replaced all other clocks when developed in the early 1300s
initially were large and driven by weights & used in monastries to warn a time-keeping monk to ring his bells
by 1335 there was a clock tolling the hours in Milan
based on escapement principle known as verge & foliot
by 1400, this technology had been scaled down enabling domestic clocks
by 1450, spring-driven clocks were developed but these were very inaccurate due to slowing down as the spring expanded, until in 1500 Henlein devised a compensation device known as a stackfeed, he created the 1st portable clock or watch, however, the clocks still lost as much as a 30min each day.
in 1641, Galileo proposed a pendulum clock but died before it was produced, leaving Huygens to produce the 1st commercially viable model in 1656, this heralded a boom in clock innovation & manufacture resulting in wooden wall clocks, grandfather clocks, the inclusion of the minute hand, the use of brass instead of iron, and the invention by Huygens of the balance or spiral spring.
in 1660, Robert Hooke devised the recoil or anchor escapement that allowed a reduction in arc of the pendulum
in 1715, George Graham devised the deadbeat escapement that ensured accuracy up to a few seconds every day
in 1721, George Graham attached a bowl of mercury to the pendulum to overcome the error caused by rise in temperature causing brass pendulum rod to expand (5 degree rise resulted in losing 5secs/day)
in 1765, Thomas Mudge devised the detached lever escapement which eventually became the standard escapement device & is still used in clocks & watches.
in 1840's, the harnessing of electricity resulted in the electric clock where electricity was used to replace the spring or pendulum & could also be used to relay the time from one clock to another in a series which was useful in factories where synchronisation was important.
in 1895, Charles Guillaume solved the temperature problem by using an alloy of nickel & steel called invar
in 1918, synchronous electric clocks became popular with home models made, but accuracy depended on the frequency of the power supply which was a problem