Three years later, he became professor of chemistry and botany in the College of Physicians and Surgeons, New York (the medical school of Columbia University), where he stayed until 1855, when he was made professor emeritus.
Tre år senere blev han professor i kemi og botanik ved College of Physicians and Surgeons, New York (det medicinske fakultet ved Columbia University), hvor han blev indtil 1855, da han trådte tilbage som professor emeritus.