Brilliant_ The Evolution of Artificial Light - Jane Brox [23]
In 1822 French physicist Augustin-Jean Fresnel designed a hive of light. His Fresnel lens—a lamp comprising concentric wicks set in bull's-eye glass and surrounded by rings of glass prisms—bent and concentrated light into a bright, narrow beam. The largest of his lenses, meant to aid ships along the most treacherous and fogbound coasts, was built of a thousand prisms and stood more than ten feet high. When placed one hundred feet or so above sea level—high enough to compensate for the curvature of the earth—its beam could be seen for twenty miles. Fresnel produced his lens in six different sizes; the smallest, a sixth-order lens used in harbors and bays, was a mere twelve inches in diameter and stood eighteen inches high.
Throughout the nineteenth century, in addition to installing Fresnel lenses and replacing old oil lamps with more dependable electric lights or gaslights, lighthouses would begin to adopt a system of flashing lights to distinguish one seamark from the next. Mariners unfamiliar with the coast could get their bearings even when daymarks—the painted patterns on lighthouse towers—disappeared with the sun. And lightships, light buoys, and sound signals such as whistles, bells, and foghorns frequently marked the more treacherous shoals.
Still, shipwrecks were a given well into the twentieth century. In the early 1920s, there were twelve working Coast Guard stations along fifty miles of the south shore of Cape Cod, and lantern-carrying surfmen patrolled the shores, scanning the waters for ships in distress. "Every night they go; every night of the year the eastern beaches see the coming and going of the wardens of Cape Cod. Winter and summer they pass and repass, now through the midnight sleet and fury of a great northeaster, now through August quiet ... the beach traced and retraced with footprints that vanish in the distances," observed Henry Beston, who chronicled life on "the Great Beach of Cape Cod."
There has just been a great wreck, the fifth this winter and the worst.... The big three-masted schooner Montclair stranded at Orleans and went to pieces in an hour, drowning five of her crew.... Older folk will tell you of the Jason, of how she struck near Pamet in a gale of winter rain, and how the breakers flung the solitary survivor on the midnight beach; others will tell of the tragic Castagna and the frozen men who were taken off while the snow flurries obscured the February sun. Go about in the cottages, and you may sit in a chair taken from one great wreck and at a table taken from another; the cat purring at your feet may be himself a rescued mariner.
Any mariner of the eighteenth century would have found it impossible to comprehend that one day a marker on the Eddystone reef would emit a light equivalent to 570,000 candles, or that such a light would not be essential to seeing a ship safely past the rocks; that there would come a time when navigators hardly needed to scan the horizon, for they would get their bearings from a prism of information—radar, GPS, and electronic charts. Data would become the new lamp.
4. Gaslight
AT THE TURN OF the nineteenth century, most people still saw by the same ancient light as always, though that would change in the decades to come. Not only would brighter, cleaner mineral fuels replace tallow and whale oil, but the story of human light would cease to be that of candles and lamps alone. It would become a story that defied linearity, one composed of inseparable strands of invention and improvement—gaslight, the safety match, electric arc lamps, kerosene, Edison's incandescent bulb, Tesla's alternating current—and as new forms of illumination overtook the old, they competed with one another in ways that stratified society and intensified the separateness