In 1765 he returned to London where was elected a fellow of the Royal Society. There he became acquainted with the civil engineer John Smeaton, who during the course of his studies on windmills had devised a descriptive scale for grading wind speed. This scale was included in the paper for which he was awarded the Copley Medal. In Defining the Wind: The Beaufort Scale and How a 19th-Century Admiral Turned Science into Poetry, author Scott Huler relates that Dalrymple's voyages had convinced him that a standard scale for measuring the speed of wind at sea would be of great value to sailors, and that he had included Smeaton's scale in his work Practical Navigation, which was written around 1790 but never published. It is believed that Dalrymple conveyed this information to Francis Beaufort, who later refined the wind scale that bears his name and that is still in use today.
