Heliograph
The Optical Dictionary · 1904 · p. 9
(a) An apparatus for taking sun photographs. (0) An instrument for measuring the intensity of sunlight. (c) A flashing mirror for sunlight signalling. (See Heliotrope.)
Bu kavram başka kaynaklarda da geçiyor
Adair's New Encyclopedia (1923)
A Dictionary of Military Terms (1918)
Chamber's Twientieth Century Dictionary (1908)
Chandler's Encyclopedia (1898)
The Standart Electrical Dictionary (1892)
The Century Dictionary: The Encyelopedic Lexicon of the English Language (1887)
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