A Horizontal Sundial Stock Photo

A horizontal sundial is a device that measures time by the position of the sun, where the sun casts a shadow from its style or gnomon (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. This horizontal sundial is in the Kirstenbosch Botanical Gardens in Cape Town, South Africa.