4 8 D O C . 5 8 J U N E 1 9 1 9 analysis of the cyanogen band lines does seem promising. For we have determined that, after long exposure of the cyanogen spectrum, the intensity extremum of the lines shows a mean displacement toward the violet, which indicates a structure for lines shows a mean displacement toward the violet, which indicates a structure for most lines in the direction of figure a here to the left. If this is the case, though, the absorption line would then have to exhibit a struc- ture according to figure b, and if it indicates a redshift, this would then have to be too small a measurement against the terrestrial light source in conformity with the measurements by Schwarz- schild, St. John, and us.[3] At the same time, these deviations must come out differently, depending on the structure of the individual lines, as is likewise confirmed by the experiment. I would now like to request, provided the K.W.I. will grant the petitioned 2000 marks, that it be possible to apply this sum toward procuring a Hartmann micro- photometer, which I assume can be obtained at this price, whereas the Koch instru- ment, based on information by Mr. Freundlich, would require 8–10,000 marks. The Hartmann instrument would also suffice for the indicated purpose, even though measurement with it is much more complicated. We are going to publish the existing results of our measurements preliminarily already[4] and in this way hope to be able to show at least that the conclusion by Schwarzschild and St. John that the theoretical effect does not occur is, in any event, not secure, even though we are not yet able to prove the contrary unequivo- cally. In expressing my utmost respect, I am devotedly, Prof. L. Grebe. 58. From David Hilbert[1] Göttingen, Whitmonday [9 June] 1919 Dear Colleague, In your last note, which is obviously very interesting to me (10 April inst.),[2] I cannot see how eq. (4a), p. 352, is accomplished—unless is taken to be = . Perhaps my misconception may be removed by a line from you, for which I would be very grateful.[3] I was very pleased to hear that you are feeling very well. What a pity that I have not seen you for so long—not even in Switzerland, where I was staying just recent- ly again for 6 weeks.[4] viol. red a b giκ δiκ(0,1)