# A tiny mirror solved the Atlantic telegraph’s weak signal problem

2026-08-13T13:47:27+00:00 | World & Diplomacy | Indian Opinion Desk

Corroboration: 1 independent outlet

In 1854, physicist William Thomson (later Lord Kelvin) devised the mirror galvanometer to solve the problem of weak signals in long submarine telegraph cables. Instead of boosting electrical power at the sending end, Thomson created a tiny mirror attached to a magnet, suspended on silk threads inside a coil of wire. A faint electrical current moved the magnet, and a reflected beam of light magnified this movement, making it visible. This allowed operators to detect signals that conventional instruments missed. The device became crucial for the first durable transatlantic telegraph connection in 1866, which finally linked Europe and North America reliably, replacing dependence on ships for urgent news. The History of the Atlantic Cable & Undersea Communications notes Thomson patented the device in 1858.

## Coverage

- timesofindia.indiatimes.com <https://timesofindia.indiatimes.com/science/in-1854-william-thomson-used-a-tiny-mirror-on-a-suspended-magnet-to-help-solve-the-problem-of-sending-telegraph-signals-across-the-atlantic/articleshow/133200329.cms>

Tags: 19th century communication, history of technology, mirror galvanometer, submarine cable, transatlantic telegraph, William Thomson
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