Mathematics and mirrors are not what most immediately associate with the military.
Gauss’s heliotrope made its debut in 1821 looking much like a surveyor’s transit pictured below,
but with a mirror mounted on top.
Gauss’s heliotrope could reflect light at precise angles for up to 20 miles to allow effective bearings to be taken.
Samuel Morse’s electric telegraph transmitted its debut message “What hath God wrought” between Washington D.C. and Baltimore, Maryland in 1844 using its code of dots and dashes.
Just 33 years later, Henry Mance’s heliograph, which combined Morse code with aspects of the heliotrope (also pictured below), was wielded for the first time by the British in their punitive Jowaki Expedition against Indian freedom fighters.
Heliographs found an ideal climate in South Africa during the Boer Wars with messages being transmitted as far as 90 miles in sunny conditions.
Some operators succeeded sending signals using the moonlight.
A well-trained team of heliographers could transmit messages of 12 to 15 words a minute.
Cloud cover or missing lines of sight made heliograph use impossible.
Early in the Boer War, the British used heliographs as they struggled to gain control of South Africa.
The more mobile that forces had to be, the more vital the heliograph since rapid mobile operations often didn’t leave time to dig and fortify telephone or telegraph lines.
Poor weather prevented Boer General’s Piet Cronje and his surrounded army from using a heliograph to coordinate a timely relief effort by Christian De Wet and his commando. Cronje would devastate the Boer war effort by surrendering his remaining 4,000 Boer soldiers to a British force 3 times larger, costing the Boers across South Africa 10% of its fighting force in one moment.
As British troops numbers climbed to the hundreds of thousands and the Boers started to be reduced to thousands, the British were able to lay increasingly more telephone line. Telephone line that they had enough numbers and fortifications to protect against Boer attempts to cut them.
These telephone lines and increasingly more secure telegraph lines would make heliographs with all their vulnerabilities and necessarily large communication teams less essential.
However, heliographs were crucial for a time in the Boer War and also used widely in many US campaigns to further dominate native American tribes (in the future states of Montana and Arizona for example).
They were even kept in supply by the British Royal Signals into the 1960s, and were still used by some forest services well into the 20th century.Gauss’s heliotrope Surveyor’s transit
To learn more see:
Evans, Nick. “THE BRITISH ARMY AND COMMUNICATIONS, 1899-1914.” Journal of the Society for Army Historical Research94, no. 379 (2016): 208-24. Accessed June 5, 2020. www.jstor.org/stable/44232704.
Nasson, Bill. The Boer War: The Struggle for South Africa. Stroud, United Kingdom: The History Press, 2011. P. 167-179.
Smith, Steven Trent. “Light Conversation: The Heliograph” https://www.historynet.com/light-conversation-heliograph.htm