The Scientific American Boy; Or, The Camp at Willow Clump Island
Chapter 13
WIGWAGGING AND HELIOGRAPHING 144
Wigwag Signals. The Wigwag Alphabet. Abbreviations. Wigwagging at Night. The Heliograph. The Single Mirror Instrument. The Sight Rod. The Screen. Focusing the Instrument. Heliograph Signaling. The International Telegraph Code. The Double Mirror Instrument.