(1579) Penetrating Power of Colored Light.

The Manufacturer and Builder 6, 1876

Special experiments in this direction (lately made in Trieste) have shown that colorless glass is the best, and next to this very light colors of any kind. When the glass is intensely colored however there is a great difference, and red glass is seen farther than green, but green farther than blue. A deep blue glass made the flame of the lamp scarcely visible at the distance of a mile, while a dark blue lantern was totally invisible; hence it was decided to use only white, red, and green glass for signal lights.

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