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).

Share Button

Engineer who removed original Fresnel lens returns to Graves

Engineer Ron Fiore explains to Dave how he devised the system to remove the original Fresnel Lens from Graves.

On the deck of Graves Light for the first time since 1975, engineer Ron Fiore explains to Dave how he devised the system to remove the original Fresnel Lens from Graves.

Well, the best part of this whole lighthouse experience continues to be all the great people we meet.

Today we met Ron Fiore, the structural engineer who devised the method of removing the gigantic First Order Fresnel lens back in 1975.

That lens blasted out a 3.2 million candlepower beam for 70 years straight. The lamp required a full-time crew to operate and maintain, so the Coast Guard had it taken out and replaced with an automated electric beacon.

Ron told us all the details about how he built a custom crane to gently lower the priceless lens – it weighed 2 tons and measured 12 feet tall and 9 feet across – down one story into the watch room.

Then he and the crew removed part of a wall to slide the lens past the sloping tower and drop it 60 feet to the dock, where a Coast Guard boat plucked it onto the deck. 

Legendary New England maritime history author Edward Rowe Snow made an appearance, instructing the crew to wave (as he was filming the feat) but the workers were too busy – and scared – to respond.

The next year Ron and his wife visited the lens again, this time at the Smithsonian!

The Fresnel lens was made in France by Barbier, Benard & Turenne in 1904, and was installed in 1905. After the 1975 removal, the Coast Guard installed an automated electric beacon, powered from land by an underwater cable. That cable broke, so in 2001 the Coast Guard installed the present solar-powered lamp, the Hydrosphere Vega VRB-25, made in the U.K.

Share Button

Castle Morro lighthouse keeper in Havana gives Graves Light a tour

The keeper of the Castle Morro lighthouse in Havana, Cuba, shows us the original 1845 Fresnel lens.

The keeper of the Castle Morro lighthouse in Havana, Cuba, shows us the original 1845 Fresnel lens. Manually wound every 3 hours, the lens sits on its original pool of mercury for smooth rotation.

As authentic as it gets: Graves Light got an up-close look at the historic 1744 Castle Morro lighthouse in Havana harbor, Cuba, and saw an original Fresnel lens in about as original a state as possible.

Enrizio, keeper of the Havana lighthouse, takes us on a visit through Castle Morro.

Enrizio, keeper of the Havana lighthouse, takes us on a visit through Castle Morro.

On a quick visit to the island last weekend, Graves Light keepers Lynn and Dave talked their way into the lighthouse just as the Morro keeper was reporting for duty.

The light is closed to the public. Lunchpail in hand, Enrizio, the friendly keeper, gave us fellow keepers a tour and took us up to the lantern room.

It was like climbing back in time. What appears to be the original Third Order bivalve Fresnel lens is still in operation.

The lens was made in about 1845 by BBT Paris, the same manufacturer of the old First Order lens at Graves Light, which is now at the Smithsonian Institution.

The keeper fired up the early hand-cranked motor that spins the lens, which still floats smoothly on its mercury bath. Half the windows in the lantern room are cracked or broken out, but the lens produces a brilliant double white flash every 15 seconds. The mechanism is still manually wound every three hours.

The lens was modified by “the French” in the 1950s with the addition of small reflecting panels to bend some of the beam 45 degrees upward so that aircraft could navigate by its light. Other than those panels and an electric lamp that uses a 70 watt halogen bulb, the entire apparatus appears completely original.

Each evening, the keeper withdraws the curtains and engages the mechanism to spin the lens. By day, the curtains are drawn to prevent the sun from entering the lens and starting a fire inside.

Share Button

Discovered: Original Fresnel Lens rotation mechanism

Polishing a century of grime from one of the brackets of the original First Order Fresnel lens rotation mechanism.

Polishing a century of grime from one of the brackets of the original First Order Fresnel lens rotation mechanism.

Ever wonder how the giant First Order Fresnel lens rotated to produce that smooth, sweeping beam lf light?

The good guys at the US Coast Guard revealed the secret by sending us the old engineering drawings of parts of the original mechanism, which are still bolted to the 5th level ceiling.

Since that ceiling is being restored, we figured we’d take the mechanism down and clean it up, which we did this week at home.

Here’s how it worked: Every two hours the Keepers wound a 300-lb weight up a 50-foot tube using a hand crank. The weight was connected by a series of pulleys (pictured) and connected to a big clockwork device, which regulated the speed and drove a gear that spun the two-ton lens.

The system was converted to an electric motor long ago, but happily the Coast Guard left all the old stuff in place, which made it possible for us to tell the story.


Share Button