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The Chesapeake lighthouse, with its splayed legs supporting a homey cottage set atop a platform rising from the sea, ranks today as a defining icon for the region. I set out recently to learn more about how those beacons came to be and soon found my way to a tale two centuries and 3,000 miles away. Spoiler alert #1: The hero of the story is a blind Irishman named Alexander Mitchell. Spoiler alert #2: The first “Chesapeake” beacon went up in the Delaware Bay.

A Shipwreck Challenge

Sailing ships were the fastest thing going in the early 1800s when it came to moving goods and people around. But sailing was a risky game in which disasters abounded. A key danger around the Delmarva peninsula involved an abundance of sandy underwater mounds known as shoals.

Ships would stumble onto these shoals in bad weather, running aground. Stuck in the muck, the vessels would get beaten to smithereens by waves and wind, stranded sailors clinging desperately to masts and rigging. Those sailors had one eye on the destruction below and another on the horizon, hoping desperately that help would arrive from land or another ship.

The U.S. government had barely gotten into the maritime-safety game at this point. The United States Life-Saving Service wouldn’t come into being until 1848. Still, lots of people tried to make things safer for sailors. Scores of patents were awarded in these years for various life-preserving gizmos, from new types of lifeboats to articles of inflatable clothing and even a “life-preserving hat,” which seems to have involved a ribbon tied under your chin and empty space set amid the fabric that would allow an air pocket to form, keeping you afloat.

Lighthouses were up here and there to help mariners find their way. But they were mostly built on dry land. No one had figured out a reliable, lasting way to put such a warning beacon atop the dangerous open-water shoals of the Delaware and Chesapeake bays. The few attempts made along those lines ended up enduring the fate of that famous Biblical house built by a foolish man on a foundation of sand.

A ‘Little Leprechaun’ Who Overcame Big Obstacles

This is where our blind Irishman enters the picture. Born in Dublin in 1780, Alexander Mitchell was one of 13 children born to William and Jane Mitchell. William traveled constantly due to his job as an inspector of government facilities. When he was at home, the family patriarch loved to play the violin and harpsichord. He called Alexander “my little Leprechaun.”

Alas, William died when Alexander was just 10 years old. The family splintered, with Alexander ending up in a batch of five kids who moved to Belfast with their mother, Jane. Somewhere in these years, Alexander probably had a bout with smallpox. Two of the accounts of his life that I reviewed in putting this together pointed to the lasting effects of that illness as the cause of his eyesight problems.

By age 16 he couldn’t read anymore. At 22 he was completely blind. The disability didn’t keep him down, however. Against his mother’s wishes, Alexander married Mary Banks, the daughter of a neighbor. Barely out of his teens, he took out a loan against the modest inheritance he was slated to receive at age 23 from his father’s estate. He used that cash to launch his own company, a brick-making operation.

Alexander Mitchell Inventor of Screwpile LighthouseThe company was a big success. Soon enough, Mitchell was building and buying houses near his home in the Ballymacarrett area of Belfast. He and Mary had five children. He was quite the socialite, famously hosting parties attended by high-society types from the world of Irish science. Mitchell played whist and backgammon with his guests, with help from a friend who would whisper descriptions to him about what was happening on the gaming table.

Mitchell was a tinkerer, too. Fascinated by math and engineering, he loved to try out the latest gizmos and come up with new inventions. Case in point: He built a custom sail for his family’s boat that attached to a pole outfitted at the bottom with an elaborate flanged screw. He wanted that pole and sail to swivel this way and that, just so, enabling him to catch the wind at the most efficient angle possible.

He was out on the water one day with his teenage son John when something interesting happened with that gizmo. Trying to coax the boat into the position where he wanted to screw in that sail, Alexander asked John to move the pole and sail out of the way for a moment. John punched the screw end of that pole into the sand that lay under shallow water beside the boat.

The wind kicked up right then, catching the sail and spinning the pole around several times. When it came time to pull the pole out of the water, it wouldn’t budge. The flanged screw had latched onto the sandy bottom with a vengeance.

The Screwpile as Retirement Project

Mitchell didn’t have a eureka moment on the day that sail spun around. Evidently, the import of what happened needed to simmer in his head for a while. But he would think about what happened with that pole now and again. He famously pointed to the corkscrews he used to open bottles of wine as an inspiration.

Maplin Sands Screwpile LighthouseMitchell retired from brick-making at age 52. A wealthy man, he could now devote himself more fully to his beloved tinkering. This, then, is when he set out to solve the problem of building a beacon on a foundation of shifting sands.

He crafted a homemade “screwpile” with wide propeller-like blades at the bottom, then had his son John row out to a shoal. The two of them spun that pile into the sand, leaving the top end of the pile sticking out above the water’s surface. It was still there the next day. And the day after that. And so on.

The concept passed more tests like that, and Mitchell soon applied for and won a patent on his screwpile technique. Then … nothing. Five years passed before he could convince anyone in a position of power to give his idea a shot.

Finally, Mitchell was hired to design a beacon in the Thames estuary at Maplin Sands, near London. The work that began there in 1838 involved 20-foot-long piles with cast iron screws 4 feet in diameter at the bottom. The piles were screwed into the sand by hand, with a team of men turning a capstan keyed onto the pile.

Construction at Maplin Sands took longer than expected. The way things worked out, Mitchell’s second job actually became the first screwpile lighthouse to shine. That happened in 1839 at Wyre Light near Fleetwood, a coastal British town northwest of Manchester.

And so the screwpile revolution began. Mitchell soon had multiple lighthouse projects under way in various corners of the British Isles. The blind inventor would regularly conduct inspections at construction sites, traversing rough seas in small boats, then climbing ladders and stepping onto unfinished platforms.

That son of his, John, seems to have been Mitchell’s right-hand man during these years. Later in life, John recalled an inspection at a project in the stretch of sea known as Belfast Lough, during which his father fell overboard, only to pop up moments later on the opposite side of the vessel “cool and collected, with his hat lost but his stick in his right hand.”

The screwpile revolution then spread to distant corners of the globe. As we’ll see in a moment, lighthouse builders in the United States would adopt Mitchell’s innovation starting in 1850. So, too, would construction engineers struggling with soft-terrain issues on other kinds of projects. In India, for example, screwpiles were used during these years to anchor railway bridges and telegraph poles.

The First “Chesapeake” Lighthouse Was in Delaware Bay

As the gateway to Philadelphia, the Delaware Bay ranked among the busiest shipping “superhighways” of the early 19th century. Alas, it was full of sandy hazards including the infamous Brandywine Shoal, which lies out in the middle of the bay, northwest of Cape May, NJ and southeast of Bowers, Del.

Brandywine Shoal Light 1894Various authorities tried every which way they could think of to help mariners avoid running aground at Brandywine. In 1823, a lightship was stationed there. In 1827, a traditional wood pile structure went up on the shoal, only to be torn apart by the sea in short order. Another crew went to work in 1835 on a plan to build a big stone pier atop the shoal and set a lighthouse atop that pier. That project was abandoned as construction costs piled up and up and up some more.

Finally, in 1850, the powers that be turned to the newfangled screwpile solution. One of the key players in that construction work was a civil engineer named George Meade. Meade would go on to become an army general. During the Civil War he was in command of the Union forces that defeated Robert E. Lee’s army at Gettysburg.

The beacon Meade and his team built didn’t look like a “Chesapeake” lighthouse. The first Brandywine Shoal Lighthouse was made of iron and had a conical shape rather than a cottage look. The light was turned on in October of 1850.

Brandywine Shoal Lighthouse played a second notable role in the history of U.S. lighthouses. The year after it was built, a fledgling federal agency called the Lighthouse Board set out to test another newfangled innovation, the Fresnel lens.

That test happened in Delaware Bay, where the new Fresnel-powered Brandywine Shoal outshone nearby lights at Cape Henlopen and Cape May by a wide margin. The board immediately set about replacing old-school reflector lights with new Fresnel lenses at lighthouses around the country. (For you Fresnel aficionados, the Brandywine Shoal lens was a third-order affair that is now on display at the Tuckerton Seaport & Baymen’s Museum in the town of that name on the Jersey Shore.)

The Lighthouse Revolution Comes to an End

The original Brandywine Shoal Lighthouse kept shining for more than six decades, lasting into the 20th century. As that lifespan unfolded, however, the Achilles heel of screwpile construction was revealed in time. While the piles at such beacons were mostly invulnerable to wind and waves, which passed right over and through them, ice was another matter. Floes riding stormy seas would thwack the piles with a ferocity that would knock them loose and put the beacon in danger.

Brandywine Shoal New and Old Side by Side in 1914At Brandywine Shoal, engineers responded to that risk by sinking extra piles around the exterior of the platform that held the lighthouse. In time, that protective fence got bigger and bigger, eventually encompassing a forest of 68 extra piles. At most other screwpile lighthouses, the preferred ice-protection strategy was to lay a protective circle of rocks outside the piles.

The demise of the original Brandywine Shoal Lighthouse came early in the 20th century. By then, the once groundbreaking beacon had begun to seem cramped and uncomfortable when compared with other lighthouse structures. In addition, the metal piles were beginning to corrode beyond the point of cost-effective repair.

In 1914, a new beacon went up next to the original. The new Brandywine Shoal Lighthouse is still shining today, more than a century later. Caisson-style construction involves cylinders that are sunk 15 or more feet into the bottom, then filled with cement. These cylinders support a platform sturdy enough to hold a tower. One measure of caisson-durability: Every caisson lighthouses ever built on the Chesapeake Bay is still standing today.

The original lighthouse building at Brandywine Shoal was torn down when the new light went up, but the platform where the original beacon stood remained in place into the 1950s. The U.S. Navy used it now and again for various purposes. I haven’t come across any detailed descriptions of what they used it for.

The 1850 Brandywine Shoal Lighthouse brought Alexander Mitchell’s screwpile revolution to America. It was the first of more than 100 such beacons that would be built in the United States. They were big not just in the Chesapeake and Delaware bays, but in the Carolinas and along the Gulf Coast, too. Screwpiles were even built as far north as Long Island Sound and on Lake Erie.

Most have long since been replaced by caisson-style lighthouses. In the Chesapeake and Delaware bays, only one old screwpile remains a functioning beacon–the Thomas Point Lighthouse near Annapolis. It’s managed by the Annapolis Maritime Museum, which runs occasional tours during the warmer months in non-pandemic years.

Two other screwpile lighthouses now rank as tourist attractions on Maryland’s Eastern Shore. The Hooper Strait Lighthouse is the visual focal point of the Chesapeake Bay Maritime Museum in St. Michaels, Md. On the waterfront in Cambridge stands a mostly faithful replica of the old Choptank River Lighthouse. Two other screwpile tourist attractions can be found on the western shore of the Bay–in Baltimore and in Solomons.

But the Screwpile Revolution Lives On

Just because screwpile lighthouses aren’t being built anymore doesn’t mean that Mitchell’s contributions to the world are in the past. In modern construction and engineering, the screwpile concept has morphed into something called helical design. The technique is used today in electric transmission towers, oil and gas pipelines, home foundations, elevated walkways, and countless other construction projects.

Here is a takeway quote on the topic at hand from Samuel P. Clemence, a professor of engineering at Syracuse University: “Most engineers don’t understand or appreciate that [Alexander Mitchell’s invention of the screwpile] was the MAJOR foundation technology of the 19th century that dramatically changed the globe.”

–written and posted by Jim Duffy for Secrets of the Eastern Shore/Whimbrel Creations LLC on Dec. 26, 2020. All rights reserved.


• In honor of his screwpile innovations, Alexander Mitchell won the prestigious Telford Medal in 1849. He died in 1868 at the ripe old age of 87.
• The drawing here of Maplin Sands Lighthouse comes from Flicker Commons. The two images of Brandywine Shoal are in the collection of the National Archives.


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