HENRY A. ROWLAND was a pioneering American physicist and educator who became the first professor of physics at Johns Hopkins University and later served as the first president of the American Physical Society. He is best known for inventing highly precise diffraction gratings and using them for advanced spectroscopic work on the solar spectrum.
Born in Honesdale, Pennsylvania, Rowland showed early scientific curiosity and went on to study at Rensselaer Polytechnic Institute (graduating in 1870). He briefly worked in industry before turning to academia, ultimately moving to Johns Hopkins in 1876 after a period of study in Berlin under Hermann von Helmholtz. His research spanned the mechanical equivalent of heat, electrical measurements, and thermodynamics—and culminated in his development of the diffraction‑grating technique and its application in astronomy.
Rowland’s work earned him numerous honors, including the Henry Draper Medal for astrophysics and the Matteucci Medal. He died in Baltimore in 1901, leaving behind a legacy of precision instrumentation and a stronger foundation for spectroscopic science.