Trinity College Clock

The Great Clock above the Great Gate of Trinity College strikes every hour with two bells, sounding the Westminster Chimes. Its most peculiar feature is a strike that hits each hour twice, once for the college and once for the city. In the mid-nineteenth century, the mathematician Charles Babbage rigged the clockwork to sound thirteen times at one o'clock, a prank that famously went unnoticed by his professors until the following morning.