The earliest clocks and watchesCopyright © David Boettcher 2006 - 2017 all rights reserved.
Mechanical clocks appeared in Europe during the thirteenth century. These were usually installed in towers, and used bells to sound the hours, hence the name "clock" from the Medieval Latin word clocca (bell). Their purpose was to sound the canonical hours, the times during the day at which prayers were said. They were weight driven mechanisms, and as time went past smaller versions started to be made for use in houses. At some stage dials and hands were added to indicate the time, with a chapter ring marking out the hours.
For some two hundred years, clocks were driven by falling weights. Although flat pieces of steel had been used as springs in locks for many centuries, the invention of the spiral coiled flat spring in the 15th century meant that a spring could be used to drive the clock mechanism instead of weights. Clocks could now be made small enough to stand on a table instead of hanging on a wall, and for the first time could be moved around while they were going. Inevitably these spring driven clocks, usually in the shape of a drum or tambour, were made smaller and smaller as their makers showed off their skills, and eventually became small enough so that they could be carried on the person as ornaments, initially on a neck chain, and then hanging from the belt. These were the first watches.
The first watches used the verge and foliot escapement as found in lantern clocks. There was no balance spring, and the timekeeping depended entirely on the inertia of the foliot as it was accelerated one way and the other by the crown wheel, or escape wheel, under the force of the main spring. In the 17th century the foliot, a bar pivoted at its middle on the verge staff with weights at its ends, was gradually superseded by the balance, which had a higher moment of inertia for a given size. The changing force of the main spring as it ran down, and friction in the train of gear wheels between the main spring and the escape wheel meant that the accuracy of time keeping was poor, and consequently these watches were only fitted with a single hour hand.
The earliest watches were more novelties than accurate instruments, and were sold to princes and very wealthy customers. The first centre of watch making was in Southern Germany, where the numerous principalities meant a good number of princes to support the trade. The man often credited with inventing the watch in the early part of the sixteenth century is Peter Henlein of Augsburg, Germany, called "erfinder der taschenuhr" or inventor of the pocket watch. Henlein's watches were more small portable clocks than what we today think of as a watch, but the an "uhr" is a watch or clock and taschenuhr is the German word for a pocket watch.
Each watch was hand made, with elaborate decoration, and encased in precious metals with exotic enamel and jewel decorations. They were made in very small numbers, and watchmakers' guilds sprang up as the established watch makers sought to restrict who could enter the trade, and thus keep supply restricted and prices high.
Early watches were not good timekeepers and were fitted with only an hour hand because of this. They used a verge escapement with a simple circular flywheel called the balance. The balance had no natural frequency and was simply flicked backwards and forwards by the escapement, the speed of this, and hence the rate of the watch, depending entirely on how hard the escapement pushed the balance. With a simple mainspring as the driving power, the rate would change significantly as the spring ran down, so two devices were invented to even out the force of the mainspring, the stackfreed and the fusee. These were used in clocks before watches were made.
In 1675 a small spiral spring called the balance spring was added to the balance. The balance spring and balance assembly has its own natural frequency of back and forth rotations, making the timekeeping of the watch less sensitive to changes in the force delivered by the main spring. The accuracy of timekeeping was improved so much that it was worth adding another hand to the watch to indicate minutes.
There has been much debate over who invented the balance spring; the English scientist Dr Robert Hooke or Christiaan Huygens of the Netherlands. It seems that Hooke had the idea first in about 1655 and had even drafted an application for a patent on his idea. However, Hooke had been working on different ways of applying springs to watch balances for some years without producing a working device, but it was Christiaan Huygens of the Netherlands who first came up with the idea of using a spiral balance spring and successfully applied this to a watch. Hooke was convinced that Huygens had been told about his idea, and there is some evidence to support this, but there is little doubt that it was Huygens who turned the idea into a practical application.
Copyright © David Boettcher 2006 - 2017 all rights reserved. This page updated January 2017. W3CMVS.