The Sundial Cannon of Åtvidaberg

In the not-too-distant past, before the invention of modern timekeeping devices, noontime —the moment when the sun is at the highest position in the sky— held special significance. Unlike other cues like the rising and setting of the sun, or the moon, or the stars, whose time changes from day to day throughout the year, the elapsed time from noon of one day to the noon of the next is almost exactly 24 hours, irrespective of the time of the year. In reality, it varies by a few seconds up to half a minute, but it’s accurate enough for most purposes.

Often harbors would announce noon by firing guns and cannons, or by dropping time balls, so that ships could readjust their clocks before they went away to sea. Noon was also signaled by observatories for the benefit of astronomers and the general public. Some observatories still do it.
Sometime in the early 1600s in Europe, a new time signaling device came into fashion. It was a sundial equipped with a tiny cannon. A magnifying glass hovered above the canon, and at noon, the glass trained a concentrated beam of sunlight on a charge of gunpowder on the touchhole, igniting the gunpowder and producing an audible bang. This device is known by various names such as sundial cannon, sun cannon, sundial gun, noon cannon and meridian cannon.

The sundial cannon was used in parks to signal noon. A smaller variety was used in many large estates to signal the time for midday meals. Some sundial cannons approached the size of a real cannon and its boom could be heard for miles.

Today, the only functioning sundial cannon is located in the town of Åtvidaberg in southeast Sweden. The Sun Cannon is housed inside a red brick tower, near Bysjön Lake, with a long opening on the side for the sun to shine through and hit the magnifying glass focused on the priming compound at the back of the cannon. The 6-pound cannon is fired everyday at 1 PM, from May to September. On sunny days the sun automatically sets it to light, but on days when clouds obscure the sun, the sun gunner on duty fires the midday salute with a match.

The cannon was installed in 1853, and was part of the English Garden at Adelsnäs Manor, at that time. Like most sundial cannons around Europe, Åtvidaberg’s Sun Cannon went silent when better chronographs became available, until it was restored in 1986 and put to working order again. Since then, the cannon has been firing away.