Article February 8, 1900 Issue

The Heliograph Described

How General White Flashes Despatches to General Buller Twenty Miles Away.

Boston Transcript

THE heliograph, which is being put to such effective use in South Africa by both Briton and Boer, is a modern adaptation of one of the oldest forms of signaling apparatus known to military science. Heliographing, as the name implies, is sun-telegraphing, and General White's signal men in despatching news from sorely pressed Ladysmith are using the same device, only in more perfected form, that the wicked small boy with a bit of looking-glass in his grimy fist employs to attract the attention of his fellows across the schoolroom by flashing the sun in their eyes.

Mirror-signaling was early used by the North American Indians, and is no doubt partially responsible for the marvelously rapid dissemination of news on the plains noted by many American army officers. The modern war heliograph is almost equally simple in theory and practice. The sending apparatus consists of a mirror mounted on a tripod and hung on both horizontal and vertical axes with adjusting screws admitting of minute changes of plane. With this mirror the sun's rays are flashed for miles, directed by painstaking adjustments into the field of vision of a receiving telescope, also tripod-mounted. The code is similar to that used in electric telegraphy. Flashes, long or short, represent dots and dashes, and the Morse or any other code, including ciphers, can be readily used.

The heliograph has been called the trump card of visual signaling, for it possesses the four cardinal military virtues —portability, rapidity, range, and secrecy. The heliograph is extremely portable, weighing, with its stand, no more than a soldier's rifle. It possesses a curious virtue of secrecy, because to people standing even at a very short distance from the point on which its rays are directed, its signals are invisible. But this fact will show how needful it is to have the sun reflected full on the distant station; and to insure this the heliograph has to follow the sun as it travels through the sky. The two screws mentioned, one giving a vertical movement and the other a horizontal movement to the mirror, about its centre, effect this, and the screws can be manipulated by the signaler while in the act of sending, without interruption to the message. The range of the heliograph is enormous with a strong sun and clear horizon, and it is therefore admirably useful in South Africa. In the 1883-85 campaigns a heliographic signal service extended north—Orange River to Molopole—a distance of 429 miles. One of the great virtues of the heliograph is its ability to pierce haze. Colonel Keyser, who was with the besieged garrison of Kandahar in 1880, reported that he opened communication with the advanced guard of the relieving force, under Sir F. Roberts, at Robat, a distance of forty-eight miles, and communications were kept up for several hours on a hazy day.

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