The history of the idea of variation of frequency with velocity is followed through Voigt, Larmor, Lorentz, and Einstein. The Michelson-Morley experiment is explainable by any contraction of dimensions in the ratio (1-ν<sup>2</sup>/<i>c</i><sup>2</sup>)<sup>½</sup>: 1 along and transverse to the direction of motion. To each contraction corresponds a different value of frequency change. The theoretical speculations pointing to the relation ν<sub><i>m</i></sub> = ν<sub>0</sub>(1 - ν<sup>2</sup>/<i>c</i><sup>2</sup>)½ are discussed, together with the significance of the experimental test by means of canal rays.
HERBERT E. IVES, "Historical Note on the Rate of a Moving Atomic Clock," J. Opt. Soc. Am. 37, 810-813 (1947)