Model Lord Kelvin’s $KR$ Law of signal dispersion ($T \propto K \times R$), gutta-percha dielectric capacitance, and mirror galvanometer decoding across the 1858–1866 ocean cables between Ireland and Newfoundland.
Low-voltage signal preserves gutta-percha dielectric integrity while mirror galvanometer resolves dispersed pulses.
When the first transatlantic telegraph cable was submerged in 1858, chief electrician Wildman Whitehouse believed that overcoming signal attenuation over 3,000 km required brute force: massive induction coils supplying up to 2,000 volts. This destroyed the delicate gutta-percha insulation, short-circuiting the line within weeks.
Conversely, Lord Kelvin (William Thomson) proved mathematically that underwater cables behave as continuous electrical capacitors. Because capacitance causes signal pulses to disperse in space and time ($T \propto K \times R$), Kelvin advocated low voltage combined with an ultrasensitive optical detection instrument: the Mirror Galvanometer. By sensing minute fractional-milliampere deflections of a tiny suspended mirror, Kelvin restored the 1866 cable and inaugurated global real-time communications.