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An antique stone sun dial.

Sun Dial

An antique stone sun dial.

A sundial is a device that measures time by the position of the Sun. In common designs such as the horizontal sundial, the sun casts a shadow from its style (a thin rod or a sharp, straight edge) onto a flat surface marked with lines indicating the hours of the day. As the sun moves across the sky, the shadow-edge progressively aligns with different hour-lines on the plate. Such designs rely on the style being aligned with the axis of the Earth's rotation. Hence, if such a sundial is to tell the correct time, the style must point towards true North (not the north or south magnetic pole) and the style's angle with horizontal must equal the sundial's geographical latitude.

Sundial

A sundial is a device that measures time by the position of the Sun. In common designs such as the horizontal…

"A form of Sun-dial that is as god to-day as any dial for determining noon." -Bodmer, 1917

Modern Sundial

"A form of Sun-dial that is as god to-day as any dial for determining noon." -Bodmer, 1917