We'll Take Him
Charles Proteus Steinmetz fled Germany in 1889 because of his political views, and came to America to continue his engineering work on transformers and electric power distribution. Unsettled at the inability to calculate losses due to magnetism in transformers and other AC apparatus, Steinmetz worked out a theoretical and experimental method for doing so. His result was the discovery of "hysterisis" properties, the phenomenon by which a material's magnetism in a given magnetic field can have two different values. The principle has subsequently been applied to positive feedback in the electrical and mechanical realms as well as in biology and many other fields.