By the time he arrived in Philadelphia, Latrobe's two friends, Scandella and Volney, had left due to concerns regarding the Alien and Sedition Acts, but Latrobe made friends with some of their acquaintances at the American Philosophical Society. Latrobe submitted several papers to the society, on his geology and natural history observations, and became a member of the society in 1799. With his charming personality, Latrobe quickly made other friends among the influential financial and business families in Philadelphia, and became close friends with Nicholas Roosevelt, a talented steam-engine builder who would help Latrobe in his waterworks projects.