Joseph Henry was born in Albany, New York, in 1797. His working-class family often struggled for money, and in his early teens Henry began working as a store clerk. He also served as an apprentice to a jeweler and watchmaker, and in his extra time he acted and wrote plays for an amateur theatrical group. Reading a popular book on natural science, he became so fascinated by the subject that he committed himself to becoming a scientist. He studied assiduously, was admitted as a student at the Albany Academy, and in 1826 became professor of mathematics and natural philosophy at that institution.

Henry's Early Experiments.

As a professor Henry made important advances in the study of electromagnetism. A British scientist, William Sturgeon, had invented the electromagnet in 1825, but Henry improved the device to its present-day form. Sturgeon had wrapped bare copper wire around a bar...