Robert Erskine

Robert Erskine (1735 – 1780) was a Scottish inventor and engineer who came to the British Thirteen Colonies in 1771 to run the ironworks at Ringwood, New Jersey, and later became sympathetic to the movement for independence. In 1776 during the American Revolutionary War, he designed an underwater cheval-de-frise installed across the Hudson River at the north end of Manhattan to prevent passage of British ships upriver. General George Washington appointed him as Geographer and Surveyor General of the Continental Army at the rank of colonel; Erskine drew more than 275 maps, mostly of the Northeast region.

Born in Scotland, Erskine attended the University of Edinburgh. As a young man, he started a business, but it failed. He invented the "Continual Stream Pump" and "Platometer", a centrifugal hydraulic engine, and experimented with other hydraulic systems. He became known as an inventor and engineer of some renown in his native land.

Erskine also became active in civic issues and increasingly gained the respect of his community. In 1771 at the age of 36, he was elected a Fellow of the Royal Society, a prestigious appointment in the scientific community.

In 1771, the owners of an ironworks near Ringwood, New Jersey, hired Erskine to replace Peter Hasenclever as ironmaster. The latter's profligate spending had nearly bankrupted the operation. Erskine immediately set about trying to make the operation profitable. His efforts were cut short by the American Revolutionary War. Erskine was sympathetic to the American cause, but worried that might he lose his workers to the army. He organized them into a militia and was appointed as a militia captain in August 1775.

Once the war broke out in earnest, the rebels were concerned that the British warships would go up the Hudson River to attack northern forts and separate New England from the rest of the colonies. Erskine, ever the engineer, designed a tetrahedron-shaped marine cheval-de-frise, a defensive barrier to prevent warships from sailing upriver. It was installed between the northern end of Manhattan and Fort Lee, New Jersey in 1776.

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