French bronze and marble noon cannon sundial c.1800.
This dial has a circular white marble base on which is an hour scale engraved with a shaped brass gnomon. There are two quadrant supports for the limbs holding the glass, both marked on the outside with a declination scale. The limbs are pivoted to the centres of the quadrants and held in position by screws. The glass, also fixed on by screws, has a biconvex lens mounted in a brass ring. The brass cannon is pivoted between two supports and has an elongated slit to accommodate the fuse.
The glass mounted above the plate would receive the sun’s rays at noon, so providing the heat to light the fuse at the end of the small cannon, causing it to fire the signal for midday.