The Clock Set with Coins

For decades, the immense clock of Big Ben in London was set with… coins. Adding or removing a simple penny on the pendulum was enough to very slightly modify the speed of the mechanism. Official British time thus depended on a tiny metal adjustment almost invisible.

The clock of the Palace of Westminster is put into service in 1859. Its mechanism must maintain exceptional precision despite the gigantic size of the hands and bells. To adjust very finely the speed of the system, clockmakers use a surprisingly simple method. They place small coins on the main pendulum. For decades, the immense clock of Big Ben in London was set with… coins.

Adding a coin slightly increases the mass and very subtly accelerates the oscillation. Each penny modifies the clock's speed by about a few fractions of a second per day. The system allows extremely precise corrections without dismantling the entire mechanism. This technique becomes famous because it contrasts strongly with the monumentality of the building. Adding or removing a simple penny on the pendulum was enough to very slightly modify the speed of the mechanism.

One of the most powerful symbols of British time finally depends on an almost artisanal adjustment. Big Ben perfectly illustrates the encounter between giant industrial engineering and delicate mechanical precision of the 19th century. Official British time thus depended on a tiny metal adjustment almost invisible.