^{page 314 note *} Cf. “Escapements and Quanta,” Phil. Mag., Oct. 1921.

^{page 315 note *} Milner, S. R. and Hawnt, J. S., Phil. Mag., May 1927.Google Scholar

^{page 315 note †} More ultimately, what it confirms is the universality of Faraday's original law, that the line-integral of electric force (force on its electrons) round any material circuit is, at each instant, equal to the rate of decrease of N, the number of magnetic tubes that the circuit encloses : as N cannot increase or decrease indefinitely, except by aid of artificial commutating devices such as Faraday himself introduced in his electric motors, it follows that all natural electromotive forces, even those derived from X-ray radiation, must be alternating.

^{page 316 note *} The introduction of imaginary coordinates, such as the imaginary time of Minkowski, to take the place of the real quantities of nature, may, however, totally change the scheme of events, if not closely safeguarded.