Heliostat
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A heliostat is a device that includes a mirror, usually a plane mirror, which turns so as to keep reflecting sunlight toward a predetermined target, compensating for the Sun's apparent motions in the sky.
Heliostat by the Viennese instrument maker Ekling (c. 1850)
A heliostat at the THÉMIS experimental station in France. The mirror rotates on an altazimuth mount.
The Solar Two solar-thermal power project near Daggett, California. Every mirror in the field of heliostats reflects sunlight continuously onto the receiver on the tower.
The 11MW PS10 near Seville in Spain. When this picture was taken, dust in the air made the converging light visible.
George Johnstone Stoney
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George Johnstone Stoney FRS was an Irish physicist. He is most famous for introducing the term electron as the "fundamental unit quantity of electricity".
George Johnstone Stoney
Stoney pictured with his daughters Edith (left) and Florence.