DISCOVERY OF ELECTRO AVES tically scattered electrons and their near neighbors, could be moved on an arc about the crystal. The crystal itself could be revolved about the axis of the incident beam. It was possible thus to measure the intensity of elastic scattering in any direction in front of the crystal face with the exception of hose directions lying within 10 or 15 degrees of the primary beam ectron A-AZimuth B-Azimuti C-Azimuth Fig. I. Schematic diagram showing disposition of primary beam, crystal, and collector. Crystal shown revolved to bring one principal azimuth after another into plane of observation. 48V 64v Fig. 2. Polar diagram showing intensity of elastic scattering in A-azimuth( Fig. I) as function of latitude angle, for series of primary-beam voltages The curves reproduced in Fig. 2 show the distribution-in-angle of inten- sity for a particular azimuth of the crystal. The curves are for a series of elec tron speeds, therefore, for a series of electron wavelengths. For a particular wavelength a diffraction beam shines out. Setting the collector on this beam at its brightest, and revolving the crystal, the intensity was found to vary in azimuth as illustrated in Fig 3. The high peak on the left represents the cross-DISCOVERY OF ELECTRON WAVE S 391 tically scattered electrons and their near neighbors, could be moved on an arc about the crystal. The crystal itself could be revolved about the axis of the incident beam. It was possible thus to measure the intensity of elastic scattering in any direction in front of the crystal face with the exception of those directions lying within 10 or 15 degrees of the primary beam. Fig. I. Schematic diagram showing disposition of primary beam, nickel crystal, and collector. Crystal shown revolved to bring one principal azimuth after another into plane of observation. Fig. 2. Polar diagram showing intensity of elastic scattering in A-azimuth (Fig. I) as function of latitude angle, for series of primary-beam voltages. The curves reproduced in Fig. 2 show the distribution-in-angle of inten￾sity for a particular azimuth of the crystal. The curves are for a series of elec￾tron speeds, therefore, for a series of electron wavelengths. For a particular wavelength a diffraction beam shines out. Setting the collector on this beam at its brightest, and revolving the crystal, the intensity was found to vary in azimuth as illustrated in Fig. 3. The high peak on the left represents the cross-