[12] Eddington, op. cit., pp. 30-32.

[13] Space, Time and Gravitation, p. 147.

[14] The Mathematical Theory of Relativity, p. 155.

APPENDIX
BOHR’S THEORY OF THE HYDROGEN SPECTRUM

THE mathematics involved in this theory is so simple that only a very slight acquaintance with elementary dynamics is required in order to understand it.

Let us consider an electron revolving in a circle about the nucleus. Let

be the mass of the electron, a the radius of its orbit,

its angular velocity. Also let