Why was Smeaton’s Eddystone Lighthouse replaced in 1882?

Smeaton’s Eddystone Lighthouse was replaced in 1882 primarily because the foundation rock upon which it stood had become undermined.1

While John Smeaton’s 1759 masonry tower was a revolutionary design that utilized interlocking, dovetailed stone blocks and a curved profile to dissipate wave energy, the structural integrity of the underlying rock eventually failed. The replacement structure, designed by Sir James N. Douglass, was built on an adjacent part of the rocks. Douglass incorporated a massive cylindrical base into the new design to better absorb the energy of incoming seas and reduce the tendency of waves to break over the lantern, a recurring issue with the previous tower.21

Following its decommissioning, the upper portion of Smeaton’s lighthouse was dismantled and relocated to Plymouth Hoe, where it remains as a monument, while the lower section of the tower still exists on the Eddystone Rocks.1