The Magnetic Dipole in Undulatory Mechanics.

that there are more possible electron positions available than there are valency electrons to fill them, and the question also arises as to which of the radii are to be selected in those cases when two types of lattice are possible. If we knew definitely just how a single electron scatters X-rays these two questions could be easily settled by a quantitative consideration of the intensities of the observed X-ray diffraction patterns. In the present state, however, of our knowledge of scattering, the carrying through of such computations does not seem worthwhile. In conclusion I wish to express my thanks to Professor Henry G. Gale for his interest in this work. 1 This investigation was commenced by the author under a NATIONAL RESEARCH FSLLOWSHIP. 2 W. L. Bragg, Phil. Mag., 42, 169-189, 1920. 3 W. P. Davey, Physic. Rev., 22, 211-220, 1923. 4 W. P. Davey, Ibid., 23, 218-231, 1924. 6T. D. Bernal, Proc. Roy. Soc., 106A, 749-773, 1924.