2 6 D O C U M E N T S 5 , 6 J A N U A R Y 1 9 2 2 could make this possible and we are so much looking forward to this prospect that you must not decline under any condition. Warm regards and good wishes for the New Year. Born and Franck. 5. From Hermann Weyl[1] Arosa, Villa Anita, 3 January 1922 Dear Colleague, Many thanks indeed for your efforts regarding the printing permission it is good that it turned out to be superfluous, as the printing had already been completed in the interim!–[2] I do not know anything more specific about the canal-ray experiment is it an experimental answer to the question of whether whatever it is that would be excited by a Bohr-like atomic jump is an ether wave?[3] (namely, the answer no)? Thus I do not know what to reply to your question: Now what??[4] —nor would I know, of course, even if I were fully informed about your experiment. This is yet another tid- bit you found for yourself, reconciling apparently completely contradictory things within an overarching principle. I already feel sorry for the poor “field” in advance but its theory has meanwhile acquired such a degree of harmony that it is—ripe for its demise it almost seems to me that it is. Best wishes for the New Year and good luck along the new path! Yours, H. Weyl. 6. To Max Born [Berlin, 6 January 1922] Dear Born, I’ll gladly come and visit you, partly to congratulate Hilbert personally, partly to tell you about the experiment, simple as it is.[1] The trick is this: According to the wave theory, the canal-ray particle emits contin[uously] variable color in different directions. Such a wave propagates in dispersive media at a velocity that is a func- tion of the location. Therefore a bending of the wave planes would have to follow, as with terrestrial refraction. But the experimental outcome is reliably negative. Cordial greetings also to Franck and your family, yours, Einstein.