The Age of Masonry Towers
The decisive engineering problem of the modern lighthouse was not light but foundation. Placing a tower on a rock that is submerged at high tide, and struck by the full weight of open-ocean waves, defeated builders for centuries.
The Eddystone Rocks, fourteen miles off Plymouth in England, became the proving ground. Henry Winstanley's ornate wooden tower of 1698 was destroyed with its builder inside during the Great Storm of 1703. John Rudyerd's timber successor burned in 1755. The breakthrough came with John Smeaton, whose 1759 tower borrowed its profile from the flared trunk of an oak, used dovetailed granite blocks keyed into the rock itself, and employed a hydraulic lime mortar that would set under water.
Smeaton's principles became the template for a century of rock lighthouse construction, carried forward most visibly by the Stevenson family in Scotland. Robert Stevenson's Bell Rock Lighthouse, completed in 1810 on a reef that is exposed only a few hours a day, is still frequently cited as one of the outstanding civil engineering achievements of its era.
Building these towers was slow, seasonal, and dangerous. Crews worked from tenders, landed only when sea state allowed, and often measured a year's progress in a few courses of stone.