Developed a medicinal powder to stop hemorrhaging and became involved in a lengthy controversy with Jacques Faynard, a French physician living in London, about which of them had invented the powder. Visited Franklin in order to demonstrate the powder (1777). Renounced British nationality, took an oath of allegiance before Franklin, and became a naturalized American citizen (1780). Appealed to Franklin to support him in his conflict with Faynard and help him market the powder in America. The powder was promoted in the Pennsylvania Gazette in the autumn of 1780, but Faynard received patent rights in England and France.