The third (Smeaton's) is renowned because of its influence on lighthouse design and its importance in the development of concrete for building; its upper portions were re-erected in Plymouth as a monument.

[5][8] The lighthouse survived its first winter but was in need of repair, and was subsequently changed to a dodecagonal (12 sided) stone clad exterior on a timber-framed construction with an octagonal top section as can be seen in the later drawings or paintings.

[13] It was built on a base of solid wood, formed from layers of timber beams, laid horizontally on seven flat steps which had been cut into the upper face of the sloping rock.

[5] A report on this case was submitted to the Royal Society by physician Edward Spry,[18] and the piece of lead is now in the collections of the National Museums of Scotland.

Following the destruction of Rudyard's tower, Robert Weston sought advice on rebuilding the lighthouse from the Earl of Macclesfield, then President of the Royal Society.

In May, following a series of visits to the rock, Smeaton proposed that the new lighthouse should be built of stone and modelled on the shape of an oak tree.

[22] Work began on the reef in August 1756, with the gradual cutting away of recesses in the rock which were designed to dovetail in due course with the foundations of the tower.

As part of the construction process, Smeaton pioneered 'hydraulic lime', a concrete that cured under water, and developed a technique of securing the blocks using dovetail joints and marble dowels.

[23] In 1841 major renovations were made,[24] under the direction of engineer Henry Norris of Messrs. Walker & Burges, including complete repointing, replacement water tanks and filling of a large cavity in the rock close to the foundations.

[29] From 1858 the tower's exterior was painted with broad red and white horizontal bands, so as to render it 'more distinctly visible during the day time'.

[30] In 1872 a 5 cwt fog bell was provided for the lighthouse; it was sounded 'five times in quick succession every half minute' in foggy weather.

Trinity House consented to the removal and delivery of the lantern and the upper four rooms of the tower, the cost of labour to be borne by Plymouth Council.

Having dismantled the upper part of the structure, Douglass infilled the old entrance way and stairwell within the frustum and fixed an iron mast to the top of the stub tower.

He expressed the hope that 'the rock below will for ages endure to support this portion of Smeaton's lighthouse, which, in its thus diminished form, is still rendering important service to the mariner, in giving a distinctive character to the Eddystone by day'.

By July 1878 the new site, on the South Rock was being prepared during the 3½ hours between ebb and flood tide; the foundation stone was laid on 19 August the following year by The Duke of Edinburgh, Master of Trinity House.

At the time the Eddystone's extra-tall (6 ft 3 in (1.91 m)) lenses were the largest in existence;[42] their superior height was achieved through the use of extra-dense flint glass in the upper and lower portions of each panel.

[39] Eighteen cisterns in the lower part of the tower were used to store up to 2,660 tons (nine months' worth) of colza oil to fuel the lamps.

[46] The lighthouse was also provided with a pair of large bells, each weighing two tons, by Gillett, Bland & Co., which were suspended from either side of the lantern gallery to serve as a fog signal; they sounded (to match the light characteristic of the lighthouse) twice every thirty seconds in foggy weather, and were struck by the same clockwork mechanism that drove the rotation of the lenses.

The mechanism required winding every hour (or every forty minutes, when the bells were in use), 'the weight to be lifted being equal to one ton';[21] shortly after opening, the lighthouse was equipped with a 0.5 h.p.

caloric engine,[35] designed 'for relieving the keepers of the excessive strain of driving the machine when both illuminating apparatus and fog bell are in use'.

As part of the automation of the lighthouse a new electric fog signal was installed and a metal halide discharge lamp replaced the incandescent light bulb formerly in use.

The light and other systems were monitored remotely, initially by Trinity House staff at the nearby Penlee Point fog signal station.