Astrolabe

Many Hands Make (the) Light Work

Join in the drive to re-create a working Fresnel lens display.

Story & Photos By Dr. Donald H. Keith, Chairman, TCI National Museum

Grand Turk lighthouse is a rare and wonderful historic structure.

Like any renovation, the Museum’s started out with a simple, concise plan that grew in complexity as we saw other things that ought to be dealt with at the same time. Once the most glaring problems were solved, other only slightly-less-glaring problems took their place.
This, “the appetite grows by eating” phenomenon, is exactly what happened when we started work on the upstairs main gallery in the Guinep House. All we wanted to do was replace the carpet.

But that meant that all the exhibits and cabinets had to be moved. The most cumbersome of these is the Fresnel lens from the lighthouse at the north point of Grand Turk. Because it had to be moved anyway, we thought, “Why don’t we move it to the front of the gallery where it would be more impressive? And we might as well take the clockwork mechanism that turned the lens out of storage and put the two objects together. It only weighs a few hundred pounds and all we have to do is carry it down two flights of stairs, lug it 50 yards over broken ground, maneuver it through the Museum’s front door, up a narrow staircase with two 90º turns and through another door to get where it needs to be. No big deal or expense, just a little elbow grease.”
Original bearing for the Fresnel Lens.But we couldn’t just dump the clockwork down next to the lens because it wouldn’t make any sense. They wouldn’t be in the right configuration to mate properly. In the current display the lens is at knee level. When the lens was in the lighthouse, it sat on top of a five-foot tall cast iron pedestal, floating in a pool of mercury with its base at the same height as the drive gear at the top of the mechanism. The light source itself was stationary while the heavy lens turned around it. The mercury acted as a low-friction bearing.
Sherlin Williams sizes up the pedestal.Then it struck us: if we had the pedestal we could put the whole team together and actually make it work! But we don’t have the pedestal. It is still in the lighthouse. Before we could evaluate the feasibility of a working lighthouse exhibit we needed to see what the pedestal looked like. Could it be removed and taken to the Museum? Would it make more sense to build a replica?
Early one blustery August morning last summer, historian Sherlin Williams and I paid a visit to the lighthouse. The grounds are a popular tour destination but the lighthouse interior is off limits for visitation. It took awhile to find out who had access, but after we explained our mission to Jerome Miller of Chukka Tours he kindly agreed to meet us there to unlock the door. The wind howled and rain beat against the sides of the lighthouse as we lugged our photographic and recording equipment up the claustrophobia-inducing steep spiral staircase and even steeper, narrow ladders that lead to the top. I counted 64 steps along the way.
When we got there, the cramped “lamp room” at the top of the lighthouse was bright and cheery compared to the gloomy interior rooms below, but as the morning wore on it became a sauna! Sherlin, who has done a lot of research on the lighthouse, observed that when the light was in service there were shades that the lighthouse keeper would pull to block the sun and keep the temperature bearable. A quick inspection of the pedestal left us with the impression that although it is in great condition, it would be difficult to remove. It is quite massive and would have to be disassembled before it could be taken down through the interior. Then there was the mercury to contend with. Was it still inside the bowl at the top of the pedestal? If so, it would be necessary to remove it, ship it out of the TCI and dispose of it properly in a hazardous waste facility — cha-ching!
The other, more attractive option was to measure and record the pedestal photographically so we could fabricate a replica to complete our exhibit. Sherlin pulled the tape and called out the measurements while I entered them on a sketch to make sure we had them all. One of the most important details was measuring the diameter of the “driven gear” on top of the pedestal that the lens had been bolted to. We must have spent an hour on this alone. After numerous attempts using different techniques, we were finally able to obtain the same count consistently: 232 teeth.
The next step was to look for help and advice from people who do this sort of thing for a living. Yes, lighthouse engineers are still around! We quickly discovered that the company that built and furnished the equipment for the Grand Turk light in 1852, Chance Brothers Lighthouse Engineers, still exists (www.chancebrothers.com). They can manufacture and restore all manner of lighthouse equipment and were quick to offer their assistance. Another message sent to the World Lighthouse Society (www.worldlighthouses.org) resulted in establishing contact with a half-dozen lighthouse specialists with a wide variety of expertise. Joseph Cocking of the Lighthouse Lamp Shop, Inc. in Florida was particularly helpful.
Then I ran across a newspaper article about Enberg Mold and Tool, a company in Florida involved in the restoration of the Statue of Liberty, six lighthouses in Florida, and the Cape Hatteras and Bodie Island lighthouses on the coast of North Carolina. I got in touch with Gary Knappenberger, the owner, and explained our vision for the new lighthouse exhibit — a small project compared to others he had undertaken. Together we worked out a plan of action and a budget for the complete project. So this is how the simple Fresnel lens exhibit is growing into a major restoration and interpretation project — but one with the potential of becoming the Museum’s most attractive and engaging exhibit.
The Grand Turk lighthouse is a rare and wonderful historic structure. Safety concerns render tours of the interior impracticable. Fortunately, the stunning Fresnel lens and intricate clockwork mechanism, removed when the lighthouse was electrified decades ago, were saved by the Museum. We also found many of the elements of the original Argand lamps that produced the light. We have the means, motive, and opportunity to create a dynamic exhibit featuring a slowly rotating lens mounted atop its pedestal, driven by gravity, and regulated by its original clockwork!
What we don’t have is the funding to make it happen. Because the original pedestal and its pool of mercury cannot be removed from the lighthouse, a replica pedestal with its bearings and huge driven gear will have to be fabricated. A restorer must be brought in to evaluate the clockwork mechanism and restore it to working order. Broken prisms in the Fresnel lens need replacement. The cost will likely exceed $50,000. The Museum is seeking sponsors to help make this plan a reality. Individuals or corporations wishing to help with in-kind or financial support should contact: Dr. Donald Keith, President of the Turks & Caicos National Museum Foundation at (361) 779-3861; email dhkeith@shipsofdiscovery.org. Help us to shine on!



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Marta Morton, owner/operator of Harbour Club Villas (www.harbourclubvillas.com) took this photo of the native Turks & Caicos rock iguana on Bay Cay. This endemic animal is being threatened by the invasive green iguana. See article on page 36.

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