Devil's Island is the northernmost point in Wisconsin, but it might as well be at the end of the world. The South end looks onto the other Apostle Islands—a conglomerate of 21 heavily wooded islands in Lake Superior. The North end of Devil's Island looks out into infinity. For all you can tell, there's nothing past the horizon but a waterfall off the edge of a flat Earth.
It's an eerie feeling, for somebody who grew up landlocked. And it gets only creepier when you set foot on Devil's Island and find that the temperature has gone up at least 15 degrees from what it was out on the lake. Add to that the echoed thud and slurp of water pounding the hollowed-out sandstone caves that line the island's coast, and you've got a romantically spooky experience.
I visited Devil's Island last month, largely to see its lighthouse—a 19th-century paean to riveted steel, topped with a vintage Fresnel lens made of crystal and brass. The result is delightful and, dare I say it, more than a little steampunky.
I'll be honest, part of what makes Devil's Island such a great place to visit is the smugness of knowing that not many other people make it there. The island does have a dock, but it's shallow—too shallow for most sailboats—and there's not really any great places to anchor. Tour barges just circle around it to get everybody a good look at the caves. I made it there, along with my husband, because we rented a sailboat with some friends and took turns hanging out on the boat while the other couple paddled a dinghy to shore.
The natural landing is made from the same sandstone as the caves and the rest of the island. Sandstone on nearby islands in the Apostle chain was quarried out and hauled away to rebuild Chicago after the Great Fire of 1871. Devil's Island never had a quarry, though—its sandstone was too brittle.
In the days before radar, the island was home to both a lighthouse and a steam-powered foghorn. The latter burned through 1000s of pounds of coal when it was in operation, all of which was brought by boat to the natural landing, and then pushed in hand-carts along this stretch of train track.
For most of the 20th century, the lighthouse and foghorn required several keepers to operate. Their families lived with them through the summer months, but the keepers stayed longer, often through a good chunk of November. At times, that meant the water between Devil's Island and the mainland froze before they could get home, forcing a days' long trek back to the nearest town.
But, as the lighthouse was fully automated in the late 70s, you're probably wondering whose laundry that is on the line. Turns out, Devil's Island is staffed by volunteer tour guides in the summer months. When I visited, a couple of retired science teachers were spending a month there, leading people like me up the lighthouse a couple times a day and reveling in woodsy solitude the rest. If this volunteer opportunity sounds like the perfect way to write a novel ... well, I called it first. Back off.
This photo was taken either in, or before, 1901, when the Fresnel lens arrived from France, and the temporary lighthouse—the big white one you see on the right—was torn down. The main lighthouse is on the left, just behind the ridge-line of one of the keeper's cottages.
The buttressing was added on about 13 years later, after keepers finally complained enough about the tower swaying in the wind. The additional structure solved that problem, but, up on the catwalk at the top of the lighthouse, you can still see grip bars attached to the exterior. Those were there to keep the keepers from falling off in a strong gale.
Behold, the Fresnel lens. (The "s" is silent. Just FYI. So you don't sound like an idiot. Like I did at first.) The last original lens left in the Apostle Islands, this thing was a miracle of science when it was first installed. Earlier lighthouses were only visible maybe 15 miles from shore, on a good, clear night, which was, typically, not when you were really worried about needing them. Fresnel lenses were invented in the early 19th century, and were still a big deal 100 years later, thanks to their ability to make the life-saving glow of a lighthouse visible more than 20 miles away, without a lot of extra weight load on the tower structure.
Every ridge you see is an individual piece of cut and polished crystal, shipped over from France as part of a modular kit, and mounted into a brass frame using the same kind of caulk that fixed windows into double-hung frames. The ridges are angled so that they reflect and concentrate the scattered, multi-directional light from the central oil-fueled fire into powerful, directional beams. Chipping, smudges and stray crap of all sorts could alter the prisms' powers, so keepers had to be careful to not touch the crystal and wore special lint-free smocks over their regular clothes.
Today, Fresnel lenses show up in traffic lights, solar power concentrators and retina identification cameras. They're also apparently good fun for destructive purposes, as well.
There's still a light at Devil's Island, but it's powered by LEDs now. Compared to the Fresnel lens standing a foot away, it's a little underwhelming.
Maggie Koerth-Baker is the science editor at BoingBoing.net. She writes a monthly column for The New York Times Magazine and is the author of Before the Lights Go Out, a book about electricity, infrastructure, and the future of energy. You can find Maggie on Twitter and Facebook.