D O C . 2 7 8 I N T E R F E R E N C E O F C A N A L R AY L I G H T 2 9 5 The would be defined by the condition that be independent of y. Thus, it would have to be valid that . Such a rotation of the mirrored virtual light source around the intersection with the X-axis can be accomplished by tilting the reflective surfaces against each other at the angle . To make the reflected im- age turn around its intersection with the X-axis, however, it is necessary that this point lie on the reflective surface, which is tilted by . This result would be verifiable best by means of the Michelson interferometer. The arrangement would be the following: Lens L is set up such that (via ) it rep- resents an infinitely remote object in the reflection plane . The mirrors and are positioned so that interference circles are visible in the telescope F, set at ∞, provided a light source at rest is used. The optical path difference1) is l. Now the canal ray K is used as the source of light. Then the interference rings disappear. But they must reappear if the mirror is rotated around A in the direction of the arrow at the angle .[8] This result still needs experimental verification, of course, although its validity is already very likely judging from the above analysis. The theoretical significance of this result for the theory of light is illuminated by the following consideration. The result applies also to the case where the distance of the canal ray K from the lens L is equal to the focal length of the latter in this case, however, a particularly vivid interpretation is permissible. In telescope F, only those parts of a wave train can result in interference that arrive simultaneously and in the same direction. But they come from K (due to the tilt of S1) from two positions, which have the distance or . It would therefore hardly be doubtful that they would come from a particle moving at the velocity v at different times. From this it would be concluded 1) Let l be calculated as positive if the mirror S1 is farther away than mirror S2.[10] β∠ d βy – λ0© 1 v c ----·y f¹ – § -------------------------- β vd c ---- f - = [p. 337] β 2 -- - β 2 - ∠-- S0 S1 S1 S2 S1 β 2 -- - f β⋅ v c --d