Graves Light gets another first-order Fresnel lens

gl-john-nelson-randy-clark-do-final-fitBig news, everybody. Graves Light received a little taste of a genuine first-order Fresnel lens, similar to the original 1905 lens that sent out a 350,000-candlepower beam across the harbor.

The Coast Guard is still in charge of the navigational aids at Graves, so we couldn’t make the beacon shine like it did before the original giant Fresnel lens was removed in 1975. Since 1905, Graves had been the most powerful lighthouse in New England. Not so any more.

So we did the next-best thing by reconstructing part of the lens with pieces from lighthouses around the world. We assembled them as part of the interior decor in a way that won’t interfere with the modern, solar-powered lamp.

What’s a first-order Fresnel lens?

John and Randy assemble the flash panels to adorn the kitchen on the watch deck.

For a lighthouse, a Fresnel lens is a beehive-shaped compound lens made up of rings of glass prisms that cast parallel beams of light.

It is named after its inventor, French physicist Augustin Jean Fresnel (1788-1827), who had a special understanding of the physics of light.

Lighthouse lenses are divided according to size and light focal length, a category called “order.” Formally there are eight orders of Fresnel lenses, with the first-order being the largest. (There is also a 3-1/2-order lens. Two larger lenses were ultimately developed.)

A first-order lens casts a beam that can be seen more than 20 miles away. Only the curvature of the Earth prevents it from shining further on a clear night.

Fresnel lenses are made of heavy glass prisms housed in large brass or bronze frames, assembled as panels and arranged in a circle. The entire assembly of an operating Fresnel lens rotated on mechanical carriage or a pool of mercury, and in some parts of the world, still does. That liquid heavy metal ensured steady, constant, friction-free rotation, regardless of the weather, on a corrosion-free surface. The Coast Guard recovered 400 pounds of mercury from Graves when it removed the lens. Our new lens is stationary and won’t be used as an aid to navigation, so there’s no rotation mechanism or mercury.

Where did the new Graves first-order Fresnel lens come from?

We assembled the new Graves lens from several antique first-order lenses from decommissioned or modernized lighthouses outside the United States. Nearly all first-order Fresnel lenses have been destroyed, or are owned by governments as legacy artifacts. No complete first-order Fresnel lens exists in private hands, anywhere in the world.

Working through Chance Brothers Lighthouse Engineers of Melbourne, Australia, we bought pieces from English lenses built between 1880 and 1920.

Wyatt designed the bronze frame by computer, and built a full-scale wooden mockup.

Wyatt designed the bronze frame by computer, and built a full-scale wooden mockup. Then he assembled the frame on the mainland to make sure everything fit.

Reconstructing a lens

A first-order Fresnel lens would generally consist of glass prisms assembled in about 45 panels.

The panels are stacked three high and arranged in a circle. The lower and upper panels are called catadioptric panels and bend the light by reflection like a mirror. The center sections, or flash panels, are dioptric prisms which concentrate the light like a magnifying glass.

We acquired glass prisms to fill 15 panels. For considerations of living space and climate control – and for the practical matter of finding enough prisms – we did not attempt to rebuild an entire first-order lens nor could we. These panels are so scarce, it appears there may be no more to be found!

The objective was to illustrate the wonder of a First Order lens without taking over our kitchen.

No shop drawings for assembling a lens like this exist. It’s been said the factories that made them in England and France were destroyed during World War II. Our own Wyatt designed a custom skeleton frame using SolidWorks software, and uploaded the specifications to a water jet cutter, producing a rigid structure out of 1/2-inch bronze plate.

The assembly in our shop allowed us to correct mistakes, make sure the glass prisms fit properly, and refine each frame to ensure a good fit-out on station.

We packed each completed panel in wooden crates, brought them to Graves Light aboard Miss Cuddy, and winched them halfway up the lighthouse to the entrance, and hand carried them up the tower for installation.

After assembly, we found that the lens focused sunlight inward and melted our first aid kit. We knew from our neighbor Sally Snowman, keeper of Boston Light, and our visit to the Castle Morro lighthouse in Havana, that the old Fresnel lens lighthouses had interior curtains to block the sun by day. Both the Boston and Havana lighthouses still have operational Fresnel lenses.

So we went to Zimman’s for a bolt of the proper cloth. Our own Keeper Lynn is creating a custom curtain to prevent the sunlight from starting a fire, without the curtain obstructing the navigational lamp.

Vital statistics

  • Manufacturer: Chance Brothers of England
  • Grade: First Order Lens
  • Origin: From several lighthouses worldwide, circa 1880-1920
  • Weight of a complete sense: 3 tons
  • Weight of our lens apparatus: 1 ton
  • Height: 9 feet
  • Diameter: 6.5 feet
  • Light strength: Approximately 350,000 candlepower with kerosene burner

Where’s the original?

The original Graves Light lens, made in Paris by Barbier, Bernard and Turenne, is in the possession of the Smithsonian Institution in Washington, D.C. It isn’t on display, but is probably crated up in a warehouse. The Smithsonian loans out many of its pieces for public display, but federal law forbids the original Graves lens from being exposed to weather, so we couldn’t move it back to the lighthouse even if the Smithsonian would let us (which it won’t.)

The Coast Guard loans out Fresnel lenses under strict conditions, but requires that they be kept in climate-controlled environments, and, for preservation purposes, forbids them to be kept in lantern rooms.

See Theresa Levitt’s biography of optical genius Augustin Fresnel and his remarkable impact on lighthouses and navigation, A Short Bright Flash: Augustin Fresnel and the Birth of the Modern Lighthouse (Norton, 2013).

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Super Moon photo amazes with its majesty

gl-supermoon-riseThe amazing photos of the Super Moon over Graves Light show how small humanity’s grandest structures are in relation to the wonders of nature.

“Thank you” to the many photographers who share their art with GravesLightStation.com, including Sean McGrath and Babak Tafreshi here.

 

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Moonrise

GL moonrise 01 2016.08.18
From Winthrop, Boston Herald photographer Mark Garfinkel captured this incredible moonrise over Graves.

A few days earlier, on the night of August 12-13, Mark caught the specactular lightning storm around the lighthouse.

We really enjoy the pictures that friends, fans, and passers-by send along to us from Winthrop, Hull, Nahant, by boat, or wherever. They help chronicle the history of Graves Light and Boston Harbor.

Take a look at Mark’s work on his blog, PictureBoston.com, and on Twitter @PictureBoston.

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Humbled against the electrical storm

Graves lightning credit Mark GNew England weather can be very humbling, even to a lighthouse.

We camped the night of August 12-13 at Graves, in the middle of a spectacular electrical storm that swept New England.

From our position at the top of the lighthouse, we had the perfect place to watch the lightning near closer and closer to Boston, and then sweep across from Plymouth to Salem as the bolts of electricity struck the earth closer and closer to us.

At that point, given that we were at the highest point, more than 100 feet above the sea, and happened to be in a bronze enclosure that conducts electricity, we thought it better to descend to the stone tower. And we didn’t have a proper camera to catch the lightning show anyway.

At the same time, from Winthrop, Boston Herald photographer Mark Garfinkel rolled out of bed and set up his tripod to catch the lightning action over Graves. Above is his picture, a masterful piece of photography that captured the Graves beacon flashing as the lightning struck.

What a magnificent show of the power and majesty of nature.

See Mark’s blog, PictureBoston.com, and follow him on Twitter @PictureBoston.

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Peregrine falcons visit Graves Light

A peregrine falcon perches on the davit atop Graves Light late in the afternoon of National Lighthouse Day.

A peregrine falcon perches on the davit atop Graves Light late in the afternoon of National Lighthouse Day.

A close-up shot of the falcon, as seen from the kitchen (watch deck), between the outer railings.

A close-up shot of the falcon, as seen from the kitchen (watch deck), between the outer railings.

A pair of peregrine falcons visited Graves Light on National Lighthouse Day, treating us to some spectacular aerobatics.

The falcons perched on the bronze davit protruding from the floor of the lamp deck by the flag, and spiraled around the lighthouse in a series of amazing high-speed dives.

They made several swoops toward delicious-looking cormorants and seagulls, circling the oil house before coming back to rest on the topmost davit.

By some persistence and a lot of luck, we managed to snap a close-up picture of one of the birds flying past the outer deck of the watch room, and zoomed in so that you can see.

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Seal pup’s mama takes good care of baby on Graves Ledge

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Graves rises out of the fog

GL Graves fog Bill ONeilBill O’Neil, our reliable neighbor from Hull, just sent us this gem of Graves Light and Fog Station enveloped in a thick fog.

The rigging basket to the right belongs to CCI Construction.

This week, CCI is completing the most exciting painting project – the very top spire of the tower. Fearless!

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Grim reminder that it’s not all fun out here

The wrecked Emily Anne sat upside down in 50 feet of water.

The wrecked Emily Anne sat upside down in 50 feet of water.

The realities of the sea and weather remind us that not everything’s as fun as it seems at the mouth of Boston Harbor.

A salvage team just raised the wreck of Emily Anne, the trusty tugboat that helped us with restoration work in 2014. The tug sank just north of Graves Light in February, 2016. A quick-thinking pilot boat captain saved Emily Anne‘s crew as she sank, upside-down, in 50 feet of water.

Because the hulk was so close to the North Channel, the Coast Guard recommended that Emily Anne be raised so it wouldn’t be a threat to navigation. And so she was, in early June, with a crane pulling her to the surface and placing her on a barge.

From there, the barge took Emily Anne to a graving yard in Chelsea, where she’ll be broken up and sold for scrap.

These pictures tell the story of the salvage operation, with a couple shots from happier days when she helped with the Graves Light restoration in 2014.

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