5923271 A soldier of the Northern Nigeria Regiment signalling with a heliograph, 1907 circa (lantern slide) by Unknown photographer, (20th century); National Army Museum, London; (add.info.: A soldier of the Northern Nigeria Regiment signalling with a heliograph, 1907 circa. Photograph, West Africa, 1907 circa. A heliograph was a device that used Morse code flashes of sunlight reflected by a mirror to send messages. The flashes were produced by momentarily pivoting the mirror, or by interrupting the beam. From a collection of 41 lantern slides, collected between 1907-1911, by Lieutenant H R S Massy, Royal Artillery, attached to the Northern Nigeria Regiment, West African Frontier Force.); by National Army Museum .