Airships past and present, together with chapters on the use of balloons in connection with meteorology, photography and the carrier pigeon (1908)
Hildebrandt, A. (Alfred), b. 1870, Story, W. H. tr · New York, D. Van Nostrand company · leaf 142
tric light, whichcan be switched on and off from below. If electric lights arearranged, one above the other in separate compartments, andshaded by glasses of different colours, a message can be signalled.The Morse code could always be used by showing the lights forlonger and shorter intervals.…
Aeronautics
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