The earliest item in the collection is an extremely rare Egyptian merkhet. The astronomy collection has a large collection of Arabic and European horary quadrants. The large sundial collection includes an altitude dial by Humfrey Cole, which is one of the earliest high-quality English scientific instruments.
The Museum’s Measuring Time gallery contains rare and important examples of early pendulum clocks including a Salomon Coster Haagsche Klokje, one of only seven surviving. The Museum also owns a wall clock signed by Jan van Call and dated 1657: this would make it the world’s oldest surviving pendulum clock but there are ongoing debates as to whether it is genuine. The van Call clock is on display at the British Museum.
There is an extensive study collection of watches and escapements. A notable item is one of the first balance spring watches by Thomas Tompion, possibly made by him at Robert Hooke’s suggestion.
The collections are particularly strong in electrical horology, with holdings including the first Shortt free pendulum clock and a splendid early example by Alexander Bain. There are two very significant developments in late 20th century timekeeping: one of the earliest quartz clocks and the first successful caesium atomic clock. The collection also includes parts of the apparatus which delivered the Greenwich time signal from 1965-90, and the first prototype for the Clock of the Long Now.
The Byzantine Sundial Calendar
One of the most exceptional items in the collection is the Byzantine Sundial Calendar. Dated to around the late 5th or 6th century CE, it is second-oldest geared mechanism known to survive (after the Antikythera Mechanism, on display at the National Archaeological Museum in Athens). Only four fragments of the instrument survive.
The largest surviving part of the instrument formed one of its faces, a travelling sundial. It is inscribed with a degree scale for setting to the user’s latitude and a month scale for setting the Sun’s declination for the time of year. A reference table lists the names of sixteen cities and provinces around the Byzantine Empire alongside their latitudes.
The instrument also functioned as a calendar. A smaller circular scale, offset from the centre, shows the day of the week. Michael Wright’s study of the gear ratios of the smaller fragments surviving from the internal mechanism indicates that the user would have moved a stem in the day-scale to turn the calendar forward each day, engaging the other larger fragment which displayed the day of the month and the phase of the Moon on the instrument’s other face. A description of a later calendar instrument suggests that this instrument may also have displayed the position of the Sun and Moon in the Zodiac.
The Wells Cathedral Clock
The Museum has an excellent collection of turret clocks. The star of the collection is the Wells Cathedral Clock (on long term loan from the Cathedral), the world’s second-oldest working clock. It was almost certainly built by the same craftsmen as the slightly earlier clock at Salisbury Cathedral, which is also operational. The Wells Clock has been in almost continuous operation since it was built in the late 14th century – mentions in the Cathedral’s records date back to 1392.
The clock mechanism has three trains of wheels, each driven by a separate weight but controlled by the same escapement. One train would have controlled the interior and exterior clock faces, one the hour actions and one the quarter-hour actions. The clock originally had a foliot balance and a verge escapement., of which signs can still be seen. In the 17th century, like many public clocks, it was fitted with a pendulum and an anchor escapement. (The Museum’s collections also include the Dover Castle Clock, one of very few clocks to retain its original foliot balance). In 1837, the mechanism was replaced, with the original placed in storage at the Cathedral. This original mechanism came to the Patent Office Museum in London in 1871, where some wheels were replaced and new bells (of steel rather than the usual bell metal) added, and became part of the Science Museum’s collections in 1884. The clock is currently on display in the Measuring Time gallery and, following an overhaul in 2009, is still wound regularly by the Museum’s conservators. Meanwhile the original clock face remains at Wells Cathedral; the mechanism there is now wound automatically.
Brand, Stewart. Clock Of The Long Now: Time And Responsibility: The Ideas Behind The World’s Slowest Computer. Basic Books, 2000.
Field, J.V. and Wright, M.T., “Gears from the Byzantines: a Portable Sundial with Calendrical Gearing”, Annals of Science, 42 (1985), pp. 87 – 138.
Howgrave-Graham, R.P. The Wells Clock. Friends of Wells Cathedral, 1978.
Thompson, David. “The Wall Clock Dated 1657, Signed Jan van Call”, Antiquarian Horology, 33(6) (2012), pp 739-761
The ancient art of time measurement
The art of time measurement is one of the great advances of humankind. This centuries-old heritage is rightfully conserved in numerous, though often little-known, museums. So as to bring these riches to life, HH Magazine presents some of the most exceptional pieces, chosen for their technical significance, historical importance, or for their beauty. This regular feature trains the spotlight on a timepiece which has been chosen and described by the curator of the horological collection of one of the approximately two hundred public or private museums which conserve clocks and watches in their collections.