Wolf Rock Lighthouse

In April 1860 approval was given to build the lighthouse and NicholasWalker, as engineer-in-chief, drew up designs for a 117 ft (36 m) masonry tower, tapering in diameter from 41 ft 8 in (12.70 m) at the base to 17 ft (5.2 m) at the top. Details of the design followed closely that of other Walker-built lighthouses Bishop Rock, Hanois and the Smalls lights . While his designs were inspired by Smeaton's third Eddystone Lighthouse, Walker introduced new innovations, not least the use of vertical as well as horizontal dovetail joints .

Nicholas's son James Douglass was appointed as resident engineer, and in July 1861 he arrived and surveyed the rock. The following March work began on excavating the foundations. In October 1862, James Walker died (at the age of 81). James Douglass replaced him as engineer-in-chief to the Trinity House; James's younger brother, William Douglass, then became resident engineer at Wolf Rock. William himself laid the first stone of the new tower on 6 August 1864. Masonry construction was completed on 19 July 1869. The finished tower was topped by a lantern storey manufactured by Chance Brothers of Smethwick to James Douglass's design. The lantern had previously been exhibited at the Paris Exhibition of 1867 as an example of the latest in lantern technology, using curved rather than flat panes of glass and helical rather than straight glazing bars.

James Chance of Chance Brothers had designed a large (first-order) rotating multi-panel optic for installation in the tower, 2.58 m (8 ft 6 in) high by 1.73 m (5 ft 8 in) diameter.In order to differentiate the light from the nearby St Agnes lighthouse (which displayed a white light) and from Les Hanois Lighthouse (which displayed a red light) it was resolved that the Wolf Rock light should revolve and flash alternately red and white; in order to achieve the required characteristic it was planned to install 'ruby' coloured panes of glass over half the panels on the optic (with the intervening panels left clear). It was known, however, that the intensity of a light was reduced when shone through coloured glass, so Chance conducted experiments to measure the precise difference. It was concluded that the comparative intensity of clear glass to red was 21 to 9 (i.e. more than double); therefore the red-covered panels on the optic were made wider than the others by the same proportion, in order to maintain an even intensity across the colour-change.

The light first shone on 1 January 1870; as planned, it displayed "alternate flashes of red and white of equal intensity every thirty seconds". The completed optic (which together with its pedestal stood 20 feet (6.1 m) high) was described by Douglass as "probably the most perfect for the purpose that has yet been constructed"; it continued in use for the next eighty-five years. The optic was rotated by a clockwork drive, that required winding every four hours. A 7-cwt bell, hung from the lantern gallery, was sounded in fog; driven by a separate clockwork mechanism, it rang three times every fifteen seconds.

In 1904 the lighthouse was modernised. A more powerful light-source was installed: a Matthews incandescent oil burner replacing the Douglass multi-wick oil burner. At the same time a reed fog signal was installed, which sounded a four-second blast every 30 seconds using compressed air produced by a small steam engine with a coke and coal-fired boiler; it remained in use until after the Second World War. (The bell was initially retained for standby use, but was decommissioned in 1906.) The light characteristic was changed in 1906, so that the flash (red or white, alternating as before) was displayed every fifteen seconds rather than every thirty.

In March 1941 the lantern was hit by aerial cannon fire, shattering the glass of the lenses. For a time afterwards the red flash was removed and it simply flashed white, every thirty seconds.

In 1955 electrification came to Wolf Rock Lighthouse: in place of the oil lamp a 1 kW tungsten filament lamp was installed, within a new fourth-order catadioptric optic (again made by Chance Brothers) the optic was provided with a new clockwork-driven revolving pedestal. 100V DC power for the light was provided by Crompton Parkinson generators, driven by Ruston-Hornsby diesel motors, which were installed in what had been the coal store. The new optic maintained the same light characteristic as the old, flashing (alternately red and white) every fifteen seconds. It was a four-sided optic, made up of two wide lens panels and two narrow ones (the wider panels being fronted with ruby glass), so that the intensity of the red light would, as before, be equivalent to that of the white. The visible range of the light was 16 nautical miles (30 km; 18 mi). An automatic lamp changer was fitted, including an emergency battery lamp in case the generator sets should fail; but provision was also made for the substitution of a multi-wick oil burner in the event of a complete electrical failure, for which a pressurised paraffin supply system was retained. In addition, as part of the 1955 upgrade, a new diaphone fog signal was installed in place of the old reed fog horn; powered by a pair of Lister diesel compressor sets, it was one of the last diaphone systems to be installed by Trinity House.

In 1972 Wolf Rock became the first lighthouse in the world to be fitted with a helipad; this greatly eased the challenge of getting keepers to and from the lighthouse in heavy seas. In the course of following decade, however, the lighthouse became fully automated the last keepers left Wolf Rock on 3 June 1987, after which the automation crew took over, remaining on the lighthouse until July the following year, whereupon the automation process was complete. During automation the red colour was removed from the light and the fourth-order optic was adapted so as to display one white flash every fifteen seconds. A more powerful lamp was fitted, which increased the range of the light to 23 nautical miles (43 km; 26 mi). Also, an electric emitter replaced the diaphone fog signal at this time. Fifteen years later the lighthouse was converted to solar power, with photovoltaic cells being installed around the exterior of the helideck support structure.