Joseph Henry (1797-1878), US physicist. Henry was born in Albany, New York, USA. By 1826 he was a professor at Albany Academy, and it was there that he conducted the research for which he is still most famous. He studied magnetism and electromagnetism, building powerful electromagnets, and an early form of the electric motor. Henry discovered the principle of electromagnetic induction, though Faraday, who discovered the same phenomenon independently, is usually credited because he published first. However, the unit of inductance is named after Henry. Taken between 1865 and 1878, this photograph is from the Brady-Handy Collection.