Sundial with a cannon

A horizontal sundial in the shape of a circular cast iron plate, on which a gnomon triangle is fixed, casting a shadow. The line of the moving shadow coincides with subsequent index lines radiating from the gnomon, ending with Roman numerals at the edge of the plate, indicating the correct time. The unusual feature of this sundial is the additional function of the gun-carriage with a miniature cannon placed on the disc, so that its barrel is on the extension of the gnomon’s line. The cannon is equipped with a device cushioning the recoil of the shot and a sliding blockade. On both sides of the cannon there are quarter-arched arms with the names of subsequent months. The outriggers moving within the arms embrace a lens, with the possibility of adjusting its perpendicular position in relation to the changing angle of incidence of the sun’s rays during particular months. A ray of sunlight focused by the lens falls on the shell of the cannon, causing a shot announcing midday. Between the gun-carriage and the gnomon one can see the coat of arms of the Potocki family under a crown surrounded by lambrequins. The dial was commissioned from the Warsaw Physico-Mathematical Institute by August Potocki, according to a bill dated 18th October, 1853.

AK