Britain’s lighthouses are losing their sweep. Many of the great beams that swooped over the seas and shores of England for over a century, almost more metaphor than mere maritime aid, are being phased out. One by one their massive, slowly turning lenses are being removed; one by one simpler flashing LEDs will wink on and off instead. Many will stay (as they are too tricky to replace); but many have gone already. The sweeping lights of Beachy Head and Portland Bill have gone; so too has Sark; so too has Flamborough.
It is astonishing that many of these lighthouses existed at all. Building 50-metre towers is hard; building them on ragged rocks in surging seas is “the most dangerous thing you can do”, says James Campbell, professor of architecture and construction history at the University of Cambridge. Early lighthouses variously fell down, burnt down, or were washed away like sandcastles in storms. Then in 1756 a Royal Society engineer called John Smeaton decided to do things differently: instead of building his foursquare to the sea he would copy the trunk of the English oak which withstood storms so well. A new style of lighthouse—tall, tapering, curved—started to grow around the English coast; today 66 are in use in England and Wales, many so slender that they sway, like trees, in high winds.
They are just some lights among many. Landlubbers will almost never notice but thousands of lights gird coastlines: some red, some green, some white; some flashing, some turning, some still; a coastal Christmas display, telling sailors where to go. They may be pretty but their placement is precise, for they act as trigonometric tripwires for sailors: sail too far this way and these lights won’t line up; veer too far that way and that light will turn red.
And above them all are the lighthouses—though their grandeur is almost an optical illusion: the great sweeping beam of Trevose comes from a tiny 35-watt bulb you can hold in the palm of your hand. Their brilliance—in every sense—lies in their Fresnel lenses, the lighthouses’ massive, slowly turning glass lenses (to picture their shape, imagine a pebble dropped into a pool then its ripples frozen) which bounce light back and back and back again until it becomes a beam that travels 30km out to sea. Each lens is vast—taller than a human and over three tonnes—but so delicately balanced on its bed of mercury that you can turn it—an elephant on ice—with the push from a single finger.
