The service which the one-fluid theory has rendered to the science of electricity,” wrote the great nineteenth-century British physicist J. J. Thompson, who discovered the electron 150 years after Franklin’s experiments, “can hardly be overestimated.” He also came up with the distinction between insulators and conductors, the idea of electrical grounding, and the concepts of capacitors and batteries. As Van Doren notes, “He found electricity a curiosity and left it a science.