Nevada County picayune., 1890-06-11
Signaling by Sunlight.

1
 A dispatch from Prescott, Ariz., mentions great achievement in hcli- ographing recently accomplished dur ing practice in the Department of Arizona. by Lieut.. Wittenmeyer, who succeeding in signaling a message by a single flash l25 miles, from Mount Reno, near Fort Mcdowell, to Mount 1 Graham, near Fort Grant, where it was received by Capt. Murray. The latter by turning his instrument flashed the message to Fort. Huachu- ca, distance of 90 miles, making distance of 215 miles with a single intervening station. The longest i distance heretofore made with q sim gle flash is said to be 70 miles.
 A hcliograph may be described as simple instrument that is used for signaling by sunlight from q plane mirror. The signals are made by i flashing reflections or by obscuring and revealing at will, by movable screen, an otherwise constant light, which is technically Y called stand ing fash The instrument working with a screen has been usually called by the inventor ''helOstat. That giving flashes has been called helio- graph or a heliotrope.
 The word heliograph, however, is commonly used to denote both, and no doubt will continue to he the ac- ccptcd name. A complete instru- ment consists essentially of two plane mirrors and sighting rod, and !, when standing fash is used, a screen. The mirrors are firmly sup ported, usually on tripod, and are fitted with vertical and horizontal tangent screws. By means of the tangent screws the mirrors can be turned on their supports so as to face in any desired direction toward the sky. When a movable flash is used, , one of tue mirrors is so mounted that motion of three or four degrees about its horizontal axis can be given it independently of the tangent screw, so that the flash can be thrown on and off the receiving station at will, and quickly,
 The screen, when used, is on a separate support, in order, when working, to avoid any shaking of the mirrors. Both mirrors are used when the signalman facing the receiving station has the sun in his rear. When the sun is in his front, or nearly at his right or left, only one mirror is used. The sighting rod as it's name implies, is an auxiliary used with the tangent screws, to put and keep the mirrors in such position that the flash can he cast with certai nty on the receiving station.
 Unless the flashes are produced rather slowly, and the dots and dashcs separated very clearly, there is great liability of confusion. Even very expert readers of these signals are liable to make mistakes, and to clearly communicate ideas the oper- ator must observe constant care and "space" hls dots and dashes with eX- i tremc nicety. The heliograph may be manipulated after night by means of clever arrangement Of two small lamps attached to the instrument. Flashes, long or short, can be pro- duced by delicate adjustment.
 Among the photographic instru- ments heretofore described in the Scientific American is one by which, when key is pressed, like teIe' graph key, the flash of light is made of long or short duration, answering to the telegraphic dot or dash. An other improvement is that in whief the flashing mirror is attached to al opera glass. Scientific American
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