Page:The Harvard Classics Vol. 51; Lectures.djvu/124

 114 never succeeded in devising any essentially different formula which shall fully express the phenomena without introducing hypotheses about the mutual action of things which have no physical existence, such as elements of currents which flow out of nothing, then along a wire, and finally sink into nothing again.

"After nearly half a century of labor of this kind, we may say that, though the practical applications of Faraday's discovery have increased and are increasing in number and value every year, no exception to the statement of these laws as given by Faraday has been discovered, no new law has been added to them, and Faraday's original statement remains to this day the only one which asserts no more than can be verified by experiment, and the only one by which the theory of phenomena can be expressed in a manner which is exactly and numerically accurate, and at the same time within the range of elementary methods of exposition."