During the 19th century the Commissioners of Irish Lights built a network of lighthouses around the Irish coast. A few beacons, towers and lightships had been in place before then, notably the historic tower at Hook Head in Co Wexford. But as maritime traffic increased, so there was a growing need for more lighthouses and navigational aids. The commissioners recruited skilled engineers, and appointed a panel of eminent scientists to advise them on lighting technologies and other technical matters.
Building lighthouses was relatively easy on the mainland, but offshore locations posed special problems. It was impossible, for example, to build conventional foundations on sandbanks. So Alexander Mitchell, a blind Irish engineer, invented a technique in 1833 for sandy areas, using "screw piles" to secure the lighthouses. Mitchell's screw pile lights at Dundalk and Cobh are still in use, testaments to the durability of his invention.
Remote outposts, such as Fastnet Rock and the Skelligs, were even more of a challenge. And it was not until 1848, after a passenger ship was wrecked at West Calf Rock, off the Co Cork coast, with the loss of 90 lives, that the Commissioners of Irish Lights tackled the problem of building a lighthouse on Fastnet Rock.
Fastnet, Ireland's most southerly outpost, has never been inhabited - and for good reason. Tiny, remote and exposed, with neither fresh water nor soil, it is at the mercy of the Atlantic. Building a secure lighthouse there was to be the commissioners' greatest challenge.
Lighthouse engineer George Halpin designed a cast-iron tower made from flanged metal plates which could be assembled on-site. Construction still took four years, during which time a colony of workers lived on the rock in wooden huts. A similar tower was built on nearby Calf Rock.
Both lighthouses trembled in heavy seas, however, and in 1881 the tower on Calf Rock snapped in two during a storm - fortunately, the keepers were on the ground floor when it happened.
It was decided to replace the Fastnet lighthouse, but it took nearly 20 years to prepare a design. The new building, designed by William Douglas, was an elegant stone tower made from 2,000 dovetailed interlocking precision-cut granite blocks.
To minimise the work that would have to be done on the rock, the blocks were cut and shaped at a Cornish quarry, then shipped by steamer to the project's depot at Crookhaven. As before, a colony of workers was installed on Fastnet, along with a temporary barrack and stores.
It took seven years to build the amazing three-dimensional stone jigsaw. The work, frequently interrupted by rough weather, was overseen by a master stonemason, James Kavanagh, from Wicklow. Kavanagh is said to have inspired his team, managing to keep morale high despite the difficult and sometimes perilous working conditions and cramped living quarters.
Throughout the seven years, Kavanagh seldom left the rock, but this dedication proved fatal. No sooner had the last stone been put in place, in June, 1903, than he was taken ill, dying shortly afterwards at Crookhaven - of apoplexy, probably brought on by exhaustion.
The lighthouse, which some say is among the world's most elegant, was completed a year later, and the lantern was lit for the first time in June, 1904. The painstaking work involved in assembling the Fastnet stone jigsaw is revealed in a fascinating series of archive photographs, which are being shown to the public for the first time in a new exhibition at the National Photographic Archive in Dublin's Temple Bar. The photographs were taken by Sir Robert Ball, who was for 30 years a scientific adviser to the Commissioners of Irish Lights. A noted mathematician, Ball was astronomer royal for Ireland at Dunsink Observatory and, intriguingly, given these photographs, he was blind in one eye.
Ball accompanied the commissioners on their annual summer tour of inspection, taking along cameras and compiling a photographic record of the trips. One of his cameras was a Kodak panoramic, which must have been a novelty at the time.
The 70 photographs selected for this exhibition portray not just the construction work on Fastnet, but also give fascinating insights into the life and work of coastal stations and towns in early 20thcentury Ireland.
In one, an inspector, in formal dress and complete with walking-stick, grips the rope of the "bosun's chair" as he is winched up from a boat. A ship laden with barrels of gas, which will be used to fuel lighthouse lanterns, prepares to leave port. Enormous navigational buoys stand stacked and ready for deployment.
Elsewhere, the keepers of remote offshore lighthouses use derricks to haul up their essential supplies.
As well as photographs, the display features a bosun's chair and navigational charts.
In these days of automated lighthouses, this exhibition is a pertinent reminder of the people who built and maintained the Irish lights. As the commissioners' motto has it, working "For the Safety of All".
Ingenious Ireland, Mary Mulvihill's book on our scientific heritage, will be published later this year.
The exhibition at the National Photographic Archive, Temple Bar, Dublin, runs until April 28th. It is open Monday to Friday, 10 a.m.5 p.m. and Saturday, 10 a.m. to 2 p.m. Admission is free.
Mizen Vision at Mizen Head, Co Cork (tel: 028-35225 or www.mizenvision.com) has an exhibition about building Fastnet lighthouse, and the story is also told in Bright Light, White Water, Bill Long's book on the lighthouses of Ireland.
There are boat trips from Schull to Fastnet in summer (tel: 028-28278).