That same year, he sailed with George Fox to Europe to continue his education, arriving in Paris with a recommendation letter addressed to Benjamin Franklin, America’s Minister to France at that time.
[3] Returning to Philadelphia, Foulke became active in the American Philosophical Society, serving as secretary in 1786.
At that time, he became equally active in his medical career: he served on the staff of the Pennsylvania Hospital, became a fellow of the College of Physicians, and held lectures on pneumatics and anatomy.
In 1793, Dr. Foulke helped identify the outbreak of yellow fever in Philadelphia alongside Dr. Benjamin Rush, and dedicated himself fully to treating patients throughout the city as the disease spread.
He is buried in the Friends Arch Street Meeting House Burial Ground in Philadelphia.