This past week, we celebrated "world hydrography day," so I thought I would reflect on this little-known science's importance to the American War for Independence. Let's begin with the definition of hydrography: the science that deals with measuring and describing the physical features of oceans, lakes, rivers, seas, and their surrounding coastal areas, especially concerning their use for navigation. Although the formal science of hydrography was not officially established until the late 18th century (by the French), evaluations of waterways had been vital to navigation safety for many centuries before, especially starting with the Age of Exploration. During the American Revolution, watermen with detailed knowledge of coastlines, rivers, and estuaries played a crucial role for both sides, but especially the British, who relied heavily on the Royal Navy for their strategic advantage.
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| 1571 pre-Mercator nautical chart from Portuguese cartographer Fernao Vaz Dourado |
Knowledge of the waterways and shorelines around Boston, New York, Philadelphia, Wilmington, and Charleston was crucial for warships, merchant vessels, smugglers, and privateers. This was especially true for the rebels, whose use of small craft and longboats was often their only defense against the diverse British ships. Local ferrymen, fishermen, and pilots were vital, and both sides competed fiercely for their services and loyalty. Failing to understand the features above and below the water, as well as the local tides, often resulted in disasters, big and small. In ancient (and maybe not so ancient) times, mariners called on Neptune, the god of the sea, for help when their knowledge of tides and shoals let them down. Here are some stories of Neptune's influence on the fight for independence...
The First Affair
The grounding of a ship before the American Revolution is a clear example of hydrography's influence. The so-called Gaspee Affair occurred on June 9, 1772. The HMS Gaspee, a British customs ship, ran aground in Rhode Island, where a group of Sons of Liberty attacked and set fire to the vessel. The British government threatened to send the American perpetrators to England for trial, but no arrests followed. Still, their threat to try Americans in England caused upset protests in the colonies, which learned about the incident from the Committees of Correspondence. The creation of these Committees of Correspondence eventually led to the founding of the First Continental Congress and, ultimately, the Declaration of Independence.
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| Grounding and burning of the Gaspee - prelude to war |
Gloucester
Neptune works both ways—he rarely takes sides. The Battle of Gloucester is a good example. It was a small fight early in the American Revolutionary War (August 8 or 9, 1775) at Gloucester, Massachusetts. Royal Navy Captain John Linzee, commanding the sloop-of-war HMS Falcon, saw two schooners coming back from the West Indies. After taking one schooner, Linzee chased the second (American) into Gloucester Harbor, where it ran aground. Linzee sent sailors to seize the prize. But, the townspeople called out their militia, who captured the British sailors sent to take the grounded ship. The militia also took back the ship. Local knowledge of the waters around Boston gave the New Englanders a big advantage against the strong land and naval forces during that crucial year.
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| Massachusetts coastline |
Aside from this incident, Gloucester is known for being the home of the legendary Marblehead sailors, whose expertise and skill in navigating coastlines and riverways played a vital role in rescuing the Continental Army from defeat and facilitating Washington's Christmas night crossing of the Delaware River, which delivered a significant victory at Trenton.
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| Marblehead Sailors helped save the Revolution |
HMS Somerset vs Neptune
The HMS Somerset began its service during the American Revolution by shelling Charlestown in 1775. The Somerset achieved great success operating in estuaries, bays, and rivers. It acted as the flagship headquarters at Bunker Hill (Breed's Hill).
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| Knowledge of waterways was critical for large ships of war |
The Somerset was involved in another brief but significant incident during the war, the Battle of Chelsea Creek. On the night of May 27, 1775, the armed schooner HMS Diana ran aground in Chelsea Creek while trying to stop Americans from driving British livestock off Noddle's Island in Boston Harbor. The American rebels set fire to the ship. HMS Somerset's tender, Britannia, was able to rescue the crew of the Diana. Later, it participated in the fierce river fighting at Fort Mifflin near Philadelphia.
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| HMS Somerset |
The battle for Fort Mifflin involved ships and boats navigating the treacherous waters of the lower Chesapeake River. It was a desperate, prolonged siege, featuring land and naval forces that used the elements and geography to their advantage. The Somerset participated in the later phase, bombarding the fort from far offshore. Meanwhile, other small vessels navigated dangerous waters in the turbulent ebb and flow of fierce combat that lasted for weeks. To prevent the British from using two nearby islands, the Americans breached the riverside dikes.
This action forced the British to build their batteries on top of the dikes and work in knee-deep water. An example of the challenges faced is when the British lost an 8-inch howitzer and a soldier drowned when the craft carrying the gun sank in the Schuylkill. While bombarding Fort Mifflin, the Augusta and Merlin ran aground. A high tide that evening was met with contrary winds that hindered the depth needed for the ships to be freed.
On October 23, 1777, the American forts focused their fire on the two stranded ships. HMS Isis maneuvered alongside the grounded sixty-four in an effort to rescue it. British accounts claimed that American gunnery caused only minor damage, though flaming wads from the ships' guns set the Augusta on fire. At midday, the Augusta exploded with a tremendous blast that shattered windows in Philadelphia. An eyewitness reported that 60 sailors, a lieutenant, and the ship's chaplain died while struggling in the water. The loud explosion was heard nearly 30 miles away in Trappe, Pennsylvania. After the Augusta's destruction, the crew of the Merlin set their ship on fire and abandoned it.
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| British bombard Fort Mifflin |
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| Knowledge of the tides and shoals was critical around New York |
New York, New York
When the British drove the Continental Army out of New York City in 1776, their knowledge of the waterways and islands proved essential. Although they had no shortage of sympathizers familiar with the waters, the Americans did as well. The farther the British moved away from the "safe zone" of New York Island (Manhattan) and Long Island, the more risky the situation became. In 1776, to prevent an attempt at naval encirclement, the rough shoreline and waters of the Bronx forced General Howe to attempt landing further north near Pelham. This delay allowed the Americans to shift forces to defend the Continental Army and keep their lines of communication intact.
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| The British landed at Pelham when the shoals near Throg's Neck proved unmanageable |
The coves along the north shore of Long Island allowed rebels to slip boats in and out without usually risking detection. This helped one of George Washington's most famous spy rings gather intelligence across the Long Island Sound to American-held Connecticut (where knowledge of the cost was just as important).
During the War of Independence, the great Sandy Hook was more than just the peninsula extending from the Jersey shore today. The "hook" stretched across the harbor's mouth as a huge sandbar, blocking ships of the line and frigates from passing in or out of Lower New York Bay except at high tide. This limited British options when they needed to send ships to sea quickly. Later in the war, a French fleet abandoned plans to attack New York for the same reason.
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| Vessels in New York Harbor had to wait for the tide to rise |
The Carolinas
In the Cape Fear area near Wilmington, North Carolina, superior knowledge of the coastal and inland waterways enabled the rebels to prevent reinforcements by sea, keeping the crucial state in American hands from February 1777 until a second wave of British troops arrived in 1780. This marked the start of a prolonged guerrilla-style war along the dangerous Cape Fear River. British warships patrolled while blockade runners attempted to smuggle valuable supplies. Both sides depended on local knowledge of the waterways to succeed.
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| In the savage guerrilla war along North Carolina's coast, both sides needed knowledge of the waterways |
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| William Moultrie |
The palmetto is very porous (spongy), and every time the British fired a cannon, the cannonball would get stuck in the fort and wouldn’t explode. If it did explode, the fort's sand walls would fall apart and put out the fire. Confused because the fort wasn’t burning, the British moved closer. Bad idea. Three of His Majesty’s ships ran aground on a sandbar, now the site of Fort Sumter. There, they became easy targets for patriots. Francis Marion, who would later become famous as the “Swamp Fox,"
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| British naval map of Sullivan Island defenses |
