heliograph

Kings African Rifles

This photo of Kings African Rifles signallers shows seven Caucasians (centre row) and 14 native troops (six seated in front with flags, six standing in back with flags, and two standing on either end with 5" diameter circular mirrors mounted on tripods). The tripod-mounted mirror instruments are 5" Mance Heliographs set up in simplex (signal-mirror) mode, with the leather carrying cases slung on the tripods, per standard practice. Heliographs were used to flash messages by Morse Code at ranges up to 30 miles or more, and saw heavy use in Africa by British, German and Boer forces from the late 1870s through WWI, with use continuing into WWII. For more on heliographs, see: Wikipedia:Heliograph Below is another photo of K.A.R.. signallers with a heliograph (believed to be from the 4th Kings African Rifles in Uganda); There's a very nice video held at the Imperial War Museum about the signallers of the Kings African Rifles with several segments showing heliographs in action (including footage of a 12" heliograph mirror in use - very rare footage) that can be viewed on the web at this link: K.A.R SIGNALS : a film of routine in remote places I've posted some other photos of Mance heliographs on Flickr here: [http://www.flickr.com/photos/signalmirror/sets/72157631978269679/]

The heliograph was used to signal using dots and dashes of reflected sunlight, and was used at ranges up to 20 miles and more. It consists of two tripods at center. The left tripod holds a mirror and a foresight to reflect and aim the light, and the right tripod a shutter to break up the reflected sunlight into dots and dashes. The thumbnail image below is a clickable link to a photo I took of a surviving example of this type of heliograph:

Seuss. The diagram you posted is of the 1888 model - some slight changes were made between that and the 1905 model shown here, though the parts and functions were, for the most part, the same. The big change was from the single-flap shutter to the six-blade shutter. Another change was the provision of azimuth adjustment screws on both ends of the mirror bar. The thumbnail below is a hyperlink to a 1913 advertisement for a model 1905 heliograph like the one in the Library of Congress photo:

The Library of Congress also holds a movie of a heliograph like that above in use by US Marines in 1915. The movie shows the heliograph being transported, set up, and operated. A copy is on YouTube, here:
www.youtube.com/watch?v=tdv11gZAUI8

The thumbnail below is a hyperlink to this still from that movie:

A modern video of a heliograph of the type in this LOC photo (operated by a complete beginner) is on YouTube here:
youtu.be/pBgH0Rz7kXY

Note the use of the short tripod - relatively rare - the typical tripod was about twice this height. Otherwise, his heliograph looks to be a fairly standard Mance Mark V 5" heliograph. Note the carrying case slung over the tripod by the shoulder strap. The leather case is lying on the ground under the tripod.