3 2 2 D O C U M E N T 3 0 6 J U N E 1 9 2 6 306. From Emil Rupp [Heidelberg,] 15 June 1926 Dear Professor, I have been occupying myself recently with performing the turned-mirror exper- iment & would like to report to you about that: Experimental setup: Hg canal ray 546 mμ. Velocity cm/sec. Decaying glow, as in the last communication.[1] Interferometer, see fig. [2] K = canal ray [3] L = lens, f = 14 cm [4] distance K – L = 5 cm [5] distance L S0S2 corresponds to f = 14 cm [6] distance of the mirrors S1S2 Instead of the narrow slit diaphragms, now diaphragms of 1 cm width bb. Mirror S2 on a revolving table that is adjustable by screw s lead of the screw = 0.3 mm. F = counterspring. Distance of the mirror’s center from the screw’s contact point 7 cm. Telescope at ∞. The interferometer is set to interferences of equal inclination. Experiments: a. The interferences of the light of Hg-glow discharge are set to sharpest focus. This screw position s is labeled as 0°. The interferences remain upon turning s from about –20° to +20°. Turning in the direction of the arrow means +. b. Then, decaying canal rays are used as the light source. Interferences at 0° ex- tremely indistinct, become more distinct from +15° on, bright & sharp between 30° & 40°, but then the distinctness drops very rapidly at 45° almost none are visible anymore. Turning in the contrary direction allows the fringes to disappear already at –10°. c. The cooling device is removed from the canal ray tube. One then obtains the glow from charge change.[7] Interferences indistinct from –20° on, distinct at 0°, 1.9 107) ⋅ [2] [3] [4] [5] [6] 2( a1 a2) – 20 cm. =