoleonic Wars). The Deal Time Ball was triggered remotely by a telegraph signal from the Royal Observatory. In some locations, the time was signalled by firing a gun — these were set off at different times depending on the location, although noon had always been a perennial favourite. In Cape Town, South Africa, a noon gun is still fired as it has been every day at noon since 1806 from a battery on Signal Hill. There is also a 9pm gun fired every night in Vancouver, British Columbia — this particular cannon is a muzzle-loader, a 12-pounder for you naval history buffs, which was cast in 1816 and has the crests of George III and the First Earl of Mulgrave, who was the Master-General of Ordnance, on the barrel.

The invention of the telegraph provided the ability for multiple locations to not only receive an accurate time signal more or less instantaneously, but also to be coordinated to the same time; this was especially essential for rail roads, the development of which spurred the evolution of time zones. The problem of setting a watch accurately had become much simpler, although a fundamental transition had occurred. For most of the history of timekeeping, the time in question was local time; to put it in simplest terms, noon was when the sun stood at its zenith in the sky. Then, gradually, the concept of mean time evolved — mean time relies on the notion of a day of average length, which is the same throughout the year, rather than on the solar day, which can vary by a quarter of an hour or more either way, depending on the time of year. The difference between mean local time and solar time is in fact nothing other than the famous equation of time, and to aid in setting clocks by a sundial (in your country manor home, far from the madding crowd where the tolling of Big Ben would have been inaudible, perhaps) pendulum clocks often had tables for the equation of time pasted inside their cabinets for easy reference. — Bloomberg

This article was originally published on Hodinkee.