Bell Rock and Skerryvore
Two Reefs, Two Towers, One Legacy
Bell Rock and Skerryvore are not the most photographed lighthouses in the world, nor the tallest, nor even the most remote. What they are is perhaps the most technically accomplished pair of lighthouse structures ever built — two granite towers raised on submerged rocks in open Scottish water during the first half of the nineteenth century, under conditions that made the engineering calculations almost secondary to the sheer problem of survival. Together they represent the high-water mark of a peculiarly Scottish tradition of lighthouse engineering associated with the Stevenson family, and both continue to stand and operate after nearly two centuries of Atlantic punishment.
The context matters. The Stevensons did not invent offshore rock lighthouse construction: John Smeaton's Eddystone of 1759 had already demonstrated that interlocking masonry could survive wave forces that would destroy a conventional tower. But Smeaton's reef lies in the relatively sheltered English Channel approaches. The Scottish reefs demanded the same techniques applied under far more hostile conditions, with shorter working seasons, rougher sea states, and logistical challenges that required the invention of entirely new ways of organising a construction workforce at sea.
Bell Rock: Rennie's Dispute and Stevenson's Achievement
Bell Rock — the Inchcape of legend — lies 18 kilometres off Arbroath on the Angus coast. The reef is a sandstone ledge that covers almost entirely at high water, leaving perhaps a metre of rock exposed at low tide for a window of perhaps four hours in every twelve. The wreck of HMS York and at least 70 other vessels in the storm of 2 January 1800 finally forced the Commissioners of Northern Lighthouses to commission a design. John Rennie, the London engineer, produced plans; Robert Stevenson, the board's own engineer, produced alternative plans; and a dispute about authorship and credit that became one of the bitterer technical controversies of the era.
Construction began in 1807 under Stevenson's direct supervision. The working platform on the rock was, for the first two seasons, a timber barrack built on iron legs bolted into the sandstone — a structure that swayed alarmingly in heavy swells and was only just adequate for housing the workmen between tides. The masons worked in the water, cutting the foundation pit while the barrack rose around them. Every stone of the tower was cut and trial-assembled on shore at Arbroath, numbered, and ferried out in the supply vessel Smeaton. The tower rises 36 metres from the rock, built from 2,835 interlocking courses of granite and sandstone, each course dovetailed and bolted to its neighbours so that the entire structure behaves as a single mass.
The light was first exhibited on 1 February 1811. The original revolving catoptric apparatus — a ring of reflectors producing a group flash — was replaced over subsequent decades as optics improved. The current character is a white flash every five seconds, visible for 18 nautical miles. The tower was automated in 1988 and is maintained by the Northern Lighthouse Board without resident keepers. Remarkably, after more than two centuries of Atlantic storms, no structural repairs to the tower itself have been necessary, though the helicopter landing platform added in the twentieth century required modifications.
Skerryvore: The Harder Problem
If Bell Rock was the achievement that established Robert Stevenson's reputation, Skerryvore is the tower that surpassed it. The commission fell to his son Alan Stevenson, appointed engineer to the Northern Lighthouse Board in 1843 — or rather, the preliminary surveys were conducted before the commission was formally established. The rock lies 19 kilometres south-west of Tiree in the Inner Hebrides, in sea conditions that are, by most meteorological measures, among the worst on the British coast. The annual average wave height in the Atlantic approaches to Tiree exceeds anything found in the southern North Sea.
The rock itself presented worse difficulties than Bell Rock. It is gneiss — among the hardest rock in the British Isles — and it lies lower and covers more completely than Bell Rock. Alan Stevenson spent the summer of 1838 conducting preliminary surveys from an open boat, camping on the rock overnight and recording its dimensions. The working barracks, erected in 1839, were destroyed in a storm in November of that year before a single stone of the tower had been laid. They were rebuilt in 1840.
The tower is 48 metres tall, making it substantially taller than Bell Rock, and built entirely from Hynish granite quarried on Tiree and dressed at a shore establishment Stevenson constructed at Hynish specifically for the purpose. The foundation course is a hydraulic fit into a socket cut 0.9 metres into the gneiss. Like Bell Rock, the courses interlock by dove-tail joints and are secured with iron ties. The section is hyperbolic — the curve of the tower's profile calculated by Stevenson to offer the least resistance to breaking wave forces while maintaining the structural stability required by the height. The light was first exhibited on 1 February 1844.
Alan Stevenson himself, writing in 1848, described Skerryvore as 'the noblest of all extant deep-sea lights.' Robert Louis Stevenson, Alan's nephew, who knew these towers through family legend, wrote: 'It seemed nothing short of a miracle to me that he had ever got it set up.' The character of the light today is a white flash every ten seconds, visible for 23 nautical miles. Skerryvore was automated in 1994.
Engineering Compared
The two towers invite comparison at almost every level. Bell Rock is sandstone-and-granite in its lower courses, granite above; Skerryvore is all granite, from a harder and more resistant seam. Bell Rock stands on a tidal flat that gives, at lowest tides, several hours of dry access; Skerryvore stands on a reef that is almost never fully clear of breaking water. Bell Rock took four working seasons to complete; Skerryvore took six. Bell Rock has 36 metres of tower; Skerryvore has 48.
The curvature of both towers follows the hyperbolic profile that Smeaton had pioneered, but Alan Stevenson refined the mathematics. The base diameter of Skerryvore is 12.8 metres, tapering to 7.6 metres at the top — a degree of flaring that distributes the base loading across a wider area of rock. The weight of the masonry itself — approximately 4,308 tonnes — acts as ballast against the overturning moment of storm waves. Wave pressure measurements taken at the station in the nineteenth century by Thomas Stevenson (Alan's brother) using a specially designed pressure gauge reached 3 tonnes per square foot in major storms, values that were then barely credible and that influenced coastal engineering practice for the rest of the century.
Both towers have survived major storms without structural failure. Skerryvore was struck by what witnesses described as a wave that completely enveloped the tower to its light room level during the Christmas storm of 1891. The structure was undamaged. Bell Rock survived the North Sea storm of January 1953 — the same event that caused the catastrophic flooding on the east coast of England and the Netherlands — with no reported structural effects.
The Stevenson Tradition
These towers were not isolated achievements. They were the product of a family firm — Robert Stevenson, his sons Alan, David and Thomas, and his grandson David Alan Stevenson — that built or substantially rebuilt more than 90 lighthouses around the Scottish coast and in various other territories between about 1790 and 1940. Bell Rock and Skerryvore represent the offshore peak of that tradition, but the same family built Ardnamurchan, the Mull of Kintyre, Dubh Artach, Flannan Isles, Cape Wrath, and dozens of others.
The shore-based infrastructure at Hynish that Alan Stevenson built for Skerryvore — including a harbour cut in the rock, workers' cottages, a granite yard and a water reservoir — still survives and has been restored by the Hebridean Trust. It is one of the most complete examples of Victorian industrial heritage in Scotland, and gives a physical sense of the scale of organisation behind the tower.
To see where Bell Rock, Skerryvore and Scotland's other offshore towers stand on the chart, Open the map — the clustering of lighthouse symbols around the Scottish western isles gives some sense of the navigational challenge the Stevensons spent a century addressing.
What They Mean Now
Both towers are listed buildings — scheduled monuments in the Scottish heritage framework — and both are active aids to navigation maintained by the Northern Lighthouse Board. Neither is accessible to visitors. The towers are serviced by helicopter, and the maintenance visits are brief. The buildings that once housed keepers at the onshore supply stations associated with each light have been converted to other uses, or in the case of Bell Rock, demolished.
The legacy is primarily in the engineering literature and, more widely, in the culture of coastal Scotland. The idea that a light can be kept burning on any reef, regardless of conditions, regardless of depth of water and wave height and the hardness of the underlying stone — that is the belief these towers embody, and it was not obvious before they were built.