After the telegraph and before the radio, the heliograph provided long-distance wireless communication.
In November 1877 Jowaki tribesmen along what is now Pakistan’s western frontier were puzzled by the brilliant staccato flashes radiating from the hilltops ringing the Bora Valley. No act of nature, the flashes were signals being passed between two columns of the British Punjab Frontier Force intent on punishing the Jowakis for months of mayhem—cutting telegraph lines, burning villages, destroying bridges. The heliograph, a mirrored instrument that could blink messages across great distances, was the latest in military communications technology, and this was the first time it had been used in a conflict. M Though the result of the two-month campaign against the Jowakis proved desultory, the “sun telegraph” was a big hit with Brigadier General Campbell C. G. Ross, commander of one of the Punjab Force columns. He reported to headquarters that “communications were kept up constantly by heliograph.” Within a few years armies around the world would come to rely on it.
For millennia fire and smoke were the only means humans had for long-range communication. At some point in history someone hit on the idea of using flags, probably the Egyptians or the Chinese, who were also the first to use pyrotechnics for signaling. Relays of couriers, on foot and horse, also became a common method of sending messages. The Persians tried shouting, but that required placing men within shouting distance of one another, a prodigious waste of manpower, and inevitably the message got garbled.
Centuries later signaling by reflecting the sun’s rays off a shiny surface came into practice, though historians cannot agree on when or where this first happened. Archaeological evidence from mountaintop ruins in Crete suggests the Minoans used silver or bronze plates to flash messages to other parts of the island as early as 2200 BC. Many believe Greeks held up polished battle shields to flash signals at the 490 BC Battle of Marathon, and on the North American plains the Ponca tribe was using pieces of reflective mica to direct hunting and war parties before the arrival of traders at the beginning of the 19th century.
In those earlier times the meaning of reflected signals was limited to an agreed-upon code—as an example, two flashes might mean “enemy sighted on your left flank” and three “right flank.” Stringing together a message like “enemy sighted left flank; 10 miles southwest of your position; estimated strength 1,000 infantry and cavalry” would have been practically impossible and slow. The lack of an easily codable signal language undoubtedly held back the military development of these primitive sun telegraphs. But all that changed in the early 19th century following the invention of two unrelated technologies: the heliotrope and Morse code.
The heliotrope was conceived by German mathematician Carl Friedrich Gauss in 1821 to improve the accuracy of geodetic surveys. It looked just like a surveyor’s transit but with a small mirror mounted on top. The continuous spot of reflected light was used as a fixed target that greatly simplified the task of taking relative bearings. Effective over a distance of 20 miles, the heliotrope had become standard kit for trigonometric survey parties by the 1840s.
Samuel F. B. Morse’s electric telegraph debuted in 1844, when its first official message, “What hath God wrought,” was transmitted between Washington, D.C., and Baltimore, Maryland, using the now familiar dots and dashes. Morse code came of age militarily during the Civil War, when Union forces mastered wire-based mobile battlefield communications.
In the years following the war, a number of American and British engineers began experimenting with combining the heliotrope and the Morse alphabet for use in signaling. But it was Henry C. Mance, a Briton working for his government’s Persian Gulf Telegraph Department in Karachi, who in 1869 first perfected a capable wireless communications apparatus he dubbed the heliograph. In 1875 Mance’s device was approved for use by the British-Indian Army, and it famously saw its first wartime use during the 1877 Jowaki Expedition.
An account from that time describes the heliograph as a “mirror mounted on a suitable stand with adjustments to revolve and incline it so that the sun’s rays can be reflected with ease and precision in any required direction.” The standard Mance mirror was a five-inch round of thick plate glass carefully silvered on one side. A small, unsilvered hole in the center was used in conjunction with a sighting rod to align the instrument with a distant station.
There were two critical requisites for the heliograph to work. First and foremost was the sun, though it worked well in moonlight, too; haze was OK, clouds were not. The second was the placement of transmitting stations on a direct line of sight. The distance between stations wasn’t critical; the separation could be 40 or 50 miles. Setup was quick and easy, and once a station could see the other’s mirror flash, signaling could commence between two stations or among many more.
In order to make a flash, a finger-key was depressed, causing the aimed mirror to pivot on its vertical axis just enough to deflect the reflection, which then disappeared from the distant receiver’s view. A short flash denoted a dot and a long one a dash. A good team of heliographers could send Morse messages at 12 to 15 words a minute.
The U.S. Army’s Signal Corps was an early adopter of the new technology, acquiring six Mance heliographs in 1877, after the instrument had proved successful in the Jowaki Expedition. In Montana, while monitoring Sioux and Cheyenne movements in the wake of Little Big Horn, Colonel Nelson A. Miles heard about the military value of the sun telegraph and asked the corps for the loan of all six. In 1878 he established a temporary, 140-mile line of heliographic communications in southeastern Montana between his base at Fort Keogh and Fort Custer. The experiment was considered a success by both Miles and the signal corps.
Down in Arizona the U.S. Army had been fighting the Chiricahua Apaches on and off since 1861. Finally in March 1886, it looked as though their leader, Geronimo, was on the verge of surrendering to Brigadier General George Crook, but instead, he and his warriors melted back into the mountain fastnesses to resume marauding. Having spent four years unsuccessfully trying to subjugate the Apaches, General Crook asked to be relieved of command, and the army ordered a reluctant Nelson Miles to replace him.
Miles, now a brigadier general, arrived in Arizona in April and immediately began organizing his campaign. Key among his plans was the creation of a vast network of heliographic stations—27 of them spanning nearly 800 air miles in a comma-shaped area some 200 miles east to west and 140 miles north to south. To equip these, Miles called in a lot of favors at the signal corps, which sent him 34 sets scrounged from army bases coast to coast. He established his heliograph observation posts on mountain peaks, each manned by three operators guarded by several soldiers. The parties were provisioned with a 30-day supply of food and water. With the aid of telescopes, the signaling parties “could identify movements at a distance of 25 miles,” according to U.S. Army historian Bruno Rolak. Their reports were flashed back to Miles’s headquarters at Fort Huachuca in southern Arizona.
There, the general gathered his forces—5,000 soldiers and 600 Indian scouts—and issued General Field Orders No. 7: “The chief objective of the troops will be to capture or destroy any band of hostile Apache Indians found in this section of country.” On May 5 a column led by Captain Henry W. Lawton marched out of the fort to the strains of “The Girl I Left Behind Me.”
It was a month before the army made contact with Geronimo’s warriors. And that contact—to Miles’s immense satisfaction—was a direct result of a sighting by a heliograph station, which flashed the report back to headquarters. The general then used the sun telegraph to route Lawton’s troops toward the Apache raiders. The battle was joined on June 6, when the soldiers overran a Chiricahua camp, capturing 19 horses and a large supply of dried meat while the Indians fled on foot.
Throughout that summer of 1886 infantry and cavalry units crisscrossed the mountains and valleys in relentless pursuit of Geronimo. Their successes were achieved in part because of the presence of the heliograph network. Unlike the Jowakis, the Apaches were well aware of the significance of the brilliant flashes (they had used shiny metal themselves for many years) and began to avoid places they knew Miles had set up observation posts. Still, as the season wore on, the two sides skirmished nearly every day. Slowly, the army managed to confine Geronimo and his band to a small sector near the Mexican border. Trapped in a hopeless situation, the warrior surrendered his forces to General Miles on September 4, 1886, at Skeleton Canyon. Thus ended one of the bloodiest chapters in the long Indian Wars.
Miles attributed much of his campaign’s success to the heliograph. Modern historians say that the general exaggerated the instrument’s role in subduing the Indians. In a memoir Miles wrote, he recalled that when he showed the sun telegraph to Geronimo, the old chief “was struck with awe and amazement.” Historian Odie B. Faulk believed that the cagey Apache’s awe was simply an act, and that as far the heliograph was concerned, “not a single battle resulted from its use”; it was merely “an expensive toy.”
In Miles’s defense, historian Rolak has noted that over 2,200 mirror messages were transmitted in Arizona alone, including reports on troop movements, supplies, and weather. “The prestige and importance of military signal communications increased considerably…thanks to the heliograph.”
The U.S. Army deployed heliographs with great success throughout the end of the 19th century, most notably during the Spanish-American War. But a new century brought a new technology that eclipsed the power of the sun—radio waves. Use of the heliograph for field signaling died out, though during World War II handheld helios were used by downed flyers to signal their positions to rescuers. The instruments found peacetime uses as well. In the early 20th century the U.S. Forest Service equipped its remote lookout stations with heliographs. For over half a century they relayed reports of wildfires to less remote stations with telephone connections.
As to the British, following the success of the mirrors on the Jowaki Expedition, the army set up very effective heliograph networks during the Second Afghan campaign (1878–1880) and the Zulu War (1879). During the Second Boer War (1899–1902), both sides made extensive use of sun telegraphs. Though little used after World War I, heliographic equipment was kept on hand by the Royal Corps of Signals into the 1960s.
Today, dedicated amateur heliographers, using homebuilt and antique instruments, gather to flash messages of good cheer, just for the fun of it. Sir Henry Mance would have been proud.
Steven Trent Smith, a five-time Emmy-award-winning television photojournalist, is a frequent contributor to World War II and Civil War Times. He has written two books on the submarine war in the Pacific: The Rescue and Wolf Pack.
Originally published in the January 2015 issue of Military History Quarterly. To subscribe, click here.