For every clock and every type of clock there is a clock movement. A clock movement is simply the inner parts that make the clock work. From the earliest mechanical clocks to the atomic clock, a movement of some kind is needed to make it tell the time.
The main types of clock movements are:
The first mechanical clocks appeared in Europe around the fourteenth century. These early clocks had weight-driven clock movements and were regulated by a verge-and-foliot escapement.
In the sixteenth century, spring-powered clocks were invented. This particular mechanical clock movement replaced the heavy drive weights and so allowed for the production of smaller, more portable timepieces. Despite the fact that as the mainspring wound down, these new clocks ran slower, they remained popular among the wealthy as a practical and portable timekeeping device for the home.
Pendulum clock movements were introduced in the seventeenth century by Dutch scientist, Christiaan Huygens. His first clock was accurate to within a minute a day, an error that was eventually reduced to within ten seconds a day.
In 1721, George Graham improved the pendulum clock's accuracy to within one second per day. Further developments occurred and by the end of the 19th century, free pendulum clocks appeared with accuracies of within one hundredth of a second. These new timepieces paved the way for the two-pendulum clock movement "slave and master"mechanism with even greater accuracy and regularity. These are the forerunners of the grandfather clock movements of today.
There are several brands of clock movements in the marketplace, some specialised, such as Takane which makes mini quartz clock movements while Kieninger clock movements are for mechanical clocks - floor, wall and mantel. Hermle clock movements are used in Seth Thomas, Howard Miller and Mason & Sullivan just to name a few.
So whether our clocks are weight driven, quartz driven or set by radio frequency to Atomic Time, were it not for their own special clock movements, they would be nothing more than paperweights and picture frames.