Souter Point lighthouse lamp, 1879.
© Science Museum / Science & Society Picture Library
Illustrated plate from 'The Electric Light Applied to Lighthouse Illumination' by James Nicholas Douglass, published in 1879. Douglass (1826-1898) designed Souter to be the first lighthouse using alternating current electricity. Maintenance could be carried out without interrupting the signal. Douglass also designed and built the fourth Eddystone lighthouse in 1879, which incorporated new electric lights capable of being seen for almost 18 nautical miles; over three miles further than the tallow candle lantern of the previous lighthouse. This meant that the Eddystone signal overlapped the signal from the lighthouse at Lizard Point in Cornwall, providing for the first time a safe passage along this coastline.