Losses in lead of electrons with energies both above and below the range previously used (2 to 11 Mev) have been measured. For the low energy group electrons from radioactive ${\mathrm{P}}^{32}$ were sent through lead laminae of two thicknesses placed in the center of a cloud chamber. In this energy region the losses in lead should be due almost entirely to ionization processes. The experimental values for the energy losses are from 2 to 4 times those given by the Bloch formula. For the high energy group the electrons and positrons produced by the Li+${\mathrm{H}}^1$ gamma-radiation were used. The values found are about 50 percent greater than the calculated losses due to ionization and radiation, but are in good accord with the previous experimental values.

• Received 25 February 1938

DOI:https://doi.org/10.1103/PhysRev.53.618