1937 C.J. DAVISSON section-in-azimuth of the beam shown in Fig. 2. Two similar peaks mark the positions of companion beams which with the first form a set of three as required by the threefold symmetry of the crystal about its(lin) direc tions-the direction of the incident beam. The lesser intermediate peaks are due to a different set of beams which is not here fully developed 状木入八N Fig 3. Curve showing intensity of elastic scattering of 54-volt primary beam as func tion of azimuth for latitude of peak in 54-volt curve of Fig. 2. The de Broglie relation was tested by computing wavelengths from the angles of the diffraction beams and the known constant of the crystal, and comparing these with corresponding wavelengths computed from the fo mula n=h/, where p, the momentum of the electrons, was obtained from the potential used to accelerate the beam and the known value of e/m for electrons. If wavelengths computed from the formula agreed with those ob- tained from the diffraction data, the de Broglie relation would be verified How nearly the theoretical values agreed with the experimental is illustrated in Fig. 4. For perfect agreement all points would fall on the line drawn through the origin. You will realize without my telling you that this series of experiments ex tending in time over a period of eight or nine years and requiring the con- struction and manipulation of intricate apparatus was not made by me alone From first to last a considerable number of my colleagues contributed to the investigation. Chief among these were my two exceptionally able collab- orators Dr C. h. Kunsman and dr L. h. germer. Dr. Kunsman worked with me throughout the early stages of the investigation, and Dr. Germer,392 1937 C. J.DAVISSON section-in-azimuth of the beam shown in Fig. 2. Two similar peaks mark the positions of companion beams which with the first form a set of three, as required by the threefold symmetry of the crystal about its (III) direc￾tions - the direction of the incident beam. The lesser intermediate peaks are due to a different set of beams which is not here fully developed. Fig. 3. Curve showing intensity of elastic scattering of 54-volt primary beam as func￾tion of azimuth for latitude of peak in 54-volt curve of Fig. 2. The de Broglie relation was tested by computing wavelengths from the angles of the diffraction beams and the known constant of the crystal, and comparing these with corresponding wavelengths computed from the for￾mula l = h/p, where p, the momentum of the electrons, was obtained from the potential used to accelerate the beam and the known value of e/m for electrons. If wavelengths computed from the formula agreed with those ob￾tained from the diffraction data, the de Broglie relation would be verified. How nearly the theoretical values agreed with the experimental is illustrated in Fig. 4. For perfect agreement all points would fall on the line drawn through the origin. You will realize without my telling you that this series of experiments ex￾tending in time over a period of eight or nine years and requiring the con￾struction and manipulation of intricate apparatus was not made by me alone. From first to last a considerable number of my colleagues contributed to the investigation. Chief among these were my two exceptionally able collab￾orators, Dr. C. H. Kunsman and Dr. L. H. Germer. Dr. Kunsman worked with me throughout the early stages of the investigation, and Dr. Germer