Measurements have been made on the scattering of $\gamma$-rays from The C″ by Al and Pb. For Al the scattering is, within experimental error, that predicted by the Klein Nishina formula. For Pb additional scattered rays were observed. The wave-length and space distribution of these are inconsistent with an extranuclear scatterer, and hence they must have their origin in the nuclei.

• Received 13 October 1930

DOI:https://doi.org/10.1103/PhysRev.36.1519