Sir Charles Wheatstone (1802-1875), British inventor. He is best known for the Wheatstone Bridge, a device for determining the resistance of an electrical component. Wheatstone was a child prodigy, and by 15 he was translating French, including a book on electricity by Volta. Aged 19, he took over the family business of making musical instruments, but devoted his time to experiments rather than business. He made important contributions to spectroscopy, telegraphy, the physics of electricity, and even cryptography. This image is from an engraving portrait from J.A. Fleming, 'fifty years of electricity', London, 1921.