The Lighthouse Stevensons - Bella Bathurst [27]
He then began concentrating on the oil lamps themselves. Twenty years previously, a Swiss scientist named Ami Argand had begun experimenting with the idea of an oil lamp which could give a purer, brighter light than the smoggy lamps then in use. As Argand’s brother later told the tale, he and Argand were eating supper one night when he broke the neck of a glass flask. Reaching over to pick it up, he accidentally moved it over the flame of the oil lamp. ‘Immediately it rose with brilliancy,’ he wrote. ‘My brother started from his seat in ecstasy, rushed upon me with a transport of joy and embraced me with rapture.’ With that broken flask – later developed into an elegant glass chimney – Argand had discovered a method of protecting and clarifying the flame from an oil lamp. Once he had added a circular wick, and a lever to raise or lower it as necessary, his invention became popular throughout Europe and beyond.
Robert, realising how useful the invention was for his purposes, tested a prototype at Inchkeith and then brought in Argand lamps for all the Scottish lights. It was, he discovered, a sharper and more reliable light than Thomas’s original lamps. Depending on the oil used, the strength of the beam could also be increased or decreased. At various stages, Robert experimented with olive and rapeseed (or colza) oil, and tried to find alternatives to the smoggy household oil then in use. He also read of a South American discovery that sheep’s tails produced an unusually brilliant light. Unfortunately, the difficulties involved in clipping the tails off thousands of reluctant sheep were found to be insuperable. Whale oil seemed the best option for Robert’s purposes; it was expensive but effective, burned cleanly and gave out the brightest light. Sperm whales, already heavily hunted in both northern and American waters, therefore provided the Scottish lighthouses with their fire for another fifty years.
With the increase in lighthouses came the need to differentiate between lights. In the Pentland Firth, for instance, where several lights would eventually be visible at one time, it was necessary to distinguish each with an individual pattern of flashes. At the time, all lights were fixed, sending out a steady beam in one direction throughout the night. Robert, pondering how best to vary the lights, began slowly to devise methods of rotating the reflectors on a central axis so they appeared instead to flash. His first few experiments were troublesome, since it seemed almost impossible to devise a smoothly balanced mechanism for the cumbersome ranks of lamps. In practice, it often required one of the keepers to spend the night pushing the light round in circles. Nevertheless, by 1806, the new lighthouse at Start Point included a clockwork mechanism ‘exhibiting a brilliant light once in every minute, and becoming gradually less luminous’.
Lenses, of course, still did not exist for lighthouses, though some experiments had been undertaken in England and France with pieces of glass placed behind the light. All lighthouse technology developed in painstaking isolation. Those researchers who were experimenting with new engineering or optical techniques were spread far away around the laboratories of Europe, and there was as yet no way of communicating their findings efficiently. Even by 1819, it was