The total cross section for Compton scattering of 319-Mev photons by electrons was measured in an indirect manner to be 2.8±0.4 mb per electron. This result is 8% smaller than the theoretical cross section given by the Klein-Nishina formula, but agrees within the experimental error.

The data also yield the triplet-production cross section for beryllium, which was found to be 36.0±3.5 mb per beryllium atom. The theoretical value is 30.2 mb per beryllium atom.

The total-absorption cross sections for 319-Mev photons in beryllium and lead were found to be 161.3±1.0 mb per beryllium atom and (37.620±0.225)×${10}^{-24\mathrm{}}$ ${\mathrm{cm}}^2$ per lead atom. The ratio of the pair-forming cross sections in beryllium to those in lead, for 319-Mev photons, was found to be (3.986±0.020)×${10}^{-3\mathrm{}}$.

The deviation from experiment of the Bethe-Heitler theory for pair production can be expressed by ${{\phi }_p}^z={{\phi }_p}^z(\mathrm{B}.\mathrm{H}.\mathrm{})[1-a{Z}^2]$, and a value $a=(1.50\mathrm{}\pm 0.08)\times {10}^{-5\mathrm{}}$ is derived from the measured absorption cross section for lead.

Tables of the principal photon interaction cross sections in beryllium at 319 Mev are included.

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