Screwpiles: The Forgotten Lighthouses

CHAPTER TWO THE SCREWPILE LIGHTHOUSES

Faster steam-powered boats and ships required better aids to navigation the world over. A blind, Irish engineer, Alexander Mitchell, created a unique design for bay and river lighthouses. The Maplin Sands Lighthouse (built at the mouth of the Thames River in 1838 and lit in 1841) was the first to use Mitchell’s screwpile design. Screwpile lighthouses were relatively inexpensive, easy to construct, and comparatively quick to build. They became especially popular after the Civil War when the U.S. Lighthouse Board adopted a policy to replace inside (bays, sounds, and rivers) light vessels with screwpile lighthouses. Most screwpile lighthouses were made with iron piles, though a few were made with wooden piles covered with metal screw sleeves (these sleeves were probably adopted because they were less expensive and easier to insert into the bottom, plus the sleeve protected the wood from marine boring invertebrates). The typical screwpile lighthouse was hexagonal or octagonal in plan, consisting of a central pile, which was set first, and six or eight perimeter piles that were then screwed in place around it. The screwpile design, with its wide screw (typically two feet in diameter) imbedded at least 10 feet into the river bottom, provided added resistance to movement. The design required no machinery for installation, only a capstan and a large crew of men—or mules—to turn the piles into the bottom. The screwpile cottage lighthouses were quick to build and economical as well, usually costing about $15,000 in the mid 1800s (equivalent to $400,000 in 2018). 1

The first screwpile-type lighthouse built in the United States was at Brandywine Shoal, near Cape May, New Jersey, in the Delaware Bay, an area served by a lightship since 1823. An ordinary straight-pile lighthouse stood briefly there in 1828 until ice destroyed it. Major Hartman Bache of the Army Corps of Topographical Engineers began work in 1848 and completed the lighthouse in 1850, at a construction cost of $53,317. Alexander Mitchell served as consultant. During construction, 30 men turned the four-foot capstan to auger the screwpiles into the bay’s bottom. 2 In areas such as the Florida Keys, where the bottom is soft coral rock, a diskpile foundation supported the lighthouses. Wrought-iron piles were driven through a cast-iron or semi-steel disk, which rested on the sea floor, until a shoulder on the pile prevented further penetration. The disk diffused the weight of the tower more evenly over the bottom. In coral reef areas where sand is also prevalent, a cast-steel screw, fitted to the end of the pile, gave it more anchoring ability. By 1900, over 100 spider-like, cottage-type screwpile lighthouses found their footings in the Chesapeake Bay, Carolina sounds, Delaware Bay, along the Gulf of Mexico, at least two in Long Island Sound, and one even at Maumee Bay (1855), Lake Erie, Ohio. 3 James River Lights The need for more aids to navigation on the James River was clear, but it was more than 15 years after Captain Beverly Kennon of the U.S. Navy recommended specific

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