Thomas Point Shoal Lighthouse

      Thomas Point Shoal Lighthouse is an iconic image of Maryland and Chesapeake Bay. It provides a reassuring mark for mariners. Its image is routinely borrowed for art and souvenirs. It was the runner-up image on the Maryland state quarter. A national historic landmark, it holds the distinction of surviving as the only light of its type in its original Chesapeake location. 

      Get to know the Thomas Point Shoal Lighthouse, as I have as a tour guide, and you’ll learn even more reasons to be impressed.

      History: It’s 143 years old. Built in 1875 to mark the shallow water about a mile from Thomas Point, it replaced a stone tower built on shore in 1825. 

Illumination: It’s a lesson in the evolution of lenses to aid navigation. In 1820s’ France, engineer and physicist Augustin Fresnel developed the design for a series of prisms that concentrate light. The secret of the Fresnel lens is the precise circular arrangement of the prisms to focus the beam. In 1875, a fourth order Fresnel lens standing about two and a half feet tall, was installed in Thomas Point Shoal Lighthouse. 

      With advances in plastic technology, the glass lens was removed in the early 1990s. The current acrylic lens light was made in New Zealand in 1996, based on Fresnel’s optical principles.

       The light flashes every five seconds and is visible for 16 nautical miles. 

     Engineering: in England during the 1830s, Alexander Mitchel invented and patented the wrought-iron screwpile design for a lighthouse foundation. The first screwpile lighthouse foundation was installed in 1838 at Maplin Sands mudflats in the Thames River estuary. As the name suggests, the 10-inch diameter pilings for Thomas Point Shoal were literally screwed into the soft soils under the water.

Rather than directly confront the power of the water, these foundations allowed waves to pass through the iron pilings that supported the wooden cottage housing the light and its keepers. Between 1854 and 1910, at least 40 screwpile cottage lighthouses were constructed on the Chesapeake Bay. 

      Economy: Screwpiles were less expensive than other foundation designs.

      Ghosts: In 1903, First Assistant Keeper Henry Addicks disappeared from the lighthouse. Suicide was suspected, and his body was never found. Ghost stories began.

       Automation: For hundreds of years, keepers busily tended a flame that illuminated the light. Technology gradually replaced constant human attention. In 1964 Thomas Point Shoal Light was the last manned lighthouse on the Bay.

      In 1986, it was fully automated. Coast Guard keepers now monitor the light from their offices on land. 

       Power: First oil and then kerosene illuminated the light. Generators provided power in the 20th century until the 1950s, when an underwater electric cable was stretched from shore. In 1977, solar panels were installed. Power from the sun is collected by panels and stored in batteries that keep the light shining. 

       Ice: A solid freeze of the Bay was more common in the past, when ice was the greatest threat to lighthouses. Tending the lighthouse was serious business. After two other lighthouses were swept away by ice flows, the Office of the Lighthouse Inspector warned: “As there appears to be a mis-apprehension on the part of some Light Keepers as to their duty under circumstances when the Station is endangered by ice or other causes, they are reminded that this position of Light Keeper is one of danger, as well as trust, that they must remain by their light as long as the house stands; it is better to resign now, rather than be dismissed for desertion, when danger arises.”

       Accessibility: You can experience the Thomas Point Shoal Lighthouse without isolation and danger by taking a fun and educational tour that departs from the Annapolis Maritime Museum. Tours begin on June 9, rsvp; $80:

       Volunteers are needed to help guide tours and for restoration work on the lighthouse: ­