turret clock

Public clocks played an important timekeeping role in daily life until the 20th century, when accurate watches became cheap enough for ordinary people to afford. Today the time-disseminating functions of turret clocks are not much needed, and they are mainly built and preserved for traditional, decorative, and artistic reasons. To turn the large hands and run the striking train, the mechanism of turret clocks must be more powerful than that of ordinary clocks. Traditional turret clocks are large pendulum clocks run by hanging weights, but modern ones are often run by electricity.

• Illustration — Verge and foliot tower clock mechanism in the De Wyck (De Vick) clock, built in Paris by Henri de Wyck in 1379.

Water clocks are reported as early as the 16th century B.C. and were used in the ancient world, but these were domestic clocks. Beginning in the Middle Ages around 1000 A.D. striking water clocks were invented, which rang bells on the canonical hours for the purpose of calling the community to prayer. Installed in clock towers in cathedrals, monasteries and town squares so they could be heard at long distances, these were the first turret clocks. By the 13th century towns in Europe competed with each other to build the most elaborate, beautiful clocks. Water clocks kept time by the rate of water flowing through an orifice. Since the rate of flow varies with pressure which is proportional to the height of water in the source container, and viscosity which varies with temperature during the day, water clocks had limited accuracy. Other disadvantages were that they required water to be manually hauled in a bucket from a well or river to fill the clock reservoir every day, and froze solid in winter.

The first all-mechanical clocks which emerged in Europe in the late 13th century kept time with a verge escapement and foliot (also known as crown and balance wheels). In the second half of the 14th century, over 500 striking turret clocks were installed in public buildings all over Europe. The new mechanical clocks were easier to maintain than water clocks, as the power to run the clock was provided by turning a crank to raise a weight on a cord, and they also did not freeze during winter, so they became the standard mechanism used in the turret clocks being installed in bell towers in churches, cathedrals, monasteries and town halls all over Europe. The verge and foliot timekeeping mechanism in these early mechanical clocks was very inaccurate, as the primitive foliot balance wheel did not have a balance spring to provide a restoring force, so the balance wheel was not a harmonic oscillator with an inherent resonant frequency or "beat"; its rate varied with variations in the force of the wheel train. The error in the first mechanical clocks may have been several hours per day. Therefore, the clock had to be frequently reset by the passage of the sun or stars overhead.

The pendulum clock was invented and patented in 1657 by Dutch scientist Christiaan Huygens, inspired by the superior timekeeping properties of the pendulum discovered beginning in 1602 by Italian scientist Galileo Galilei. Pendulum clocks were much more accurate than the previous foliot clocks, improving timekeeping accuracy of the best precision clocks from 15 minutes per day to perhaps 10 seconds a day. Within a few decades most tower clocks throughout Europe were rebuilt to convert the previous verge and foliot escapement to pendulums. Almost no examples of the original verge and foliot mechanisms of these early clocks have survived to the present day. The accuracy of the pendulum clock was increased by the invention of the anchor escapement in 1657 by Robert Hooke, which quickly replaced the primitive verge escapement in pendulum clocks. The first tower clock with the new escapement was the Wadham College Clock, built at Wadham College, Oxford, UK, in 1670, probably by clockmaker Joseph Knibb. The anchor escapement reduced the pendulum's width of swing from 80 to 100° in the verge clock to 3-6°. This greatly reduced the energy consumed by the pendulum, and allowed longer pendulums to be used. While domestic pendulum clocks usually use a seconds pendulum 1.0 meter long, tower clocks often use a 1.5 second pendulum, 2.25 m long, or a two-second pendulum, 4 m long. Tower clocks had a source of error not found in other clocks: the varying torque on the wheel train caused by the weight of the huge external clock hands as they turned, which was made worse by seasonal snow, ice and wind loads on the hands. The variations in force, applied to the pendulum by the escape wheel, caused the period of the pendulum to vary. During the 19th century specialized escapements were invented for tower clocks to mitigate this problem. In the most common type, called gravity escapements, instead of applying the force of the gear train to push the pendulum directly, the escape wheel instead lifted a weighted lever, which was then released and its weight gave the pendulum a push during its downward swing. This isolated the pendulum from variations in the drive force. One of the most widely used types was the three-legged gravity escapement invented in 1854 by Edmund Beckett (Lord Grimsthorpe).

Electric turret clocks and hybrid mechanical/electric clocks were introduced in the late 19th century. Some mechanical turret clocks are wound by an electric motor. These are still considered to be mechanical clocks.

This table shows some of the turret clocks which were installed throughout Europe. It is not complete and mainly serves to illustrate the rate of adoption. There are hardly any surviving turret clock mechanisms that date before 1400, and because of extensive rebuilding of clocks the authenticity of those that do survive is disputed. What little is known of their mechanisms is mostly gleaned from manuscript sources. The "country" column refers to the present (2012) international boundaries. For example, Colmar was in Germany in 1370, but is now in France.

The verge and foliot escapement is thought to have been introduced sometime at the end of the thirteenth century, so very few if any of these clocks had foliot mechanisms; most were water clocks or in a few cases, possibly mercury. • Year — Country — Place — Location — Name — Type — Mention — Comment • 1283 — England — Dunstable — Priory — horologium — not known — Annals of the priory 1283 – Eodem anno fecimus horologium quod est supra pulpitum collocatum. — Probably a verge and foliot clock because it was mounted over the rood screen, where refilling a water clock would have been difficult, it has been proposed as the earliest known mechanical clock. • 1284 — England — Exeter — Cathedral — Exeter cathedral clock — nowrap|not known — grant made July 1284 to Roger de Ropford, bellfounder, to repair "orologium" — It is unlikely that this 1284 clock was a verge and foliot clock. The clock mentioned in the grant was probably a water clock. In 1423, a new clock was installed, which is probably the one from which remnants of the striking train can still be seen. • 1286 — England — London — St Paul's Cathedral — Bartholomo Orologiario clock — not known — Compotus Bracini 1286 — probably a water clock • 1288 (?) — England — Oxford — Merton College — not known — bursarial accounts "Expense orologii" — probably a water clock • 1290 — England — Norwich — Norwich Cathedral — not known — Sacrist's roll 1290 "In emendacione orologio" — probably a water clock • 1291 — England — Ely — Ely Abbey — not known — Sacrist's roll 1291 "pro custodia orologii" — probably a water clock • 1292 — England — Canterbury — Christchurch Cathedral — novum orolgium — not known — list of Prior Henry of Eastry's works "novum orologium mangum in Ecclesia" — probably a water clock

During the fourteenth century, the emergence of the foliot replaced the high-maintenance water clocks. It is not known when that happened exactly and which of the early 14th century clocks were water clocks and which ones use a foliot. The Heinrich von Wieck clock in Paris dating from 1362 is the first clock of which it is known with certainty that it had a foliot and a verge escapement. The fact that there is a sudden increase in the number of recorded turret clock installations points to the fact that these new clocks use verge & foliot. This happens in the years 1350 and onwards. • Year — Country — Place — Location — Name — Type — Mention — Comment • 1304 — Germany — Erfurt — Benedict abbey St. Peter — "Schelle" — not known — consecration of "Petronella" and "Scolastica" — probably a mechanical alarm clock • 1305 — Germany — Augsburg — cathedral — not known — the "Domkustos" E. v. Nidlingen donates to the cathedral a "good and well adjusted clock" — probably a mechanical alarm clock • 1306 — England — Salisbury — Salisbury Cathedral — not known — composition concluded 26 August 1306 "Before the clock of the cathedral had struck one no person was to purchase or cause to be purchased.... — probably a water clock • 1308 — France — Cambrai — Cathedral — not known — mention of a clock, which was mended and equipped with moving figures in 1348, and fitted with a strike and an angel in 1398 • 1309 — Italy — Milan — church St. Eustorgio — not known — mention of a metal clock, which was repaired in 1333 and 1555 • 1314 — France — Caen — church St. Pierre — not known — mention of a striking clock • 1316 — Poland — Brzeg — town hall — not known — weights of the clock still present. New bell cast for clock 1370, replaced by new clock 1414 • 1322 — England — Norwich — Norwich Cathedral priory — Norwich Cathedral astronomical clock — astronomical clock — Sacrist's roll of Norwich cathedral of 1322 to 1325 mentions the construction and installation of a clock which had a large astronomical dial and automata including 59 images and a choir or procession of monks — earliest detailed account of the organisation and of the craftsmen and materials involved in such a project • 1325–43 — France — Cluny — collegiate church — not known — Petrus de Chastelux builds a new clock • 1327 — England — St Albans — St Albans Cathedral — astronomical clock — drawings — Earliest clock for which there is detailed description of the escapement, this had a 'strob' escapement, a variation of a verge and foliot with two escape wheels. • 1336 — Italy — Milan — town — public striking clock with 24-hour dial — Annales Mediolanenses Anonymi — According to Bilfinger, this is the first mechanical striking clock and could have been made by de Dondi. This is the first time a clock is mentioned that strikes consecutive hours, e.g. once at 1, twice at two, etc. and that strikes day and night. As there are detailed descriptions of what the clock does, it was considered a novelty. Another candidate for the first mechanical clock. • 1348–64 — Italy — Padua — Castle Tower — Astrarium — astronomical clock with strike, verge and crown balance wheel — Il Tractatus Astarii — Giovanni de Dondi • 1351 — England — Windsor Castle — Great Tower — made in London by three Lombards (from Italy) who arrived 8/4/1352 and left on 24 May 1352 • 1351 — Italy — Orvieto — clock tower next to the cathedral — striking clock with jacquemart • 1352–1354 — France — Strasbourg — cathedral — astronomical clock. Three dials: bottom year dial with saint days, middle hour dial, top hourly procession of 3 kings before Maria, at the top a crowing rooster. — taken out of service in 1547 • 1353 — Italy — Genoa — striking clock • 1354 — Italy — Florence — Palazzo Vecchio • 1355–71 — Italy — Reggio — striking clock • 1356 — Italy — Bologna — castle tower — striking clock • 1356–1361 — Germany — Nuremberg — Frauenkirche — striking clock with display of the prince-electors around the Kaiser — substituted in 1508/09 with the clock on the outside of the Frauenkirche • 1359 — Germany — Frankenberg — Pfarrkirche — astronomical clock with the three kings around the Virgin Mary • 1359 — Italy — Siena — city tower — Bartolo Giordi mounts a clock on the city tower • 1361 — Germany — Frankfurt — cathedral — astronomical clock — made by Jacob, improved 1383, taken out of service 1605 • 1361 — Germany — Munich — city tower — mention of existing clock • 1362 — Belgium — Brussels — St Nicholas church — not known — mention of a turret clock • 1362 — Italy — Ferrara — castle tower — clock mounted on castle tower • 1362–1370 — France — Paris — Tour de l'Horloge — verge and foliot striking clock — Froissart's poem "L'Horloge amoureuse" mentions the clock. Drawing exists. — a drawing of the going train shows a door frame construction. Built by the German Heinrich von Wiek. • 1364 — Germany — Augsburg — Perlachturm — striking clock — clock was repaired in 1369 and a quarter strike was added in 1526 • 1365–1367 — England — London — Westminster Palace — not known — a clock tower on the north wall at the end of the King's Garden opposite the entrance to the great hall was begun in 1365 and finished in 1367. • 1366 — Spain — Toledo — cathedral — goldsmith Gonzalo Perez supplies a clock for the tower of the cathedral • 1366–1368 — Switzerland — Zurich — Petersturm — striking clock — Master Chunrad von Cloten builds a striking clock for the Petersturm • 1366 — England — Kent — Queenborough Castle — striking clock • 1367 — Poland — Wrocław — town hall — mention of existing town hall clock • 1368 — England — Kings Langley — Kings Langley Manor — striking clock — Edward III provided a patent giving safe conduct to three Flemish clockmakers. These people probably built the clock. — after the expiry of the patent in 1369 John Lincoln was appointed as Royal clock keeper. • 1368 — Czechia — Opava — Town council signs contract with master Swelbel to furnish a clock • 1369 — Germany — Mainz — Pfarrkirche St. Quentin — striking clock • 1370 — France — Colmar — cathedral tower — striking clock • 1370 — Poland — Świdnica — the town council engages the services of master Swelbel to furnish a clock, that is as good or better than the clock at Wroclaw. • 1371 — England — York — York Minster — striking clock — Fabric Rolls of York Minster record purchase of a new clock made by John Clareburgh in 1371 or £13 6s. 8d. • 1372 — Belgium — Golzinne — castle — striking clock — Louis Defiens furnishes a striking clock for the castle • 1372–1373 — France — Strasbourg — cathedral — striking clock — Heinrich Halder mounts a striking clock on the cathedral tower • 1376 — Belgium — Ghent — Belfried — striking clock • 1376 — France — Sens — a clock with several bells is manufactured • 1376 — France — Beauté-sur-Marne — castle — Pierre de S. Béate furnishes a clock for the castle • 1377 — Belgium — Dendermonde — belfry — Jan van Delft manufactures a clock for the belfry • 1377 — France — Valenciennes — town hall — the town hall clock is replaced and fitted with 2 striking figures • 1377 — Italy — Vicenza — town hall — striking clock — Master Facius Pisanus manufactures a new striking clock for the town hall • 1377 — Belgium — Ypres — belfry — striking clock with several bells • 1380 — Germany — Bamberg — cathedral — clock installed at the cathedral • 1380 — France — Nieppe — castle — Pierre Daimville engaged to furnish a metal clock weighing 300 pounds for the castle, which already has an existing clock • 1382–84 — Germany — Hamburg — Nikolaikirche — striking clock — Blacksmith Schinkel furnishes a public striking clock for the Nikolaikirche • 1383–1384 — France — Dijon — Notre-Dame — striking clock — the clock taken from Courtrai in Belgium in 1382 is mounted on the tower of Notre-Dame • 1383 — Germany — Fritzlar — mention of a turret clock • 1383 — France — Lyon — eglise St. Jean — striking clock — mention of a small striking clock at St. Jean • 1384 — Germany — Friedberg — striking clock — Wernher von Ilbenstedt manufactures a striking clock • 1384 — Germany — Minden — cathedral — mention of the cathedral clock being repaired • 1385 — Switzerland — Luzern — Graggenturm — striking clock — Blacksmith H. Halder furnishes a striking clock for the Graggenturm and leaves a manual for the treatment of the clock — The operating instructions for this clock were written down, and clearly refer to a verge and foliot clock. the "frowen gemuete [happy/agitated mood]" is the foliot. • 1386 — Germany — Braunschweig — Katharinenkirche — Marquard furnishes a clock for the Katharinenkirche. The cathedral already had a clock in 1346 • 1386 — England — Salisbury — Salisbury Cathedral — Salisbury Cathedral clock — Striking Clock — Deed — might not be the clock on display at the cathedral • 1386 — Germany — Würzburg — cathedral — clock at the cathedral mentioned • 1388 — France — Béthune — belfry — striking clock — The citizens of Bethune want to re-construct the existing belfry and put up a clock. "... pour pouvoir reconstruire leur beffroi qui etait a present moult demolis et venus k ruyne et en peril de keir (tomber) de jour en jour et en obtenir l'autorisation d'y placer une orloge pour memore des heures de jour et de nuit sicomme il est en pluseurs autres lieux et bonnes villes du paus environ". — We have a reference here on how common turret clocks have become – they refer to " a clock to remind of the hours of the day and the night as it is now common in other places and good towns...". This is also a reference that shows that turret clocks struck the time day and night. • 1388 — Germany — Magdeburg — Cathedral — striking clock — mention of a striking clock at the cathedral • 1389 — France — Rouen — belfry — striking clock with quarter strike — Jehan de Felains paid 70 Livres for a clock with a quarter strike for the belfry • 1391 — France — Metz — cathedral — striking clock with quarter strike — Manufactured by Heinrich von Wieck • 1392 — France — Chartres — striking clock — clockmaker and blacksmith Philibert Mauvoisin instructed to make a striking clock resembling the one at the Paris castle • 1392 — Germany — Hanover — market church — blacksmiths Meistorpe and Hans Krieten furnish a clock for the market church • 1392–1393 — England — Wells — Wells Cathedral — striking clock — if this is the clock now shown at the British Museum in London is questionable • 1394 — Germany — Stralsund — Nikolaikirche — astronomical clock — Nikolaus Lilienfeld furnished a clock for the Nikolaikirche • 1395 — Germany — Doberan — church — astronomical clock — an astronomical clock similar to the one in Stralsund is put up at the church • 1395 — Germany — Speyer — Altburgtor — striking clock — a striking clock is reported at the Altburgtor and at the Predigerkirche • 1398–1401 — Germany — Villingen — astronomical clock — Master Claus Gutsch manufactures an astronomical clock after the Strasbourg clock. It becomes apparent that even small towns can afford to put up public striking clocks. Turret clocks are now common throughout Europe. No surviving clock mechanisms (apart from the claims from Salisbury and Wells) is known from this era.