A heliograph is a mirror mounted on a tripod for solar signaling, usually using Morse code sent either with a tilting mechanism or a shutter (as on an Aldis lamp). They were used, in some form or other, in military campaigning from ancient times up until the advent of wireless. In the history of our nation, they were particularly useful in the Army campaigns against the Apache.
So, what do you think is the distance record for signal received by heliograph? Make your guess. (Answer after the jump.)
183 miles, by Captain W.A. Glassford of the Signal Corps and his sergeants, between stations on the peaks of Mount Ellen, Utah, and Mount Uncompahgre, Colorado. September 17, 1894. (From the Dead Media Project.)