This book was written was to mark last year's bicentenary of the great Bell Rock Lighthouse, the oldest surviving rock lighthouse in the world. From this lighthouse stemmed the fame of the Stevenson family of engineers and the book is largely about them. Although successive generations of Stevensons built many harbours, improved the navigation of several major rivers, and built some big bridges, the lighthouses are their most visible monument – if you can call them visible, perched, as so many of them are, on impossibly remote cliff edges or on lumps of rock miles out at sea. They were frequently built under appalling conditions, with the heroic Stevensons and their workforce battling high seas and violent gales to mark the hazards which had destroyed lives and ships for hundreds of years.

The Commissioners of Northern Lights, founded in 1786, had an ‘in-house’ engineer from the start, appointing Thomas Smith early in 1787. Thomas Smith was both the stepfather and the father-in-law of Robert Stevenson, the founder of a dynasty of engineers concerned with the lighthouse business in Scotland and across the British Empire until the middle of the twentieth century. This continuity ensured a consistently high quality, both in the construction of the towers and in the lighting apparatus, in stark contrast to Trinity House, the English lighthouse authority, which only appointed its first ‘in-house’ engineer, James Nicholas Douglass, in 1862, after criticism of the shortcomings of its lighthouses was published in a government report in 1861.

The pride with which the achievements of the Northern Lights Commissioners and their engineers were regarded meant that many models and artefacts, particularly the optics as they were superseded by advances in technology, were given by the Commissioners to the Royal Scottish Museum. Until as recently as 1992, these were splendidly displayed in the museum as one of its core exhibits. The author is a curator at the Museum and has done full credit to its remarkable collection, most of which is, alas, no longer on show. She also tells a mesmerizing tale of human endeavour.

To set the Bell Rock Lighthouse in its historical context, the author gives a fine overview of the perils of coastal navigation before science began to be applied to the lighting devices on top of the towers, pointing out that it is no surprise to find the Pharos of Alexandria included as one of the seven wonders of the ancient world. There is some doubt as to whether it was actually lit, but even so it served the invaluable purpose of distinguishing the port from the flat shoreline of North Africa which otherwise lacked any identifying features. Sea marks, which included prominent church towers as well as specially constructed beacons, were for centuries the only useful indicators of location and were often lit with candles or oil lamps or with wood or coal fires. However, these primitive forms of light were hopelessly unreliable, only visible intermittently, and treacherous guides if confused with other shore lights. Maps and charts only began to appear, at least in Scotland, in the mid-sixteenth century, first as highly confidential documents to be used for military purposes and only later as published information available to all. They, too, are a crucial part of the multifaceted history of the search for reliable navigational aids and form a fascinating part of the book.

The design of the Bell Rock Lighthouse and its method of construction was greatly influenced by Smeaton's Eddystone Lighthouse, built in the middle of the eighteenth century and the third of four structures on that perilous reef, whose story gets a chapter to itself before the history of the Bell Rock unfolds, followed by its successors, such as Alan Stevenson's Skerryvore Lighthouse, described by his nephew, Robert Louis Stevenson, as ‘the noblest of all extant deep-sea lights’. All aspects of these lighthouses are covered, including the development of the optics which the towers were built to house and which are all too often overlooked or misunderstood. Apart from anything else the sheer beauty of these instruments, particularly of the great glass refracting lenses, is demonstrated in the book's fine colour illustrations.

If a criticism can be made of the book, it is that the contribution of others towards the Stevenson family's success is sometimes underplayed. For instance, it is made clear that the French engineer Augustin Fresnel was wholly responsible for the revolutionary concept of stepped refracting glass lighthouse lenses, which were to replace parabolic metal reflectors, themselves developed by the French and not by the Stevensons. However, the crucial contribution Augustin's brother, Léonor, made to Alan Stevenson's achievements in the later development of these lenses, particularly the first all-glass first-order fixed lens, is barely mentioned.

Downplaying the contribution of others is a failing of which the Stevensons themselves were frequently guilty. In his 1824 account of the construction of the Bell Rock Lighthouse, Robert Stevenson omits all mention of John Rennie's role. Rennie was in fact its design engineer and Stevenson was the resident engineer under him, a fact that has been conclusively proved by the recent discovery of Rennie's crucial first report on the structure. The author certainly tackles what has been a contentious issue for over a century, but does not take sides. Overall Northern Lights is a wonderful book, lucidly written, sumptuously illustrated and with an excellent bibliography.