History of Science Museum: Collection Database Search


Horizontal dials

The most familiar type of sundial is the horizontal dial. The hour lines are in the plane of the horizon and radiate from the base of the shadow-casting gnomon, which is angled upwards parallel to the earth's axis. The cannon dial [4] adds a playful extra feature: the lens focuses the sun's rays onto a charge of gunpowder and sets off the gun at noon.

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