Elementary treatise on physics experimental and applied for the use of colleges and schools (1890)
Ganot, A. (Adolphe), 1804-1887, Atkinson, E. (Edmund) · New York : W. Wood · leaf 600
es. In order that all points of the horizon may besuccessively illuminated, the lens is continually moved round the lamp bya clockwork motion, the rate of which varies with different lighthouses.Hence, in different parts the light alternately appears and disappears afterequal intervals of time.… … -608J PJiotography. 583 enabled to distinguish the lighthouses from one another, and hence to knowtheir position. Of late years the use of the electric light has been substituted for thatof oil lamps. A description of the apparatus will be given in a subsequentchapter. PHOTOGRAPHY. 60S.…
Physics
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