Installation of the chain was supervised by a thirty-three-year-old artillery engineer Thomas Machin of Boston. He had "gone out with the Tea Party" in 1773 and, two years later, laid out overnight on Breed's (Bunker) Hill. Lieutenant Machin was a well-educated English immigrant with practical experience in civil engineering. In the spring of 1777, he had succeeded in stretching a light chained boom across the Hudson River near Bear Mountain. Within six months, that obstruction was outflanked and destroyed by British forces under Sir Henry Clinton. http://www.hudsonriver.com/halfmoonpress/stories/0298link.htm