unitedstatesarmysignalcorps

Army signal corps soldiers during the Spanish-American war

from Florida Memory

• signal mirror said:

  Heliograph: The two tripods held by the two soldiers at right comprise a US Army Signal Corps heliograph - a tripod-mounted device for sending messages by flashes of sunlight using Morse or Myer code, with a range up 30 miles or so. This heliograph is set up in duplex, or "dual-mirror" mode, the mode used when the sun was behind the signalers. The job of the dark-suited soldier at the extreme right was to keep the sun beam reflected by the dual 4.5 inch square mirrors on his tripod in constant alignment on the target as the sun moved, using vernier elevation and azimuth screws. The job of the light-suited soldier in the middle was to open and close the shutter flap on his tripod to produce the dots and dashes of the code. A diagram showing this heliograph (albeit in single-mirror mode), taken from [1], is here (click on the thumbnail to magnify), and see [1] for the dual-mirror mode diagram. An 1893 photograph of this type of heliograph (albeit in single-mirror mode), taken from [2], is here (click on the thumbnail to magnify) To learn more about heliographs, you can read [1] and [2], as well as this Wikipedia article: en.wikipedia.org/wiki/Heliograph You can also see this Flickr gallery (click on the thumbnail): [http://www.flickr.com/photos/signalmirror/galleries/72157630246445306/] and this set (click on the thumbnail) : (Historical Photographs of American Heliographs) [http://www.flickr.com/photos/signalmirror/sets/72157631040759962/] [ 1 ] Annual Report of the Chief Signal Officer of the Army to the Secretary of War for the Year 1888, Government Printing Office, 1889 The new standard heliograph is discussed in Appendix I, pp. 42-47, and depicted on page 46, here: books.google.com/books?id=E2nPAAAAMAAJ&pg=PA46&dq... [2] "The Heliograph", The Compass, Vol. II, No. 11, June 1, 1893, page 161 books.google.com/books?id=tX0SAAAAYAAJ&pg=PA161

• Florida Memory said:

  signal mirror Thanks for the great information!